Bibliography on CO2 Effects on Vegetation and Ecosystems: 1990-1999 Literature 

Michael H. Jones and Peter S. Curtis, editors

ORNL/CDIAC-129

July 2000

(http://cdiac.esd.ornl.gov/epubs/cdiac/cdiac129/cdiac129.html)


     1    
Abarzua, S., R. Altenburger, R. Callies, L.H. Grimme, A. Mayer, D. Leibfritz, and U.
Schiewer. 1993. Ammonium rhythm in cultures of the cyanobacterium microcystis- firma.
Physiologia Plantarum 89(3):659-663.

Over a period of several days, rhythmic changes in extracellular NH4+ concentration take place in
cultures of the cyanobacterium Microcystis firma (Breb et Lenorm.) Schmidle, strain Gromov/St.
Petersb. 398, under conditions of restricted CO2 supply and light/dark alternation. The changes are
enhanced by nitrate supply. Among the various processes generating intracellular NH4+ (NH4+
uptake, NO3- reduction, protein and amino acid degradation, photorespiration), NO3- reduction
appears as the one most important. This can be concluded from experiments with and without nitrate
and/or ammonium in the medium. In the presence of saturating CO2, continuous light, or continuous
darkness, rhythmic NH4+ oscillations are not induced. Studies of the incorporation of NH4+ nitrogen
by in vivo N-15-NMR show that if CO2 is supplied, N-15 is accumulated in several components with
the following time course: in the first hour in Gln (delta), in the second hour in the alpha- amino
groups of most nonbranched amino acids, in the third hour in gamma-aminobutyric acid (GABA), Orn
(delta) and Lys (epsilon), and in the sixth hour in Ala. Carbon limitation, however, results in
accumulation of label in the amide nitrogen of glutamine only.

KEYWORDS: METABOLISM, N-15, NMR-SPECTROSCOPY, NUCLEAR MAGNETIC-
RESONANCE


     2    
Abdin, O.A., X.M. Zhou, B.E. Coulman, D. Cloutier, M.A. Faris, and D.L. Smith. 1998. Effect
of sucrose supplementation by stem injection on the development of soybean plants. Journal of
Experimental Botany 49(329):2013-2018.

Over the past half decade several stem injection methods have been developed for cereal plants. These
methods allow researchers to administer solutions to cereal plants to study their effects on plant
physiology. However, little work has been done to extend this technique to non-cereals. An
experiment was conducted to test an injection technique that could be suitable for soybean plants
(Glycine max [L.] Merr.), and to study the effect of long-term injection of sucrose on the growth of
soybean plants. An injection setup comprising a supporting stand and a fluid injection system was
established. Pressure was applied to the plunger of a 5 ml syringe using ceramic bricks to force test
solutions into the plants. Solutions of 0, 150, and 300 g sucrose I-1 were injected into soybean plants
for 8 weeks starting at the seedling VC stage. Distilled water had the greatest uptake rate, followed
by the 150, and then the 300 g sucrose I-1 solutions. The overall average uptake during the injection
period was 77.3 ml. Average sucrose uptake values were 11.8 and 13.5 g per plant for the 150 and
300 g sucrose I-1 treatments. This represented approximately 65% of the total dry weight of the
plants. Sucrose injection increased leaf area and pod number relative to the control plants. Nodule
numbers were lower for sucrose injected treatments, but their dry weights were higher than the
control. Above-soil dry matter was higher for the plants injected with 300 g sucrose I-1 than those
injected with water. The injection system tested was able to administer concentrated solutions into
soybean plants for most of their period of growth and development. The sucrose supplementation had
positive effects on soybean growth but suppressed photosynthesis.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, GROWTH, LEAVES,
MAIZE, NITROGEN, PEDUNCLE PERFUSION, PHOTOSYNTHESIS, WHEAT, YIELD


     3    
Abdullaev, A.A., B.B. Dzhumaev, Z.N. Abdurakhmanova, V.L. Kaler, and I.M. Magmedov.
1992. Integral effect of environmental-factors on photosynthetic metabolism of carbon in cotton
leaves. Soviet Plant Physiology 39(2):140-144.

We used the method of mathematical experiment planning (a 2(3) scheme) to study the influence of
environmental factors separately or in combination on the photosynthetic rate and distribution of C-14
among products of photosynthetic carbon metabolism in the cotton (Gossypium hirsutum L.) leaf
Increase of light intensity during cultivation accelerated photosynthesis and stimulated incorporation
of C-14 into phosphoglyceric acid (PGA), sugar diphosphate (SDP), fructose monophosphate (FMP),
and malate, but suppressed incorporation of C-14 into sucrose, glucose monophosphate (GMP), and
glycerate. Temperature increase by itself and in any combination with other factors at the upper level
suppressed photosynthesis. Elevated temperature increased accumulation of the label in PGA,
sucrose, and malate, but lowered it in GMP, alanine, glycine, and serine. Growing plants at enhanced
CO2 concentration led to acceleration of photosynthesis and increase of the share of C-14 in SDP,
GMP, and malate, but decrease of it in sucrose, alanine, glycine, and serine. Very perceptible effects
of interaction are discernible in different combinations of factors. All three factors at the upper level
appreciably induced activity of phosphoenolpyruvate carboxylase (PEPCase) in cotton leaves.

KEYWORDS: PHYSIOLOGY


     4    
Aben, S.K., S.P. Seneweera, O. Ghannoum, and J.P. Conroy. 1999. Nitrogen requirements for
maximum growth and photosynthesis of rice, Oryza sativa L-cv. Jarrah grown at 36 And 70 Pa CO2.
Australian Journal of Plant Physiology 26(8):759-766.

The hypothesis that growth of rice (Oryza sativa L. cv. Jarrah) at elevated atmospheric CO2 partial
pressure alters leaf nitrogen (N) concentrations required to support maximum dry mass production
and photosynthetic rates during the period of rapid tiller initiation was tested by growing plants for
30 days in unstirred sand/hydroponic culture with N concentrations of 5, 20, 40, 60 and 100 mg N
L-1. Maximum growth and photosynthetic potential was greater at 70 than 36 Pa CO2 at all N
concentrations in the solution. Elevated CO2 reduced leaf N concentrations required to support 90%
of maximum growth and photosynthetic rates (critical concentration) from 40 to 27 g kg(-1) for
growth and from 45 to 30 g kg(-1) for photosynthesis. Morphological changes at elevated CO2
included increased tiller numbers and reduced leaf area ratio. The latter could be explained by lower
plant N concentrations which occurred at high CO2 at each N concentration in the solution, primarily
due to lower leaf blade and root N concentrations. Changes in tiller numbers at high CO2 were
unrelated to leaf or plant N but were strongly correlated with leaf soluble carbohydrate
concentrations. We conclude that elevated CO2 alters the nutritional physiology of rice during the
rapid tillering phase in a way that increases the efficiency of N utilisation for growth and
photosynthesis.

KEYWORDS: ACCLIMATION, CAPACITY, COTTON, ELEVATED CO2, LEAVES, NUTRITION,
PLANTS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, WHEAT


     5    
Aber, J.D., S.V. Ollinger, C.A. Federer, P.B. Reich, M.L. Goulden, D.W. Kicklighter, J.M.
Melillo, and R.G. Lathrop. 1995. Predicting the effects of climate change on water yield and forest
production in the northeastern United States. Climate Research 5(3):207-222.

Rapid and simultaneous changes in temperature, precipitation and the atmospheric concentration of
CO2 are predicted to occur over the next century. Simple, well-validated models of ecosystem
function are required to predict the effects of these changes. This paper describes an improved version
of a forest carbon and water balance model (PnET-II) and the application of the model to predict
stand- and regional-level effects of changes in temperature, precipitation and atmospheric CO2
concentration. PnET-II is a simple, generalized, monthly time- step model of water and carbon
balances (gross and net) driven by nitrogen availability as expressed through foliar N concentration.
Improvements from the original model include a complete carbon balance and improvements in the
prediction of canopy phenology, as well as in the computation of canopy structure and
photosynthesis. The model was parameterized and run for 4 forest/site combinations and validated
against available data for water yield, gross and net carbon exchange and biomass production. The
validation exercise suggests that the determination of actual water availability to stands and the
occurrence or non-occurrence of soil-based water stress are critical to accurate modeling of forest
net primary production (NPP) and net ecosystem production (NEP). The model was then run for the
entire NewEngland/New York (USA) region using a 1 km resolution geographic information system.
predicted long- term NEP ranged from -85 to + 275 g Cm-2 yr(-1) for the 4 forest/site combinations,
and from -150 to 350 g C m(-2) yr(-1) for the region, with a regional average of 76 g Cm-2 yr(-1).
A combination of increased temperature (+6 degrees C), decreased precipitation (-15%) and
increased water use efficiency (2x, due to doubling of CO2) resulted generally in increases in NPP
and decreases in water yield over the region.

KEYWORDS: DEPOSITION, ECOSYSTEMS, ELEVATED CO2, MODEL, REGIONAL-ANALYSIS,
RESPONSES


     6    
Ackerly, D.D., and F.A. Bazzaz. 1995. Plant-growth and reproduction along co2 gradients -
nonlinear responses and implications for community change. Global Change Biology 1(3):199-207.

The effects of rising atmospheric CO2 concentrations on natural plant communities will depend upon
the cumulative responses of plant growth and reproduction to gradual, incremental changes in
climatic conditions. We analysed published studies of plant responses to elevated CO2 to address
whether reproductive and total biomass exhibit similar enhancement to elevated vs. ambient CO2
concentrations, and to assess the patterns of plant response along gradients of CO2 concentrations.
In six annual plant species, mean enhancement at double ambient vs. ambient CO2 was 1.13 for total
biomass and 1.30 for reproductive biomass. The two measures were significantly correlated, but there
was considerable scatter in the relationship, indicating that reproductive responses cannot be
consistently predicted from enhancement of total biomass. Along experimental CO2 gradients
utilizing three concentrations, there was a great diversity of response patterns, including positive,
negative, non-monotonic and non-significant (nat) responses. The distribution of response patterns
differed for plants grown in stands compared to those grown individually. Positive responses were
less frequent in competitive environments, and non- monotonic responses were more frequent. These
results emphasize that interpolation of plant response based on enhancement ratios measured at
elevated vs. ambient CO2 concentrations is not sufficient to predict community responses to
incremental changes in atmospheric conditions. The consequences of differential response patterns
were assessed in a simulation of community dynamics for four species of annual plants. The model
illustrates that the final community composition at a future point in time depends critically on both
the magnitude and the rate of increase of atmospheric CO2.

KEYWORDS: ANNUALS, ATMOSPHERIC CO2, CO2-INDUCED CLIMATE CHANGE,
COMPETITION, ELEVATED CO2, ENRICHMENT, LIQUIDAMBAR- STYRACIFLUA, OLD-
FIELD PERENNIALS, PINUS-TAEDA SEEDLINGS, RESOURCE USE


     7    
Ackerly, D.D., J.S. Coleman, S.R. Morse, and F.A. Bazzaz. 1992. Co2 and temperature effects
on leaf-area production in 2 annual plant-species. Ecology 73(4):1260-1269.

We studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus
retroflexus, under three day/night temperature regimes (18-degrees/14-degrees, 28- degrees/22-
degrees, and 38-degrees/31-degrees-C) and two concentrations of carbon dioxide (400 and 700-mu-
L/L). The production of whole-plant leaf area during the first 30 d of growth was analyzed in terms
of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, production of
branch leaves. Temperature and CO2 influenced leaf area production through effects on the rate of
development, determined by the production of nodes on the main stem (the plastochron index), and
through shifts in the relationship between whole-plant leaf area and the number of main stem nodes.
In Abutilon, leaf initiation rate was highest at 38- degrees, but area of individual leaves was greatest
at 28- degrees. Total leaf area was greatly reduced at 18-degrees due to slow leaf initiation rates.
Elevated CO2 concentration increased leaf initiation rate at 28-degrees, resulting in an increase in
whole-plant leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was
increased by elevated CO2 at 28-degrees. Individual leaf area was greatest at 28-degrees, and was
increased by elevated CO2 at 28-degrees but decreased at 38-degrees. Branch leaf area displayed a
similar response to CO2, but was greater at 38- degrees. Overall, whole-plant leaf area was slightly
increased at 38-degrees relative to 28-degrees, and elevated CO2 levels resulted in increased leaf area
at 28-degrees but decreased leaf area at 38-degrees. The effects on leaf area closely parallel rates of
biomass accumulation in the same experiment, suggesting that responses of developmental processes
to elevated CO2 and interacting factors may play an important role in mediating effects on plant
growth.

KEYWORDS: C-3, CANOPY, CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, GROWTH,
LEAVES, LIGHT, PHOTOSYNTHESIS, RESPONSES, SUNFLOWER


     8    
Acock, B., M.C. Acock, and D. Pasternak. 1990. Interactions of CO2 enrichment and temperature
on carbohydrate production and accumulation in muskmelon leaves. Journal of the American Society
for Horticultural Science 115(4):525-529.



     9    
Acock, B., and G.W. Wall. 1995. A simple conductimetric co2 analyzer with automatic recalibration
.1. Design, implementation, and functionality. Agronomy Journal 87(1):70-75.

Controlled-environment plant growth cabinets may be used to investigate the long-term effect of
elevated carbon dioxide concentration ([CO2]) on plant growth. Infrared gas analyzers (IRGAs) are
normally used to monitor and control [CO2] in plant cabinets. With many cabinets in use, however,
it soon becomes impractical to purchase an individual IRGA for each cabinet, A more economical
method of monitoring and controlling [CO2] relies on the change in electrical conductivity when CO2
is dissolved in demineralized water, This work describes the design, implementation, and functionality
of an inexpensive conductimetric system for controlling [CO2] in plant growth cabinets, Regressing
electrical conductivity against [CO2] over the range 0 to 1000 mu L L(-1) yields a quadratic
response. Calibration drift inherent in the conductimetric CO2 analyzer requires that each analyzer
be recalibrated periodically. Automatically recalibrating with an IRGA every 900 s gave control of
the [CO2] within the plant enclosures to within 10 to 15 mu L L(-1) of the set point, The [CO2]
control system is robust enough to maintain this accuracy regardless of the desired [CO2] set point
or the mass of plant material within the plant growth cabinet, In this approach, only one IRGA is
required to control [CO2] in many plant growth cabinets if each cabinet has a dedicated
conductimetric CO2 analyzer.



     10   
Adams, R.M., R.A. Fleming, C.C. Chang, B.A. McCarl, and C. Rosenzweig. 1995. A
reassessment of the economic-effects of global climate-change on US agriculture. Climatic Change
30(2):147-167.

This study uses recent GCM forecasts, improved plant science and water supply data and refined
economic modeling capabilities to reassess the economic consequences of long-term climate change
on U.S. agriculture. Changes in crop yields, crop water demand and irrigation water arising from
climate change result in changes in economic welfare. Economic consequences of the three GCM
scenarios are mixed; GISS and GFDL-QFlux result in aggregate economic gains, UKMO implies
losses. As in previous studies, the yield enhancing effects of atmospheric CO2 are an important
determinant of potential economic consequences. Inclusion of changes in world food production and
associated export changes generally have a positive affect on U.S. agriculture. As with previous
studies, the magnitude of economic effects estimated here are a small percentage of U. S. agricultural
value.



     11   
Adamse, P., and S.J. Britz. 1992. Amelioration of uv-b damage under high irradiance .1. Role of
photosynthesis. Photochemistry and photobiology 56(5):645-650.

Sensitivity to ultraviolet-B radiation (UV-B, 280-315 nm) is generally reduced when background
irradiance is high. We tested the involvement of photosynthesis in the amelioration of UV-B damage
by treating plants at high PAR (photosynthetically- active radiation. 400-700 nm; 1000 mumol m-2
s-1) with supplemental UV-B at double ambient levels of biologically- effective radiation (18 kJ m-2
d-1) and either ''ambient'' (450 mumol mol-1) or short term elevated (750 mumol mol-1) CO2 levels.
Responses to UV-B were assessed by photosynthetic gas exchange, leaf expansion and production
of UV-absorbing compounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.)
previously demonstrated to be relatively sensitive (cv. Poinsett) and insensitive (cv. Ashley) to UV-B.
Except for marginal leaf interveinal chlorosis observed in Poinsett, both cultivars responded similarly.
UV-B had little direct effect on leaf photosynthesis, but it did cause reductions in leaf area and
corresponding increases in leaf dry matter per area. Increased CO2 stimulated plant growth,
counteracting the effect of UV-B on leaf growth and indicating an important role for photosynthesis.
In contrast, the accumulation of UV-absorbing flavonoid compounds was enhanced by UV-B
exposure but was not affected by CO2 enrichment.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CELL-SUSPENSION CULTURES, LIGHT,
PETROSELINUM- HORTENSE, PHOTON FLUX- DENSITY, PHYTOCHROME, PLANTS,
RADIATION, SENSITIVITY


     12   
Adamsen, F.J., P.J. Pinter, E.M. Barnes, R.L. LaMorte, G.W. Wall, S.W. Leavitt, and B.A.
Kimball. 1999. Measuring wheat senescence with a digital camera. Crop Science 39(3):719-724.

Documenting crop senescence rates is often difficult because of the need for frequent sampling during
periods of rapid change and the subjective nature of human visual observations. The purpose of this
study was to determine the feasibility of using images produced by a digital camera to measure the
senescence rate of wheat and to compare the results with changes in greenness determined by two
established methods. Measurements were made as part of an experiment to determine the effects of
elevated CO2 and limited soil nitrogen on spring wheat (Triticum aestivum L.) at the University of
Arizona's Maricopa Agricultural Center, near Phoenix, AZ. "Greenness" measurements were made
during senescence of the crop with a color digital camera, a hand-held radiometer, and a SPAD
chlorophyll meter. The green to red (GIR) for each pixel in an image was calculated and the average
GIR computed for cropped images from a digital camera representing 1 m(2) for each treatment and
sample date. The normalized difference vegetation index (NDVI) was calculated from the red and
near-infrared canopy reflectances measured with a hand held radiometer. A SPAD reading was
obtained from randomly selected flag leaves. All three methods of measuring plant greenness showed
similar temporal trends. The relationships between GIR with NDVI and SPAD were linear over most
of the range of GIR. However, NDVI was more sensitive at low values than GIR. GIR was more
sensitive above G/R values of 1.2 than SPAD because the upper limits of SPAD measurements were
constrained by the amount of chlorophyll in the leaf, while GIR responded to both chlorophyll
concentration in the leaves as well as the number of leaves present. Color digital imaging appears
useful for quantifying the senescence of crop canopies. The cost of color digital cameras is expected
to decrease and the quality and convenience of use to improve.

KEYWORDS: CHLOROPHYLL METER, CROP, EFFICIENCY, RED, VEGETATION INDEXES,
WINTER-WHEAT, YIELD


     13   
Agar, I.T., J. Streif, and F. Bangerth. 1997. Effect of high CO2 and controlled atmosphere (CA)
on the ascorbic and dehydroascorbic acid content of some berry fruits. Postharvest Biology and
Technology 11(1):47-55.

High CO2 concentrations as well as controlled atmosphere storage are widely used to extend the
storage and shelf-life of many fruits. To investigate the effect of these storage procedures on several
berry fruits, strawberries, raspberries, currants and blackberries were stored at three different elevated
CO2 concentrations, with or without a parallel reduction in O-2. Vitamin C content (ascorbic acid
plus dehydroascorbic acid) was reduced by high CO2 concentrations (10-30% CO2), particularly in
strawberries. This reduction in vitamin C was moderate in black currants and blackberries and almost
absent in raspberries and red currants when compared with strawberries. Reducing the O-2
concentration in the storage atmosphere in the presence of high CO2 had little effect on the vitamin
C content. Ascorbic acid was more diminished al high CO2 than dehydroascorbic acid. This suggests
a stimulating effect of high CO2 concentrations on the oxidation of ascorbic acid and/or an inhibition
of mono- or dehydroascorbic acid reduction to ascorbic acid. (C) 1997 Elsevier Science B.V.

KEYWORDS: HYDROGEN- PEROXIDE, O2, PLANTS


     14   
Aggangan, R.T., A.M. O'Connell, J.F. McGrath, and B. Dell. 1999. The effects of Eucalyptus
globulus Labill. leaf letter on C and N mineralization in soils from pasture and native forest. Soil
Biology and Biochemistry 31(11):1481-1487.

The effects of addition of Eucalyptus globulus leaf litter on carbon and nitrogen mineralization in soils
from a pasture and a native forest were evaluated using a long-term laboratory aerobic incubation
assay (29 weeks at 20 degrees C) in leaching microlysimeters, The amount of added leaf litter
significantly influenced microbial respiration, microbial biomass and N turnover in both the native
forest and pasture soils. Cumulative CO2-C respired increased with increasing rate of leaf litter
addition when leaf litter was mixed through the soil or placed on the soil surface. These increases
were associated with increases in microbial biomass C content. Cumulative net N mineralization
declined in ail treatments when litter was added and was lowest when leaf litter was mixed with soil.
When leaf litter was added in increasing amounts to the soil surface, there was a concomitant increase
in microbial biomass N content (r(2) = 0.79, n = 8), indicating that the reduction in net N
mineralization was primarily due to immobilization of N in microbial tissues. In contrast, when litter
was mixed with soil in increasing amounts, there was a decrease in microbial biomass N in forest soil
and an increase in pasture soil. Consequently, changes in the rate of net N mineralization were not
well related to changes in microbial biomass N content. It is suggested that this may be due to the
greater activity and more rapid turnover of microorganisms where litter was incorporated resulting
in more of the immobilized N being partitioned into metabolic products or dead microbial cells.
Incorporation of litter may also have enhanced loss N through denitrification, (C) 1999 Published by
Elsevier Science Ltd. All rights reserved.

KEYWORDS: DECOMPOSITION, DENITRIFICATION, EXTRACTION METHOD,
IMMOBILIZATION, LITTER, MICROBIAL BIOMASS CARBON, NITROGEN MINERALIZATION,
PLANT RESIDUES, RESPIRATION, WESTERN-AUSTRALIA


     15   
Agren, G.I. 1996. Nitrogen productivity or photosynthesis minus respiration to calculate plant
growth? Oikos 76(3):529-535.

One approach to calculate plant growth rate is from models of photosynthesis, respiration and
allocation. This requires that processes with characteristic time constants of seconds to minutes be
scaled to hours or days. Another approach is to use aggregate models defined at the time scale of
growth, hours and days. I use such an aggregate model, the nutrient productivity, to compare the
performance of the two approaches on growth experiments with small, nitrogen-limited birch plants.
The problems of error aggregation when using the large number of parameters required to scale from
the detailed level of photosynthesis and respiration to the aggregate level of growth are in this case
such that whole plant growth rate is more accurately predicted with the nutrient productivity model.

KEYWORDS: ALLOCATION, BETULA-PENDULA ROTH, BIOMASS, BIRCH SEEDLINGS,
CARBON, CLIMATE, ECOSYSTEMS, ELEVATED CO2, NUTRITION, STRESS


     16   
Agren, G.I., R.E. McMurtrie, W.J. Parton, J. Pastor, and H.H. Shugart. 1991. State-of-the-art
of models of production decomposition linkages in conifer and grassland ecosystems. Ecological
Applications 1(2):118-138.

We review the state-of-the-art of models of forests and grasslands that could be used to predict the
impact of a future climate change arising from increased atmospheric carbon dioxide concentration.
Four levels of resolution are recognized: physiologically based models, population models, ecosystem
models, and regional or global models. At the physiological level a number of important processes
can be described in great detail, but these models often treat inadequately interactions with nutrient
cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand,
encapsulate relationships between the plants and the soil system, but at the expense of requiring more
ad hoc formulations of processes. At the regional and global scale we have so far only steady-state
models, which cannot be used to predict transients caused by climate change. However, our
conclusion is that, in spite of the gaps in knowledge, there are several models based on dominant
processes that are well enough understood for the predictions of those models to be taken seriously.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BOUTELOUA-GRACILIS, CARBON
DIOXIDE, CO2-INDUCED CLIMATE CHANGE, EVEN- AGED STANDS, LOLIUM-PERENNE
L, NITROGEN PRODUCTIVITY, PLANT GROWTH, SIMULATION-MODEL, THEORETICAL-
ANALYSIS


     17   
Ahmadi, H., W.V. Biasi, and E.J. Mitcham. 1999. Control of brown rot decay of nectarines with
15% carbon dioxide atmospheres. Journal of the American Society for Horticultural Science
124(6):708-712.

Effects of short-term exposure to a 15% CO2 atmosphere on nectarines [Prunus persica (L.) Batsch
(Nectarine Group) 'Summer Red'] inoculated with Monilinia fructicola (Wint.) Honey (causal agent
of brown rot) were investigated, Nectarines were inoculated with spores of M.fructicola and
incubated at 20 degrees C for 24, 48 or 72 hours and then transferred to storage in either air or air
enriched with 15% CO2 at 5 degrees C. Fruit were removed from storage after 5 and 16 days and
were examined for brown rot decay immediately and after ripening in air for 3 days at 20 degrees C.
Noninoculated nectarines were stored and treated likewise for evaluation of postharvest fruit
attributes to determine their tolerance to 15% CO2. Incubation period after inoculation, storage
duration, and storage atmosphere had highly significant effects on fruit decay, 'Summer Red'
nectarines tolerated a 15% CO2 atmosphere for 16 days at 5 degrees C. Development of brown rot
decay in fruit inoculated 24 hours before 5 or 16 days storage in 15% CO2 at 5 OC was arrested.
After 3 days ripening in air at 20 degrees C, the progression of brown rot disease was rapid in all
inoculated nectarines, demonstrating the fungistatic effect of 15% CO2. The quantity of fungal cell
wall materials (estimated by glucosamine concentration) was compared to visual estimation of
decayed area and visual rating of fungal sporulation. The glucosamine assay defined the onset and
progress of brown rot infection more precisely than either of the two visual tests.

KEYWORDS: FRUIT, IPRODIONE, MOLD, SUPPRESSION, SWEET CHERRIES, TISSUE,
TOMATO PRODUCTS


     18   
Ahmed, F.E., A.E. Hall, and M.A. Madore. 1993. Interactive effects of high-temperature and
elevated carbon- dioxide concentration on cowpea [vigna-unguiculata (L) walp]. Plant, Cell and
Environment 16(7):835-842.

Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive
failure under heat stress. Heat stress affects two stages of reproductive development in cowpea
[Vigna unguiculata (L.) Walp.], and genotypes are available with tolerance and sensitivity to heat
during these different stages. The objectives of this study were to determine the responses of these
cowpea lines to ambient and elevated [CO2], under heat stress and optimal temperature, and test
whether differences in carbohydrate supplies due to genotypes, CO2 enrichment and heat stress are
associated with differences in sensitivity to heat during reproductive development. Plants were grown
in reach-in growth chambers and subjected to day/night temperatures of either 33/20 or 33/30-
degrees-C, and [CO2] levels of either 350 or 700 mumol mol-1. Under intermediate night
temperature (33/20-degrees-C), all lines set substantial numbers of pods. Under high night
temperature (33/30-degrees-C) with either ambient or elevated [CO2], one heat-sensitive line
produced no flowers and the other set no pods, whereas the heat-tolerant line abundantly set pods.
High night temperature reduced the overall carbohydrate content of the plants, especially peduncle
sugars, and caused decreases in photosynthetic rates. The high pod set of the heat-tolerant line, under
high night temperature, was associated with higher levels of sugars in peduncles compared with the
heat-sensitive lines. The heat-tolerant line accumulated substantial shoot biomass, exhibited less
accumulation of starch in leaves, and possibly had less down- regulation of photosynthesis in response
to CO2 enrichment and heat stress than the heat-sensitive lines. Elevated [CO2] resulted in higher
overall carbohydrate levels in heat- sensitive lines (starch in leaves, stems and peduncles), but it did
not increase their heat tolerance with respect to flower production or pod set. Heat-induced damage
to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles,
indicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat-
tolerant line was the most responsive genotype to elevated [CO2] with respect to pod production
under either high or intermediate temperatures.

KEYWORDS: ABSCISSION, ACCLIMATION, AIR- TEMPERATURE, CO2, COTTON, HEAT-
STRESS, LEAVES, LONG-TERM EXPOSURE, PHOTOSYNTHETIC INHIBITION,
REPRODUCTIVE RESPONSES


     19   
Aikman, D.P. 1996. A procedure for optimizing carbon dioxide enrichment of a glasshouse tomato
crop. Journal of Agricultural Engineering Research 63(2):171-183.

The procedure consists of two parts. A Gompertz model for the kinetics of fruit growth is used
predict the time distribution of photosynthate subsequent harvests. This is combined with predictions
of future market prices to compute estimates, one for each day from first anthesis, of a factor to
convert CO2 assimilate to expected financial value, based on the worth anticipated from partitioning
to fruit. A model of the climate and the crop regime is used to predict temperatures and hence allow
for the temperature dependence of fruit growth. The conversion estimates are revised to include the
deferred benefit given by additional photosynthesis through increasing early vegetative growth, and
hence subsequent photosynthesis and yield. This revision also extends the set of conversion factors
to include any period before first anthesis. Given the current environmental variables and conversion
factor for that day, a real-time system can use a crop photosynthesis model to predict the cash benefit
for any CO2 concentration. The cost of maintaining a concentration can be obtained from a prediction
of the ventilation air exchange rate and the unit price of CO2. The CO2 set-point is evaluated as the
concentration that maximizes the net profit rate. (C) 1996 Silsoe Research Institute

KEYWORDS: CO2- ENRICHMENT, CUCUMBER, FRUIT- GROWTH, GREENHOUSES,
LYCOPERSICON-ESCULENTUM MILL, MODEL, PLANTS, TEMPERATURE, VENTILATION


     20   
Akimoto, M., A. Shirai, K. Ohtaguchi, and K. Koide. 1998. Carbon dioxide fixation and
polyunsaturated fatty acid production by the red alga Porphyridium cruentum. Applied Biochemistry
and Biotechnology 73(2-3):269-278.

Focusing on CO2 fixation, photoautotrophic cultivation of the red alga Porphyridium cruentum was
investigated by means of a batch culture under a 5% CO2-enriched atmosphere. The alg-al growth
kinetics was successfully described with a logistic model, and simulation of a continuous culture
under the optimum growth conditions (30 degrees C, 12 klux and 1.18 g-cells/L) showed that the
algal CO2-fixation activity could reach 0.66 g- CO2/(L X d). Under the same growth conditions,
eicosapentaenoic acid (20:5 n-3, EPA) and arachidonic acid (20:4 n-6, ARA) yields were similarly
calculated to be 3.6 mg-EPA/(L X d) and 6.5 mg-ARA/(L X d), respectively.

KEYWORDS: CULTIVATION, GROWTH, LIGHT-INTENSITY, TEMPERATURE


     21   
Akin, D.E., B.A. Kimball, J.R. Mauney, R.L. Lamorte, G.R. Hendrey, K. Lewin, J. Nagy, and
R.N. Gates. 1994. Influence of enhanced co2 concentration and irrigation on sudangrass digestibility.
Agricultural and Forest Meteorology 70(1-4):279-287.

An experimental line of sudangrass (Sorghum bicolor L. Moench) was included in the free-air CO2
enrichment (FACE) project in 1991 at the University of Arizona Maricopa Agricultural Center to
evaluate the effect of ambient (approximately 370 mumol mol- 1) and enriched (550 mumol mol-1)
CO2 in well-watered or water- stressed plots. Our specific objective was to determine modifications
caused by these environmental effects on the percentages of morphological parts and the fiber
components, and on the in vitro digestibility in vegetative and mature harvests. Enrichment with CO2
did not (P > 0.05) change the percentages of morphological parts or fiber components, or the
digestibility of any of the morphological components. Protein levels tended to be lower in CO2-
enriched plants. However, water-stressed plants tended to have a higher proportion of leaves (blades
and sheaths) and a lower proportion of stems, were more digestible, and had lower amounts of anti-
quality, aromatic compounds within the plant cell. Stems had the highest digestibility of all
morphological components (about 75% in vegetative plants) despite the lowest levels of protein.
Stems also showed the greatest changes caused by all treatments, including a 20% decline in
digestibility from vegetative to mature samples. The results indicate that enriching CO2 to 550 mumol
mol-1 did not reduce digestibility of sudangrass.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT


     22   
Akin, D.E., B.A. Kimball, W.R. Windham, P.J. Pinter, G.W. Wall, R.L. Garcia, R.L. Lamorte,
and W.H. Morrison. 1995. Effect of free-air co2 enrichment (face) on forage quality of wheat.
Animal Feed Science and Technology 53(1):29-43.

Wheat (Triticum aestivum L., cultivar 'Yecora rojo') was grown in ambient (370 mu mol mol(-1)) or
enriched (550 mu mol mol(- 1)) concentrations of CO2 in the free-air CO2 enrichment (FACE)
project, and components were analyzed for in vitro digestibility, fiber constituents, and crude protein.
Four replicated plots of each CO2 treatment were split for irrigation: 'wet' regions received 60 cm
of water and 'dry' regions received 30 cm of water through underground tubes. Enriched CO2
concentrations had no effect on in vitro digestion of intact sections of young (26-32-day-old plants)
leaf blades except at 24-27 h incubation, at which time enriched leaves were lower in digestibility than
control ones. Enriched CO2 concentrations increased the content of acid detergent fiber (ADF) and
cellulose of young wet leaves, Sections of main shoots at 26 days tended to have increased
digestibility with elevated CO2 levels. Enriched CO2 concentrations did not alter the digestibility of
flag leaves from 105-day-old plants or of flag leaves, uppermost stems, and sheaths from plants at full
grain maturity, Enriched CO2 levels reduced the acid detergent lignin (ADL) and tended to reduce
the protein of leaves from 105-day-old plants. For mature leaf blades, neutral detergent fiber, ADF,
and cellulose were, or tended to be, higher while protein content tended to be lower in elevated CO2-
grown plants; for both CO2 treatments, 'dry' leaves were higher in digestibility and lower in ADL than
'wet' samples. Mature stems plus sheaths had lower protein contents in plants grown in elevated CO2.
Results indicated that enriched CO2 concentrations to 550 mu mol mol(-1) did not substantially alter
wheat in vitro digestibility, regardless of irrigation treatment. Elevated CO2 altered fiber components
and protein, but these were not consistent among parts and harvests.

KEYWORDS: CELL-WALLS, ECOSYSTEMS, MICROSPECTROPHOTOMETRY, PHENOLIC
CONSTITUENTS


     23   
Akin, D.E., L.L. Rigsby, G.R. Gamble, W.H. Morrison, B.A. Kimball, P.J. Pinter, G.W. Wall,
R.L. Garcia, and R.L. Lamorte. 1995. Biodegradation of plant-cell walls, wall carbohydrates, and
wall aromatics in wheat grown in ambient or enriched co2 concentrations. Journal of the Science of
Food and Agriculture 67(3):399-406.

Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 mu mol
mol(-1)) or enriched (to 550 mu mol mol(-1)) concentrations of atmospheric CO2 in the free- air CO2
enrichment (FACE) system were analyzed for potential changes in biodegradation of constituents due
to predicted increases in atmospheric levels of CO2. The first internodes below the grain were
incubated with the lignocellulose- degrading white rot fungus, Phanerochaete chrysosporium K-3,
or incubated without microorganisms. Plant samples were then analyzed for dry weight loss,
disposition of specific cell types to biodegradation using electron microscopy, carbohydrates and
lignin using solid state NMR spectroscopy, and ester- and ether-linked aromatics using gas
chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%) and both
carbohydrate and aromatic portions of the wheat stems proportionately more carbohydrates were
removed by the fungus from the stems. Enriched CO2 did not affect the chemical composition of
wheat stems or the biodegradation by P chrysosporium of plant cell walls or wall components for the
most part. Data from various methods all indicated that enriched CO2 did not substantially alter the
biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an
influence on C cycling due to CO2 concentrations in this study.

KEYWORDS: ECOSYSTEMS, LIGNINS, PHENOLIC CONSTITUENTS


     24   
Alagusundaram, K., D.S. Jayas, N.D.G. White, W.E. Muir, and R.N. Sinha. 1995. Controlling
cryptolestes-ferrugineus (stephens) adults in wheat stored in bolted-metal bins using elevated carbon-
dioxide. Canadian Agricultural Engineering 37(3):217-223.

Experiments were conducted in two 5.56 m-diameter farm bins to determine the mortality of caged
adult rusty grain beetles, Cryptolestes ferrugineus (Stephens) (Coleoptera: cucujidae), under elevated
carbon dioxide (CO2) concentrations. The bins were filled with wheat to a depth of 2.5 m. Dry ice
was used to create high CO2 concentrations in the wheat bulks. Two different modes of application
of dry ice were used: (i) pellets on the grain surface and in the aeration duct and (ii) pellets on the
grain surface and blocks in insulated boxes on the grain surface. The pellets exposed to the ambient
conditions on the grain surface and in the aeration duct sublimated quickly and had to be replenished
at frequent intervals. Dry ice blocks in insulated boxes, however, maintained high CO2 concentrations
without replenishment for over 15 d. In both modes of application, the observed CO2 concentrations
in the intergranular gas were about 15% and 30% (all the CO2 concentrations given in this article are
on a volume basis) at 2.05 m and 0.55 m above the floor, respectively. At 0.55 m above the floor, the
mortality of rusty grain beetle adults was more than 90% while in the top portions of the bulk (2.05
m above the floor) the mortality was only 30%. On an average about two thirds of the insects were
killed. The use of controlled atmosphere treatment within an integrated pest management context is
outlined.

KEYWORDS: INSECTS


     25   
Alberto, A.M.P., L.H. Ziska, C.R. Cervancia, and P.A. Manalo. 1996. The influence of increasing
carbon dioxide and temperature on competitive interactions between a C3 crop, rice (Oryza sativa)
and a C-4 weed (Echinochloa glabrescens). Australian Journal of Plant Physiology 23(6):795-802.

Many of the most troublesome weeds in agricultural systems are C-4 plants. As atmospheric CO2
increases it is conceivable that competitive ability of these weeds could be reduced relative to C-3
crops such as rice. At the International Rice Research Institute (IRRI) in the Philippines, rice (IR72)
and one of its associated C-4 weeds, Echinochloa glabrescens, were grown from seeding to maturity
using replacement series mixtures (100:0, 75:25, 50:50, 25:75, and 0:100, % rice:%weed) at two
different CO2 concentrations (393 and 594 mu L L(-1)) in naturally sunlit glasshouses. Since
increasing CO2 may also result in elevated growth temperatures, the response of rice to each CO2
concentration was also examined at day/night temperatures of 27/21 and 37/29 degrees C. At 27/21
degrees C, increasing the CO2 concentration resulted in a significant increase in above ground
biomass (+47%) and seed yield (+55%) of rice when averaged over all mixtures. For E. glabrescens,
the C-4 species, no significant effect of CO2 concentration on biomass or yield was observed. When
grown in mixture, the proportion of rice biomass increased significantly relative to that of the C- 4
weed at all mixtures at elevated CO2. Evaluation of changes in competitiveness (by calculation of
plant relative yield (PRY) and replacement series diagrams) of the two species demonstrated that, at
elevated CO2, the competitiveness of rice was increased relative to that of E. glabrescens. However,
at the higher growth temperature (37/29 degrees C), growth and reproductive stimulation of rice by
elevated CO2 was reduced compared to the lower growth temperature. This resulted in a reduction
in the proportion of rice:weed biomass present in all mixtures relative to 27/21 degrees C and a
greater reduction in PRY in rice relative to E. glabrescens. Data from this experiment suggest that
competitiveness could be enhanced in a C-3 crop (rice) relative to a C-4 weed (E. glabrescens) with
elevated CO2 alone, but that simultaneous increases in CO2 and temperature could still favour a C-4
species.

KEYWORDS: DRY-MATTER, ENRICHMENT, GROWTH, NITROGEN, PLANTS, WHEAT


     26   
Alcamo, J., G.J.J. Kreileman, M.S. Krol, and G. Zuidema. 1994. Modeling the global society-
biosphere-climate system .1. Model description and testing. Water, Air, and Soil Pollution 76(1-2):1-
35.

This paper describes the IMAGE 2.0 model, a multi-disciplinary, integrated model designed to
simulate the dynamics of the global society-biosphere-climate system. The objectives of the model
are to investigate linkages and feedbacks in the system, and to evaluate consequences of climate
policies. Dynamic calculations are performed to year 2100, with a spatial scale ranging from grid (0.5-
degrees x 0.5-degrees latitude- longitude) to world regional level, depending on the sub-model. The
model consists of three fully linked sub-systems: Energy- Industry, Terrestrial Environment, and
Atmosphere-Ocean. The Energy-Industry models compute the emissions of greenhouse gases in 13
world regions as a function of energy consumption and industrial production. End use energy
consumption is computed from var-ious economic/demographic driving forces. The Terrestrial
Environment models simulate the changes in global land cover on a grid-scale based on climatic and
economic factors, and the flux of CO2 and other greenhouse gases from the biosphere to the
atmosphere. The Atmosphere-Ocean models compute the buildup of greenhouse gases in the
atmosphere and the resulting zonal-average temperature and precipitation patterns. The fully linked
model has been tested against data from 1970 to 1990, and after calibration can reproduce the
following observed trends: regional energy consumption and energy-related emissions, terrestrial flux
of CO2 and emissions of greenhouse gases, concentrations of greenhouse gases in the atmosphere,
and transformation of land cover. The model can also simulate long term zonal average surface and
vertical temperatures.

KEYWORDS: CARBON-CYCLE, CO2, SENSITIVITY


     27   
Alcamo, J., G.J. Vandenborn, A.F. Bouwman, B.J. Dehaan, K.K. Goldewijk, O. Klepper, J.
Krabec, R. Leemans, J.G.J. Olivier, A.M.C. Toet, H.J.M. Devries, and H.J. Vanderwoerd.
1994. Modeling the global society-biosphere-climate system .2. Computed scenarios. Water, Air, and
Soil Pollution 76(1-2):37-78.

This paper presents scenarios computed with IMAGE 2.0, an integrated model of the global
environment and climate change. Results are presented for selected aspects of the society- biosphere-
climate system including primary energy consumption, emissions of various greenhouse gases,
atmospheric concentrations of gases, temperature, precipitation, land cover and other indicators.
Included are a ''Conventional Wisdom'' scenario, and three variations of this scenario: (i) the
Conventional Wisdom scenario is a reference case which is partly based on the input assumptions of
the IPCC's IS92a scenario; (ii) the ''Biofuel Crops'' scenario assumes that most biofuels will be derived
from new cropland; (iii) the ''No Biofuels'' scenario examines the sensitivity of the system to the use
of biofuels; and (iv) the ''Ocean Realignment'' scenario investigates the effect of a large-scale change
in ocean circulation on the biosphere and climate. Results of the biofuel scenarios illustrate the
importance of examining the impact of biofuels on the full range of greenhouse gases, rather than only
CO2. These scenarios also indicate possible side effects of the land requirements for energy crops.
The Ocean Realignment scenario shows that an unexpected, low probability event can both enhance
the build-up of greenhouse gases, and at the same time cause a temporary cooling of surface air
temperatures in the Northern Hemisphere. However, warming of the atmosphere is only delayed, not
avoided.



     28   
Allen, D.J., I.F. McKee, P.K. Farage, and N.R. Baker. 1997. Analysis of limitations to CO2
assimilation on exposure of leaves of two Brassica napus cultivars to UV-B. Plant, Cell and
Environment 20(5):633-640.

Apex and Bristol cultivars of oilseed rape (Brassica napus) were irradiated with 0.63 W m(-2) of UV-
B over 5 d. Analyses of the response of net leaf carbon assimilation to intercellular CO2 concentration
were used to examine the potential limitations imposed by stomata, carboxylation velocity and
capacity for regeneration of ribulose 1,5-bisphosphate on leaf photosynthesis. Simultaneous
measurements of chlorophyll fluorescence were used to estimate the maximum quantum efficiency
of photosystem II (PSII) photochemistry, the quantum efficiency of linear electron transport at
steady-state photosynthesis, and the light and CO2-saturated rate of linear electron transport.
Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) content and activities were assayed in
vitro. In both cultivars the UV-B treatment resulted in decreases in the light-saturated rate of CO2
assimilation, which were accompanied by decreases in carboxylation velocity and Rubisco content
and activity. No major effects of UV-B were observed on end-product inhibition and stomatal
limitation of photosynthesis or the rate of photorespiration relative to CO2 assimilation. In the Bristol
cultivar, photoinhibition of PSII and loss of linear electron transport activity were observed when
CO2 assimilation was severely inhibited, However, the Apex cultivar exhibited no major inhibition
of PSII photochemistry or linear electron transport as the rate of CO2 assimilation decreased. It is
concluded that loss of Rubisco is a primary factor in UV-B inhibition of CO2 assimilation.

KEYWORDS: ENHANCED RADIATION, HIGHER-PLANTS, ORYZA-SATIVA,
PHOTOSYNTHETIC ELECTRON-TRANSPORT, PHOTOSYSTEM, PISUM-SATIVUM,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, ULTRAVIOLET-RADIATION, VIGNA-
SINENSIS L


     29   
Allen, L.H. 1992. Free-air co-2 enrichment field experiments - an historical overview. Critical
Reviews in Plant Sciences 11(2-3):121-134.

KEYWORDS: CARBON DIOXIDE, CO2, COTTON, CROPS, FUMIGATION, GROWN SOYBEANS,
PHOTOSYNTHETIC ACCLIMATION, PLANTS, SULFUR-DIOXIDE, SYSTEM


     30   
Allen, L.H., E.C. Bisbal, and K.J. Boote. 1998. Nonstructural carbohydrates of soybean plants
grown in subambient and superambient levels of CO2. Photosynthesis Research 56(2):143-155.

Elevated carbon dioxide (CO2) concentration increases plant photosynthesis, biomass and
carbohydrate accumulation. Since plants have grown in low CO2 (200 to 300 mu mol mol(-1)) for
the last several million years, how will they use extra photoassimilate as the atmospheric CO(2
)continues to rise? The objectives were to determine the effects of past, present and projected future
levels of CO2 on diurnal and seasonal patterns of total nonstructural carbohydrate (TNC)
concentration of soybean [Glycine max (L.) Merr.] tissues. Plants were grown at 160, 220, 280, 330,
660 and 990 mu mol mol(-1) CO2 in outdoor, sunlit chambers wherein CO2 uptake rates were
measured continuously. Early morning and fate afternoon plant samples were taken at eight dates.
The TNC concentration of leaves, petioles and stems increased as CO:! increased. Canopy
photosynthetic rates also increased with increasing CO2, apparently without any negative impact of
increased leaf TNC. Concentrations of TNC in all vegetative tissues were lower in the morning than
the afternoon, which indicates overnight mobilization and utilization of carbohydrates for growth
processes. The concentration of TNC was lowest in ail plant components during rapid vegetative
growth at Vg to R2 developmental stages. Leaves of all plants, especially those grown in
superambient CO2, contained large pools of TNC at plant maturity, which indicated that not all of
the reserves were utilized for seed yield. Soybean cultivars for the future should be designed to utilize
carbohydrates more readily for seed production so that greater benefit can be realized from rising
atmospheric CO2.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, EXPORT, L MERR PLANTS, LEAF, LEAVES,
LIGHT, PHOTOSYNTHETIC RESPONSE, REPRODUCTIVE GROWTH, STARCH
CONCENTRATION, TEMPERATURE


     31   
Allen, L.H., E.C. Bisbal, K.J. Boote, and P.H. Jones. 1991. Soybean dry-matter allocation under
subambient and superambient levels of carbon-dioxide. Agronomy Journal 83(5):875-883.

Rising atmospheric carbon dioxide concentration [CO2] is expected to cause increases in crop growth
and yield. The objective of this study was to investigate effects of subambient, as well as
superambient, [CO2] on soybean [Glycine max (L.) Merr.] dry matter production and allocation for
two reasons: to assess response of plants to prehistoric as well as future expected CO2 levels and to
increase confidence in [CO2] response curves by imposing a wide range of [CO2] treatments.
Soybean was grown in outdoor, sunlit, controlled- environment chambers at CO2 levels of 160, 220,
280, 330, 660, and 990-mu-mol (CO2) mol-1 (air). Total dry matter growth rates during the linear
phase of vegetative growth were 5.0, 8.4, 10.9, 12.5, 18.2, and 20.7 g m-2 d-1 for the above
respective [CO2]. Samples taken from 24 to 94 d after planting showed that the percentage of total
plant mass in leaf trifoliolates decreased with increasing [CO2] whereas the percentage in structural
components (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted
in 38, 53, 62, 100, 120, and 92% seed yield with respect to the 330-mu-mol mol-1 treatment. Total
dry weight responses were similar. Late season spider mite damage of the 990 and 280-mu-mol mol-1
treatments reduced yields. These data confirm not only that rising CO2 should increase plant growth,
but also that plant growth was probably seriously limited by atmospheric [CO2] in preindustrial
revolution times back to the previous global glaciation.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CHAMBERS, DEVELOPMENTAL STAGES,
PHOTOSYNTHESIS, PLANT GROWTH, TRANSPIRATION RESPONSES, WATER-USE, WEIGHT,
YIELD


     32   
Allen, L.H., B.G. Drake, H.H. Rogers, and J.H. Shinn. 1992. Field techniques for exposure of
plants and ecosystems to elevated co-2 and other trace gases. Critical Reviews in Plant Sciences
11(2-3):85-119.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CARBON-DIOXIDE CONCENTRATIONS,
ESTUARINE MARSH, OPEN-AIR FUMIGATION, OPEN-TOP CHAMBERS, PORTABLE
CHAMBER, SOYBEAN CANOPIES, TRANSPIRATION RESPONSES, VENTILATED CHAMBER,
WATER-VAPOR EXCHANGE


     33   
Allen, L.H., R.R. Valle, J.W. Jones, and P.H. Jones. 1998. Soybean leaf water potential responses
to carbon dioxide and drought. Agronomy Journal 90(3):375-383.

Rising CO2 can have direct effects on crop water relations and indirect effects on water available for
growth. We studied the effects of elevated CO2 and drought on leaf water relations of soybean
[Glycine max (L.) Merr. cv. Bragg] and considered the hypothesis of osmotic adjustment mediated
by increased photosynthesis (Hypothesis 1) vs. the hypothesis of water conservation mediated by
decreased stomatal conductance (Hypothesis 2) to explain improved water relations of plants growing
under elevated CO2. In Exp. 1, soybean was grown at 330, 450, 660, and 800 mu mol mol(-1) CO2
in sunlit, closed- circulation, controlled-environment chambers under well-watered conditions. Leaf
total water potential (WP), osmotic potential (OP), and turgor potential (TP) were measured at
midday during V4 to R6 stages of development. In Exp. 2 (well-watered, R1-R3) and Exp. 3 (13-d
drying cycle, R6 seed filling), soybean was grown at 330 and 660 mu mol mol(-1) CO2 and WP, OP,
and TP were measured five times per day on sunlit and shaded leaves. In Exp. 3, stomatal
conductance (g(s)) and transpiration rate (TR) of leaves were also measured. Experiments 1 and 2
showed that elevated CO2 increased TP and decreased OP, but did not affect leaf WP, thus favoring
Hypothesis 1. In Exp. 3, leaf WP was higher in elevated than ambient CO2. Diurnal TP was higher
in elevated than ambient CO2 at the beginning of drought, and was maintained longer each day as
drought progressed. At the end of drought, TP and WP was higher in elevated than ambient CO2.
Elevated CO2 leaves had lower TR because of lower g(s) than ambient CO2 counterparts. Thus, Exp.
3 supported Hypothesis 2, that both stressed and nonstressed plants in elevated CO2 have a better
water status (e.g., higher TP) than plants in ambient CO2 due to water conservation mediated by
decreased g(s). Remobilization of leaf nutrients during seed filling may limit the capability for osmotic
adjustment. Regardless of the mechanisms, growth of plants in elevated CO2 should be less affected
by drought than plants in ambient CO2.

KEYWORDS: DIFFERENT CO2 ENVIRONMENTS, FIELD, LEAVES, MAIZE, NITROGEN,
OSMOTIC ADJUSTMENT, PLANT GROWTH, STRESS, USE EFFICIENCY, YIELD


     34   
Allen, L.H., R.R. Valle, J.W. Mishoe, and J.W. Jones. 1994. Soybean leaf gas-exchange responses
to carbon-dioxide and water-stress. Agronomy Journal 86(4):625-636.

As global carbon dioxide concentrations rise, we need to understand the combination of direct effects
of this gas and the anticipated effects of climate change, including drought, on physiology and growth
of all crops. Effects Of CO2 on plants begin at the leaf level; our objectives, therefore, were to
determine interrelationships among factors governing gas exchange responses of soybean [Glycine
max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimilation and
transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled-
environment chambers at 330 and 660 mumol CO2 Mol-1 air. Leaflets at high CO2, either water-
stressed or well-watered, had higher photosynthetic and lower transpiration rates, and therefore
higher water-use efficiencies (WUE), than those at Control CO2 levels. As irrigation was withheld
during an 11-d period, WUE decreased about 30 to 50% with respect to the well- watered
treatments. Midday leaf temperature and leaf-to-air vapor pressure gradient levels increased as the
water stress progressed. For water stress treatments, midday leaf conductance (G(lw)) was generally
higher and residual internal conductance (G(r)) was generally lower in low than in high CO2. Ratios
of midday G(r)/G(lc), were nearly constant throughout the period in both the stressed and the well-
watered treatments. The ratios of intercellular C(i), to ambient C(a), CO2 concentration (i.e.,
C(i)/C(a)) during the water stress period remained similar to the respective nonstressed treatments
within each CO2 level. These findings support the concept that leaf conductances are governed by
CO2 assimilation rates under water-stressed as well as unstressed conditions.

KEYWORDS: ABSCISIC- ACID, CARBOXYLASE, DIFFERENT CO2 ENVIRONMENTS, FIELD,
GROWTH, LEAVES, PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, TRANSPIRATION
RATE, WHEAT


     35   
Allen, L.H., R.R. Valle, J.W. Mishoe, J.W. Jones, and P.H. Jones. 1990. Soybean leaf gas-
exchange responses to CO2 enrichment. Soil and Crop Science Society of Florida Proceedings
49:192-198.



     36   
Almeida, J.P.F., A. Luscher, M. Frehner, A. Oberson, and J. Nosberger. 1999. Partitioning of
P and the activity of root acid phosphatase in white clover (Trifolium repens L.) are modified by
increased atmospheric CO2 and P fertilisation. Plant and Soil 210(2):159-166.

The growth response of white clover (Trifolium repens L.) to the expected increase in atmospheric
partial pressure of CO2 (p(CO2)) may depend on P availability. A decrease in the rate of transpiration
due to increased p(CO2) may reduce the amount of P transported to the shoot, thereby causing a
change in the partitioning of P between the root and shoot. To test these hypotheses, four
concentrations of P in the nutrient solution, combined with two p(CO2) treatments, were applied to
nodulated white clover plants. Compared to ambient p(CO2) (35 Pa), twice ambient p(CO2) (70 Pa)
reduced the rate of transpiration but did not impair the total P uptake per plant. However, at twice
ambient p(CO2) and a moderate to high supply of P, concentrations of structural P and soluble P (Pi)
were lower in the leaves and higher in the roots. The activity of root acid phosphatase was lower at
twice ambient p(CO2) than at ambient p(CO2); it depended on the Pi concentration in the roots. At
the highest P concentration, twice ambient p(CO2) stimulated photosynthesis and the growth rate of
the plant without affecting the concentration of nonstructural carbohydrates in the leaves. However,
at the lower P concentrations, plants at twice ambient p(CO2) lost their stimulation of photosynthesis
in the afternoon, they accumulated nonstructural carbohydrates in the leaves and their growth rate
was not stimulated; indicating C-sink limitation of growth. P nutrition will be crucial to the growth
of white clover under the expected future conditions of increased p(CO2).

KEYWORDS: AIR, BEAN-PLANTS, CARBON DIOXIDE, DRY-MATTER, ENRICHMENT,
GROWTH, MAGNESIUM-DEFICIENCY, PHOSPHORUS, SOURCE-SINK RELATIONS,
SUBTERRANEUM L


     37   
Alvarez, R., M. Alconada, and R. Lavado. 1999. Sewage sludge effects on carbon dioxide-carbon
production from a desurfaced soil. Communications in Soil Science and Plant Analysis 30(13-
14):1861-1866.

Desurfaced soils are found near cities in the Pampean Region of Argentina because A horizons were
used for brick production. These soils are not suitable for agriculture. Application of sewage sludge
is a tool for improving soil productivity, but its effects on the environment are not thoroughly
understood. Production of carbon dioxide (CO2)-carbon (C) in the field from a desurfaced soil in
which 25 Mg dry matter ha(-1) of sewage sludge were applied the first year and 10 Mg dry matter
ha(-1), the second year was evaluated during a corn (Zea mays L.) growing cycle. Microbial biomass
and metabolic activity were also measured. Sludge applications produced an increase of the CO2-C
efflux in the field of 30-50% during summer. Microbial biomass was not affected by sludge some
months after the application, but metabolic activity and organic matter mineralization were enhanced.
The increase of the CO2-C emission from the soil represented 21% of the sludge C applied the year
of the experiment and 15% of the C applied the year before. Consequently, an important quantity of
the sludge C was retained in the soil.

KEYWORDS: CROPS, GLUCOSE, HEAVY-METALS, MAIZE, MANURE, MICROBIAL BIOMASS
DYNAMICS, RESIDUE


     38   
Ambus, P., and G.P. Robertson. 1999. Fluxes of CH4 and N2O in aspen stands grown under
ambient and twice-ambient CO2. Plant and Soil 209(1):1-8.

Elevated atmospheric CO2 has the potential to change below- ground nutrient cycling and thereby
alter the soil-atmosphere exchange of biogenic trace gases. We measured fluxes of CH4 and N2O in
trembling aspen (Populus tremuloides Michx.) stands grown in open-top chambers under ambient and
twice-ambient CO2 concentrations crossed with `high' and low soil-N conditions. Flux measurements
with small static chambers indicated net CH4 oxidation in the open-top chambers. Across dates, CH4
oxidation activity was significantly (P < 0.05) greater with ambient CO2 (8.7 mu g CH4-C m(-2) h(-
1)) than with elevated CO2 (6.5 mu g CH4-C m(-2) h(-1)) in the low N soil. Likewise, across dates
and soil N treatments CH4 was oxidized more rapidly (P < 0.05) in chambers with ambient CO2 (9.5
mu g CH4-C m(-2) h(-1)) than in chambers with elevated CO2 (8.8 mu g CH4-C m(-2) h(-1)).
Methane oxidation in soils incubated in serum bottles did not show any response to the CO2
treatment. We suggest that the depressed CH4 oxidation under elevated CO2 in the field chambers
is due to soil moisture which tended to be higher in the twice-ambient CO2 treatment than in the
ambient CO2 treatment. Phase I denitrification (denitrification enzyme activity) was 12-26% greater
under elevated CO2 than under ambient CO2 in the `high' N soil; one sampling, however, showed a
39% lower enzyme activity with elevated CO2. In both soil N treatments, denitrification potentials
measured after 24 or 48 h were between 11% and 21% greater (P < 0.05) with twice- ambient CO2
than with ambient CO2. Fluxes of N2O in the open- top chambers and in separate 44 cm(2) cores +/-
N fertilization were not affected by CO2 treatment and soil N status. Our data show that elevated
atmospheric CO2 may have a negative effect on terrestrial CH4 oxidation. The data also indicated
temporary greater denitrification with elevated CO2 than with ambient CO2. In contrast, we found
no evidence for altered fluxes of N2O in response to increases in atmospheric CO2.

KEYWORDS: ATMOSPHERIC METHANE CONSUMPTION, DENITRIFICATION, ELEVATED
CARBON-DIOXIDE, ENRICHMENT, GAS FLUXES, GRASSLAND, NITROUS-OXIDE,
RESPONSES, TALLGRASS PRAIRIE, TEMPERATE FOREST SOILS


     39   
Amiro, B.D., J.I. MacPherson, and R.L. Desjardins. 1999. BOREAS flight measurements of
forest-fire effects on carbon dioxide and energy fluxes. Agricultural and Forest Meteorology
96(4):199-208.

Fire is the dominant stand-replacing agent in the Canadian boreal forest, but few quantitative
measurements are available on the micrometeorological effects of fire. Airborne flux measurements
during the BOREAS experiment were referenced to age of burn along a 500-km transect through
Saskatchewan and Manitoba, Canada. These data for 1-, 5-, and 7-year-old burns were supplemented
with 15- and 30-year-old-burn data from the BOREAS northern study site near Thompson, Manitoba.
Data were available near midday only and included the June, July and September campaigns during
1994, and July of 1996. Surface radiometric temperature increased by up to 6 degrees C and
remained elevated even 15 years after fire. Net radiation was largely unaffected whereas albedo
decreased in the first year post-fire but recovered by the fifth year. Sensible heat flux increased by 10-
20% for the first few years after the fire and then decreased. Latent heat flux slightly decreased after
the fire, causing the Bowen ratio to increase by ca. 50% for 7 years post-fire. The CO2 flux was
reduced for the 15-year period after fire with the greatest reduction to ca. 25% of control areas
during the year following fire. However, diurnal and annual data are needed to determine the total
impact of fire on the boreal-forest carbon balance. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ASPEN FOREST, ATMOSPHERE, ECOSYSTEMS, EXCHANGES, MICROBIAL
BIOMASS, NORTHERN, PINE FOREST, SOIL RESPIRATION, WATER-VAPOR, WILDFIRE


     40   
Amoroso, G., C. Weber, D. Sultemeyer, and H. Fock. 1996. Intracellular carbonic anhydrase
activities in Dunaliella tertiolecta (Butcher) and Chlamydomonas reinhardtii (Dangeard) in relation
to inorganic carbon concentration during growth: Further evidence for the existence of two distinct
carbonic anhydrases associated with the chloroplasts. Planta 199(2):177-184.

Using mass-spectrometric measurements of O-18 exchange from (CO2)-C-13-O-18 intracellular
carbonic anhydrase (CA) activity was investigated in the unicellular green algae Dunaliella tertiolecta
and Chlamydomonas reinhardtii which were either grown on air enriched with 5% CO2 (high-C-i
cells) or on air (low-C-i cells). In D. tertiolecta high- and low-C-i cells had detectable levels of
internal CA activity when measured under in-vivo conditions and this activity could be split up into
three distinct forms. One CA was not associated with the chloroplasts, while two isozymes were
found to be located within the plastids. The activities of all intracellular CAs were always about
twofold higher in low than in high -C-i cells of D. tertiolecta and the chloroplastic enzymes were
completely induced within 4 h of adaptation to air. One of the chloroplastic CAs was found to be
soluble the other was insoluble. In addition to the physical differences, MgSO4 in vitro caused a more
than twofold stimulation of the soluble activity while the insoluble form of CA remained rather
unaffected. In C. reinhardtii, MgSO4 increased the soluble CA activity by 346% and the
concentration of MgSO4 required for half-maximum stimulation was between 10 and 15 mM. Again,
the insoluble CA activity was not affected by MgSO4. Furthermore, the soluble isoenzyme was
considerably more sensitive to ethoxyzolamide, a potent inhibitor of CA, than the insoluble enzyme.
The concentration of inhibitor causing 50% inhibition of soluble CA activity was 110 and 85 mu M
ethoxyzolamide for D. tertiolecta and C. reinhardtii, respectively. From these data we conclude that
the two chloroplast-associated CAs are distinct enzymes.

KEYWORDS: CELL-SURFACE, CO2, CYANOBACTERIUM SYNECHOCOCCUS PCC7942,
INCREASES, INTACT CHLOROPLASTS, MICROALGAE, O-18 EXCHANGE,
PHOTOSYNTHESIS, SALINA, TRANSPORT


     41   
Amthor, J.S. 1991. Respiration in a future, higher-CO2 world. Plant, Cell and Environment
14(1):13-20.

Apart from its impact on global warming, the annually increasing atmospheric [CO2] is of interest
to plant scientists primarily because of its direct influence on photosynthesis and photorespiration in
C3 species. But in addition, 'dark' respiration, another major component of the carbon budget of
higher plants, may be affected by a change in [CO2] independent of an increase in temperature.
Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an increase in
[CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on
respiration rate may be direct or indirect. Mechanisms responsible for various observations are
proposed. These proposed mechanisms relate to changes in: (1) levels of nonstructural carbohydrates,
(2) growth rate and structural phytomass accumulation, (3) composition of phytomass, (4) direct
chemical interactions between CO2 and respiratory enzymes, (5) direct chemical interactions between
CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate.
Because a range of (possibly interactive) effects exist, and present knowledge is limited, the impact
of future [CO2] on respiration rate cannot be predicted. Theoretical considerations and types of
experiments that can lead to an increase in the understanding of this issue are outlined.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, DARK RESPIRATION, ENERGY
OVERFLOW, GAS-EXCHANGE, GROWTH, LEAF, PHOTOSYNTHESIS, PLANTS,
TEMPERATURE


     42   
Amthor, J.S. 1994. Scaling co2-photosynthesis relationships from the leaf to the canopy.
Photosynthesis Research 39(3):321-350.

Responses of individual leaves to short-term changes in CO2 partial pressure have been relatively well
studied. Whole-plant and plant community responses to elevated CO2 are less well understood and
scaling up from leaves to canopies will be complicated if feedbacks at the small scale differ from
feedbacks at the large scale. Mathematical models of leaf, canopy, and ecosystem processes are
important tools in the study of effects on plants and ecosystems of global environmental change, and
in particular increasing atmospheric CO2, and might be used to scale from leaves to canopies. Models
are also important in assessing effects of the biosphere on the atmosphere. Presently, multilayer and
big leaf models of canopy photosynthesis and energy exchange exist. Big leaf models - which are
advocated here as being applicable to the evaluation of impacts of 'global change' on the biosphere -
simplify much of the underlying leaf-level physics, physiology, and biochemistry, yet can retain the
important features of plant- environment interactions with respect to leaf CO2 exchange processes
and are able to make useful, quantitative predictions of canopy and community responses to
environmental change. The basis of some big leaf models of photosynthesis, including a new model
described herein, is that photosynthetic capacity and activity are scaled vertically within a canopy (by
plants themselves) to match approximately the vertical profile of PPFD. The new big leaf model
combines physically based models of leaf and canopy level transport processes with a biochemically
based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2
exchange measurements, although a need exists for further testing of this and other canopy
physiology models with independent measurements of canopy mass and energy exchange at the time
scale of 1 h or less.

KEYWORDS: C-3 PLANTS, CARBON DIOXIDE, DARK RESPIRATION, LIGHT-INTENSITY,
PHOTOSYNTHETIC CO2 FIXATION, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE,
SOURCE-SINK RELATIONS, STOMATAL CONDUCTANCE, SUNFLOWER LEAVES, WATER-
USE EFFICIENCY


     43   
Amthor, J.S. 1995. Predicting effects of atmospheric CO2 partial pressure on forest photosynthesis.
Journal of Biogeography 22(2-3):269-280.

A mechanistic (i.e. hierarchic or explanatory) model of forest canopy mass and energy exchange that
has been previously tested with eddy-correlation measurements in the field - albeit only at present
ambient CO2 partial pressure - was used to predict photosynthetic response of a deciduous Quercus-
Acer forest in eastern North America to atmospheric CO2 partial pressure. Four partial pressures of
CO2 were used in simulations: 28 (pre- industrial), 36 (present), 54 and 72 Pa. This is (one of) the
first set(s) of predictions of forest photosynthetic response to CO2 partial pressure made by a
mechanistic forest physiology model shown to accurately predict independent field measurements of
whole-forest CO2 exchange at the hourly time scale. The model includes a biochemically based
Farquhar-type model of leaf mesophyll CO2 assimilation, which is central to its ability to predict
photosynthetic response to different CO2 partial pressures. Whole-forest photosynthesis was
positively related to CO2 partial pressure, as expected. This was the case under both clear and cloudy
skies, but the relative response to CO2 was greater under a clear sky compared to a cloudy sky (the
clear sky day was also warmer). Instantaneous water use efficiency (mel CO2 assimilated per mol
H2O transpired) was positively related to atmospheric CO2 partial pressure for all conditions included
in the simulations. Model predictions indicate that (1) present forest photosynthesis and water use
efficiency may be significantly greater than they were in pre- industrial times (per unit ground area
of forest) and (2) future higher CO2 partial pressures could further stimulate forest photosynthesis
and water use efficiency, unless future climatic changes have significant negative effects on
photosynthesis or acclimation and adaptation processes markedly downregulate photosynthesis in
response to greater CO2 partial pressure.

KEYWORDS: C-3 PLANTS, CANOPY, DECIDUOUS FOREST, ELEVATED CO2, GAS-
EXCHANGE, GROWTH, MODELS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, RISING
CO2, SOLAR RADIATION


     44   
Amthor, J.S. 1995. Terrestrial higher-plant response to increasing atmospheric [co2] in relation to
the global carbon-cycle. Global Change Biology 1(4):243-274.

Terrestrial higher plants exchange large amounts of CO2 with the atmosphere each year; c. 15% of
the atmospheric pool of C is assimilated in terrestrial-plant photosynthesis each year, with an about
equal amount returned to the atmosphere as CO2 in plant respiration and the decomposition of soil
organic matter and plant litter. Any global change in plant C metabolism can potentially affect
atmospheric CO2 content during the course of years to decades. In particular, plant responses to the
presently increasing atmospheric CO2 concentration might influence the rate of atmospheric CO2
increase through various biotic feedbacks. Climatic changes caused by increasing atmospheric CO2
concentration may modulate plant and ecosystem responses to CO2 concentration. Climatic changes
and increases in pollution associated with increasing atmospheric CO2 concentration may be as
significant to plant and ecosystem C balance as CO2 concentration itself. Moreover, human activities
such as deforestation and livestock grazing can have impacts on the C balance and structure of
individual terrestrial ecosystems that far outweigh effects of increasing CO2 concentration and
climatic change. In short-term experiments, which in this case means on the order of 10 years or less,
elevated atmospheric CO2 concentration affects terrestrial higher plants in several ways. Elevated
CO2 can stimulate photosynthesis, but plants may acclimate and (or) adapt to a change in
atmospheric CO2 concentration. Acclimation and adaptation of photosynthesis to increasing CO2
concentration is unlikely to be complete, however. Plant water-use efficiency is positively related to
CO2 concentration, implying the potential for more plant growth per unit of precipitation or soil
moisture with increasing atmospheric CO2 concentration. Plant respiration may be inhibited by
elevated CO2 concentration, and although a naive C balance perspective would count this as a benefit
to a plant, because respiration is essential for plant growth and health, an inhibition of respiration can
be detrimental. The net effect on terrestrial plants of elevated atmospheric CO2 concentration is
generally an increase in growth and C accumulation in phytomass. Published estimations, and
speculations about, the magnitude of global terrestrial- plant growth responses to increasing
atmospheric CO2 concentration range from negligible to fantastic. Well-reasoned analyses point to
moderate global plant responses to CO2 concentration. Transfer of C from plants to soils is likely to
increase with elevated CO2 concentrations because of greater plant growth, but quantitative effects
of those increased inputs to soils on soil C pool sizes are unknown. Whether increases in leaf-level
photosynthesis and short-term plant growth stimulations caused by elevated atmospheric CO2
concentration will have, by themselves, significant long-term (tens to hundreds of years) effects on
ecosystem C storage and atmospheric CO2 concentration is a matter for speculation, not firm
conclusion. Longterm field studies of plant responses to elevated atmospheric CO2 are needed. These
will be expensive, difficult, and by definition, results will not be forthcoming for at least decades.
Analyses of plants and ecosystems surrounding natural geological CO2 degassing vents may provide
the best surrogates for long-term controlled experiments, and therefore the most relevant information
pertaining to long-term terrestrial-plant responses to elevated CO2 concentration, but pollutants
associated with the vents are a concern in some cases, and quantitative knowledge of the history of
atmospheric CO2 concentrations near vents is limited. On the whole, terrestrial higher-plant responses
to increasing atmospheric CO2 concentration probably act as negative feedbacks on atmospheric CO2
concentration increases, but they cannot by themselves stop the fossil-fuel-oxidation-driven increase
in atmospheric CO2 concentration. And, in the very long-term, atmospheric CO2 concentration is
controlled by atmosphere-ocean C equilibrium rather than by terrestrial plant and ecosystem
responses to atmospheric CO2 concentration.

KEYWORDS: DIOXIDE CONCENTRATION, ELEVATED CO2, GAS-EXCHANGE, PARTIAL-
PRESSURE, PAST 2 CENTURIES, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE-1;5-
BISPHOSPHATE CARBOXYLASE-OXYGENASE, STOMATAL DENSITY, VOSTOK ICE-CORE,
WATER-USE EFFICIENCY


     45   
Amthor, J.S. 1998. Perspective on the relative insignificance of increasing atmospheric CO2
concentration to crop yield. Field Crops Research 58(2):109-127.

Average yield of most crops in many countries increased significantly during the past 50 to 100 years.
Although atmospheric CO2 concentration, [CO2](a), also increased during that time period, and
although crop growth and yield can respond positively to [CO2](a) increase, yield increases were due
mainly to factors other than increasing [CO2](a). Similarly, some yield increases prior to 1900 were
also associated primarily with factors other than changes in [CO2](a). In particular, past national
average yield increases were the result chiefly of technological advances such as nitrogen fertilization;
selection of genotypes with increased harvest index and disease resistance; mechanization of planting,
cultivation, and harvesting; and chemical weed and pest control. If technology continues to increase
average yields at recent rates, near-future increases in [CO2](a) will have only small impacts on yield
in comparison to technology in many countries. Conversely, if future increases in [CO2](a) are the
main drivers of future yield increases, those yield increases will be small. These points are
demonstrated through a comparison of (i) long-term records of yield, (ii) data from key controlled-
[CO2] experiments, and (iii) records of past [CO2](a). Finally, it is noted that continued [CO2](a)
increase may bring with it climatic changes that could have negative or positive impacts on future
yield. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: 18TH-CENTURY ENGLAND, AGRICULTURAL PRODUCTIVITY, CARBON
DIOXIDE, CLIMATE, ENRICHMENT, PHOTOSYNTHESIS, RESPONSES, SPECULATIONS,
TRENDS, WHEAT


     46   
Amthor, J.S., R.J. Mitchell, G.B. Runion, H.H. Rogers, S.A. Prior, and C.W. Wood. 1994.
Energy content, construction cost and phytomass accumulation of glycine-max (L) merr and
sorghum-bicolor (L) moench grown in elevated co2 in the field. New Phytologist 128(3):443-450.

Grain sorghum [Sorghum] bicolor (L.) Moench, a C-4 crop] and soybean [Glycine max (L.) Merr.
cv. Stonewall, a C-3 crop] plants were grown in ambient (c. 360 mu l l(-1)) and twice- ambient (c.
720 mu l l(-1)) CO2 levels in open-top chambers in soil without root constriction. Plant dry mass,
energy content, composition and construction cost (i.e. amount of carbohydrate required to
synthesize a unit of plant dry mass) were assessed at the end of the growing season. Elevated CO2
(a) increased phytomass accumulation (kg per plant) in both species, (b) had little affect on energy
concentration (MJ kg(-1) plant) but caused large increases in the amount of plant energy per ground
area (MJ m(-2) ground), and (c) did not alter specific growth cost (kg carbohydrate kg(-1) plant
growth) but greatly increased growth cost per ground area (kg carbohydrate m(-2) ground) because
growth was enhanced. For soybean, twice-ambient CO2 resulted in a 50 % increase in the amount
of nitrogen and energy in grain (seed plus pod) per ground area. This response to elevated CO2 has
important implications for agricultural productivity during the next century because the rate of human
population growth is exceeding the rate of increase of land used for agriculture so that future food
demands can only be met by greater production per ground area.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, LEAVES, MAINTENANCE, NITROGEN,
PHOTOSYNTHESIS, PLANTS, RESPIRATION, RESPONSES, YIELD


     47   
Andalo, C., B. Godelle, M. Lefranc, M. Mousseau, and I. TillBottraud. 1996. Elevated CO2
decreases seed germination in Arabidopsis thaliana. Global Change Biology 2(2):129-135.

The impact of elevated [CO2] on seed germination was studied in different genotypes of Arabidopsis
thaliana from natural populations. Two generations of seeds were studied: the maternal generation
was produced in the greenhouse (present-day conditions), the offspring generation was produced in
two chambers where the CO2 concentration was either the present atmospheric concentration (about
350 ppm) or elevated (700 ppm). The seeds were tested for proportion of germinated seeds and mean
germination time in both chambers to study the impact of elevated [CO2] during seed production and
germination. Elevated [CO2] during maturation of seeds on the mother-plants decreased the
proportion of germinated seeds, while elevated [CO2] during germination had no effect on the
proportion of germinated seeds. However, when seeds were both produced and germinated under
elevated [CO2] (situation expected by the end of next century), germination was slow and low.
Moreover, the effect of the [CO2] treatment differs among genotypes of Arabidopsis: there is a
strong treatment x genotype interaction. This means that there is ample genetic variance for a
selective response modiying the effects of high levels of [COP] in natural populations of Arabidopsis
thaliana. The outcome at the community level will depend on what seeds are available, when they
germinate and the resulting competition following germination.

KEYWORDS: GROWTH, PLANTS


     48   
Andalo, C., C. Raquin, N. Machon, B. Godelle, and M. Mousseau. 1998. Direct and maternal
effects of elevated CO2 on early root growth of germinating Arabidopsis thaliana seedlings. Annals
of Botany 81(3):405-411.

Individuals of Arabidopsis thaliana, collected in different natural populations, were grown in
controlled and elevated CO2 in a glasshouse. Following germination, root growth of progeny of
different lines of these populations was studied in control and elevated atmospheric CO2. No
significant direct effect of atmospheric CO2 concentration could be demonstrated on root growth.
An important parental effect was apparent, namely that root length and branching were decreased in
seeds collected from a mother plant which had been grown in elevated CO2. This was correlated with
smaller seeds, containing less nitrogen. These parental effects were genetically variable. We conclude
that CO2 may affect plant fitness via parental effects on seed size and early root growth and that the
genetic variability shown in our study demonstrates that Arabidopsis populations will evolve in the
face of this new selective pressure. (C) 1998 Annals of Botany Company.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ELONGATION, ENRICHMENT, PLANT,
QUALITY, SEED-GERMINATION, SENECIO-VULGARIS, TEMPERATURE, TRITICUM-
AESTIVUM L, WHEAT


     49   
Anderson, J.M. 1991. The effects of climate change on decomposition processes in grassland and
coniferous forests. Ecological Applications 1(3):326-347.

Current models of climate change predict a reduction of area covered by northern coniferous forests
and tundra, and an increase in grasslands. These scenarios also indicate a northerly shift in agricultural
regions, bringing virgin soils under cultivation. The direct effects of man on tundra,boreal forest, and
temperate grassland ecosystems are likely to result in less carbon mobilization from soils and
vegetation than from tropical forests. However, as a consequence of climate change, carbon
mineralization rates from arctic and sub-arctic soils could be very rapid under warmer and drier
conditions because of low stabilization of soil organic matter (SOM) and enhanced microbial
responses to small changes in soil moisture and temperature. Predicting the response of these systems
to climate change is complicated where the edaphic environment regulating SOM dynamics is not a
direct function of macroclimatic conditions. Grasslands contain a greater proportion of highly
stabilized SOM than coniferous forests, distributed over greater depth in the soil profile, which is less
susceptible to changes in mineralization rates. It is concluded that short-term responses of soil
processes to climate change are more predictable in well-drained grassland and forest soils than in
waterlogged soils of the tundra and boreal region. Over longer periods of time, however, plant
species and soil types will alter in response to new temperature and moisture regimes above- and
belowground interacting with the effects of carbon enrichment and changes in nutrient availability.
The dynamics of these plant-soil interactions and the future status of soils in different life zones as
sources or sinks of carbon is poorly understood. More data are also needed on the distribution of
waterlogged forest soils in the boreal zone and responses to warming, which include the production
of methane as well as CO2. The primary recommendation for future research is for integrated studies
on plant and soil processes.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DOUGLAS-FIR, LEAF-LITTER
DECOMPOSITION, LONG-TERM DECOMPOSITION, NITROGEN-AVAILABILITY, NORTHERN
HARDWOODS, SCOTS PINE FOREST, SOIL ORGANIC MATTER, SPRUCE-LICHEN
WOODLAND, TEMPERATE ECOSYSTEMS


     50   
Anderson, P.D., and P.T. Tomlinson. 1998. Ontogeny affects response of northern red oak
seedlings to elevated CO2 and water stress - I. Carbon assimilation and biomass production. New
Phytologist 140(3):477-491.

The interactive influences of elevated carbon dioxide, water stress, and ontogeny on carbon
assimilation and biomass production were investigated in northern red oak, a species having episodic
shoot growth characteristics. Seedlings were grown from acorns through three shoot-growth hushes
(8-11 wk) in controlled-environment chambers at 400, 530 or 700 mu mol mol(-1) CO2 and under
well watered or water-stressed soil- moisture regimes. Increasing CO2 growth concentration from
400 to 700 mu mol mol(-1) resulted in a 34 % increase in net assimilation rate (A), a 31 % decrease
in stomatal conductance to water vapour (g(s)) and a 141 % increase in water use efficiency (WUE)
in well watered seedlings. In contrast, water- stressed seedlings grown at 700 mu mol mol(-1) CO2
demonstrated a 69 % increase in A, a 23 % decrease in g(s), and a 104 % increase in WUE.
However, physiological responses to increased CO2 and water stress were strongly modified by
ontogeny. During active third-flush shoot growth, A in first-flush and second- flush foliage of water-
stressed seedlings increased relative to the quiescent phase following cessation of second-flush
growth by an average of 115 %; g(s) increased by an average of 74 %. In contrast, neither A nor gs
in comparable foliage of well watered seedlings changed in response to active third-flush growth.
Whereas seedling growth was continuous through three flushes in well watered seedlings, growth of
water-stressed seedlings was minimal following the leaf-expansion stage of the third flush. Through
three growth flushes total seedling biomass and biomass allocation to root, shoot and foliage
components were very similar in water-stressed seedlings grown at 700 mu mol mol(-1) CO2 and
well watered seedlings grown at 400 mu mol mol(-1) CO2. Enhancement effects of elevated CO2 on
seedling carbon (C) assimilation and biomass production may offset the negative impact of moderate
water stress and are likely to be determined by ontogeny and stress impacts on carbon sink demand.

KEYWORDS: ATMOSPHERIC CO2, DIOXIDE ENRICHMENT, DROUGHT, GAS-EXCHANGE,
GROWTH-RESPONSE, LEAVES, PHOTOSYSTEM, QUERCUS-RUBRA L, RISING CO2, USE
EFFICIENCY


     51   
Andersson, N.E. 1991. The influence of constant and diurnally changing CO2 concentrations on
plant-growth and development. Journal of Horticultural Science 66(5):569-574.

Plants of Ficus benjamina and miniature rose (Rosa hybrida cv. Red Minimo) were grown under four
CO2 treatments. Two had constant CO2 levels (600 and 900 ppm) and the other two had diurnal
changes in CO2 levels, one increasing from 600 to 1500 ppm and one decreasing from 1500 to 600
ppm, each in four steps of 300 ppm during the day-time. In all treatments 900 ppm CO2 was
maintained during the night when supplementary light was used, except in the treatment with constant
600 ppm where 600 ppm was also continued throughout the night. Plant growth was monitored under
both decreasing and increasing natural daylength and irradiance. The tallest plants and greatest
increment in height for Ficus occurred with plants grown under constant CO2 concentration at 600
ppm and also with increasing CO2 concentration. In both experiments the dry weight per pot was
lowest when plants were grown under a constant CO2 concentration at 900 ppm. In both experiments
with miniature roses the number of flower buds was significantly increased under diurnally changing
CO2 concentration or when the CO2 level was constant at 600 ppm compared with a constant 900
ppm. Time to flowering was decreased by constant CO2 at 900 ppm as compared with the other
treatments.

KEYWORDS: ATMOSPHERES, CARBON-DIOXIDE ENRICHMENT, DURATION, EXCHANGE,
LIGHT-INTENSITY, ROSE, YIELD


     52   
Andrade, J.L., and P.S. Nobel. 1996. Habitat, CO2 uptake and growth for the CAM epiphytic
cactus Epiphyllum phyllanthus in a Panamanian tropical forest. Journal of Tropical Ecology 12:291-
306.

In the tropical forest of Barro Colorado Island, habitat characteristics, diel acidity changes, CO2
uptake and growth were investigated for the epiphytic cactus Epiphyllum phyllanthus (L.) Haw. It
occurred most frequently in tree cavities with its roots in canopy soil and was especially abundant on
two tree species: Platypodium elegans J. Vogel and Tabebuia guayacan (Seem.) Hemsl. Its maximum
net CO2 uptake rates were low under natural conditions (1.4 mu mol m(-2) s(- 1)) but were
comparable to those of other CAM and C-3 epiphytes under wet conditions in a screenhouse. Under
both natural conditions and in the screenhouse, partial shade enhanced growth and CAM activity.
When plants grew under a photosynthetic photon flux of c. 4 mol m(-2) d(-1), their nocturnal acidity
increase and total net CO2 uptake were twice as much as for plants growing at lower (an average of
2.4 mol m(-2) d(-1)) and higher (7.7 mol m(-2) d(-1)) photosynthetic photon fluxes. Stem elongation
was 27% greater at the intermediate photosynthetic photon flux. Seedlings of E. phyllanthus survived
three months of drought and responded rapidly to rewetting, recovering fully within three days.
Transpiration rates and nocturnal acidity increases also recovered to the values of well-watered plants
a few days after rewetting, indicating that this species can take advantage of episodic rainfall during
the dry season.

KEYWORDS: ACCUMULATION, C-3 BROMELIADS, COMPARATIVE ECOPHYSIOLOGY,
CRASSULACEAN ACID METABOLISM, LEAF, OPUNTIA FICUS INDICA, SHADE, VASCULAR
EPIPHYTES


     53   
Andre, M., and H. Ducloux. 1993. Interaction of co2 enrichment and water limitations on
photosynthesis and water efficiency in wheat. Plant Physiology and Biochemistry 31(1):103-112.

Wheat plants (Triticum aestivum L. cv. Capitole) were grown in twin closed growth chambers with
continuous monitoring of CO2 and water exchanges. During the vegetative stage the effect Of CO2
enrichment, from 330 to 660 mul-1, was studied under irradiance of 660 muE m-2 s-1 with an
optimum watering. Comparisons were made with successive experiments in which daily water supply
was fixed to a fraction (0.62-0.50-0.25) of the maximal transpiration of previous experiments. In a
well- watered canopy, doubling CO2 decreased transpiration by only 8%. Water use efficiency was
increased (factor 1.45) mainly by the stimulation of photosynthesis. Under restricted water supply,
photosynthesis of plants was more limited than transpiration. The inhibition of photosynthesis and the
increase of water use efficiency can be predicted by a simple diffusion model applied to the response
curve of photosynthesis to CO2, measured on canopy in standard conditions of watering. The main
hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water
availability, without closure by patching. Under enriched CO2, the same reduction of leaf surface by
water limitation was observed. Photosynthesis was less affected. Therefore, water-use-efficiency was
again increased. Doubling CO2 concentration can compensate for water stress inhibition on CO2
assimilation. That model also predicts interactions of CO2 and water stress observed on water-use-
efficiency which was increased by a factor up to 5 in comparison with well-watered plants in standard
atmosphere. The implications of this study for global change models are discussed.

KEYWORDS: ASSIMILATION, CARBON-DIOXIDE ENRICHMENT, CONDUCTANCE,
EXCHANGES, GROWTH, PHASEOLUS-VULGARIS L, PLANTS, SEEDLINGS, STRESS, YIELD


     54   
Andrews, J.A., K.G. Harrison, R. Matamala, and W.H. Schlesinger. 1999. Separation of root
respiration from total soil respiration using carbon-13 labeling during Free-Air Carbon Dioxide
Enrichment (FACE). Soil Science Society of America Journal 63(5):1429-1435.

Soil respiration constitutes a major component of the global carbon cycle and is likely to be altered
by climatic change. However, there is an incomplete understanding of the extent to which various
processes contribute to total soil respiration, especially the contributions of root and rhizosphere
respiration. Here, using a stable carbon isotope tracer, we separate thf relative contributions of root
and soil heterotrophic respiration to total soil respiration in situ. The Free-Air Carbon dioxide
Enrichment (FACE) facility in the Duke University Forest (NC) fumigates plots of an undisturbed
loblolly pine (Pinus taeda L.) forest with CO2 that is strongly depleted in C-13. This labeled CO2 is
found in the soil pore space through live root and mycorrhizal respiration and soil heterotroph
respiration of labile root exudates. By measuring the depletion of (CO2)-C-13 in the soil system, we
found that the rhizosphere contribution to soil CO2 reflected the distribution of fine roots in the soil
and that late in the growing season roots contributed 55% of total soil respiration at the surface, This
estimate may represent an upper limit on the contribution of roots to soil respiration because high
atmospheric CO2 often increases in root density and/or root activity in the soil.

KEYWORDS: CO2, DECIDUOUS FOREST, FATE, FLUXES, LITTER, ORGANIC-MATTER,
PONDEROSA PINE, RHIZOSPHERE, SEEDLINGS


     55   
Andrews, T.J., G.S. Hudson, C.J. Mate, S. Voncaemmerer, J.R. Evans, and Y.B.C. Arvidsson.
1995. Rubisco - the consequences of altering its expression and activation in transgenic plants.
Journal of Experimental Botany 46:1293-1300.

Transgenic tobacco (Nicotiana tabacum W38) hemizygous for a single antisense gene directed against
Rubisco's small subunit had 35% of the Rubisco content of control leaves (15% when homozygous).
CO2 assimilation (at 1000 mu mol quanta m(-2) s(- 1) and 350 mu bar CO2) by the hemizygous
leaves was reduced to 40% of that of the controls without material effect on stomatal conductance,
chlorophyll content or other photosynthetic components. Leaf soluble protein was reduced
commensurately with the reduction in Rubisco. CO2 assimilation rate in the hemizygous leaves
remained limited by Rubisco activity at all, even very high, CO2 concentrations. This led to a simple,
hyperbolic response of photosynthesis to intraplastid CO2 concentration from which the in vivo
catalytic properties of Rubisco were inferred and compared with those of isolated Rubisco in vitro.
Using a similar approach, the content of Rubisco activase was suppressed by incorporating a partial
cDNA for activase into the tobacco genome in the antisense orientation with respect to a cauliflower
mosaic virus 35S promoter. The progeny of a primary transformant with two anti- activase inserts
had from <1% to 20% of the activase content of control plants. Quite severe suppression of activase,
to less than 5% of the amount present in control leaves, was required before effects on photosynthesis
and growth became apparent, indicating that one activase tetramer must be able to service,
continuously, as many as 200 Rubisco octamers. Plants with lower activase contents could not grow
unless the atmosphere was enriched with CO2. Their Rubisco was less carbamylated and they had
lower CO2 assimilation rates than the controls. The rate of release of 2'-carboxyarabinitol-1-
phosphate from Rubisco after illumination of the anti-activase leaves was also impaired. Older anti-
activase plants accumulated increasing amounts of Rubisco in their younger leaves, but were unable
to carbamylate it. The photosynthetic rate per carbamylated Rubisco active site in the strongly
suppressed anti-activase leaves was only approximately 25% of that seen in control leaves, suggesting
that activase may not only promote carbamylation of uncarbamylated Rubisco sites, but also
accelerate turnover at carbamylated sites.

KEYWORDS: 2-CARBOXYARABINITOL 1-PHOSPHATE, ACTIVITY INVIVO, ANTISENSE GENE,
CATALYSIS, GROWTH, PHOTOSYNTHESIS, RIBULOSE BISPHOSPHATE CARBOXYLASE,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SLOW INACTIVATION,
TOBACCO NICOTIANA-TABACUM


     56   
Andriolo, J.L., J. LeBot, C. Gary, G. Sappe, P. Orlando, B. Brunel, and C. Sarrouy. 1996. An
experimental set-up to study carbon, water and nitrate uptake rates by hydroponically grown plants.
Journal of Plant Nutrition 19(10-11):1441-1462.

The experimental system described allows concomitant hourly measurements of CO2, H2O, and NO3
uptake rates by plants grown hydroponically in a greenhouse. Plants are enclosed in an airtight
chamber through which air flows at a controlled speed. Carbon dioxide exchange and transpiration
rates are determined from respective differences of concentrations of CO2 and water vapor of the air
at the system inlet and outlet. This set-up is based on the ''open-system'' principle with improvements
made on existing systems. For instance, propeller anemometers are used to monitor air flow rates in
the chamber. From their signal it is possible to continuously adjust air speed to changing
environmental conditions and plant activity. The air temperature inside the system therefore never
rises above that outside. Water and NO3 uptake rates are calculated at time intervals from changes
in the volume and the NO3 concentration of the nutrient solution in contact with the roots. The
precise measurement of the volume of solution is achieved using a balance which has a higher
precision than any liquid level sensors. Nitrate concentration is determined in the laboratory from
aliquots of solution sampled at time intervals. A number of test runs are reported which validate the
measurements and confirm undisturbed conditions within the system. Results of typical diurnal
changes in CO2, H2O, and NO3 uptake rates by fruiting tomato plants are also presented.

KEYWORDS: CROP, DIOXIDE, ELEVATED CO2, GAS-EXCHANGE, LIFE-CYCLE, OPEN-TOP
CHAMBERS, PHOTOSYNTHESIS, SYSTEM, TOMATO, TRANSPIRATION


     57   
Angell, R., and T. Svejcar. 1999. A chamber design for measuring net CO2 exchange on rangeland.
Journal of Range Management 52(1):27-31.

Net carbon exchange of terrestrial ecosystems will likely change as atmospheric CO2 concentration
increases, Currently, little is known of the annual dynamics or magnitude of CO2 flux on many native
and agricultural ecosystems. Remoteness of many ecosystems has limited our ability to measure CO2
flux on undisturbed vegetation. Today, many plant ecologists have portable photosynthesis systems
with which they make single- leaf photosynthesis measurements. Utility of this equipment is enhanced
when canopy-level CO2 flux is also measured. We designed a portable 1-m(3) closed chamber for
use in measuring CO2 exchange in short statured vegetation with widely varied canopy structure. The
design includes external ductwork equipped with doors which are used to open the chamber for
ventilation with outside air between measurements. The chamber was tested on a Wyoming big
sagebrush (Artemisia tridentata ssp. Wyomingensis Nutt.)/Thurber's needlegrass (Stipa thurberiana
Piper) community using 10 plots equally divided between shrub and interspace, The ductwork and
doors provided adequate ventilation to allow consecutive measurements of CO2 nux without
removing the chamber from the plot. The chamber could differentiate CO2 flux between plots with
sagebrush and those with grass only, even at relatively low fluxes, Net CO2 uptake per unit ground
area was greater (P = 0.04) on sagebrush-grass plots (7.6 +/- 1.4 mu mol m(-2) s(-1)) than on
interspace plots without sagebrush (3.1 +/- 1.0 pmol m(-2) s(- 1)). Chamber and leaf temperature
increased by an average of 0.5 and 1.2 degrees C, respectively, during measurements.

KEYWORDS: CARBON-CYCLE, FLUXES, SYSTEM, TUNDRA ECOSYSTEMS


     58   
Apel, P., and M. Peisker. 1995. Variability of photosynthetic gas exchange parameters, dark
respiration, and stomatal numbers in species of Polygonum. Physiologia Plantarum 95(3):365-372.

Within the genus Polygonum a large variation was found between species with regard to stomatal
number, gas phase resistance, intracellular resistance and dark respiration. Interspecific variation in
CO2 compensation concentration and intercellular CO2 concentration at constant external
concentration were comparatively small. Correlations were found between stomatal number and gas
phase resistance, stomatal number and Gamma, and Gamma and the product of dark respiration rate
and intracellular resistance. The influence of dark respiration and stomatal number on photosynthetic
gas exchange is discussed. It was concluded that dark respiration in light was enhanced by 22% as
a mean value in 9 Polygonum species and by 62% in Polygonum lapathifolium.

KEYWORDS: CONDUCTANCE, LEAVES, PLANTS


     59   
Apple, M.E., M.S. Lucash, D.M. Olszyk, and D.T. Tingey. 1998. Morphogenesis of Douglas-fir
buds is altered at elevated temperature but not at elevated CO2. Environmental and Experimental
Botany 40(2):159-172.

Global climatic change as expressed by increased CO2 and temperature has the potential for dramatic
effects on trees. To determine what its effects may be on Pacific Northwest forests, Douglas-fir
(Pseudotsuga menziesii) seedlings were grown in sun-lit controlled environment chambers at ambient
or elevated (+ 4 degrees C above ambient) temperature, and at ambient or elevated (+ 200 ppm above
ambient) CO2. In 1995-1996 and 1996- 1997, elevated CO2 had no effect on vegetative bud
morphology, while the following unusual morphological characteristics were found with greater
frequency at elevated temperature than at ambient: rosetted buds with reflexed and loosened outer
scales, convoluted inner scales, clusters of small buds, needles elongating between scales, needle
primordia with white, hyaline apical extensions, and buds with hardened scales inside of unbroken
buds. Buds became rosetted in elevated temperature chambers after temperatures exceeded 40
degrees C in July, 1996. Rosettes were induced within 48-h in buds placed in a 40 degrees C oven;
fewer rosettes formed at 20 degrees C. Induction was reversible in buds transferred from 40 to 20
degrees C, implying that resetting is a physical rather than a growth phenomenon. It appears that
rosettes form after long- term exposure to elevated temperature and after shorter periods of exposure
to intense heat. Elevated temperature influences bud morphology and may therefore influence the
overall branching structure of Douglas-fir seedlings. (C) 1998 Elsevier Science B.V. All rights
reserved.

KEYWORDS: ACCUMULATION, BUDBURST, CHILLING REQUIREMENT, DORMANCY,
FROST DAMAGE, HEAT-SHOCK PROTEINS, INTERIOR, POPULATIONS, SEEDLINGS,
SHOOT


     60   
Arakelyan, V.V., G.B. Ibragimova, and Y.S. Nasyrov. 1993. Effects of light, co2, and temperature
on carbonic-anhydrase activity in C3-plants. Russian Journal of Plant Physiology 40(6):759-767.

Carbonic anhydrase activity was studied in cotton (Gossypium hirsutum L.) and Triticale plants
exposed to various light intensities, temperatures, and CO2 concentrations in the air. The activity was
measured using an original method based on the HCO3- dehydration reaction, which is carried out
in conditions resembling those occurring in the chloroplast stroma in vivo. Carbonic anhydrase
activity in stromal fractions from cotton and triticale plant chloroplasts appears to respond to
environmental changes. Plant exposure to increased light intensities and temperatures results in
increased activity, whereas high ambient CO2 concentrations lower carbonic anhydrase activity. After
examining in vitro the HCO3- dehydration reaction, which in vivo is catalyzed by carbonic anhydrase,
we concluded that the physiological role of the stromal enzyme consists of preventing local CO2
depletion in the carboxylation sites. Thus, high temperatures and low ambient CO2 concentrations
enhance carbonic anhydrase activity, while impeding CO2 transport from the air to the carboxylation
sites in the leaf. This accelerates HCO3- dehydration and reduces its concentration in the stroma,
thereby producing an additional driving force for HCO3- transport to the chloroplast.



     61   
Archer, S., D.S. Schimel, and E.A. Holland. 1995. Mechanisms of shrubland expansion - land-use,
climate or co-2. Climatic Change 29(1):91-99.

Encroachment of trees and shrubs into grasslands and the 'thicketization' of savannas has occurred
worldwide over the past century. These changes in vegetation structure are potentially relevant to
climatic change as they may be indicative of historical shifts in climate and as they may influence
biophysical aspects of land surface-atmosphere interactions and alter carbon and nitro en cycles.
Traditional explanations offered to account for the historic displacement of grasses by woody plants
in many arid and semi-arid ecosystems have centered around changes in climatic, livestock grazing
and fire regimes. More recently, it has been suggested that the increase in atmospheric CO2 since the
industrial revolution has been the driving force. In this paper we evaluate the CO2 enrichment
hypotheses and argue that historic, positive correlations between woody plant expansion and
atmospheric CO2 are not cause and effect.

KEYWORDS: AMERICAN SOUTHWEST, ATMOSPHERIC CO2, CARBON DIOXIDE,
DESERTIFICATION, ECOSYSTEMS, ELEVATED CO2, GROWTH, INCREASING CO2,
NATURAL VEGETATION, PAST 2 CENTURIES


     62   
Arienzo, M., G. Basile, R. Dandria, V. Magliulo, and A. Zena. 1995. Irrigation with carbonated
water and nutrient availability - tests on strawberry plants. Agrochimica 39(1):61-72.

A research was carried out to study the nutrient availability and yield performances of a strawberry
crop cv. 'Chandler' in response to equivalent depths (100% of ETM) of CO2 enriched water and plain
water applied with different irrigation frequencies. Plots were arranged in a complete randomized
block design replicated four times, using mulch and a drip irrigation system adopting 4 1/h emitters.
The crop was covered by a plastic tunnel following treatment differentiation. The statistical analysis
revealed an increased availability of Cu, Zn, Ca, Mg, and Mn for the CO2 treatment, probably linked
with the pH reduction (from 7,5 to 6,5). The increased nutrient uptake in the CO2 enriched water
treatment may be the cause of the commercial yield enhancement (8,6 %) and reduction in the weight
of deformed berries (-12,1 %).

KEYWORDS: DIOXIDE


     63   
Arisi, A.C.M., G. Cornic, L. Jouanin, and C.H. Foyer. 1998. Overexpression of iron superoxide
dismutase in transformed poplar modifies the regulation of photosynthesis at low CO2 partial
pressures or following exposure to the prooxidant herbicide methyl viologen. Plant Physiology
117(2):565-574.

Chloroplast-targeted overexpression of an Fe superoxide dismutase (SOD) from Arabidopsis thaliana
resulted in substantially increased foliar SOD activities. Ascorbate peroxidase, glutathione reductase,
and monodehydroascorbate reductase activities were similar in the leaves from all of the lines, but
dehydroascorbate reductase activity was increased in the leaves of the FeSOD transformants relative
to untransformed controls. Foliar H2O2, ascorbate, and glutathione contents were comparable in all
lines of plants. Irradiance-dependent changes in net CO, assimilation and chlorophyll a fluorescence
quenching parameters were similar in all lines both in air (21% O-2) and at low (1%) O-2. CO2-
response curves for photosynthesis showed similar net CO2-exchange characteristics in all lines. In
contrast, values of photochemical quenching declined in leaves from untransformed controls at
intercellular CO2 (Ci) values below 200 mu L L-1 but remained constant with decreasing Ci in leaves
of FeSOD transformants. When the O-2 concentration was decreased from 21 to 1%, the effect of
FeSOD overexpression on photochemical quenching at limiting Ci was abolished. At high light (1000
mu mol m(-2) s(-1)) a progressive decrease in the ratio of variable (F-v) to maximal (F-m)
fluorescence was observed with decreasing temperature. At 6 degrees C the high-light-induced
decrease in the F-v/F-m ratio was partially prevented by low O-2 but values were comparable in all
lines. Methyl viologen caused decreased F- v/F-m ratios, but this was less marked in the FeSOD
transformants than in the untransformed controls. These observations suggest that the rate of
superoxide dismutation limits flux through the Mehler-peroxidase cycle in certain conditions.

KEYWORDS: ASCORBATE PEROXIDASE, CHLOROPHYLL FLUORESCENCE, ELEVATED
LEVELS, HYDROGEN- PEROXIDE, OXIDATIVE STRESS TOLERANCE, PHOTOINHIBITION,
QUANTUM YIELD, SPINACH-CHLOROPLASTS, TEMPERATURE, TRANSGENIC PLANTS


     64   
Arnone, J.A. 1997. Indices of plant N availability in an alpine grassland under elevated atmospheric
CO2. Plant and Soil 190(1):61-66.

The objective of this study was to estimate whether elevated atmospheric [CO2] alters plant N
availability in a native high- elevation grassland in the Swiss Alps using two integrative, relatively
non-disruptive methods. Estimates based on seasonal net plant N uptake, and those based on the
amounts of NH4+-N plus NO3--N captured by ion exchange resin (IER) bags, did not differ in plots
treated with ambient (355 mu L L-1) and elevated (680 mu L L-1) [CO2] in either the second (1993)
or third (1994) growing season under treatment with elevated [CO2]. The results of this study
suggest that the effects of rising atmospheric [CO2] on plant N availability may be negligible in this
grassland. The results also contrast the relatively large effects of elevated atmospheric [CO2]
(increases and decreases) reported for highly disturbed artificial systems.

KEYWORDS: CARBON DIOXIDE, COMMUNITIES, EXCHANGE, FEEDBACK, GROWTH
FORMS, NITROGEN-AVAILABILITY, NUTRIENT AVAILABILITY, RESPONSES, SOIL-
NITROGEN, TUNDRA


     65   
Arnone, J.A. 1997. Temporal responses of community fine root populations to long- term elevated
atmospheric CO2 and soil nutrient patches in model tropical ecosystems. Acta Oecologica-
International Journal of Ecology 18(3):367-376.

Biomass and length density of fine roots, as well as overall allocation of dry matter to root growth,
of C-3 plants has been shown to increase under elevated CO2. However, it is uncertain whether the
stimulatory effect of elevated CO2 on fine root population size in plant communities will persist, or
whether fine root populations at high CO2 simply reach their maximum sooner (or possibly later) than
those produced under ambient CO2. It is also unclear whether increased nutrient demand at the stand-
level under elevated CO2 will lead to more intense nutrient foraging via enhanced fine root
proliferation into relatively nutrient-rich soil microsites. I addressed these questions in a 530 day
experiment with model tropical plant communities established in four equivalent ecosystem (17 m(3))
in which plants shared a common low fertility soil. Fine root (less than or equal to 2 mm empty set)
populations (biomass and length density) in ecosystems maintained at elevated CO2 (610 mu l l(-1))
increased more rapidly than those in ecosystems maintained at ambient CO2 (340 mu l l(-1)) during
the first half of the experiment and also remained greater over the entire experiment. The data also
indicate that: (1) fine root populations at both CO2 levels eventually stabilize, (2) stabilization occurs
sooner under elevated CO2 (occupation of the soil volume), and (3) steady-state populations under
elevated CO2 may be slightly larger than those maintained under ambient CO2. Fine root proliferation
into artifically nutrient- enriched microsites was dramatic in all ecosystems (22% to 75% greater than
into non-enriched soil). However, proliferation into enriched microsites was not enhanced by elevated
CO2. Thus, elevated CO2 may not enhance exploitation of nutrient- rich microsites even in low
fertility soils, suggesting that increased plant nutrient capture under elevated CO2 also may be
unlikely.

KEYWORDS: AMAZONIAN FORESTS, BIOMASS, CARBON DIOXIDE, ENRICHMENT,
GROWTH, MICROSITES, PLANT- COMMUNITIES, PROLIFERATION, RAIN-FOREST, UPTAKE
KINETICS


     66   
Arnone, J.A. 1999. Symbiotic N-2 fixation in a high Alpine grassland: effects of four growing
seasons of elevated CO2. Functional Ecology 13(3):383-387.

1. Increasing carbon dioxide concentration (E: 680 mu l CO2 litre(-1) vs ambient, A: 355 mu l CO2
litre(-1)) around late- successional Alpine sedge communities of the Swiss Central Alps (2450 m) for
four growing seasons (1992-1995) had no detectable effect on symbiotic N-2 fixation in Trifolium
alpinum-the sole N-2-fixing plant species in these communities (74 +/- 30 mg N m(-2) year(-1), A
and E plots pooled). 2. This result is based on data collected in the fourth growing season showing
that elevated CO2 had no effect on Trifolium above-ground biomass (4.4 +/- 1.7 g m(-2), A and E
plots pooled, n = 24) or N content per unit land area (124 +/- 51 mg N m(-2), A and E pooled), or
on the percentage of N Trifolium derived from the atmosphere through symbiotic N-2 fixation
(%Ndfa: 61.0 +/- 4.1 across A and E plots) estimated using the N-15 dilution method. 3. Thus, it
appears that N inputs to this ecosystem via symbiotic N-2 fixation will not be dramatically affected
in the foreseeable future even as atmospheric CO2 continues to rise.

KEYWORDS: ATMOSPHERIC CO2, ECOSYSTEM, ENRICHMENT, GAS-EXCHANGE,
NITROGENASE ACTIVITY, NODULATION, REDUCTION, RESPONSES, TRIFOLIUM-REPENS
L, TUNDRA


     67   
Arnone, J.A., and P.J. Bohlen. 1998. Stimulated N2O flux from intact grassland monoliths after
two growing seasons under elevated atmospheric CO2. Oecologia 116(3):331-335.

Long-term exposure of native vegetation to elevated atmospheric CO2 concentrations is expected
to increase C inputs to the soil and, in ecosystems with seasonally dry periods, to increase soil
moisture. We tested the hypothesis that these indirect effects of elevated CO2 (600 mu l l(-1) vs 350
mu l l(-1)) would improve conditions for microbial activity and stimulate emissions of nitrous oxide
(N2O), a very potent and long-lived greenhouse gas. After two growing seasons, the mean N2O
efflux from monoliths of calcareous grassland maintained at elevated CO2 was twice as high as that
measured from monoliths maintained at current ambient CO2 (70 +/- 9 vs 37 +/- 4 mu g N2O m(-2)
h(-1) in October, 27 +/- 5 vs 13 +/- 3 mu g N2O m(-2) h(-1) in November after aboveground
harvest). The higher N2O emission rates at elevated CO2 were associated with increases in soil
moisture, soil heterotrophic respiration, and plant biomass production, but appear to be mainly
attributable to higher soil moisture. Our results suggest that rising atmospheric CO2 may contribute
more to the total greenhouse effect than is currently estimated because of its plant- mediated effects
on soil processes which may ultimately lead to increased N2O emissions from native grasslands.

KEYWORDS: CALCAREOUS GRASSLAND, CARBON-DIOXIDE ENRICHMENT,
DENITRIFICATION, ECOSYSTEMS, INCREASE, METHANE, NITROUS-OXIDE PRODUCTION,
SHORTGRASS STEPPE, SOIL-NITROGEN, STOMATAL RESPONSES


     68   
Arnone, J.A., and J.C. Gordon. 1990. Effect of nodulation, nitrogen-fixation and CO2 enrichment
on the physiology, growth and dry mass allocation of seedlings of alnus-rubra bong. New Phytologist
116(1):55-66.



     69   
Arnone, J.A., and G. Hirschel. 1997. Does fertilizer application alter the effects of elevated CO2
on Carex leaf litter quality and in situ decomposition in an alpine grassland? Acta Oecologica-
International Journal of Ecology 18(3):201-206.

The purpose of our investigation was to determine: (1) whether fertilization with NPK would result
in an improvement in leaf litter quality of the dominant species (Carer curvula) in a high alpine
grassland in Switzerland; and especially (2) if fertilization improves the quality of leaf litter produced
under elevated atmospheric CO2 and compensates for the suppressive effects of high CO2 on the in
situ decomposition rates of C. curvula litter, observed at this site in an earlier study. Fertilizer
application (40 k(g) N ha(-1) yr(-1)) resulted in 34% higher leaf litter [N] but did not change C:N or
lignin N ratios, when viewed across both CO2 treatments. Improvement in the mean N quality of litter
produced under elevated CO2 resulting from fertilization appeared to lead to a significantly faster
mean decomposition rate (+ 60%), but fertilization had no significant effect on decomposition of litter
produced under ambient CO2. We conclude that the potential stimulatory effect of an increase in
atmospheric N deposition on litter quality and decomposition rates may partially compensate for the
inhibitory effects of rising atmospheric CO2 in these high alpine grassland ecosystems.

KEYWORDS: ECOSYSTEMS, NITROGEN, RESPONSES


     70   
Arnone, J.A., and C. Kestenholz. 1997. Root competition and elevated CO2: Effects on seedling
growth in Linum usitatissimum populations and Linum Silene cretica mixtures. Functional Ecology
11(2):209-214.

1. Root competition can be an important determinant of the performance of neighbours within plant
populations and communities. Because plants often maintain larger root systems and allocate more
of their carbon to root systems under elevated atmospheric CO2 than they do at lower CO2
concentrations, root-root interactions could play an increasingly important role in determining
competitive outcomes among individuals and plant species as global CO2 concentration continues
to rise. 2. We established 12 pure stands of Linum usitatissimum (flax) and 12 mixed stands of Linum
and its naturally co-occurring weed species Silene cretica in opaque plastic trays each filled with the
same amount of nutrient-rich soil mix. In half of the trays from each of these stand types, vertical
waterproof partitions separated the root systems of individual plants from each other to prevent root
competition, while in the other half no partitions were present. Half of the trays from all treatments
were allowed to grow under low atmospheric CO2 concentration (320 mu ll(-1)) and the other half
under elevated CO2 (600 mu ll(-1)), in daylight growth: chambers for 30 days from seedling
emergence until harvest in mid-June. All trays received equal amounts of water so that soils in the low
CO2 treatment were maintained at field capacity. 3. Our results indicate that under high soil fertilities:
(1) intra-specific root-root interactions alone play a relatively insignificant role in determining plant
biomass production within pure Linum populations and (2) the impact of an aggressive species
(Silene) on co-occurring less aggressive species (Linum) becomes more severe under elevated CO2
as a result of amplified interspecific root competition.

KEYWORDS: AMBIENT, ANNUALS, ATMOSPHERIC CO2, C-3, CARBON DIOXIDE,
COMMUNITIES, ECOSYSTEMS, ENRICHMENT, PLANTS, RESPONSES


     71   
Arnone, J.A., and C. Korner. 1993. Influence of elevated co2 on canopy development and red -
far- red ratios in 2-storied stands of ricinus-communis. Oecologia 94(4):510-515.

Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to
differential responses of overstory and understory plants or plant parts. In the long term, seedling
recruitment, competition, and thus population or community structure may be affected. Aside from
the possible differential direct effects of elevated CO2 on photosynthesis and growth, both the
quantity and quality of the light below the overstory canopy could be indirectly affected by CO2-
induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order
to explore such possible interactions, we compared canopy leaf area development, canopy light
extinction and the quality of light beneath overstory leaves of two-storied monospecific stands of
Ricinus communis exposed to ambient (340 mul-1) and elevated (610 mul-1) CO2. Plants in each
stand were grown in a common soil as closed ''artificial ecosystems'' with a ground area of 6.7 m2.
LAI of overstory plants in all ecosystems more than doubled during the experiment but was not
different between CO2 treatments at the end. As a consequence, extinction of photosynthetically
active radiation (PAR) was also not altered. However, under elevated CO2 the red to far-red ratio
(R: FR) measured beneath overstory leaves was 10% lower than in ecosystems treated with ambient
CO2. This reduction was associated with increased thickness of palisade layers of overstory leaves
and appears to be a plausible explanation for the specific enhancement of stem elongation of
understory plants (without a corresponding biomass response) under elevated CO2. Col enrichment
led to increased biomass of overstory plants (mainly stem biomass) but had no effect on understory
biomass. The results of this study raise the possibility of an important indirect effect of elevated CO2
at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio beneath
overstory canopies may affect understory plant development independently of the effects of PAR
extinction.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, CHLOROPHYLL
CONTENT, CLOVER TRIFOLIUM-REPENS, GROWTH, LEAF ANATOMY, LIGHT-QUALITY,
PLANTS, RAIN-FOREST, RESPONSES


     72   
Arnone, J.A., and C. Korner. 1995. Soil and biomass carbon pools in model communities of
tropical plants under elevated co2. Oecologia 104(1):61-71.

The experimental data presented here relate to the question of whether terrestrial ecosystems will
sequester more C in their soils, litter and biomass as atmospheric CO2 concentrations rise. Similar
to our previous study with relatively fertile growth conditions (Korner and Arnone 1992), we
constructed four rather nutrient-limited model communities of moist tropical plant species in
greenhouses (approximately 7 m(2) each). Plant communities were composed of seven species (77
individuals per community) representing major taxonomic groups and various life forms found in the
moist tropics. Two ecosystems were exposed to 340 mu l CO2 l(-1) and two to 610 mu l l(-1) for
530 days of humid tropical growth conditions. In order to permit precise determination of C
deposition in the soil, plant communities were initially established in C-free unwashed quartz sand.
Soils were then amended with known amounts of organic matter (containing C and nutrients).
Mineral nutrients were also supplied over the course of the experiment as timed-release full-balance
fertilizer pellets. Soils represented by far the largest repositories for fixed C in all ecosystems. Almost
5 times more C (ca. 80% of net C fixation) was sequestered in the soil than in the biomass, but this
did not differ between CO2 treatments. In addition, at the whole-ecosystem level we found a
remarkably small and statistically non-significant increase in C sequestration (+4%; the sum of C
accretion in the soil, biomass, litter and necromass). Total community biomass more than quadrupled
during the experiment, but at harvest was, on average, only 8% greater (i.e. 6% per year; n.s.) under
elevated CO2, mainly due to increased root biomass (+15%, P = 0.12). Time courses of leaf area
index of all ecosystems suggested that canopy expansion was approaching steady state by the time
systems were harvested. Net primary productivity (NPP) of all ecosystems - i.e. annual accumulation
of biomass, necromass, and leaf litter (but not plant-derived soil organic matter) - averaged 815 and
910 g m(-2) year(-1) at ambient and elevated CO2, respectively. These NPPs are remarkably similar
to those of many natural moist tropical forested ecosystems. At the same time net productivity of soil
organic matter reached 7000 g dry matter equivalent per m(2) and year (i.e. 3500 g C m(-2) year(-1)).
Very slight yet statistically significant CO2- induced shifts in the abundance of groups of species
occurred by the end of the experiment, with one group of species (Elettaria cardamomum, Ficus
benjamina, F: pumila, Epipremnum pinnatum) gaining slightly, and another group (Ctenanthe
lubbersiana, Heliconia humilis, Cecropia peltata) losing. Our results show that: (1) enormous amounts
of C can be deposited in the ground which are normally not accounted for in estimates of NPP and
net ecosystem productivity; (2) any enhancement of C sequestration under elevated atmospheric CO2
may be substantially smaller than is believed will occur (yet still very important), especially under
growth conditions which permit close to natural NPP; and (3) species dominance in plant
communities is likely to change under elevated CO2, but that changes may occur rather slowly.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, C-3, COMPETITION, DIOXIDE, ENRICHMENT,
ESTUARINE MARSH, GROWTH, NITROGEN, TUSSOCK TUNDRA


     73   
Arnone, J.A., J.G. Zaller, C. Ziegler, H. Zandt, and C. Korner. 1995. Leaf quality and insect
herbivory in model tropical plant- communities after long-term exposure to elevated atmospheric co2.
Oecologia 104(1):72-78.

Results from laboratory feeding experiments have shown that elevated atmospheric carbon dioxide
can affect interactions between plants and insect herbivores, primarily through changes in leaf
nutritional quality occurring at elevated CO2. Very few data are available on insect herbivory in plant
communities where insects can choose among species and positions in the canopy in which to feed.
Our objectives were to determine the extent to which CO2-induced changes in plant communities and
leaf nutritional quality may affect herbivory at the level of the entire canopy. We introduced
equivalent populations of fourth instar Spodoptera eridania, a lepidopteran generalist, to complex
model ecosystems containing seven species of moist tropical plants maintained under low mineral
nutrient supply. Larvae were allowed to feed freely for 14 days, by which time they had reached the
seventh instar. Prior to larval introductions, plant communities had been continuously exposed to
either 340 mu l CO2 l(-1) or to 610 mu l CO2 l(-1) for 1.5 years. No major shifts in leaf nutritional
quality [concentrations of N, total non-structural carbohydrates (TNC), sugar, and starch; ratios of:
C/N, TNC/N, sugar/N, starch/N; leaf toughness] were observed between CO2 treatments for any of
the species. Furthermore, no correlations were observed between these measures of leaf quality and
leaf biomass consumption. Total leaf area and biomass of all plant communities were similar when
caterpillars were introduced. However, leaf biomass of some species was slightly greater - and for
other species slightly less (e.g. Cecropia peltata) - in communities exposed to elevated CO2. Larvae
showed the strongest preference for C. peltata leaves, the plant species that was least abundant in all
communities, and fed relatively littie on plants species which were more abundant. Thus, our results
indicate that leaf tissue quality, as described by these parameters, is not necessarily affected by
elevated CO2 under relatively low nutrient conditions. Hence, the potential importance of CO2-
induced shifts in leaf nutritional quality, as determinants of herbivory, may be overestimated for many
plant communities growing on nutrient-poor sites if estimates are based on traditional laboratory
feeding studies. Finally, slight shifts in the abundance of leaf tissue of various species occurring under
elevated CO2 will probably not significantly affect herbivory by generalist insects. However,
generalist insect herbivores appear to become more dependent on less-preferred plant species in cases
where elevated CO2 results in reduced availability of leaves of a favoured plant species, and this
greater dependency may eventually affect insect populations adversely.

KEYWORDS: ALLOCATION, CARBON-DIOXIDE ATMOSPHERES, CHLOROPHYLL CONTENT,
ECOSYSTEMS, ENRICHMENT, FOREST, GROWTH, JUNONIA-COENIA, LEPIDOPTERA,
RESPONSES


     74   
Arp, W.J. 1991. Effects of source-sink relations on photosynthetic acclimation to elevated CO2.
Plant, Cell and Environment 14(8):869-875.

While photosynthesis of C3 plants is stimulated by an increase in the atmospheric CO2 concentration,
photosynthetic capacity is often reduced after long-term exposure to elevated CO2. This reduction
appears to be brought about by end product inhibition, resulting from an imbalance in the supply and
demand of carbohydrates. A review of the literature revealed that the reduction of photosynthetic
capacity in elevated CO2 was most pronounced when the increased supply of carbohydrates was
combined with small sink size. The volume of pots in which plants were grown affected the sink size
by restricting root growth. While plants grown in small pots had a reduced photosynthetic capacity,
plants grown in the field showed no reduction or an increase in this capacity. Pot volume also
determined the effect of elevated CO2 on the root/shoot ratio: the root/shoot ratio increased when
root growth was not restricted and decreased in plants grown in small pots. The data presented in this
paper suggest that plants growing in the field will maintain a high photosynthetic capacity as the
atmospheric CO2 level continues to rise.

KEYWORDS: ATMOSPHERIC CO2, CARBOHYDRATE CONTENT, CARBON-DIOXIDE
ENRICHMENT, CO2- ENRICHMENT, COTTON PLANTS, LEAVES, LIQUIDAMBAR-
STYRACIFLUA, LONG-TERM EXPOSURE, PINUS-TAEDA SEEDLINGS, PLANT GROWTH


     75   
Arp, W.J., and B.G. Drake. 1991. Increased photosynthetic capacity of scirpus-olneyi after 4 years
of exposure to elevated co2. Plant, Cell and Environment 14(9):1003-1006.

While a short-term exposure to elevated atmospheric CO2 induces a large increase in photosynthesis
in many plants, long-term growth in elevated CO2 often results in a smaller increase due to reduced
photosynthetic capacity. In this study, it was shown that, for a wild C3 species growing in its natural
environment and exposed to elevated CO2 for four growing seasons, the photosynthetic capacity has
actually increased by 31%. An increase in photosynthetic capacity has been observed in other species
growing in the field, which suggests that photosynthesis of certain field grown plants will continue
to respond to elevated levels of atmospheric CO2.

KEYWORDS: ATMOSPHERIC CO2, C-3, CARBON DIOXIDE, ESTUARINE MARSH, FIELD,
INSITU, LEAVES, PLANTS


     76   
Arp, W.J., B.G. Drake, W.T. Pockman, P.S. Curtis, and D.F. Whigham. 1993. Interactions
between C-3 and C-4 salt-marsh plant-species during 4 years of exposure to elevated atmospheric
co2. Vegetatio 104:133-143.

Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3
pathway but less of plants with the C4 pathway. An increase in the CO2 concentration can therefore
be expected to change the competitive interactions between C3 and C4 species. The effect of long
term exposure to elevated CO2 (ambient CO2 concentration + 340 mumol CO2 mol-1) on a salt
marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass
of the C3 sedge Scirpus olneyi growing in a pure stand, while the biomass of the C4 grass Spartina
patens in a monospecific community was not affected. In the mixed C3/C4 community the C3 sedge
showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species
declined. The C4 grass Spartina patens dominated the higher areas of the salt marsh, while the C3
sedge Scirpus olneyi was most abundant at the lower elevations, and the mixed community occupied
intermediate elevations. Scirpus growth may have been restricted by drought and salt stress at the
higher elevations, while Spartina growth at the lower elevations may be affected by the higher
frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allows
Scirpus to grow at higher elevations where it in turn may affect the growth of Spartina.

KEYWORDS: COMMUNITIES, COMPETITION, ENRICHMENT, FIELD, GRASS, GROWTH,
LIQUIDAMBAR- STYRACIFLUA, PERENNIALS, PINUS-TAEDA SEEDLINGS, STRESS


     77   
Arp, W.J., J.E.M. Van Mierlo, F. Berendse, and W. Snijders. 1998. Interactions between
elevated CO2 concentration, nitrogen and water: effects on growth and water use of six perennial
plant species. Plant, Cell and Environment 21(1):1-11.

Two experiments are described in which plants of six species mere grown for one full season in
greenhouse compartments with 350 or 560 mu mol mol(-1) COL. In the first experiment two levels
of nitrogen supply were applied to study the interaction between CO2 and nitrogen, In the second
experiment two levels of mater supply were added to the experimental set-up to investigate the three-
way interaction between CO2, nitrogen and water, Biomass and biomass distribution were determined
at harvests, while water use and soil moisture were monitored throughout the experiments, In both
experiments a positive effect of CO2 on growth was found at high nitrogen concentrations but not
at low nitrogen concentrations, However, plants used much less water in the presence of low nitrogen
concentrations, Drought stress increased the relative effect of elevated CO2 on growth, Available soil
moisture was used more slowly at high CO2 during drought or at high nitrogen concentrations, while
at low nitrogen concentrations decreased water use resulted in an increase in soil moisture, The
response to the treatments was similar in all the species used, Although potentially faster growing
species appeared to respond better to high CO2 when supplied with a high level of nitrogen,
inherently slow-growing species were more successful at low nitrogen concentrations.

KEYWORDS: ACCLIMATION, C-3, CARBON DIOXIDE, COTTON, DRY-MATTER,
ENRICHMENT, HEATHLAND ECOSYSTEMS, NUTRITION, STRESS, YIELD


     78   
Ashenden, T.W., R. Baxter, and C.R. Rafarel. 1992. An inexpensive system for exposing plants
in the field to elevated concentrations of co2. Plant, Cell and Environment 15(3):365-372.

An inexpensive, potentially mobile field exposure system is described which may be easily constructed
by a small workshop. It may be operated as an open-top with a frustrum or covered with a
polycarbonate 'lid'. The system is cost-effective for CO2 exposure work because the small size allows
provision of CO2-enriched atmospheres over prolonged periods at relatively low cost. A preliminary
assessment of the chambers has been made and concentrations can be maintained at +/- 6% for a
target atmosphere of 680 cm3 m-3 CO2 under normal operating conditions. Other chamber
environmental conditions are reported.

KEYWORDS: AIR-POLLUTION, CHAMBERS


     79   
Asner, G.P., T.R. Seastedt, and A.R. Townsend. 1997. The decoupling of terrestrial carbon and
nitrogen cycles. BioScience 47(4):226-234.

KEYWORDS: ATMOSPHERIC CARBON, BIOMASS, CO2, FOREST ECOSYSTEMS, GLOBAL
CHANGE, GRASSLAND, LAND-USE, LONG-TERM, NUTRIENT LIMITATION, SOILS


     80   
Atkin, O.K., M. Schortemeyer, N. McFarlane, and J.R. Evans. 1999. The response of fast- and
slow-growing Acacia species to elevated atmospheric CO2: an analysis of the underlying components
of relative growth rate. Oecologia 120(4):544-554.

In this study we assessed the impact of elevated CO2 with unlimited water and complete nutrient on
the growth and nitrogen economy of ten woody Acacia species that differ in relative growth rate
(RGR). Specifically. we asked whether fast- and slow-growing species systematically differ in their
response to elevated CO2. Four slow-growing species from semi- arid environments (Acacia aneura,
A. colei, A. coriacea and A. tetragonophylla) and six fast-growing species from mesic environments
(Acacia dealbata, A. implexa, A. mearnsii, A. melanoxylon, A. irrorata and A. saligna) were grown
in glasshouses with either ambient (similar to 350 ppm) or elevated (similar to 700 ppm) atmospheric
CO2. All species reached greater final plant mass with the exception of A. aneura, and RGR,
averaged across all species, increased by 10% over a 12-week period when plants were exposed to
elevated CO2. The stimulation of RGR was evident throughout the 12-week growth period. Elevated
CO2 resulted in less foliage area per unit foliage dry mass, which was mainly the result of an increase
in foliage thickness with a smaller contribution from greater dry matter content per unit fresh mass.
The net assimilation rate (NAR, increase in plant mass per unit foliage area and time) of the plants
grown at elevated CO2 was higher in all species (on average 30% higher than plants in ambient CO2)
and was responsible for the increase in RGR. The higher NAR was associated with a substantial
increase in foliar nitrogen productivity in all ten Acacia species. Plant nitrogen concentration was
unaltered by growth at elevated CO2 for the slow-growing Acacia species, but declined by 10% for
faster- growing species. The rate of nitrogen uptake per unit root mass was higher in seven of the
species when grown under elevated CO2, and leaf area per unit root mass was reduced by elevated
CO2 in seven of the species. The absolute increase in RGR due to growth under elevated CO2 was
greater for fast- than for slow-growing Acacia species.

KEYWORDS: ALPINE, CARBON DIOXIDE, EFFICIENCY, FOREST, GRASSLAND, LEAF-AREA,
NITROGEN ECONOMY, PLANTS, TREES


     81   
Atkinson, C.J., and J.M. Taylor. 1996. Effects of elevated CO2 on stem growth, vessel area and
hydraulic conductivity of oak and cherry seedlings. New Phytologist 133(4):617-626.

Plants of Quercus robur L. and Prunus avium L. x P. pseudocerasus Lind, were grown in either
ambient (350 vpm) or elevated (700 vpm) CO2. The intention was to examine the effects of elevated
CO2 on the morphological and functional development of the stem. The relationships between stem
longitudinal transport capacity and development were explored in several ways: stem hydraulic
function was related to stem cross-sectional area, supplied leaf area and total stem vessel lumen area.
The mean total vessel number and the total vessel lumen area per stem, for both species, was
determined from basal sections of the xylem. In Prunus seedlings grown in different CO2
concentrations there was no significant change in the mean vessel size or number of vessels per stem.
Quercus seedlings grown at elevated CO2 showed a significant increase in both vessel number and
mean vessel size. When total stem vessel area was calculated it had increased twofold for Quercus
plants grown at elevated CO2. Measured stem hydraulic conductivity was shown to increase linearly
with supplied leaf area, except in Quercus seedlings grown at elevated CO2. Stem hydraulic
conductivity for Quercus seedlings grown at elevated CO2 did not change with the increase in
supplied leaf area. This absence of an increase in the stem hydraulic conductivity appeared to relate
to changes in total stem vessel area. Despite total stem vessel area being greater at elevated CO2 than
that at ambient, it similarly did not increase with supplied leaf area. The implications of this change
in the relationship between leaf area and stem hydraulic conductivity are discussed with respect to
the possible effects the change might have on the plant's water balance. The possible causes and
significance of the changes in xylem anatomy are also considered in relation to direct effects caused
by CO2 or indirect effects on changes in cambial maturity and tree growth.

KEYWORDS: ATMOSPHERIC CO2, CAVITATION, DIAMETER, EMBOLISM, TRANSPIRATION,
TREES, WATER-STRESS, WOODY-PLANTS, XYLEM


     82   
Atkinson, C.J., J.M. Taylor, D. Wilkins, and R.T. Besford. 1997. Effects of elevated CO2 on
chloroplast components, gas exchange and growth of oak and cherry. Tree Physiology 17(5):319-
325.

Specific chloroplast proteins, gas exchange and dry matter production in oak (Quercus robur L.)
seedlings and clonal cherry (Prunus avium L. x pseudocerasus Lind.) plants were measured during
19 months of growth in climate-controlled greenhouses at ambient (350 vpm) or elevated (700 vpm)
CO2. In both species, the elevated CO2 treatment increased the PPFD saturated-rate of
photosynthesis and dry matter production. After two months at elevated CO2, Prunus plants showed
significant increases in leaf (55%) and stem (61%) dry mass but not in root dry mass. However, this
initial stimulation was not sustained: treatment differences in net assimilation rate (A) and plant dry
mass were less after 10 months of growth than after 2 months of growth, suggesting acclimation of
A to elevated CO2 in Prunus. In contrast, after 10 months of growth at elevated CO2, leaf dry mass
of Quercus increased (130%) along with shoot (356%) and root (219%) dry mass, and A was also
twice that of plants grown and measured at ambient CO2. The amounts of Rubisco and the thylakoid-
bound protein cytochrome f were higher in Quercus plants grown for 19 months in elevated CO2 than
in control plants, whereas in Prunus there was less Rubisco in plants grown for 19 months in elevated
CO2 than in control plants. Exposure to elevated CO2 for 10 months resulted in increased mean leaf
area in both species and increased abaxial stomatal density in Quercus. There was no change in leaf
epidermal cell size in either species in response to the elevated CO2 treatment. The lack of
acclimation of photosynthesis in oak grown at elevated CO2 is discussed in relation to the production
and allocation of dry matter. We propose that differences in carbohydrate utilization underlie the
differing long-term CO2 responses of the two species.

KEYWORDS: ATMOSPHERIC CO2, BIOCHEMISTRY, CARBON DIOXIDE, LEAF
DEVELOPMENT, PHOTOSYNTHETIC ACCLIMATION, PRODUCTIVITY, PRUNUS-AVIUM,
RESPONSES, TOMATO PLANTS, TREES


     83   
Atkinson, C.J., P.A. Wookey, and T.A. Mansfield. 1991. Atmospheric-pollution and the sensitivity
of stomata on barley leaves to abscisic-acid and carbon-dioxide. New Phytologist 117(4):535-541.

Spring barley (Hordeum vulgare L. cv. Klaxon) plants were exposed to mixtures of SO2 + NO2 (at
concentrations of 24-35 nl l-1 of each gas, depending upon fumigation system), or to charcoal-
filtered, or unfiltered ambient air during the period in which the second, and subsequent, leaves were
emerging. The ability of individual detached leaves to regulate water loss was then examined after
terminating the pollutant treatment. Observations of diurnal changes in stomatal resistance of well-
watered plants, using a viscous flow porometer, failed to indicate any major alterations which could
be attributed to prior exposure to SO2 + NO2. By contrast, when an ABA solution (10(-1) mol m-3)
was applied to detached leaves, the stomata of polluted plants were less responsive than plants
previously exposed to control air. The dynamics of the observed responses strongly implicated
impaired physiology of the guard cells rather than mechanical changes in the epidermis that might,
for example, result from damage to the cuticle. Stomatal closure was considerably slower in polluted
leaves compared with the controls. This decline in responsiveness to ABA was observed using leaves
excised from well-watered plants and in the absence of any externally visible injury. The ability of
stomata to respond to a range of CO2 concentrations from 195- 735-mu-mol mol-1 was also
examined using individual leaves, attached to the plant, in an environmentally controlled cuvette. Here
the stomata of leaves which had been fumigated with SO2 + NO2 behaved in a similar manner to the
non-fumigated leaves, both showing closure in elevated CO2 concentrations.

KEYWORDS: CONDUCTANCE, FUMIGATION, NITROGEN-DIOXIDE, NO2, PLANTS, SO2,
SULFUR-DIOXIDE, SYSTEM, WHEAT LEAVES


     84   
Austin, M.P. 1992. Modeling the environmental niche of plants - implications for plant community
response to elevated CO2 levels. Australian Journal of Botany 40(4-5):615-630.

No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant
communities in response to elevated CO2. However indirect effects of CO2 via temperature increases
can be tested by reference to natural analogues. Physiologists, vegetation modellers of climate change
and community ecologists assume very different temperature responses for plants. Physiologists often
assume a skewed non-monotonic curve with a tail towards low temperatures, forest modellers using
FORET type models, a symmetric curve, and community ecologists a skewed response with a tail
towards high temperatures. These assumptions are reviewed in relation to niche theory, and recent
propositions concerning the continuum concept. Confusion exists between the different approaches
over the shape of response curves to temperature. Distinctions need to be made between responses
due to growth (physiological response), potential fitness (fundamental niche) and observed
performance (realised niche). These types of response should be quantified and related to each other
if process-models are to be tested for predictive success by reference to naturally occurring
communities and temperature gradients. An example of a statistical method for quantifying the
realised environmental niche respone of a species to temperature is provided. It is based on
generalised linear modelling (GLM) of presence/absence data on Eucalyptus fastigata for 8377 sites
in southern New South Wales, Australia. Seven environmental variables or factors are considered:
mean annual temperature, mean annual rainfall, mean monthly solar radiation, topographic position,
rainfall seasonality, lithology, and soil nutrient status. The temperature response is modelled with a
beta-function, log y = a + alpha log (t - a) + delta log (b - t), where t is temperature and letters are
parameters. The probability of occurrence is shown to be a skewed function of mean annual
temperature. Any process-models of climate change for vegetation incorporating temperature changes
due to elevated CO2 must be capable of generating such realised environmental niche responses for
species.

KEYWORDS: DISTRIBUTIONS, ECOSYSTEMS, FIELD, FOREST, GRADIENTS, GROWTH,
NORTH-AMERICA, SIMULATION, SPECIES RESPONSE, VEGETATION


     85   
Awmack, C.S., R. Harrington, and S.R. Leather. 1997. Host plant effects on the performance of
the aphid Aulacorthum solani (Kalt.) (Homoptera : Aphididae) at ambient and elevated CO2. Global
Change Biology 3(6):545-549.

In future elevated CO2 environments, chewing insects are likely to perform less well than at present
because of the effects of increased carbon fixation on their host plants. When the aphid, Aulacorthum
solani was reared on bean (Vicia faba) and tansy (Tanacetum vulgare) plants under ambient and
elevated CO2, performance was enhanced on both hosts at elevated CO2. The nature of the response
was different on each plant species suggesting that feeding strategy may influence an insect's response
to elevated CO2. On bean, the daily rate of production of nymphs was increased by 16% but there
was no difference in development time, whereas on tansy, development time was 10% shorter at
elevated CO2 but the rate of production of nymphs was not affected. The same aphid clone therefore
responded differently to elevated CO2 on different host plants. This increase in aphid performance
could lead to larger populations of aphids in a future elevated CO2 environment.

KEYWORDS: ALLOCATION, ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION,
ENRICHMENT, INSECT HERBIVORE INTERACTIONS, LEPIDOPTERA, NOCTUIDAE,
PHYTOCHEMISTRY, POPULATIONS, RESPONSES


     86   
Azconbieto, J., M.A. Gonzalezmeler, W. Doherty, and B.G. Drake. 1994. Acclimation of
respiratory o-2 uptake in green tissues of field-grown native species after long-term exposure to
elevated atmospheric co2. Plant Physiology 106(3):1163-1168.

C-3 and C-4 plants were grown in open-top chambers in the field at two CO2 concentrations, normal
ambient (ambient) and normal ambient + 340 mu L L(-1) (elevated). Dark oxygen uptake was
measured in leaves and stems using a liquid-phase Clark-type oxygen electrode. High CO2 treatment
decreased dark oxygen uptake in stems of Scirpus olneyi (C-3) and leaves of Lindera benzoin (C-3)
expressed on either a dry weight or area basis. Respiration of Sparfina patens (C-4) leaves was
unaffected by CO2 treatment. Leaf dry weight per unit area was unchanged by CO2, but respiration
per unit of carbon or per unit of nitrogen was decreased in the C-3 species grown at high CO2. The
component of respiration in stems of S. olneyi and leaves of L. benzoin primarily affected by long-
term exposure to the elevated CO2 treatment was the activity of the cytochrome pathway. Elevated
CO2 had no effect on activity and capacity of the alternative pathway in S. olneyi. The cytochrome
c oxidase activity, assayed in a cell-free extract, was strongly decreased by growth at high CO2 in
stems of S. olneyi but it was unaffected in S. patens leaves. The activity of cytochrome c oxidase and
complex III extracted from mature leaves of L. benzoin was also decreased after one growing season
of plant exposure to elevated CO2 concentration. These results show that in some C-3 species
respiration will be reduced when plants are grown in elevated atmospheric CO2. The possible
physiological causes and implications of these effects are discussed.

KEYWORDS: CARBOHYDRATE STATUS, CARBON-DIOXIDE ENRICHMENT, DARK
RESPIRATION, EFFLUX, INHIBITION, LEAF RESPIRATION, LEAVES, PHOTOSYNTHESIS,
PLANTS, WORLD


     87   
Azevedo, R.A., R.M. Alas, R.J. Smith, and P.J. Lea. 1998. Response of antioxidant enzymes to
transfer from elevated carbon dioxide to air and ozone fumigation, in the leaves and roots of wild-
type and a catalase-deficient mutant of barley. Physiologia Plantarum 104(2):280-292.

A catalase-deficient mutant (RPr 794) and the wild-type (cv. Maris Mink) barley (Hordeum vulgare
L.) counterpart. were grown for 3 weeks in high CO2 (0.7%) and then transferred to air and ozone
(120 nl l(-1)) in the light and shade for a period of 3 days. Leaves and roots were analysed for
catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD. EC 1.15.1.1) and glutathione reductase
(GR, EC 1.6.4.2) activities. CAT activity in the leaves of the RPr 79/4 catalase-deficient mutant was
around 5 10% of that determined in Maris Mink. but in the roots, both genotypes contained
approximately the same levels of activity. CAT activity in Maris Mink increased in the leaves after
transferring plants from 0.7% CO2 to air or ozone, reaching a maximum of 5-fold. after 4 days in
shade and ozone. For the catalase-deficient mutant. only small increases in CAT activity were
observed in light/air and light/ozone treatments. In the roots. CAT activity decreased consistently in
both genotypes, after plants were transferred from 0.7% CO2. The total soluble SOD activity in the
leaves and roots of both genotypes increased after plants were transferred from 0.7% CO2. The
analysis of SOD isolated from leaves following non- denaturing PAGE, revealed the presence of up
to eight SOD isoenzymes classified as Mn-SOD or Cu/Zn-SODs: Fr-SOD was not detected.
Significant changes in Mn- and Cu/Zn-SOD isoenzymes were observed; however, they could not
account for the increase in total SOD activity. Ill leaves. GR activity also increased in Maris Mink and
RPr 79/4, following transfer from 0.7% CO2: however, no constant pattern could be established,
while in roots, GR activity was reduced after 4 days of the treatments. The data suggest that elevated
CO2 decreases oxidative stress in barley leaves and that soluble CAT and SOD activities increased
rapidly after plants were transferred from elevated CO2. irrespective of the treatment (light, shade,
air or ozone).

KEYWORDS: ARABIDOPSIS-THALIANA, ASCORBATE PEROXIDASE, DIFFERENTIAL
RESPONSE, GLUTAMINE-SYNTHETASE, GLUTATHIONE-REDUCTASE, HORDEUM
VULGARE L, NICOTIANA-PLUMBAGINIFOLIA L, OXIDATIVE STRESS, SUPEROXIDE-
DISMUTASE, TRANSGENIC TOBACCO


     88   
Baattrup-Pedersen, A., and T.V. Madsen. 1999. Interdependence of CO2 and inorganic nitrogen
on crassulacean acid metabolism and efficiency of nitrogen use by Littorella uniflora (L.) Aschers.
Plant, Cell and Environment 22(5):535-542.

The hypothesis is tested that crassulacean acid metabolism (CAM) in isoetids is a mechanism which
not only conserves inorganic carbon but also plays a role in nitrogen economy of the plants, This
hypothesis was tested in an outdoor experiment, where Littorella uniflora (L,) Aschers, were grown
at two CO2 and five inorganic nitrogen concentrations in a crossed factorial design. The growth of
Littorella responded positively to enhanced nitrogen availability at high but not at low CO2 indicating
that growth was limited by nitrogen at high CO2 only. For the nitrogen-limited plants, the capacity
for CAM (CAM(cap)) increased with the degree of nitrogen limitation of growth and an inverse
coupling between CAM and tissue-N was found. Although this might indicate a role of CAM in
economizing on nitrogen in Littorella, the hypothesis was rejected for the following reasons: (1)
although CAM(cap) was related to tissue-N no relationship between tissue-N and ambient CAM
activity (CAM(ambient)) was found whereas a close relationship would be expected if CAM was
regulated by nitrogen availability; (2) the photosynthetic nitrogen use efficiency for high CO2-grown
plants declined with increased CAM(ambient) and with CAM(cap); and (3) growth per unit tissue-N
per unit time declined with increased CAM(ambient) and CAM(cap).

KEYWORDS: ACCLIMATION, ACQUISITION, AQUATIC CAM PLANTS, CARBON
ASSIMILATION, GROWTH, MACROPHYTES, PHOTOSYNTHETIC PERFORMANCE


     89   
Bacanamwo, M., and J.E. Harper. 1997. Response of a hypernodulating soybean mutant to
increased photosynthate supply. Plant Science 124(2):119-129.

Growth chamber studies were conducted to determine if increased photoassimilate supply, through
light enhancement and CO2 enrichment, could reverse the deleterious plant growth and enhance
nodule function traits of NOD1-3, a hypernodulating mutant of Williams. Both light enhancement and
CO2 enrichment increased nodule number, acetylene reduction activity plant(-1) (but not specific
activity) and dry matter accumulation in all tissues in both genotypes. Total biomass and specific
nitrogenase activity were always less in the mutant than in Williams 82, indicating that the inferiority
of the mutant may not be reversed by enhanced photoassimilate supply. Under all growth conditions,
the mutant allocated relatively more photosynthate to nodules and less photosynthate to roots,
compared to the control. Despite this, the decreased growth of the mutant relative to the control was
not solely attributable to excessive nodulation of the mutant, since decreased growth was observed
even on uninoculated plants. It is suggested that light enhancement and CO2 enrichment may have
stimulated nodulation through increased photosynthate supply, independent of the nodulation
autoregulatory signal. (C) 1997 Elsevier Science Ireland Ltd.

KEYWORDS: ACETYLENE-REDUCTION ASSAY, CARBON DIOXIDE, CULTIVAR ENREI, CV
BRAGG, GLYCINE-MAX, NITROGENASE ACTIVITY, NODULATION MUTANTS, ROOT
NODULE ACTIVITY, SUPERNODULATING MUTANT, WILD-TYPE


     90   
Bachelet, D., D. Brown, M. Bohm, and P. Russell. 1992. Climate change in thailand and its
potential impact on rice yield. Climatic Change 21(4):347-366.

In Thailand, the world's largest rice exporter, rice constitutes a major export on which the economy
of the whole country depends. Climate change could affect rice growth and development and thus
jeopardize Thailand's wealth. Current climatic conditions in Thailand are compared to predictions
from four general circulation models (GCMs). Temperature predictions correlate well with the
observed values. Predictions of monthly rainfall correlate poorly. Virtually all models agree that
significant increases in temperature (from 1 to 7-degrees-C) will occur in the region including
Thailand following a doubling in atmospheric carbon dioxide (CO2) concentration. The regional
seasonality and extent of the rise in temperature varies with each model. Predictions of changes in
rainfall vary widely between models. Global warming should in principle allow a northward expansion
of rice-growing areas and a lengthening of the growing season now constrained by low temperatures.
The expected increase in water-use efficiency due to enhanced CO2 might decrease the water deficit
vulnerability of dryland rice areas and could make it possible to slightly expand them.

KEYWORDS: AMBIENT


     91   
Bachelet, D., and C.A. Gay. 1993. The impacts of climate change on rice yield - a comparison of
4 model performances. Ecological Modelling 65(1-2):71-93.

Increasing concentrations of carbon dioxide (CO2) and other greenhouse gases are expected to
modify the climate of the earth in the next 50-100 years. Mechanisms of plant response to these
changes need to be incorporated in models that predict crop yield estimates to obtain an
understanding of the potential consequences of such changes. This is particularly important in Asia
where demographic forecasts indicate that rice supplies worldwide will need to increase by 1.6%
annually to the year 2000 to match population growth estimates. The objectives of this paper are (1)
to review the major hypotheses and/or experimental results regarding rice sensitivity to climate
change and (2) to evaluate the suitability of existing rice models for assessing the impact of global
climate change on rice production. A review of four physiologically-based rice models (RICEMOD,
CERES-Rice, MACROS, RICESYS) illustrates their potential to predict rice responses to elevated
CO2 and increased temperature. RICEMOD does not respond to increases in CO2 nor to large
increases in temperature. Both MACROS and CERES (wetland rice) responses to temperature and
CO2 agree with recent experimental data. RICESYS is an ecosystem model which predicts herbivory
and inter-species competition between rice and weeds but does not respond to CO2. Its response to
increasing temperature also agrees with experimental data.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, CROP PLANTS,
DRY-MATTER PRODUCTION, DYNAMICS, ECOSYSTEMS, PLANT GROWTH, RESPONSES,
SIMULATION-MODEL, TEMPERATURE


     92   
Backhausen, J.E., and R. Scheibe. 1999. Adaptation of tobacco plants to elevated CO2: influence
of leaf age on changes in physiology, redox states and NADP-malate dehydrogenase activity. Journal
of Experimental Botany 50(334):665-675.

Transgenic tobacco plants (Nicotiana tabacum L. cv. Xanthi) with altered chloroplast NADP-malate
dehydrogenase (NADP-MDH) content were grown under ambient or under doubled atmospheric
CO2 in order to analyse the effect of elevated CO2 on the redox state of the chloroplasts. Since large
differences exist between the individual leaves of tobacco plants, gas exchange characteristics,
enzyme capacities and metabolite contents were measured separately for each leaf of the plants, Large
variations between leaves of different age were found in nearly every parameter analysed, and the
differences between younger and older leaves were, in most cases, larger than the differences between
comparable leaves at ambient or elevated CO2. For all parameters (chlorophyll fluorescence, P700
reduction, NADP-MDH activation) that are indicative for the redox situation in the electron transport
chains and in the chloroplast stroma, more oxidized values were determined under elevated CO2. The
increased redox state of ferredoxin, observed at ambient conditions in the NADP-MDH-under-
expressing plants, disappeared under elevated CO2. It was concluded that the reduced rate of
photorespiration under elevated CO2 decreases the amount of excess electrons. Interestingly, this
lowered not only the activation state of NADP-MDH, but also the expression of the enzyme in the
wild-type plants. The results are discussed with respect to a possible interaction between stromal
reduction state and gene expression.

KEYWORDS: ACCLIMATION, CHLOROPHYLL FLUORESCENCE, DEVELOPMENTAL-
CHANGES, EXPRESSION, ISOLATED SPINACH- CHLOROPLASTS, LEAVES,
PHOTOSYNTHETIC ELECTRON-TRANSPORT, QUANTUM YIELD, SATURATING LIGHT,
TRANSCRIPTION FACTOR


     93   
Badger, M. 1992. Manipulating agricultural plants for a future high CO2 environment. Australian
Journal of Botany 40(4-5):421-429.

This paper discusses the potential ways in which C3 plant performance may benefit from a future
high-CO2 environment. These include increases in the efficiencies for light, nitrogen and water
utilisation, particularly at elevated temperatures, resulting from the improvement which will occur in
the performance of the primary carboxylating enzyme, Rubisco. However, while growth experiments
at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the potential
gains are greatly ameliorated by a redistribution of plant resources. This primarily occurs via a
reduction in the leaf area ratio which offsets increases in the net assimilation rate. In addition, there
may be an overcommitment of nitrogen in key photosynthetic components such as Rubisco and the
thylakoid electron transport system. It is concluded that plants may not be genetically adapted to
optimise their growth and performance at elevated CO2 and that consideration should be given to
exploring avenues for manipulating plants for more optimal responses. Targets for improvement of
growth at elevated CO2 include (1) altering source-sink relations; (2) improving the redistribution
of nitrogen between the photosynthetic machinery and the rest of the plant; and (3) changing the
response of stomata to CO2 and humidity to increase water-use efficiency even further than is
currently predicted.

KEYWORDS: ACCLIMATION, C-3, CARBON DIOXIDE, DEPENDENCE, GROWTH,
PHOTOSYNTHESIS, RESPONSES, TEMPERATURE, TRANSPIRATION


     94   
Badiani, M., A. Dannibale, A.R. Paolacci, F. Miglietta, and A. Raschi. 1993. The antioxidant
status of soybean (glycine-max) leaves grown under natural co2 enrichment in the field. Australian
Journal of Plant Physiology 20(3):275-284.

The effects of progressively higher CO2 levels on the foliar antioxidant status were studied by
growing soybean (Glycine max Merrill cv. Cresir) plants at decreasing distances from natural CO2
sources of geothermal origin in central Italy. When compared with neighbouring controls grown
under normal CO2 concentration (C), soybean leaves grown at 2 x C, 7 x C and more than 20 x C
showed a substantial reduction in the size of ascorbate pool and in the activity of Cu,Zn-superoxide
dismutase; both the content of ascorbic acid and the activity of ascorbate peroxidase declined at 2 x
C and 7 x C and recovered to the control values at 20 x C. The foliar titre of glutathione disulfide and
the activities of glutathione disulfide reductase and Mn-superoxide dismutase progressively increased
as CO2 concentration increased in ambient air. The results obtained suggest that the immanent risk
of dioxygen toxicity associated with photosynthetic electron flow could be reduced in the presence
of high CO2 levels. On the other hand, depending on both the CO2 exposure regimes and the cell
compartment considered, high CO2 could promote oxidative processes which cause GSH oxidation
and require an enhanced cellular ability to scavenge superoxide anion and hydrogen peroxide.

KEYWORDS: ACCUMULATION, EXCESS SULFUR, FLOW, PLANTS, RESPIRATION,
TEMPERATURE


     95   
Badiani, M., A.R. Paolacci, A. Fusari, I. Bettarini, E. Brugnoli, M. Lauteri, F. Miglietta, and
A. Raschi. 1998. Foliar antioxidant status of plants from naturally high-CO2 sites. Physiologia
Plantarum 104(4):765-771.

We compared the foliar antioxidant status of native Agrostis stolonifera L. communities growing at
two distinct CO2-enriched sites of geothermal origin (E) and at a control field location with normal
CO2. Compared to the control, plants from both E- sites showed an increased size of the GSH pool,
essentially due to enhanced GSSG levels, and a consequent decrease in the ratio between reduced and
oxidised glutathione forms. Such differences were maintained and even enhanced in the vegetatively-
propagated progenies of control and E-plants, grown under both greenhouse conditions and normal
CO2 levels. The above results confirmed previous observations on native and crop plants exposed
to elevated CO2 It is therefore suggested that changes in the glutathione redox balance might be of
adaptive significance under conditions of permanent exposure to high CO2.

KEYWORDS: ACTIVE OXYGEN, DETOXIFICATION, DROUGHT STRESS, ELEVATED CO2,
ENZYMES, EXCESS SULFUR, GLUTATHIONE, GLYCINE, LEAVES, PICEA-ABIES


     96   
Bailey, S., J. Rebbeck, and K.V. Loats. 1999. Interactive effects of elevated ozone plus carbon
dioxide on duckweeds exposed in open-top chambers. Ohio Journal of Science 99(2):19-25.

The response of Lemna minor L. and Spirodela polyrhiza (L.) Schleiden to projected future ambient
levels of O-3 and CO2 was studied under field conditions. The two duckweed species were treated
with either charcoal-filtered air (CF), ambient O-3 (lXO(3)), tn ice ambient O-3 (2XO(3)), twice
ambient CO2 plus twice ambient O-3 (2XCO(2)+2XO(3)), or chamberless open-air (OA). Two
experiments were conducted. In Experiment I, L. minor was treated for 15 d with a cumulative O-3
exposure of 14.4 ppm.h. No O-3 effects were observed during Experiment I. Dry weight of individual
fronds and photosynthesis per frond increased in L minor exposed to 2XCO(2)+2XO(3)(-) air. In
Experiment II after 25 d of treatment (cumulative O-3 exposure of 16.2 ppm h), negative effects of
2XO(3) on the photosynthetic and growth rates of L. minor were observed. Dark respiration of L
minor significantly increased in 2XO(3)-air compared with controls, but declined significantly in
2XCO(2)+2XO(3)-air compared to those grown in 2XO(3)-air. Photosynthesis and drg weight per
frond increased in 2XCO(2)+2XO(3)-air when compared with all other treatments. Measurement of
A/C-i (assimilation versus intercellular CO2 concentration) curves in L. minor showed a significant
reduction in carboxylation efficiency and maximum rates of photosynthesis in 2XCO(2)+2XO(3)-air
compared with other treatments when expressed per weight. No differences in carboxylation
efficiency were detected between treatments when expressed per frond. After 25 d of treatment,
photosynthesis (per frond) and dry weight of S. polyrhiza were reduced in 2XO(3)-air, but final frond
number was unaffected. Dark respiration of S. polyrhiza was unaffected in 2XO(3)(-) air, but when
exposed to 2XCO(2)+2XO(3)-air, it declined significantly. Although S. polyrhiza photosynthesis per
frond increased in 2XCO(2)+2XO(3)-air, dry weight was unaffected when compared with all other
treatments. Only when comparisons were made between S. polyrhiza grown in 2XCO(2)+2XO(3)-air
and 2XO(3)-air, were significant increases in dry weight observed. The addition of 2XCO(2) to
2XO(3)-air resulted in amelioration of negative O-3 effects for most responses for both duckweed
species.

KEYWORDS: ASPEN CLONES, ATMOSPHERIC CO2, CO2 CONCENTRATION, FIELD,
GROWTH, O-3, PHASEOLUS-VULGARIS L, PHOTOSYNTHETIC RESPONSES, PLANTS,
SULFUR-DIOXIDE


     97   
Baille, M., R. RomeroAranda, and A. Baille. 1996. Gas-exchange responses of rose plants to CO2
enrichment and light. Journal of Horticultural Science 71(6):945-956.

This paper describes the response of gas exchange rates and water use efficiency of rose plants, by
means of the characterization in situ and the analysis of the response of photosynthesis, transpiration
and water use efficiency of whole plants to CO2 enrichment under the irradiance conditions prevailing
in greenhouses of southern France. Net CO2 assimilation (A(n)) and transpiration (E) of whole rose
plants (Rosa hybrida, cv. Sonia) were measured during winter and spring periods. The response of
A(n) to light and CO2 were fitted to a double hyperbola function (r(2) = 0.84). Maximum net
assimilation rate (A(nmax)), light and CO2 utilization efficiencies (alpha(1), alpha(c)) as well as light
and CO2 compensation points (Gamma(1), Gamma(c)) were calculated for the whole plant and
compared with leaf and canopy data in the literature. The whole-plant characteristics generally had
values intermediate between those related to leaf and canopy. Light saturation at subambient air CO2
concentration (C-a) was reached for relatively low PFFD values (300 mu mol m(-2) s(- 1)), whereas
at ambient and enriched C-a light saturation occurs for PPFD approximate to 1000 mu mol m(-2) s(-
1). Doubling C-a from 350 to 700 mu mol mol(-1) increased A(nmax) and alpha(1) by respectively
40% and 30%, while reducing Gamma(1) by 27%. A threefold increase of C-a from 350 to 1050 mu
mol mol(-1) induced a reduction of 20% of E. Instantaneous transpirational water use efficiency,
WUE (=A(n)/E), is relatively insensitive to PPFD, although a slight decrease with PPFD is observed
at high CO2 concentration, but shows marked variations with C-a and leaf to air vapour pressure
deficit (D- 1). Increase of C-a from 350 to 1000 mu mol mol(-1) gave about 50% increase in WUE.
Increase of D-1 from 0 to 2 kPa induced 30% decrease in WUE at ambient C-a and 50% decrease
at 1000 mu mol mol(-1).

KEYWORDS: CARBON DIOXIDE, CROP, LEAF CONDUCTANCE, LEAVES, NET
PHOTOSYNTHESIS, PRODUCTIVITY, SWEET-PEPPER, TOMATO, TRANSPIRATION, WATER-
USE EFFICIENCY


     98   
Bainbridge, G., P. Madgwick, S. Parmar, R. Mitchell, M. Paul, J. Pitts, A.J. Keys, and M.A.J.
Parry. 1995. Engineering rubisco to change its catalytic properties. Journal of Experimental Botany
46:1269-1276.

The initial steps of carbon assimilation and photorespiration are catalysed by ribulose-1,5-
bisphosphate carboxylase/oxygenase (EC 4.1.1.39). Natural variation in the kinetic properties of the
enzyme suggest that it is possible to alter the enzyme to favour the carboxylation activity relative to
oxygenation, Mutagenesis in vitro of the gene encoding the large subunit of the enzyme from
Anacystis nidulans has been used to modify catalytic properties. Residues at the C-terminal end of
loop 6 of the beta/alpha barrel structure of the large subunit influence specificity towards the gaseous
substrates, CO2 and O-2. None of the residues altered by mutagenesis appear to interact directly with
the transition state analogue and their effect on the reaction of the enediolate intermediate with the
gaseous substrates and stabilization of the resulting transition state intermediates by lysine 334 must
be indirect. Interactions with other parts of the enzyme must also be important in determining
substrate specificity, Backbone carbonyl groups close to lysine 334 interact with lysine 128; mutation
of lysine 128 to residues of less positive polarity reduces enzyme activity and favours oxygenation
relative to carboxylation, the likely effects on assimilation rates of altering the kinetic properties of
Rubisco have been modelled. A leaf with cyanobacterial Rubisco may out-perform a higher plant
Rubisco at elevated CO2 and cool temperatures.

KEYWORDS: 1,5-BISPHOSPHATE CARBOXYLASE, ACTIVE-SITE, CO2/O2 SPECIFICITY,
LARGE SUBUNIT, RHODOSPIRILLUM-RUBRUM, RIBULOSE BISPHOSPHATE
CARBOXYLASE, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SITE-DIRECTED
MUTAGENESIS, SUBSTRATE-SPECIFICITY


     99   
Baker, J.T., S.L. Albrecht, D. Pan, L.H. Allen, N.B. Pickering, and K.J. Boote. 1994. Carbon-
dioxide and temperature effects on rice (oryza-sativa L, CV ir-72). Soil and Crop Science Society
of Florida Proceedings 53:90-97.

The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of
possible future increases in global air temperatures have stimulated interest in the effects of [CO2]
and temperature on the growth and yield of food crops. This study was conducted to determine the
effects and possible interactions of elevated [CO2] and temperature on the development, growth and
yield of rice (Oryza sativa L., cv. IR-72). Rice plants were grown season-long in outdoor, naturally
sunlit, controlled-environment, plant growth chambers. Chamber air temperatures were controlled
to follow a continuously and diurnally varying, near sine-wave control setpoint that operated between
maximum (daytime) and minimum (nighttime) values. Day/night (maximum/minimum) air temperature
treatments were: 32/23, 35/26, and 38/29-degrees-C. Dewpoint air temperatures were maintained at
18, 21, 24- degrees-C in the 32/23, 35/26, 38/29-degrees-C dry bulb air temperature treatment,
respectively. Daytime [CO2] was controlled to 330 and 660 mumol CO2 mol-1 air in each of the air
temperature treatments. The time interval between appearance of successive mainstrem leaves during
reproductive development was reduced by increasing air temperature treatment (P less-than-or-equal-
to 0.05) but was not affected by [CO2] enrichment. In this experiment [CO2] enrichment did not
affect (P less-than-or-equal-to 0.10) grain yield, components of grain yield, final above ground
biomass or harvest index. Increasing temperature during growth, particularly from the 35/26 to
38/29-degrees-C reduced grain yield, individual grain mass, and harvest index. The reduced grain
yields with increasing temperature treatment suggest potential detrimental effects on rice production
in some areas if air temperatures increase.



     100  
Baker, J.T., and L.H. Allen. 1993. Contrasting crop species responses to co2 and temperature -
rice, soybean and citrus. Vegetatio 104:239-260.

The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of
possible future increases in global air temperatures have stimulated interest in the effects of these
climate variables on plants and, in particular, on agriculturally important food crops. Mounting
evidence from many different experiments suggests that the magnitude and even direction of crop
responses to [CO2] and temperature is almost certain to be species dependent and very likely, within
a species, to be cultivar dependent. Over the last decade, [CO2] and temperature experiments have
been conducted on several crop species in the outdoor, naturally- sunlit, environmentally controlled,
plant growth chambers by USDA-ARS and the University of Florida, at Gainesville, Florida, USA.
The objectives for this paper are to summarize some of the major findings of these experiments and
further to compare and contrast species responses to [CO2] and temperature for three diverse crop
species: rice (Oryza sativa, L.). soybean (Glycine max, L.) and citrus (various species). Citrus had the
lowest growth and photosynthetic rates but under [CO2] enrichment displayed the greatest
percentage increases over ambient [CO2] control treatments. In all three species the direct effect of
[CO2] enrichment was always an increase in photosynthetic rate. In soybean, photosynthetic rate
depended on current [CO2] regardless of the long-term [CO2] history of the crop. In rice,
photosynthetic rate measured at a common [CO2], decreased with increasing long-term [CO2]
growth treatment due to a corresponding decline in RuBP carboxylase content and activity. Rice
specific respiration decreased from subambient to ambient and superambient [CO2] due to a decrease
in plant tissue nitrogen content and a decline in specific maintenance respiration rate. In all three
species, crop water use decreased with [CO2] enrichment but increased with increases in temperature.
For both rice and soybean, [CO2] enrichment increased growth and grain yield. Rice grain yields
declined by roughly 10% per each 1-degrees-C rise in day/night temperature above 28/21-degrees-C.

KEYWORDS: ATMOSPHERIC CO2, CANOPY PHOTOSYNTHESIS, CARBON-DIOXIDE
CONCENTRATION, CLIMATE SENSITIVITY, DARK RESPIRATION, DEVELOPMENTAL
STAGES, ELEVATED CO2, SHORT- TERM, SOUR ORANGE TREES, WATER-USE EFFICIENCY


     101  
Baker, J.T., and L.H. Allen. 1994. Assessment of the impact of rising carbon-dioxide and other
potential climate changes on vegetation. Environmental Pollution 83(1-2):223-235.

The projected doubling of current levels of atmospheric carbon dioxide concentration ([CO2]) during
the next century along with increases in other radiatively active gases have led to predictions of
increases in global air temperature and shifts in precipitation patterns. Additionally, stratospheric
ozone depletion may result in increased ultraviolet-B (UV-B) radiation incident at the Earth's surface
in some areas. Since these changes in the Earth's atmosphere may have profound effects on
vegetation, the objectives of this paper are to summarize some of the recent research on plant
responses to [CO2], temperature and UV-B radiation. Elevated [CO2] increases photosynthesis and
usually results in increased biomass, and seed yield. The magnitude of these increases and the specific
photosynthetic response depends on the plant species, and are strongly influenced by other
environmental factors including temperature, light level, and the availability of water and nutrients.
While elevated [CO2] reduces transpiration and increases photosynthetic water-use efficiency,
increasing air temperature can result in greater water use, accelerated plant developmental rate, and
shortened growth duration. Experiments on UV-B radiation exposure have demonstrated a wide
range of photobiological responses among plants with decreases in photosynthesis and plant growth
among more sensitive species. Although a few studies have addressed the interactive effects of [CO2]
and temperature on plants, information on the effects of UV-B radiation at elevated [CO2] is scarce.
Since [CO2], temperature and UV-B radiation may increase concurrently, more research is needed
to determine plant responses to the interactive effects of these environmental variables.

KEYWORDS: DIFFERENT CO2 ENVIRONMENTS, DRY-MATTER PRODUCTION, FIELD
CONDITIONS, HIGH ATMOSPHERIC CO2, MILD WATER-STRESS, NET PHOTOSYNTHESIS,
PHOTON FLUX- DENSITY, PLANT GROWTH, SOYBEAN CANOPY PHOTOSYNTHESIS,
ULTRAVIOLET-B RADIATION


     102  
Baker, J.T., L.H. Allen, and K.J. Boote. 1990. Growth and yield responses of rice to carbon-
dioxide concentration. Journal of Agricultural Science 115:313-320.

Rice plants (Oryza sativa L., cv. IR30) were grown in paddy culture in outdoor, naturally sunlit,
controlled-environment, plant growth chambers at Gainesville, Florida, USA, in 1987. The rice plants
were exposed throughout the season to subambient (160 and 250), ambient (330) or superambient
(500, 660, 900 mu-mol CO2/mol air) CO2 concentrations. Total shoot biomass, root biomass,
tillering, and final grain yield increased with increasing CO2 concentration, the greatest increase
occurring between the 160 and 500 mu-mol CO2/mol air treatments. Early in the growing season,
root:shoot biomass ratio increased with increasing CO2 concentration; although the ratio decreased
during the growing season, net assimilation rate increased with increasing CO2 concentration and
decreased during the growing season. Differences in biomass and lamina area among CO2 treatments
were largely due to corresponding differences in tillering response. The number of panicles/plant was
almost entirely responsible for differences in final grain yield among CO2 treatments. Doubling the
CO2 concentration from 330 to 660 mu-mol CO2/mol air resulted in a 32% increase in grain yield.
These results suggest that important changes in the growth and yield of rice may be expected in the
future as the CO2 concentration of the earth's atmosphere continues to rise.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, CROP PLANTS, DRY-MATTER,
ENRICHMENT, ICE CORE, LEAF-AREA, PLANT GROWTH, TEMPERATURE, WHEAT


     103  
Baker, J.T., L.H. Allen, and K.J. Boote. 1992. Response of rice to carbon-dioxide and
temperature. Agricultural and Forest Meteorology 60(3-4):153-166.

The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of
possible future increases in global air temperatures have stimulated interest in the effects of [CO2]
and temperature on the growth and yield of food crops. This study was conducted to determine the
effects and possible interactions of [CO2] and temperature on the growth and yield of rice (Oryza
sativa L., cultivar IR-30). Rice plants were grown for a season in outdoor, naturally sunlit, controlled-
environment, and plant growth chambers. Temperature treatments of 28/21/25, 34/27/31, and
40/33/37- degrees-C (daytime dry bulb air temperature/night-time dry bulb air temperature/paddy
water temperature) were maintained in [CO2] treatments of 330 and 660-mu-mol CO2 mol-1 air. In
the 40/33/37-degrees-C temperature treatment, plants in the 330-mu- mol mol-1 [CO2] treatment
died during stem extension while the [CO2] enriched plants survived but produced sterile panicles.
Plants in the 34/27/31-degrees-C temperature treatments accumulated biomass and leaf area at a
faster rate early in the growing season than plants in the 28/21/25-degrees-C temperature treatments.
Tillering increased with increasing temperature treatment. Grain yield increases owing to [CO2]
enrichment were small and non-significant. This lack of [CO2] response on grain yield was attributed
to the generally lower levels of solar irradiance encountered during the late fall and winter when this
experiment was conducted. Grain yields were affected much more strongly by temperature than
[CO2] treatment. Grain yields declined by an average of approximately 7-8% per 1-degrees-C rise
in temperature from the 28/21/25 to 34/27/31-degrees-C temperature treatment. The reduced grain
yields with increasing temperature treatment suggests potential detrimental effects on rice production
in some areas if air temperatures increase, especially under conditions of low solar irradiance.

KEYWORDS: AIR- TEMPERATURE, CLIMATE SENSITIVITY, CO2- ENRICHMENT,
ENVIRONMENTS, ORYZA SATIVA L, PHOTOSYNTHESIS, PLANT GROWTH, TRANSPIRATION,
WHEAT, YIELD


     104  
Baker, J.T., L.H. Allen, and K.J. Boote. 1992. Temperature effects on rice at elevated co2
concentration. Journal of Experimental Botany 43(252):959-964.

The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of
possible future increases in global air temperatures have stimulated interest in the effects of these
climate variables on agriculturally important food crops. This study was conducted to determine the
effects of [CO2] and temperature on rice (Oryza sativa L., cv. IR-30). Rice plants were grown
season-long in outdoor, naturally sunlit, controlled-environment, plant growth chambers in
temperature regimes ranging from 25/18/21-degrees-C to 37/30/34-degrees-C (daytime dry bulb air
temperature/night-time dry bulb air temperature/paddy water temperature) and [CO2] of 660-mu-mol
CO2 mol-1 air. An ambient chamber was maintained at a [CO2] of 330-mu-mol mol-1 and
temperature regime of 28/21/25- degrees-C. Carbon dioxide enrichment at 28/21/25-degrees-C
increased both biomass accumulation and tillering and increased grain yield by 60%. In the 660-mu-
mol mol-1 [CO2] treatment, grain yield decreased from 10.4 to 1.0 Mg ha-1 with increasing
temperature from 28/21/25-degrees-C to the 37/30/34-degrees-C temperature treatment. Across this
temperature range, the number of panicles plant-1 nearly doubled while the number of seeds panicle-1
declined sharply. These results indicate that while future increases in atmospheric [CO2] are likely
to be beneficial to rice growth and yield, potentially large negative effects on rice yield are possible
if air temperatures also rise.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CLIMATE SENSITIVITY, ENRICHMENT,
GROWTH, ORYZA SATIVA L, PHOTOSYNTHESIS, RESPONSES, TRANSPIRATION, WHEAT,
YIELD


     105  
Baker, J.T., L.H. Allen, K.J. Boote, and N.B. Pickering. 1997. Rice responses to drought under
carbon dioxide enrichment .1. Growth and yield. Global Change Biology 3(2):119-128.

Projections of future climate change include a strong likelihood of a doubling of current atmospheric
carbon dioxide concentration ([CO2]) and possible shifts in precipitation patterns. Drought stress is
a major environmental limitation for crop growth and yield and is common in rainfed rice production
systems. This study was conducted to determine the growth and grain yield responses of rice to
drought stress under [CO2] enrichment. Rice (cv. IR-72) was grown to maturity in eight naturally
sunlit, plant growth chambers in atmospheric carbon dioxide concentrations [CO2] of 350 and 700
mu mol CO2 mol(-1) air. In both [CO2], water management treatments included continuously hooded
(CF) controls, flood water removed and drought stress imposed at panicle initiation (PI), anthesis
(ANT), and both panicle initiation and anthesis (PI & ANT). The [CO2] enrichment increased
growth, panicles plant(-1) and grain yield. Drought accelerated leaf senescence, reduced leaf area and
above-ground biomass and delayed crop ontogeny. The [CO2] enrichment allowed 1-2 days more
growth during drought stress cycles. Grain yields of the PI and PI & ANT droughts were similar to
the CF control treatments while the ANT drought treatment sharply reduced growth, grain yield and
individual grain mass. We conclude that in the absence of air temperature increases, future global
increases in [CO2] should promote rice growth and yield while providing a modest reduction of near
10% in water use and so increase drought avoidance.

KEYWORDS: CO2- ENRICHMENT, CULTIVAR, INCREASE, NUTRITION, ORYZA SATIVA L,
WHEAT


     106  
Baker, J.T., L.H. Allen, K.J. Boote, and N.B. Pickering. 1997. Rice responses to drought under
carbon dioxide enrichment .2. Photosynthesis and evapotranspiration. Global Change Biology
3(2):129-138.

Future climate change is projected to include a strong likelihood of continued increases in
atmospheric carbon dioxide concentration ([CO2]) and possible shifts in precipitation patterns. Due
mainly to uncertainties in the timing and amounts of monsoonal rainfall, drought is common in rainfed
rice production systems. The objectives of this study were to quantify the effects and possible
interactions of [CO2] and drought stress on rice (Oryza sativa, L.) photosynthesis, evapotranspiration
and water-use efficiency. Rice (cv. IR-72) was grown to maturity in eight naturally sunlit, plant
growth chambers in atmospheric carbon dioxide concentrations [CO2] of 350 and 700 mu mol CO2
mol(-1) air. In both [CO2], water management treatments included continuously flooded controls,
flood water removed and drought stress imposed at panicle initiation, anthesis, and both panicle
initiation and anthesis. Potential acclimation of rice photosynthesis to long-term [CO2] growth
treatments of 350 and 700 mu mol mol(-1) was tested by comparing canopy photosynthesis rates
across short-term [CO2] ranging from 160 to 1000 mu mol mol(-1). These tests showed essentially
no acclimation response with photosynthetic rate being a function of current short-term [CO2] rather
than long- term [CO2] growth treatment. In both long-term [CO2] treatments, photosynthetic rate
saturated with respect to [CO2] near 510 mu mol mol(-1). Carbon dioxide enrichment significantly
increased both canopy net photosynthetic rate (21-27%) and water-use efficiency while reducing
evapotranspiration by about 10%. This water saving under [CO2] enrichment allowed photosynthesis
to continue for about one to two days longer during drought in the enriched compared with the
ambient [CO2] control treatments.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBOXYLASE, DIFFERENT CO2
ENVIRONMENTS, DRY-MATTER PRODUCTION, ELEVATED CO2, PLANT GROWTH,
SOYBEAN LEAVES, TEMPERATURE, TRANSPIRATION


     107  
Balaguer, L., J.D. Barnes, A. Panicucci, and A.M. Borland. 1995. Production and utilization of
assimilates in wheat (triticum- aestivum L) leaves exposed to elevated o-3 and/or co2. New
Phytologist 129(4):557-568.

This study examined the effects of elevated ozone (O-3) and/or carbon dioxide (CO2) on the diel
allocation of photosynthetically fixed carbon in fully expanded leaves of young (growth stages 4-5)
spring wheat (Triticum aestivum L. cv. Hanno). Plants were grown in controlled environment
chambers and exposed to two O-3 regimes ['non-polluted' air (CF), < 5 nmol mol(-1); 'polluted' air,
CF + 75 nmol mol(-1) 7 h d(-1)] and two CO2 treatments ('ambient', 354 mu mol mol(-1); 'elevated',
700 mu mol mol(-1)) over a 30 d period. Neutral sugars (predominantly sucrose) were found to be
the most abundant form of carbohydrate accumulated by leaves during the day, but significant
quantities of starch and high degree of polymerization (d.p.) fructans were also present. Elevated
concentrations of O-3 and/or CO2 were found to have marked effects on diel patterns of export,
storage and respiration, whilst the proportions of fixed carbon allocated to each of these processes
were broadly similar. O-3 depressed the rate of net CO2 assimilation (-20%) and reduced stomatal
conductance (- 19%). This was reflected in a reduced amount of carbohydrate accumulated in, and
exported by, source tissue during the day. Effects of O-3 on the rate of CO2 fixation were aggravated
by an increased demand for carbon by dark respiratory processes. In contrast, doubling the
atmospheric concentration of CO2 enhanced the rate of net CO2 assimilation (+ 47%) and reduced
the proportion of fixed carbon retained in the leaf blade, increasing the rate of export. The favourable
carbon balance of CO2 enriched leaves was further enhanced by a decrease in the cost of maintenance
respiration, whilst simultaneous measurements of CO2 efflux and O-2 uptake at night suggested a
shift in the substrates metabolized at high CO2. Effects of elevated CO2 and O-3 on the carbon
balance of individual leaf blades over a single 24 h light/dark cycle were entirely consistent with the
cumulative effects of the gases on plant growth over a 30 d period. O-3 reduced the rate of plant
growth (-10%), but there were differential effects of O-3 on the growth of root and shoot which
exacerbated the decrease in assimilate availability induced by O-3. In contrast the favourable effects
of CO2 enrichment on the carbon balance of individual source leaves was reflected in the enhanced
accumulation of dry matter in existing sinks, and the initiation of new sinks (i.e. increased tillering).
In the combined treatment (elevated CO2 + O-3), O-3 counteracted the favourable effects of CO2
enrichment on the carbon balance of individual leaves, and the combined effects of the individual
gases on the diel partitioning of photosynthetically fixed carbon in fully expanded leaf blades was
reflected in a decreased rate of plant growth at elevated CO2, a situation further exacerbated by O-3-
induced shifts in the relative partitioning of carbon between root and shoot. There was no evidence
that CO2 enrichment afforded additional protection against O-3 damage: the extent of the O-3-
induced reduction in photosynthesis, carbohydrate availability and growth observed at elevated CO2
was similar to that induced by O-3 in ambient air, despite additive effects of the gases on stomatal
conductance that would reduce the effective dose of O-3 by approximate to 30%. The wider
ecological significance of interactions between elevated CO2 and O-3 is discussed in the light of other
recent findings.

KEYWORDS: AIR- POLLUTANTS, CARBON DIOXIDE, CLIMATE CHANGE, GAS-EXCHANGE,
LEAF BLADES, MAINTENANCE RESPIRATION, OPEN-TOP CHAMBERS, OZONE, PICEA-
ABIES L, SOURCE-SINK RELATIONS


     108  
Balaguer, L., E. Manrique, A. de los Rios, C. Ascaso, K. Palmqvist, M. Fordham, and J.D.
Barnes. 1999. Long-term responses of the green-algal lichen Parmelia caperata to natural CO2
enrichment. Oecologia 119(2):166-174.

Acclimation to elevated CO2 was investigated in Parmelia caperata originating from the vicinity of
a natural CO2 spring, where the average daytime CO2 concentration was 729 +/- 39 mu mol mol(-1)
dry air. Thalli showed no evidence of a down- regulation in photosynthetic capacity following long-
term exposure to CO2 enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate
carboxylase/oxygenase (Rubisco) content, apparent quantum yield of CO2 assimilation, and the light-
saturated rate of CO2 assimilation (measured under ambient and saturating CO2 concentrations) were
similar in thalli from the naturally CO2 enriched site and an adjacent control site where the average
long-term CO2 concentration was about 355 mu mol mol(-1). Thalli from both CO2 environments
exhibited low CO2 compensation points and early saturation of CO2 uptake kinetics in response to
increasing external CO2 concentrations, suggesting the presence of an active carbon- concentrating
mechanism. Consistent with the lack of significant effects on photosynthetic metabolism, no changes
were found in the nitrogen content of thalli following prolonged exposure to elevated CO2. Detailed
intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae
located in the elongation zone of thalli originating from elevated CO2, an effect associated with a
reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although
these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced
limitations to CO2 assimilation in lichens originating from the CO2-enriched site. The light-saturated
rate of CO2 assimilation measured at the average growth CO2 concentration was found to be
significantly lower in thalli originating from a CO2-enriched atmosphere compared with that of thalli
originating and measured at ambient CO2, At lower photosynthetic photon flux densities, the light
compensation point of net CO2 assimilation was significantly higher in thalli originating from elevated
CO2 and this effect was associated with higher usnic acid content.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, CHLOROPHYTA, ELEVATED CO2,
EXCHANGE, GROWTH, PHOTOBIONTS, PHOTOSYNTHESIS, PLANTS, RISING
ATMOSPHERIC CO2, WATER-CONTENT


     109  
Balaguer, L., F. Valladares, C. Ascaso, J.D. Barnes, A. DelosRios, E. Manrique, and E.C.
Smith. 1996. Potential effects of rising tropospheric concentrations of CO2 and O-3 on green-algal
lichens. New Phytologist 132(4):641-652.

Parmelia sulcata Taylor was used as a model to examine the effects of elevated CO2 and/or O-3 on
green algal lichens. Thalli were exposed for 30 d in duplicate controlled- environment chambers to
two atmospheric concentrations of CO2 ('ambient' [350 mu mol mol(-1)] and 'elevated' [700 mu mol
mol(-1)] 24 h d(-1)) and two O-3 regimes ('non-polluted' air [CF, < 5 nmol mol(-1)] and 'polluted'
air [15 nmol mol(-1) overnight rising to a midday maximum of 75 nmol mol(-1)]), in a factorial
design. Elevated CO2 or elevated O-3 depressed the light saturated rate of CO2 assimilation (A(sat))
measured at ambient CO2 by 30%, and 18%, respectively. However, despite this effect ultrastructural
studies revealed increased lipid storage in cells of the photobiont in response to CO2- enrichment.
Simultaneous exposure to elevated O-3 reduced CO2- induced lipid accumulation and reduced A(sat)
in an additive manner. Gold-antibody labelling revealed that the decline in photosynthetic capacity
induced by elevated CO2 and/or O-3 was accompanied by a parallel decrease in the concentration of
Rubisco in the algal pyrenoid (r = 0.93). Interestingly, differences in the amount of Rubisco protein
were not correlated with changes in pyrenoid volume. Measurements of in vivo chlorophyll-
fluorescence induction kinetics showed that the decline in A(sat) induced by elevated CO2 and/or O-3
was not associated with significant changes in the photochemical efficiency of photosystem (PS)II.
Although the experimental conditions inevitably imposed some stress on the thalli, revealed a
significant decline in the efficiency of PS II photochemistry, and enhanced starch accumulation in the
photobiont over the fumigation period, the study shows that the green-algal lichen symbiosis might
be influenced by future changes in atmospheric composition. Photosynthetic capacity, measured at
ambient CO2, was found to be reduced after a controlled 30 d exposure to elevated CO2 and/or O-3
and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal
chloroplasts.

KEYWORDS: BISPHOSPHATE CARBOXYLASE OXYGENASE, CARBON, CHLORELLA,
CHLOROPHYLL FLUORESCENCE, GAS-EXCHANGE, GROWTH, OZONE, PARMELIA-
SULCATA, PHOTOSYNTHESIS, ULTRASTRUCTURE


     110  
Baldocchi, D. 1994. A comparative-study of mass and energy-exchange rates over a closed C-3
(wheat) and an open C-4 (corn) crop .2. Co2 exchange and water-use efficiency. Agricultural and
Forest Meteorology 67(3-4):291-321.

Major differences exist between the photosynthetic and transpiration rates Of C3 and C4 leaves as
a result of biochemical and physiological factors. Whether or not differences between CO2 and water
vapor exchange rates Of C3 and C4 species scale from leaf to field dimensions is poorly known. The
aim of this work is to improve our understanding on how environmental, architectural and
physiological variables affect the flux densities Of CO2 and water vapor over C3 and C4 crop stands
during day and night periods. Experimental data were obtained over a closed wheat and an open com
stand using the eddy correlation method. Interpretation of the field measurements is aided by the use
of a canopy photosynthesis/evaporation model. The flux density of absorbed photosynthetically active
radiation (Q(a)) had a disproportionate influence on CO2 flux densities measured over a closed C3
and an open C4 crop. Variations in Q(a) explained over 88% of the variance in daytime CO2 flux
densities, F(c). At night, canopy radiative temperature was the main environmental factor controlling
the respiratory CO2 efflux by the two crops. Leaf area index and growth stage were the plant
variables that affected F(c) most. Incremental increases in leaf area index enhanced the com crop's
ability to absorb incident solar radiation and enlarged the com's sink strength for CO2. Heading by
the wheat caused rates of daytime CO2 gains to decrease and rates of night-time CO2 losses to
increase. Water use efficiency of the wheat crop improved as the absolute humidity deficit of the
atmosphere decreased. Water use efficiency of the com, on the other hand, was relatively insensitive
to humidity deficits. With regard to canopy CO2 exchange and water use efficiency, differences in
canopy structure between the wheat and com overwhelmed physiological differences. The closed C3
wheat crop assimilated CO2 at a higher rate than the sparse C4 com canopy, even though com uses
a more efficient photosynthetic pathway. Consequently, water use efficiency of the com was not
greater than values measured over the wheat, Instead, water use efficiencies of the two crops were
similar. The com crop assimilated CO2 at a lower rate than wheat because the com's canopy quantum
yield was lower and because its sparse canopy absorbed less photosynthetically active radiation than
the closed wheat stand.

KEYWORDS: ASSIMILATION, CANOPY, CARBON DIOXIDE, FLUX MEASUREMENTS, LEAF-
AREA INDEX, PHOTOSYNTHESIS, SOIL RESPIRATION, STOMATAL CONDUCTANCE,
VAPOR, WINTER-WHEAT


     111  
Baldocchi, D.D., and P.C. Harley. 1995. Scaling carbon-dioxide and water-vapor exchange from
leaf to canopy in a deciduous forest .2. Model testing and application. Plant, Cell and Environment
18(10):1157-1173.

The scaling of CO2 and water vapour transfer from leaf to canopy dimensions was achieved by
integrating mechanistic models for physiological (photosynthesis, stomatal conductance and soil/root
and bole respiration) and micrometeorological (radiative transfer, turbulent transfer and surface
energy exchanges) processes, The main objectives of this paper are to describe a canopy
photosynthesis and evaporation model for a temperate broadleaf forest and to test it against field
measurements, The other goal of this paper is to use the validated model to address some
contemporary ecological and physiological questions concerning the transfer of carbon and water
between forest canopies and the atmosphere, In particular, we examine the role of simple versus
complex radiative transfer models and the effect of environmental (solar radiation and CO2) and
ecophysiological (photosynthetic capacity) variables on canopy-scale carbon and water vapour fluxes.

KEYWORDS: CLIMATE CHANGE, CO2 CONCENTRATIONS, ELEVATED CO2, PATTERNS,
PHOTOSYNTHESIS, PLANT CANOPIES, SENSIBLE HEAT, STOMATAL CONDUCTANCE,
TEMPERATURE, TRANSPIRATION


     112  
Ball, A.S. 1991. Degradation by Streptomyces viridosporus t7a of plant-material grown under
elevated CO2 conditions. Fems Microbiology Letters 84(2):139-142.

The biodegradability of plant material derived from wheat grown under different concentrations of
atmospheric CO2 was investigated using the lignocarbohydrate solubilising actinomycete,
Streptomyces viridosporus. Growth of S. viridosporus and solubilisation of lignocarbohydrate were
highest when wheat grown at ambient CO2 concentrations (350 ppm) was used as C-source. Growth
of S. viridosporus and solubilisation were reduced when the plant material was derived from wheat
grown at 645 PPM CO2. The results suggest that modifications in plant structure occur when wheat
is grown under conditions of elevated atmospheric CO2 which make it more resistant to microbial
digestion.

KEYWORDS: ENZYME, LIGNIN DEGRADATION, LIGNOCELLULOSE, POLYMERIC LIGNIN,
STRAW


     113  
Ball, A.S. 1997. Microbial decomposition at elevated CO2 levels: effect of litter quality. Global
Change Biology 3(4):379-386.

The decomposition of senesced plant litter represents an important intermediate step in the cycling
of nutrients between above-and below-ground systems. The rate of decomposition of plant litter is
sensitive to fluctuations in a number of parameters, including environmental conditions, and
particularly to changes in the quality of the litter. Increased C:N ratios of litter are thought to be one
possible consequence of growth of plants under elevated [CO2]. This response is likely to reduce the
rate of decomposition of the litter. Evidence from the growth of plants in both pot and field studies
suggests that growth of C3 plants in elevated atmospheric [CO2] (600-700 mu mol mol(-1)) may lead
to a significant increase in either/both the C:N and the lignin: N ratios of litter. Short-term
decomposition of lifter from plants showing this response in elevated [CO2] has confirmed that
decomposition occurs at a significantly lower rate. The limited studies of both the response of C4
plants to elevated [CO2] and the subsequent degradability of the senescent litter suggest that no
differences in litter quality or degradability occur. In terms of litter quality the response of plants
therefore appears to be dependent upon photosynthetic type; the C:N and lignin:N ratios of litter from
C3 plants exposed to elevated [CO2] are increased, leading to lower degradation rates, while the
nutrient ratios and degradation rates of lifter from C4 plants grown in elevated [CO2] remain
unchanged. To date, very few ecosystem studies of decomposition have been carried out. Further
work is required at the ecosystem level to determine whether the effects observed in laboratory, pot
and field studies are also observed in long-term, complex ecosystem studies. Clearly if these results
are repeated at the ecosystem level then significant changes in the cycling of C and N in important
terrestrial ecosystems may occur as a results of elevated [CO2].

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, ECOSYSTEMS,
HARDWOOD LEAF LITTER, LIGNIN CONTENT, MASS-LOSS, NITROGEN DYNAMICS, PLANT-
MATERIAL, RESPONSES, SOIL


     114  
Ball, A.S., and B.G. Drake. 1997. Short-term decomposition of litter produced by plants grown in
ambient and elevated atmospheric CO2 concentrations. Global Change Biology 3(1):29-35.

The effects of elevated atmospheric CO2 (ambient + 340 mu mol mol(-1)) on above-ground litter
decomposition were investigated over a 6-week period using a field-based mesocosm system. Soil
respiratory activity in mesocosms incubated in ambient and elevated atmospheric CO2 concentrations
were not significantly different (t-test, P > 0.05) indicating that there were no direct effects of
elevated atmospheric CO2 on litter decomposition. A study of the indirect effects of CO2 on soil
respiration showed that soil mesocosms to which naturally senescent plant litter had been added
(0.5% w/w) from the C-3 sedge Scirpus olneyi grown in elevated atmospheric CO2 was reduced by
an average of 17% throughout the study when compared to soil mesocosms to which litter from
Scirpus olneyi grown in ambient conditions had been added. In contrast, similar experiments using
senescent material from the C-4 grass Spartina patens showed no difference in soil respiration rates
between mesocosms to which litter from plants grown in elevated or ambient CO2 conditions had
been added. Analysis of the C:N ratio and lignin content of the senescent material showed that, while
the C:N ratio and lignin content of the Spartina patens litter did not vary with atmospheric CO2
conditions, the C:N ratio (but not the lignin content) of the litter from Scirpus olneyi was significantly
greater (t-test; P < 0.05) when derived from plants grown under elevated CO2 (105:1 compared to
86:1 for litter derived from Scirpus olneyi grown under ambient conditions). The results suggest that
the increased C:N ratio of the litter from the C-3 plant Scirpus olneyi grown under elevated CO2 led
to the lower rates of biodegradation observed as reduced soil respiration in the mesocosms. Further
longterm experiments are now required to determine the effects of elevated CO2 on C partitioning
in terrestrial ecosystems.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, DYNAMICS, FORESTS, INSITU, LEAF
LITTER, LEAVES, NITROGEN, RESPIRATION, SOIL


     115  
Ball, A.S., and B.G. Drake. 1998. Stimulation of soil respiration by carbon dioxide enrichment of
marsh vegetation. Soil Biology and Biochemistry 30(8-9):1203-1205.

KEYWORDS: ELEVATED ATMOSPHERIC CO2, INSITU, NITROGEN, PLANTS


     116  
Ball, M.C., M.J. Cochrane, and H.M. Rawson. 1997. Growth and water use of the mangroves
Rhizophora apiculata and R-stylosa in response to salinity and humidity under ambient and elevated
concentrations of atmospheric CO2. Plant, Cell and Environment 20(9):1158-1166.

Two mangrove species, Rhizophora apiculata and R. stylosa, mere grown for 14 weeks in a
multifactorial combination of salinity (125 and 350 mol m(-3) NaCl), humidity (43 and 86% relative
humidity at 30 degrees C) and atmospheric CO2 concentration (340 and 700 cm(3) m(-3)). Under
ambient [CO2], growth responses to different combinations of salinity and humidity were consistent
with interspecific differences in distribution along natural gradients of salinity and aridity in northern
Australia. Elevated [CO2] had little effect on relative growth rate when it was limited by salinity but
stimulated growth when limited by humidity. Both species benefited most from elevated [CO2] under
relatively low salinity conditions in which growth was vigorous, but relative growth rate was
enhanced more in the less salt-tolerant and more rapidly growing species, R. apiculata. Changes in
both net assimilation rate and leaf area ratio contributed to changes in relative growth rates under
elevated [CO2], with leaf area ratio increasing with decrease in humidity. Increase in water use
efficiency under elevated [CO2] occurred with increase, decrease or no change in evaporation rates;
water use characteristics which depended an both the species and the growth conditions. In summary,
elevated [CO2] is unlikely to increase salt tolerance, but could alter competitive rankings of species
along salinity x aridity gradients.

KEYWORDS: AUSTRALIA, AVICENNIA-MARINA, CARBON DIOXIDE, COTTON,
ENRICHMENT, GAS-EXCHANGE, MANGLE L, PHOTOSYNTHETIC ACCLIMATION, PLANT-
RESPONSES, RED MANGROVE


     117  
Ball, M.C., and R. Munns. 1992. Plant-responses to salinity under elevated atmospheric
concentrations of CO2. Australian Journal of Botany 40(4-5):515-525.

This review explores effects of elevated CO2 concentrations on growth in relation to water use and
salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and
distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt
toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux
from a highly saline soil is still considerable. To maintain internal ion concentrations within
physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt
storage and/or salt export by either retranslocation or secretion from glands. Hence the balance
between carbon gain and the expenditure of water in association with salt uptake is critical to leaf
longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such
as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of
water loss and growth. These low evaporation rates are further reduced under elevated CO2
conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants
grown under elevated CO2 conditions might be expected to contain lower salt concentrations than
those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt
concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions
despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in
both C3 and C4 non-halophytes. These results imply shoot/root communication in regulation of the
salt balance to adjust to environmental factors affecting the availability of water and ions at the roots
(salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric
concentrations of water vapour and carbon dioxide).

KEYWORDS: AUSTRALIAN MANGROVE FOREST, AVICENNIA-MARINA, BARLEY, CARBON
DIOXIDE, DROUGHT, GAS-EXCHANGE, GROWTH, LIMITATIONS, OSMOTIC ADJUSTMENT,
PHOTOSYNTHESIS


     118  
Bandara, D.C., H. Nobuyasu, K.G. Ofosu-Budu, T. Ando, and K. Fujita. 1998. Effect of CO2
enrichment on biomass production, photosynthesis, and sink activity in soybean cv. Bragg and its
supernodulating mutant nts 1007. Soil Science and Plant Nutrition 44(2):179-186.

Soybean (Glycine max L. Merr.) cv. Bragg and its supernodulating mutant nts 1007 were grown in
pots containing vermiculite with a N-free nutrient solution in order to examine the effect of elevated
CO2 concentration (100+20 Pa CO2) on biomass production, photosynthesis, and biological nitrogen
fixation. The whole plant weight increase in Bragg was higher than in the mutant at a high CO2
concentration. Apparent photosynthetic activities of the upper leaves in both Bragg and the mutant
increased up to 14 d after treatment initiation by the CO2 enrichment and thereafter decreased to
some extent. Both leaf area and leaf thickness of Bragg increased more than in nts 1007. With the
elevated CO2 concentration, biological nitrogen fixation (BNF) also responded in the same manner
as biomass production in both Bragg and nts 1007. The increase of BNF in Bragg was largely due
to an increase in nodule weight. Starch contents in the leaves of both Bragg and the mutant increased
significantly by CO2 enrichment, with a higher increase in Bragg than in its mutant. Sugar content
in leaf differed only slightly in both Bragg and the mutant. N content in leaf decreased in both Bragg
and its mutant, with the decrease being more pronounced in Bragg. However, in other plant parts
(roots, stem, and petiole + pods), N content increased in the mutant while in Bragg, it decreased in
the pod. N accumulation rate was higher in Bragg than in the mutant and increased more in Bragg
than in the mutant by CO2 enrichment. The ureide content in leaf decreased in Bragg but increased
in the mutant by elevated CO2 concentration. In the nodules, ureide content increased in both Bragg
and the mutant by CO2 enrichment. Based on these results, it is suggested that in terms of biomass
production and photosynthetic rate, Bragg responded more to elevated CO2 concentration than its
mutant nts 1007. The alleviation of the stunted vegetative growth of the mutant by CO2 enrichment
was limited despite the significant increase in the photosynthetic activity, presumably due to the
limitation of sink activity in the growing parts and not to insufficient supply of N through BNF.

KEYWORDS: CARBON, DINITROGEN FIXATION, GROWTH, L MERRILL MUTANTS,
LEGUMES, NITRATE APPLICATION, NITROGEN, NTS1007, PLANTS, ROOTS


     119  
Barnes, J.D., J.H. Ollerenshaw, and C.P. Whitfield. 1995. Effects of elevated co2 and/or o-3 on
growth, development and physiology of wheat (triticum-aestivum L). Global Change Biology
1(2):129-142.

Two cultivars of spring wheat (Triticum aestivum L. cvs. Alexandria and Hanno) and three cultivars
of winter wheat (cvs. Riband, Mercia and Haven) were grown at two concentrations of CO2 [ambient
(355 mu mol mol(-1)) and elevated (708 mu mol mol(-1))] under two O-3 regimes [clean air (< 5
nmol mol(-1) O- 3) and polluted air (15 nmol mol(-1) O-3 at night rising to a midday maximum of
75 nmol mol(-1))] in a phytotron at the University of Newcastle-upon-Tyne. Between the two-leaf
stage and anthesis, measurements of leaf gas-exchange, non-structural carbohydrate content, visible
O-3 damage, growth, dry matter partitioning, yield components and root development were made in
order to examine responses to elevated CO2 and/or O-3. Growth at elevated CO2 resulted in a
sustained increase in the rate of CO2 assimilation, but after roughly 6 weeks' exposure there was
evidence of a slight decline in the photosynthetic rate (c.-15%) measured under growth conditions
which was most pronounced in the winter cultivars. Enhanced rates of CO2 assimilation were
accompanied by a decrease in stomatal conductance which improved the instantaneous water use
efficiency of individual leaves. CO2 enrichment stimulated shoot and root growth to an equivalent
extent, and increased tillering and yield components, however, non-structural carbohydrates still
accumulated in source leaves. In contrast, long-term exposure to O-3 resulted in a decreased CO2
assimilation rate (c.-13%), partial stomatal closure, and the accumulation of fructan and starch in
leaves in the light. These effects were manifested in decreased rates of shoot and root growth, with
root growth more severely affected than shoot growth. In the combined treatment growth of O-3-
treated plants was enhanced by elevated CO2, but there was little evidence that CO2 enrichment
afforded additional protection against O-3 damage. The reduction in growth induced by O-3 at
elevated CO2 was similar to that induced by O-3 at ambient CO2 despite additive effects of the
individual gases on stomatal conductance that would be expected to reduce the O-3 flux by 20%, and
also CO2-induced increases in the provision of substrates for detoxification and repair processes.
These observations suggest that CO2 enrichment may render plants more susceptible to O-3 damage
at the cellular level. Possible mechanisms are discussed.

KEYWORDS: AIR- POLLUTANTS, ATMOSPHERIC CARBON-DIOXIDE, CARBOXYLASE-
OXYGENASE, GAS-EXCHANGE, MODERN GREEK CULTIVARS, PICEA-ABIES L, PLANT
GROWTH, SOURCE-SINK RELATIONS, SPRING WHEAT, WINTER-WHEAT


     120  
Barnes, J.D., and T. Pfirrmann. 1992. The influence of co2 and o-3, singly and in combination, on
gas-exchange, growth and nutrient status of radish (raphanus- sativus L). New Phytologist
121(3):403-412.

Five days after emergence radish (Raphanus sativus L. cv. Cherry Belle) plants were transferred to
a phytotron at the GSF Munchen, where they were exposed in four large controlled climate chambers
to two at atmospheric concentrations of CO2 ('ambient', daily means of almost-equal-to 385-mu-mol
mol-1; elevated, daily means of almost-equal-to 765-mu-mol mol-1) and two O3 regimes ('non-
polluted' air, 24 h mean of 20 nmol mol-1; polluted air, 24 h mean of 73 nmol mol-1) Leaf gas-
exchange measurements were made at intervals, and visible O3 damage, effects on growth, dry matter
partitioning and mineral composition were assessed at a final whole-plant harvest after 27 d. In 'non-
polluted air' CO2 enrichment resulted in a progressive stimulation in A(sat), whilst there was a decline
in g(s) which decreased E (i.e. improved WUE(i)). The extra carbon fixed in elevated CO2 stimulated
growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on shoot growth or leaf
area. Moreover, a decline in SLA and LAR in CO2-enriched plants suggested that less dry matter was
invested in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly
in the root + hypocotyl) in elevated CO2, indicating that total uptake of these nutrients was not
affected by CO2, and there was an increase in the C:N ratio in root (+ hypocotyl) tissue. In contrast,
O3 depressed A(sat), (almost-equal-to 26 %) and induced slight stomatal closure, with the result that
WUE(i) declined. All plants exposed to 'polluted' air developed typical visible symptoms of O3 injury,
and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained
at the expense of the root. In addition, O3 increased the P and K concentration in shoot and root
(+hypocotyl) tissue, indicating enhanced uptake of these nutrients from the growth medium.
However, there was no affect of O3 on tissue concentrations of N, S, Mg and Ca. Interactions
between the gases were complex, and often subtle. In general, elevated CO2 counteracted (at least
in part) the detrimental effects of phytotoxic concentrations of O3, whilst conversely, O3 reduced the
impact of elevated CO2. Moreover, there were indications that cumulative changes in source:sink
relations in O3-exposed plants may limit plant response to CO2-enrichment to an even greater extent
in the long-term. The future ecological significance of interactions between CO2 and O3 are
discussed.

KEYWORDS: ABIES L KARST, ACID MIST, AIR- POLLUTANTS, CARBON DIOXIDE,
ENRICHMENT, OZONE ALTERS, PHOTOSYNTHESIS, PLANTS, USE EFFICIENCY, WHEAT


     121  
Barnes, J.D., T. Pfirrmann, K. Steiner, C. Lutz, U. Busch, H. Kuchenhoff, and H.D. Payer.
1995. Effects of elevated CO2, elevated O-3 and potassium deficiency on Norway spruce [Picea abies
(L) Karst]: Seasonal changes in photosynthesis and non-structural carbohydrate content. Plant, Cell
and Environment 18(12):1345-1357.

Two clones of 5-year-old Norway spruce [Picea abies (L.) Karst.] were exposed to two atmospheric
concentrations of CO2 (350 and 750 mu mol mol(-1)) and O-3 (20 and 75 nmol mol(-1)) in a
phytotron at the GSF-Forschungszentrum (Munich) over the course of a single season (April to
October), The phytotron was programmed to recreate an artificial climate similar to that at a high
elevation site in the Inner Bavarian Forest, and trees were grown in Large containers of forest soil
fertilized to achieve contrasting levels of potassium nutrition, designated well-fertilized or K-deficient.
Measurements of the rate of net CO2 assimilation were made on individual needle year age classes
over the course of the season, chlorophyll fluorescence kinetics were recorded after approximately
23 weeks, and seasonal changes in non-structural carbohydrate composition of the current year's
foliage were monitored. Ozone was found to have contrasting effects on the rate of net CO2
assimilation in different needle age classes. After c. 5 months of fumigation, elevated O-3 increased
(by 33%) the rate of photosynthesis in the current year's needles, However, O-3 depressed (by 30%)
the photosynthetic rate of the previous year's needles throughout the period of exposure, Chlorophyll
fluorescence measurements indicated that changes in photosystem II electron transport played no
significant role in the effects of O-3 on photosynthesis, The reasons for the contrasting effects of O-3
on needles of different ages are discussed in the light of other recent findings, Although O-3 enhanced
the rate at which CO2 was fixed in the current year's foliage, this was not reflected in increases in the
non-structural carbohydrate ate content of the needles, The transfer of ambient CO2-grown trees to
a CO2-enriched atmosphere resulted in marked stimulation in the photosynthetic rate of current and
previous year's foliage, However, following expansion of the current year's growth, the
photosynthetic rate of the previous year's foliage declined, The extent of photosynthetic adjustment
in response to prolonged exposure to elevated CO2 depended upon the clone, providing evidence of
intraspecific variation in the long-term response of photosynthesis to elevated CO2, The increase in
photosynthesis induced by CO2 enrichment was associated with increased foliar concentrations of
glucose, fructose and starch (but no change in sucrose) in the new growth, CO2 enrichment
significantly enhanced the photosynthetic rate of K-deficient needles, but there was a strong CO2*soil
interaction in the current year's needles, indicating that the long-term response of trees to a high CO2
environment may depend on soil fertility, Although the rate of photosynthesis and non- structural
carbohydrate content of the new needles were increased in O-3-treated plants grown at higher levels
of CO2, there was no evidence that elevated CO2 provided additional protection against O-3 damage,
Simultaneous exposure to elevated O-3 modified the effects of elevated CO2 on needle
photosynthesis and non-structural carbohydrate content, emphasizing the need to take into account
not only soil nutrient status but also the impact of concurrent increases in photochemical oxidant
pollution in any serious consideration of the effects of climate change on plant production.

KEYWORDS: ACID MIST, AIR- POLLUTANTS, ATMOSPHERIC CO2, CARBON DIOXIDE, GAS-
EXCHANGE, LONG-TERM EXPOSURE, NET PHOTOSYNTHESIS, NONSTOMATAL
LIMITATION, OPEN-TOP CHAMBERS, STOMATAL CONDUCTANCE


     122  
Barr, A.G., K.M. King, G.W. Thurtell, and M.E.D. Graham. 1990. Humidity and soil-water
influence the transpiration response of maize to CO2 enrichment. Canadian Journal of Plant Science
70(4):941-948.



     123  
Barrett, D.J., and R.M. Gifford. 1995. Acclimation of photosynthesis and growth by cotton to
elevated CO2: Interactions with severe phosphate deficiency and restricted rooting volume.
Australian Journal of Plant Physiology 22(6):955-963.

Acclimation of photosynthesis and growth at three CO2 concentrations (376, 652 and 935 mu mol
mol(-1)) was examined in cotton grown under three growth-limiting phosphate (P) supplies (2.1, 6.1
and 18.2 mg P plant(-1)) and where biomass allocation between roots and shoots was altered by pots
of three different sizes (0.32 X 10(-3), 0.72 X 10(-3) and 1.56 x 10(-3) m(3) pot(-1)). Phosphate
supplies were chosen such that carbon gain at ambient CO2 increased linearly with P supply. Relative
growth rates of these plants were 5-10-times less and photosynthetic rates 3-16-times less than for
cotton supplied with abundant nutrients. Pot sizes were chosen so that root biomass and root:shoot
ratios decreased with a decrease in rooting volume. Maximum carboxylation rates per unit leaf area
(V-cmax) were lower in leaves grown at two elevated CO2 concentrations, compared with ambient
CO2 concentrations, under all P and pot size treatments indicating that acclimation of photosynthesis
had occurred. The degree of photosynthetic acclimation to elevated CO2 was not related to the
degree by which whole plant carbon gain was stimulated by elevated CO2 concentration at the
different P supplies, or to the degree by which allocation to root and shoots was altered by pot size.
Thus there is no simple relationship between photosynthetic and growth acclimation by cotton to
elevated CO2. At ambient CO2, the maximum carboxylation rate increased linearly with an increase
in leaf P per unit area (mg P m(-2)), but rates were lower at elevated CO2 for a given P content m(-
2). V-cmax also increased linearly with an increase in leaf P concentration (mg P g(-1) structural dry
weight). However, values of V-cmax were similar for plants grown at ambient and elevated CO2, for
a given P concentration. Acclimation of photosynthesis at elevated CO2 was associated with an
increase in leaf starch determined 5 h into the light period. However, increased starch concentration
with an increase in P supply was not associated with any decline in V-cmax.

KEYWORDS: ACCUMULATION, ATMOSPHERIC CO2, CARBON DIOXIDE, GLYCINE-MAX,
LEAVES, LONG-TERM EXPOSURE, NITROGEN, PHOSPHORUS-NUTRITION, PLANTS,
RESPONSES


     124  
Barrett, D.J., and R.M. Gifford. 1995. Photosynthetic acclimation to elevated CO2 in relation to
biomass allocation in cotton. Journal of Biogeography 22(2-3):331-339.

Biomass allocation to leaf tissues and photosynthetic acclimation to CO2 by cotton were investigated
in two experiments. Plants were grown at ambient and elevated CO2 concentrations with growth
restricting phosphorus supplies in both experiments and in root restricting pot volumes in the first
experiment. In both experiments, elevated CO2 concentrations decreased the maximum carboxylation
rate (V- cmax) and the CO2 saturated rate of photosynthesis indicative of photosynthetic acclimation
to elevated CO2 concentrations. In the first experiment, the percentage reduction in V-cmax under
elevated CO2 concentration was least at a P supply of 2.1 mg P plant(-1), greatest at 6.1 mg P plant(-
1), but then decreased at 18.2 mg P plant(-1). The greater acclimation at the middle P supply was
associated with a higher ratio of leaf mass to plant mass (LMR) than in other treatments and the lesser
acclimation at the highest P treatment coincided with a lower LMR. In the second experiment the
reduction in V-cmax at elevated CO2 was less than in the first experiment but was also associated
with a greater allocation of dry matter to leaf tissues during growth. In both experiments, V-cmax
was not correlated to the relative degree of biomass enhancement at elevated CO2 nor with the
degree of root growth restriction in small pots. These data support the hypothesis that acclimation
of photosynthesis to elevated CO2 concentrations is mediated by shifts in allocation between leaves
and the rest of the plant, induced by environmental conditions during growth, such that carbohydrate
supply remains in balance with the utilization capacity of sink tissues.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, GAS-EXCHANGE, GROWTH, LEAVES,
LIMITATIONS, PLANTS, SOURCE-SINK RELATIONS


     125  
Barrett, D.J., and R.M. Gifford. 1999. Increased C-gain by an endemic Australian pasture grass
at elevated atmospheric CO2 concentration when supplied with non- labile inorganic phosphorus.
Australian Journal of Plant Physiology 26(5):443-451.

Limited phosphorus (P) availability in Australia's highly weathered soils may constrain an increase in
terrestrial net primary productivity (NPP) with the globally increasing atmospheric CO2
concentration. We examined whether an Australian temperate pasture grass (Danthonia richardsonii)
grown in sand culture and supplied solely with virtually insoluble Al- and Fe-phosphate was able to
increase C-gain when exposed to elevated (731 mu mol mol(-1)) compared with ambient (379 mu
mol mol(-1)) CO2 concentrations. When supplied with 8 mg kg(-1) insoluble P concentration, total
citrate efflux by root systems (mu mol h(-1)), plant P uptake, shoot photosynthesis rates and plant
mass were all significantly greater at elevated than at ambient CO2 after a growth period of between
55 and 63 days. In this treatment, although the P concentration of the rooting medium limited growth
at ambient CO2, elevated CO2 increased P-uptake from the non-labile source, increased
photosynthesis rates per unit shoot soluble-P and increased plant mass. At P concentrations lower
than 8 mg kg(-1), plant mass, specific citrate efflux and maximum leaf carboxylation rates were
limited by the amount of P available in the rooting medium and no CO2 effect was observed. In all
treatments, carbon supply did not appear to limit citrate efflux. Where an increase in P uptake at
elevated CO2 was achieved, it was due to an increase in root mass (indicative of a potentially larger
soil volume explored) rather than to increased specific rates of citrate efflux. Above 8 mg kg(-1), the
supplied P concentration was sufficient that minimal rates of specific citrate efflux alone solubilised
enough P for growth and a strong CO2 effect on plant mass, photosynthesis and P uptake was
observed.

KEYWORDS: ACCLIMATION, GROWTH, LIMITATIONS, LUPINUS-ALBUS, ORGANIC-ACIDS,
PHOSPHATE, PHOTOSYNTHESIS, PROTEOID ROOTS, ROOT EXUDATION,
SOLUBILIZATION


     126  
Barrett, D.J., A.E. Richardson, and R.M. Gifford. 1998. Elevated atmospheric CO2
concentrations increase wheat root phosphatase activity when growth is limited by phosphorus.
Australian Journal of Plant Physiology 25(1):87-93.

Wheat seedlings were grown in solution culture under adequate and limited phosphorus treatments
at current ambient and elevated (approximately 2X ambient) CO2 concentrations. Acid
phosphomonoesterase ('phosphatase') activity of root segments was measured using p-nitrophenyl
phosphate as substrate. When plant growth was P-limited, elevated CO2 concentrations increased
phosphatase activity more than at ambient CO2. This result (1) was evident when expressed on a unit
root dry weight or root length basis, indicating that increased root enzyme activity was unlikely to
be associated with CO2-induced changes in root morphology; (2) occurred when plants were grown
aseptically, indicating that the increase in phosphatase activity originated from root cells rather than
root-associated microorganisms; (3) was associated with shoot P concentrations below 0.18%; (4)
occurred only when wheat roots were grown under P deficiency but not when a transient P deficiency
was imposed; and (5) suggest that a previously reported increase in phosphatase activity at elevated
CO2 by an Australian native pasture grass (Gifford, Lutze and Barrett 1996; Plant and Soil 187, 369-
387) was also a root mediated response. The observed increase in phosphatase activity by plant roots
at elevated CO2, if confirmed for a wide range of field pasture and crop species, is one factor which
may increase mineralisation of soil organic P as the anthropogenic increase of atmospheric CO2
concentrations continues. But, whether a concomitant increase in plant uptake of P occurs will
depend on the relative influence of root and microbial phosphatases, and soil geochemistry in
determining the rate of mineralisation of soil organic P for any given soil.

KEYWORDS: ACCLIMATION, BIOMASS, CARBON DIOXIDE, DEFICIENCY, EFFICIENCY,
ENRICHMENT, ORGANIC PHOSPHORUS, PHOTOSYNTHESIS, PLANT-ROOTS, SOIL


     127  
Bartak, M., I. Nijs, and I. Impens. 1996. The effect of long-term exposure of Lolium perenne L
plants to elevated CO2 and/or elevated air temperature on quantum yield of photosystem 2 and net
photosynthesis. Photosynthetica 32(4):549-562.

The effects of long-term exposure of Lolium perenne L. plants to CO2 concentration elevated to 700
mu mol (CO2) mol(-1) (EC) and air temperature elevated by 4 degrees C (ET) on the quantum yield
of electron transport of photosystem 2, PS2 (phi(2)) and on the potential yield of photochemical
reactions of PS2 (F- v/F-m) measured by the chlorophyll (Chl) fluorescence method, were studied.
The plants were exposed for 6 months in opened field greenhouses to four treatments simulating
global atmospheric changes: (1) ambient CO2 (AC) and ambient air temperature, AT (ACAT -
control), (2) EC and AT (ECAT), (3) AC and ET (ACET), and (4) EC and ET (ECET). When the
plants were exposed to stepwise increased irradiance, a decrease in phi(2) was found under both AC
and EC measuring concentrations. At high irradiances a significantly higher yield of PS2 was detected
when measured under EC compared to AC regardless of long-term CO2 and temperature treatment
(i.e., positive short- term. effect of EC). The short-term effect of EC on phi(2) as related to net
photosynthetic rate (P-N) Shift was detected from irradiance response curves. At high irradiances and
AC, phi(2) was reduced in comparison to control for the plants of EC and ET treatments (i.e.,
negative long-term effect of treatment). The long-term effect of both EC and ET on the yield of PS2
was attributed to a down-regulation of P-N caused by the treatment. The phi(2) was related to the
actual rate of photosynthesis and the relationship between phi(2) and phi(CO2) was linear over a wide
range of irradiances. No effect of long- term treatments on the dark-adapted F-v/F-m ratio was found
in plants cultivated under natural greenhouse irradiance.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DEPENDENCE, ELECTRON-TRANSPORT,
FLOW, GROWTH, LEAVES, LIGHT, REDUCTION, RESPONSES, RISING CO2


     128  
Bartak, M., I. Nijs, and I. Impens. 1998. The susceptibility of PS II of Lolium perenne to a sudden
fall in air temperature - response of plants grown in elevated CO2 and/or increased air temperature.
Environmental and Experimental Botany 39(1):85-95.

The effect of a sudden fall in air temperature from 20 to 5 degrees C on fast kinetics of chlorophyll
fluorescence, maximum yield of the photosystem II photochemical reactions (Fv/Fm), quantum yield
of the photosystem II electron transport (Phi(II)) coefficients of photochemical (qP), non-
photochemical quenching (qN) was studied in Lolium perenne using a modulated chlorophyll
fluorescence technique. Before fluorescence measurement, the plants were cultivated in the
treatments simulating the likely future climate characterized with elevated air temperature and CO2
concentration and combination of both. On fast kinetics curves the risetimes of the I and D points
characterizing the redox state of Q(A) were affected by lowering the air temperature. At 5 degrees
C both the I and D points were reached later than at 20 degrees C. Also the I to D risetime was
prolonged at 5 degrees C and it was found significantly longer in plants cultivated in ambient + 4
degrees C temperature. While a significant difference was found in the area over the rising part of the
fluorescence curve between 20 and 5 degrees C, no difference was found in area over the relaxation
curve part. Lowering of air temperature to 5 degrees C had no effect on Fv/Fm values in control
plants and in the plants cultivated in elevated CO2 but brought significant decrease in plants cultivated
in the ambient + 4 degrees C air temperature. Both Phi(II) and qP decreased with the temperature
lowered to 5 degrees C while the values of qN increased. The changes in fluorescence parameters
indicated altered functioning of PS II at low temperature. The changes in parameters are discussed
as a consequense of decreased enzymatic activity, decreased turnover of plastoquinone pool and
photoinhibition. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: CARBON DIOXIDE, CENTERS, CHLOROPHYLL FLUORESCENCE, LEAVES,
PHOTOINHIBITION, PHOTOSYNTHESIS, PHOTOSYSTEM, QUANTUM YIELD, SENSITIVITY,
VIOLAXANTHIN DEEPOXIDATION


     129  
Barton, C.V.M., and P.G. Jarvis. 1999. Growth response of branches of Picea sitchensis to four
years exposure to elevated atmospheric carbon dioxide concentration. New Phytologist 144(2):233-
243.

Branch bags were used to expose branches on mature Sitka spruce trees to either ambient [CO2] (A)
or elevated [CO2] (E) for 4 yr. This paper reports the effects of this treatment on the growth,
development and phenology of the branches, including shoot expansion, shoot numbers, needle
dimensions, needle numbers and stomatal density. The effect of elevated [CO2] on the relationship
between leaf area and sapwood area was investigated. Exposure to elevated [CO2] doubled
photosynthetic rates in current-fear shoots and, despite some downregulation, 1-yr-old E shoots also
had higher rates of photosynthesis than their A counterparts. Thus, the amount of assimilate fixed by
E branches was substantially more than that fixed by A branches; hen-ever, this increase in the local
production of assimilate did not lead to an increase in non-structural carbohydrate or stimulate
growth or meristematic activity within the E branches. There was a very consistent relationship
between leaf area and stem cross-sectional area that was not influenced by [CO2]. However,
unbagged branches had thicker stems than bagged branches, resulting in a slightly lower ratio of leaf
area to cross-sectional area. The implications of the results for the modelling of growth and allocation
and the potential utility of the branch bag technique are discussed.

KEYWORDS: ALLOCATION, ASSIMILATION, CO2- ENRICHMENT, MORPHOLOGY,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, PINE, RESISTANCE, STOMATAL
CONDUCTANCE, TREES


     130  
Barton, C.V.M., H.S.J. Lee, and P.G. Jarvis. 1993. A branch bag and co2 control-system for long-
term co2 enrichment of mature sitka spruce [picea-sitchensis (bong) carr]. Plant, Cell and
Environment 16(9):1139-1148.

This paper describes the construction and performance of branch bags and a CO2 control system used
to fumigate branches of mature Sitka spruce trees with air enriched in CO2 (700 mu mol mol(-1)).
It contains some examples of results obtained using the system over the course of the first two
growing seasons. The branch bags have run continuously for 2 years with very few problems. CO2
concentrations were within 20 mu mol mol(-1) of the target concentration for more than 90% of the
time. Temperatures within the bags were slightly higher than ambient (1-2 degrees C) and this had
some effect on phenology. Attenuation of quantum flux density (photosynthetically active radiation)
was 10-15%. The branch bag system has enabled investigation into the effects of elevated CO2 on
mature tissue without the problems and expense of fumigating whole trees. Growth in elevated CO2
resulted in an increase in starch and a decrease in soluble protein content of needles. Stomatal
conductance was higher in elevated CO2 grown needles, and there was some evidence of an increase
in photosynthetic capacity.

KEYWORDS: TREES


     131  
Basile, G., M. Arienzo, and A. Zena. 1993. Soil nutrient mobility in response to irrigation with
carbon- dioxide enriched water. Communications in Soil Science and Plant Analysis 24(11-
12):1183-1195.

In our experiments, carbonated water (CW) modified the equilibria in soil. Application of CW
decreased the soil pH about 1.5 units one hour after irrigation ended. Minimal, though well defined,
differences in soil pH were observed between the two carbonated treatments. The same relationship
between the treatments was not found in pH levels of the leachate. This seems strictly related to the
temporal and spatial changes in the carbon dioxide (CO2) acidifying effect caused by chemical and
biological factors as water descended the soil column. The temporary reduction in soil pH in the CW
treatment induced the highest nutrient mobility for most of the elements.

KEYWORDS: CO2


     132  
BassiriRad, H., K.L. Griffin, J.F. Reynolds, and B.R. Strain. 1997. Changes in root NH4+ and
NO3- absorption rates of loblolly and ponderosa pine in response to CO2 enrichment. Plant and Soil
190(1):1-9.

Root growth and physiological uptake capacity for NH4+ and NO3- were examined for seedlings of
loblolly and ponderosa pine grown for 160 days under two CO2 levels, ambient (35 Pa) and ambient
plus 35 Pa (70 Pa). Fraction of biomass allocated to active fine roots as well as total N (NH4+ +
NO3-) absorption per unit root dry mass were unaffected by CO2. On a whole-plant basis, elevated
CO2 led to a significant increase in N acquisition in loblolly but not in ponderosa pine. However, even
in loblolly pine where CO2 significantly increased plant N acquisition, the relative increase, in biomass
far exceeded the gain in N, i.e. a 60% increase in total dry weight was accompanied by only a 30%
increase in N gain in response to high CO2. We suggest that the commonly reported decline in tissue
N concentration of these and other species at high CO2 is largely caused by inability of the root
systems to sufficiently compensate for increased N demand. Elevated CO2 significantly altered root
uptake capacity of the different N forms, i.e., high CO2 significantly increased NO3- absorption rates,
but decreased NH4+ absorption rates in both species though the decrease in loblolly was insignificant.
However, elevated CO2 increased root respiration rate in loblolly pine while significantly decreasing
it in ponderosa pine. This indicates that CO2-induced changes in plant preference for inorganic N
forms is not simply regulated by root energy status. If changes in plant preference for inorganic N
forms represent typical responses to elevated CO2, the results could have important implications for
N dynamics in managed and natural plant communities.

KEYWORDS: AMMONIUM, AVAILABILITY, BARLEY, CARBON DIOXIDE, ELEVATED
ATMOSPHERIC CO2, GROWTH, L SEEDLINGS, NITRATE ABSORPTION, NITROGEN
CONCENTRATION, PLANT NUTRITION


     133  
Bassirirad, H., K.L. Griffin, B.R. Strain, and J.F. Reynolds. 1996. Effects of CO2 enrichment
on growth and root (NH4+)-N-15 uptake rate of loblolly pine and ponderosa pine seedlings. Tree
Physiology 16(11-12):957-962.

We examined changes in root growth and (NH4+)-N-15 uptake capacity of loblolly pine (Pinus taeda
L.) and ponderosa pine (Pinus ponderosa Douglas. Ex Laws.) seedlings that were grown in pots in
a phytotron at CO2 partial pressures of 35 or 70 Pa with NH4+ as the sole N source. Kinetics of N-
15-labeled NH4+ uptake were determined in excised roots, whereas total NH4+ uptake and uptake
rates were determined in intact root systems following a 48-h labeling of intact seedlings with N-15.
In both species, the elevated CO2 treatment caused a significant downregulation of (NH4+)-N-15
uptake capacity in excised roots as a result of a severe inhibition of the maximum rate of root
(NH4+)-N-15 uptake (V-max). Rates of (NH4+)-N-15 uptake in intact roots were, however,
unaffected by CO2 treatment and were on average 4- to 10-fold less than the V-max in excised roots,
suggesting that (NH4+)-N-15 absorption from the soil was not limited by the kinetics of root
(NH4+)-N-15 uptake. Despite the lack of a CO2 effect on intact root absorption rates, (NH4+)-N-15
uptake on a per plant basis was enhanced at high CO2 concentrations in both species, with the relative
increase being markedly higher in ponderosa pine than in loblolly pine. High CO2 concentration
increased total (NH4+)-N-15 uptake and the fraction of total biomass allocated to fine roots (< 2 mm
in diameter) to a similar relative extent. We suggest that the increased uptake on a per plant basis in
response to CO2 enrichment is largely the result of a compensatory increase in root absorbing
surfaces.

KEYWORDS: AMMONIUM, CARBON-DIOXIDE CONCENTRATION, DRY-MATTER,
ELEVATED CO2, LIMITATION, NITROGEN, NUTRITION, PHOTOSYNTHESIS, PLANTS,
RESPONSES


     134  
Bassirirad, H., J.F. Reynolds, R.A. Virginia, and M.H. Brunelle. 1997. Growth and root NO3-
and PO43- uptake capacity of three desert species in response to atmospheric CO2 enrichment.
Australian Journal of Plant Physiology 24(3):353-358.

In a phytotron experiment, we examined growth and rates of NO3- and PO43- uptake in seedlings
of two desert C-3 shrubs (Larrea tridentata and Prosopis glandulosa) and a desert C-4 perennial grass
(Bouteloua eriopoda) grown under CO2 partial pressures of 35 or 70 Pa. Plants were grown in soil
but uptake studies were conducted on roots of intact seedlings placed in nutrient solutions containing
both NO3- and PO43-. Elevated CO2 increased total biomass by 69 and 55% in Larrea and Prosopis
seedlings and by 25% in Bouteloua. NO3- and PO43- uptake rates were more than doubled in
Bouteloua at high compared to ambient CO2. In contrast, CO2 enrichment inhibited root NO3-
uptake capacity in Larrea by about 55% without a significant effect on PO43- absorption rate; rates
of NO3- and PO43- and uptake in Prosopis were insensitive to CO2 treatment. Elevated CO2
enhanced the proportion of biomass allocated to the fine roots in Bouteloua but markedly reduced
this fraction in Larrea and Prosopis. Foliar N concentration of both shrubs decreased in response to
elevated CO2, but was unaffected in Bouteloua. We suggest that compensatory changes in root size
and activity are critical in determining interspecies variation in plant nutrient relations under high
CO2.

KEYWORDS: CARBON DIOXIDE, COMPETITION, DRY-MATTER, ELEVATED CO2, MINERAL
NUTRITION, NITROGEN, PHOSPHATE, PLANTS, RHIZOSPHERE, SEEDLINGS


     135  
Bassirirad, H., R.B. Thomas, J.F. Reynolds, and B.R. Strain. 1996. Differential responses of root
uptake kinetics of NH4+ and NO3- to enriched atmospheric CO2 concentration in field-grown
loblolly pine. Plant, Cell and Environment 19(3):367-371.

The nitrogen requirement of plants is predominantly supplied by NH4+ and/or NO3- from the soil
solution, but the energetic cost of uptake and assimilation is generally higher for NO3- than for
NH4+. We found that CO2 enrichment of the atmosphere enhanced the root uptake capacity for
NO3-, but not for NH4+, in field-grown loblolly pine saplings. Increased preference for NO3- at the
elevated CO2 concentration was accompanied by increased carbohydrate levels in roots. The results
have important implications for the potential consequences of global climate change on plant- and
ecosystem-level processes in many temperate forest ecosystems.

KEYWORDS: ABSORPTION, AMMONIUM, ASSIMILATION, BARLEY, FLUXES, FORESTS,
PLANTS, RESPIRATION


     136  
Bassirirad, H., D.T. Tissue, J.F. Reynolds, and F.S. Chapin. 1996. Response of Eriophorum
vaginatum to CO2 enrichment at different soil temperatures: Effects on growth, root respiration and
PO43- uptake kinetics. New Phytologist 133(3):423-430.

In a phytotron experiment, we examined responses of a tussock sedge, Eriophorum vaginatum L.,
to changes in atmospheric CO2 concentration and soil temperature. We were particularly interested
in phosphorus (P) acquisition and below ground plant characteristics that regulated its uptake in
response to CO2 enrichment. Plants were grown at two CO2 partial pressures, 35 and 70 Pa, three
soil temperature regimes, 5, 15 and 25 degrees C and a constant ambient air temperature of 15
degrees C. Elevated CO2 increased total plant biomass production, but decreased tissue P
concentration. Although high CO2 enhanced root carbohydrate concentration, it inhibited root
respiration with no significant effect on root PO43- absorption capacity or root:shoot ratio.
Surprisingly, there were no significant interactions between CO2 and soil temperature. The inability
of Eriophorum to exhibit root-level compensatory adjustments, e.g. increased root:shoot ratio or
PO43- absorption capacity, was largely responsible for the observed decline in tissue P concentration
under elevated CO2 conditions. This could ultimately limit longterm growth responses of Eriophorum
to CO2 enrichment in the field where P availability is limiting. We found that uptake of PO43- in
response to elevated CO2 was independent of changes in root respiration, but changes in root
respiration could have important implications for ecosystem carbon budget under elevated CO2
levels. Our data indicated that although root respiration on a per unit biomass basis declined in
response to CO2 enrichment, this effect was counterbalanced by increased root biomass, so that high
CO2 stimulated root respiration on a whole-plant basis by 30%. This might help to explain why long-
term exposure to high CO2 increases CO2 efflux from Eriophorum-dominated ecosystems.

KEYWORDS: ALASKAN TUSSOCK TUNDRA, CARBON DIOXIDE, ECOSYSTEMS, ELEVATED
CO2, NITROGEN, NUTRIENT ACQUISITION, NUTRITION, PHOSPHATE ABSORPTION,
PHOTOSYNTHESIS, PLANTS


     137  
Bassman, J.H., and J.C. Zwier. 1991. Gas-exchange characteristics of Populus trichocarpa,
Populus  deltoides and Populus trichocarpa X Populus deltoides clones. Tree Physiology 8(2):145-
159.

Responses of net photosynthesis, dark respiration, photorespiration, transpiration, and stomatal
conductance to irradiance, temperature, leaf-to-air vapor density difference (VDD), and plant water
stress were examined in two Populus trichocarpa clones (one from a moist, coastal climate in western
Washington and one from a dry, continental climate in eastern Washington), one P. deltoides clone,
and two P. trichocarpa x P. deltoides clones. Light saturation of photosynthesis in greenhouse-grown
trees occurred at about 800- mu-mol m-2 s-1 for P. deltoides, P. trichocarpa x P. deltoides, and the
eastern Washington ecotype of P. trichocarpa, but at about 600-mu-mol m-2 s-1 for the western
Washington ecotype of P. trichocarpa. Average net photosynthesis (at saturating irradiance and the
optimum temperature of 25-degrees-C) was 20.7, 18.8, 18.2 and 13.4-mu-mol CO2 m-2 s-1 for P.
deltoides, P. trichocarpa x P. deltoides, and the eastern and western Washington clones of P.
trichocarpa, respectively. In all clones, net photosynthesis decreased about 14% as VDD increased
from 3 to 18 g H2O m-3. Stomatal conductance decreased sharply with decreasing xylem pressure
potential (XPP) in all clones except the western Washington clone of P. trichocarpa. Stomata in this
clone were insensitive to changes in XPP and did not control water loss. Complete stomatal closure
(stomatal conductance < 0.05 cm s-1) occurred at about -2.0 MPa in the eastern Washington clone
of P. trichocarpa and around -1.25 MPa in the P. deltoides and P. trichocarpa x P. deltoides clones.
Transpiration rates were highest in the P. trichocarpa x P. deltoides clone and lowest in the western
Washington clone of P. trichocarpa. The P. deltoides clone and eastern Washington clone of P.
trichocarpa had the highest water use efficiency (WUE) and the western Washington clone of P.
trichocarpa had the lowest WUE. The hybrids were intermediate. It was concluded that: (1) gas
exchange characteristics of eastern and western Washington clones of P. trichocarpa reflected
adaptation to their native environment; (2) crossing the western Washington clone of P. trichocarpa
with the more drought resistant P. deltoides clone produced plants better adapted to the interior
Pacific Northwest climate, although the stomatal response to soil water deficits in the hybrid was
conservative compared with that of the eastern Washington clone of P. trichocarpa; and (3)
introducing eastern Washington clones of black cottonwood into breeding programs is likely to yield
lines with favorable growth characteristics combined with enhanced WUE and adaptation to soil
water deficits.



     138  
Bassow, S.L., K.D.M. McConnaughay, and F.A. Bazzaz. 1994. The response of temperate tree
seedlings grown in elevated co2 to extreme temperature events. Ecological Applications 4(3):593-
603.

Mean global temperatures have been predicted to increase in the next century, if so the frequency of
extreme temperature events may also increase. Extreme temperatures may damage plant tissue and
consequently limit the survival of certain plant species in a region. Elevated concentrations of CO2
in the atmosphere alter plant allocation, physiology, and growth, and may accentuate or ameliorate
the damage from extreme temperatures. In this paper we explore the interactive effects of
atmospheric CO2 concentration, nutrient levels, and exposure to extreme temperatures on seedlings
of three species of temperate deciduous trees. A1-d exposure to extreme heat (45-degrees-C)
significantly decreased conductance the following day and decreased biomass as measured at both
35 and 105 d following the extreme temperature event, regardless of atmospheric CO2 concentration.
The most shade-tolerant species, striped maple, was most severely impacted by the extreme heat
event in both CO2 environments. Furthermore, striped maple seedlings grown in elevated CO2
concentrations had a significantly greater decrease in biomass due to the extreme heat event as
compared with striped maple plants grown in ambient CO2 concentrations at 35 d after the heat
event; however, al the end of the growing season at 105 d post treatment, this difference was not
significant. A one-night exposure to low temperatures (4- degrees-C) did not affect biomass for any
of these species. With an increase in global mean temperatures, the frequency of extreme temperature
events, particularly hot weather events, may increase and may extend to shaded understory sites. If
the frequency of extremely high temperatures increases, the role that temperature extremes may play
in changing competitive interactions and thus affecting community composition may increase in
importance, as these temperatures appear to severely alter plant survival and growth in some species.

KEYWORDS: ATMOSPHERIC CO2, CLIMATE, ECOSYSTEMS, ENRICHMENT, FOLIAGE
TEMPERATURE, HEAT-SHOCK PROTEINS, NIGHT TEMPERATURE, PLANTS,
THERMOTOLERANCE, VARIABILITY


     139  
Batjes, N.H. 1998. Mitigation of atmospheric CO2 concentrations by increased carbon sequestration
in the soil. Biology and Fertility of Soils 27(3):230-235.

The International Panel on Climate Change distinguished three main options for the mitigation of
atmospheric CO2 concentrations by the agricultural sector: (1) reduction of agriculture-related
emissions, (2) creation and strengthening of C sinks in the soil, and (3) production of biofuels to
replace fossil fuels. Options for sustained sequestration of C in the soil through adapted management
of land resources are reviewed in the context of the ongoing discussion on the need to reduce
greenhouse gas concentrations in the atmosphere. Enhanced sequestration of atmospheric CO2 in the
soil, ultimately as stable humus, may well prove a more lasting solution than (temporarily)
sequestering CO2 in the standing biomass through reforestation and afforestation. Such actions will
also help to reverse processes of land degradation, thus contributing to sustained food productivity
and security for the people in the regions concerned.

KEYWORDS: C STORAGE, CYCLE, DECOMPOSITION, ELEVATED CO2, FERTILIZATION,
MANAGEMENT, NITROGEN, ORGANIC-MATTER, TURNOVER, WORLD


     140  
Battaglia, M., and P.J. Sands. 1998. Process-based forest productivity models and their application
in forest management. Forest Ecology and Management 102(1):13-32.

Few process-based forest productivity models have become incorporated into forest management
systems. The prevalent perception is that process-based models are suited only for research
applications and that management questions will be solved only by using descriptive empirical models.
This is despite the fact that the latter can neither deal satisfactorily with changing environmental and
management conditions nor answer all questions currently asked by managers. This paper develops
the proposition that the end-use specifies the design and scale of forest simulation models, and that
given the range of questions now asked in forest management a range of models is required. The
spatial and temporal resolution, and the input and output data required to address typical forest
management questions is examined. A survey of recent literature examines in which areas, and by
whom, existing forest productivity models are being applied. It is concluded that many current
management questions can be adequately answered using models in which a phenomenological
approach is applied to predict annual forest growth at the stand-scale. Lumped-parameter process-
based models and hybrid models provide the most immediate means through which our understanding
of the biological processes underlying forest growth can be included in forest management systems.
However, more detailed process-based models can Flay an important role in validating simpler
models, in the development of generalizations applicable over long time scales and for testing
hypotheses about the way trees function and respond to interacting stresses. Guidelines are also given
on model structures appropriate for different classes of management questions. (C) 1998 Elsevier
Science B.V.

KEYWORDS: DECISION-SUPPORT SYSTEMS, DOUGLAS-FIR, DRY-MATTER
ACCUMULATION, ELEVATED CO2, GROWTH-MODELS, ORIENTED GROWTH, PINUS-
RADIATA, SITE INDEX, SPRUCE, YIELD


     141  
Batts, G.R., R.H. Ellis, J.I.L. Morison, and P. Hadley. 1998. Canopy development and tillering
of field-grown crops of two contrasting cultivars of winter wheat (Triticum aestivum) in response to
CO2 and temperature. Annals of Applied Biology 133(1):101-109.

Elevated CO2 (691 cf. 371 mu mol CO2 mol(-1) air) and warmer temperatures (over the range 1.0
degrees C below to 1.6 degrees C above ambient) increased light interception by crops of two
contrasting cultivars (Hereward and Soissons) of winter wheat (Triticum aestivum L.) during winter
growth in the field. The fractional interception of light by the canopy increased more rapidly initially
in Soissons than in Hereward, but Hereward showed a much greater response to CO2 (35% increase
in Hereward but only 7% in Soissons) at 500 degrees Cd after sowing. By terminal spikelet
formation, in contrast, fractional interception was greater in Hereward than in Soissons, while the
effect of CO2 was the same in both cultivars (9%). Thus, although differences in the relative response
of canopy development to CO2 were detected between cultivars initially, differences were negligible
during later development. The greater interception of light by the canopy in elevated CO2, at any one
temperature, resulted from increased tillering. The number of tillers plant(-1) at terminal spikelet was
a linear function of main stem dry mass at this developmental stage but with a greater response in
elevated CO2, viz 2.3 and 3.8 tillers g(-1) main stem dry mass at 371 and 691 mu mol CO2 mol(-1)
air, respectively; these relations were unaffected by cultivar.

KEYWORDS: YIELD


     142  
Batts, G.R., R.H. Ellis, J.I.L. Morison, P.N. Nkemka, P.J. Gregory, and P. Hadley. 1998. Yield
and partitioning in crops of contrasting cultivars of winter wheat in response to CO2 and temperature
in field studies using temperature gradient tunnels. Journal of Agricultural Science 130:17-27.

Diverse cultivars of winter wheat (Triticum aestivum L.) were grown in the field in 1993/94 and
1994/95 at Reading UK in temperature gradient tunnels at normal atmospheric (c. 370) or elevated
CO2 concentration (c. 700 mu mol CO2 mol(-1) air). In 1993/94, grain yield of cv. Avalon was
insensitive to mean temperature (between 8.8 and 10.9 degrees C), while elevated CO2 increased
yield by 1.3 t ha(-1) (12.6%). In all other cultivars, warming reduced grain yield and CO2 increased
grain yield. In 1993/94, in cvs Galahad and Mercia the effects of CO2 and temperature on yield were
additive. However, for cv. Hereward in both years and for cv. Soissons in 1994/95, there were
negative interactions between the effects of CO2 and temperature on yield: the maximum benefit of
doubling CO2 to grain yield, 4.5 and 2.7 t ha(-1) (65 and 29%) respectively, occurred at cooler
temperatures; there was no benefit from doubling CO2 (i.e. 0%) once the temperature had increased
above the seasonal mean by 2.2-2.6 degrees C in cv. Hereward and by 1.3 degrees C in cv. Soissons.
The beneficial effect of doubling CO2 on grain yield in cvs Galahad, Hereward, Mercia and Soissons
was negated by an increase in mean seasonal temperature of only 0.7-2.0 degrees C. Warming
decreased root dry mass at anthesis in 1994/95 while it increased at elevated CO2 (49 and 186%,
coolest and warmest regime, respectively). Carbon partitioned to roots declined progressively with
warming, while at elevated CO2 there was an average of 56% increase in allocation to roots. The
relative impacts of both CO2 and temperature were greater on root dry mass than on either grain
yield or total above-ground biomass, while the effects on grain and biomass yield varied considerably
between cultivars, suggesting that the impact of rising CO2 and temperature are likely to be
dependent on cultivar.

KEYWORDS: CARBON DIOXIDE, DURATION, ENRICHMENT, NITROGEN,
PHOTOSYNTHESIS, PLANT-RESPONSES, PRODUCTIVITY, ROOT-GROWTH, SYSTEM,
TRITICUM-AESTIVUM CROPS


     143  
Batts, G.R., J.I.L. Morison, R.H. Ellis, P. Hadley, and T.R. Wheeler. 1997. Effects of CO2 and
temperature on growth and yield of crops of winter wheat over four seasons. European Journal of
Agronomy 7(1-3):43-52.

Crops of winter wheat (Triticum aestivum L. cv. Hereward) were grown in the field in four
consecutive seasons from 1991/1992 to 1994/1995 at Reading, UK, within polyethylene-covered
tunnels along which a temperature gradient was superimposed on the ambient temperature variation
at normal atmospheric (ca. 370) or an increased [CO2] (ca. 700 mu mol CO2 mol(-1) air), producing
many environments from one sowing date in each season at one location. Mean seasonal temperatures
varied by up to 4 degrees C along the temperature gradient. Increased [CO2] had no effect on crop
duration, or on the rate of reproductive development, which had the same temperature sensitivity
across all years, A 2 degrees C warming, on the 4-year ambient mean temperature (10 degrees C),
reduced crop duration by 42 days (from 254), and reduced the reproductive phase by 16 days (from
130). Crop biomass generally declined with increase in mean temperature, and was greater at
increased [CO2], with the effect of increased [CO2] varying with temperature and between years (6-
34% range in relative stimulation by increased [CO2]). Grain yield was substantially reduced by
warmer temperatures, and increased by doubling [CO2], but the effect varied greatly between pears
and with temperature (7-168% range). There were both positive and negative interactions of
temperature and increased [CO2] on biomass and grain yield. In all 4 years, the increase in grain yield
from doubling [CO2] was negated by an increase in mean seasonal temperature of only 1.0-2.0
degrees C, Year-to-year variation in the responses of biomass and grain yield to [CO2] and
temperature resulted from differences in environmental conditions, influencing biomass partitioning
and altering the role of different yield components. (C) 1997 Elsevier Science B.V.

KEYWORDS: CARBON DIOXIDE, DURATION, ELEVATED CO2, FIELD, MODEL,
PRODUCTIVITY, RESPONSES, TRITICUM-AESTIVUM CROPS, VARIABILITY


     144  
Batts, G.R., T.R. Wheeler, J.I.L. Morison, R.H. Ellis, and P. Hadley. 1996. Developmental and
tillering responses of winter wheat (Triticum aestivum) crops to CO2 and temperature. Journal of
Agricultural Science 127:23-35.

Winter wheat (Triticum aestivum L., cv. Hereward) was grown in the held within four double-walled
polyethylene-covered tunnels along which near-linear temperature gradients were imposed at normal
atmospheric or at an elevated CO2 concentration (c. 700 mu mol mol(-1) CO2) in 1991/92 and in a
further experiment in 1992/93. Development was more rapid the warmer the temperature. In 1991/92
an increase in mean seasonal temperature of 3.5 degrees C reduced the duration from sowing to
harvest maturity (the stage when grain moisture content reduced naturally to 15- 18%) by c. 38 days,
and reduced the duration from the double ridge stage to harvest maturity by c. 34 days. A similar
difference resulted from only 1.6 degrees C warming in 1992/93. Although the range of mean
seasonal temperatures differed between years, the relation between temperature and rate of
development from sowing to harvest maturity was common to both years (base temperature, -0.8
degrees C; thermal time 2410 degrees C d). Carbon dioxide concentration had no effect on this
relation or on that between temperature and the rate of development from solving to the double ridge
stage and from the double ridge stage to harvest maturity. Carbon dioxide enrichment increased
tillering substantially in 1991/92; there were 200 more shoots m(-2) at terminal spikelet formation in
crops grown at elevated compared to normal CO2 (additional shoots were principally coleoptile tillers
and those developing after tiller 2) and this difference was reduced to 100 shoots m(-2) approaching
harvest maturity (additional shoots remaining were those developing after tiller 2). In contrast, no
effect of CO2 enrichment on tillering was detected at any stage of development in 1992/93. The
number of tillers per plant at terminal spikelet formation was a linear function of main stem dry weight
at this developmental stage; this relationship was not affected by year or CO2. As CO2 enrichment
increased main stem dry weight in the first year only, when main stem dry weights at normal CO2
were only one half of those values determined in the following year, it is concluded that any benefit
of increase in CO2 concentration to tillering in winter wheat may be greatest in those crop production
environments where main stem dry weights at terminal spikelet are least and vice versa.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, ENVIRONMENT, FIELD,
GROWTH, IMPACT, INITIATION, LEAF APPEARANCE, SENSITIVITY, YIELD


     145  
Bawa, K.S., and S. Dayanandan. 1998. Global climate change and tropical forest genetic resources.
Climatic Change 39(2-3):473-485.

Global climate change may have a serious impact on genetic resources in tropical forest trees. Genetic
diversity plays a critical role in the survival of populations in rapidly changing environments.
Furthermore, most tropical plant species are known to have unique ecological niches, and therefore
changes in climate may directly affect the distribution of biomes, ecosystems, and constituent species.
Climate change may also indirectly affect plant genetic resources through effects on phenology,
breeding systems, and plant-pollinator and plant seed disperser interactions, and may reduce genetic
diversity and reproductive output. As a consequence, population densities may be reduced leading
to reduction in genetic diversity through genetic drift and inbreeding. Tropical forest plants may
respond to climate change through phenotypic plasticity, adaptive evolution, migration to suitable
site, or extinction. However, the potential to respond is limited by a rapid pace of change and the non-
availability of alternate habitats due to past and present trends of deforestation. Thus climate change
may result in extinction of many populations and species. Our ability to estimate the precise response
of tropical forest ecosystems to climate change is limited by lack of long-term data on parameters that
might be affected by climate change. Collection of correlative data from long-term monitoring of
climate as well as population and community responses at selected sites offer the most cost-effective
way to understand the effects of climate change on tropical tree populations. However, mitigation
strategies need to be implemented immediately. Because many effects of climate change may be
similar to the effects of habitat alteration and fragmentation, protected areas and buffer zones should
be enlarged, with an emphasis on connectivity among conserved landscapes. Taxa that are likely to
become extinct should be identified and protected through at situ conservation programs.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, DRY FOREST, ELEVATED CO2,
INCOMPATIBILITY, PHENOLOGY, PLANT, RESPONSES, SYSTEMS, TREES


     146  
Baxter, R., T.W. Ashenden, and J.F. Farrar. 1997. Effect of elevated CO2 and nutrient status on
growth, dry matter partitioning and nutrient content of Poa alpina var vivipara L. Journal of
Experimental Botany 48(312):1477-1486.

Poa alpina var, vivipara L, was grown in an atmosphere containing either 340 or 680 mu mol CO2
mol(-1) within controlled environment chambers, The available nutrient regime was varied by altering
the supply of nitrogen and phosphorus within a complete nutrient solution, At a high, but not low,
N and P supply regime, elevated CO2 markedly increased growth, Differences between nutrient
supply, but not atmospheric CO2 concentration, altered the allometric relations between root and
shoot, Net photosynthesis of mature leaf blades and leaf N and P concentration were reduced in
plants grown at the elevated CO, concentration, The question was asked: is it possible to ascribe all
of these effects to elevated CO2 or are some due to nutrient deficiency caused by dilution with excess
carbon? Several criteria, including the nutrient content of sink tissue, root:shoot allometry and the
use of divalent cations to estimate integrated water flows are suggested in order to make this
distinction, It is concluded that only at a low supply of N and P, and elevated CO2 concentration, was
low leaf N concentration due to induced nutrient deficiency, The data are consistent with a model
where the capacity of sinks to use photosynthetically assimilated carbon sets both the rate of import
into those sinks (and thus rate of export from source leaves) and the rate of photosynthesis of source
leaves themselves.

KEYWORDS: ALLOCATION, ANTISENSE RBCS, ATMOSPHERIC CARBON-DIOXIDE,
NITROGEN, PHOSPHATE STATUS, PHOSPHORUS, PHOTOSYNTHESIS, RESPONSES,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, TOBACCO


     147  
Baxter, R., T.W. Ashenden, T.H. Sparks, and J.F. Farrar. 1994. Effects of elevated carbon-
dioxide on 3 montane grass species .1. Growth and dry-matter partitioning. Journal of Experimental
Botany 45(272):305-315.

Upland grasslands are a major component of natural vegetation within the UK. Such grasslands
support slow growing relatively stable plant communities. The response of native montane grass
species to elevated atmospheric carbon dioxide concentrations has received little attention to date.
Of such studies, most have only focused on short-term (days to weeks) responses, often under
favourable controlled environment conditions. In this study Agrostis capillaris L.(5), Festuca vivipara
L. and Poa alpina L. were grown under semi-natural conditions in outdoor open-top chambers at
either ambient (340 mu mol mol(- 1)) or elevated (680 mu mol mol(-1)) concentrations of
atmospheric carbon dioxide (CO2) for periods from 79 to 189 d, with a nutrient availability similar
to that of montane Agrostis-Fescue grassland in Snowdonia, N. Wales. Whole plant dry weight was
increased for A. capillaris and P. alpina, but decreased for F. vivipara, at elevated CO2. Major
components of relative growth rate (RGR) contributing to this change at elevated CO2 were transient
changes in specific leaf area (SLA) and leaf area ratio (LAR). Despite changes in growth rate at 680
mu mol mol(-1) CO2, partitioning of dry weight between shoot and root in plants of A. capillaris and
P. alpina was unaltered. There was a significant decrease in shoot relative to root growth at elevated
CO2 in F. vivipara which also showed marked discoloration of the leaves and increased senescence
of the foliage.

KEYWORDS: ATMOSPHERIC CO2, CO2- ENRICHMENT, COMMUNITIES, EXPOSURE,
PHOTOSYNTHESIS, PLANTS, RESPIRATION, SENESCENCE, STRESS, TEMPERATURE


     148  
Baxter, R., S.A. Bell, T.H. Sparks, T.W. Ashenden, and J.F. Farrar. 1995. Effects of elevated
co2 concentrations on 3 montane grass species .3. Source leaf metabolism and whole-plant carbon
partitioning. Journal of Experimental Botany 46(289):917-929.

Agrostis capillaris L.(5), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top
chambers at either ambient (340 +/- 3 mu mol mol(-1)) or elevated (680 +/- 4 mu mol mol(- 1))
concentrations of atmospheric carbon dioxide (GO,) for periods from 79-189 d. Photosynthetic
capacity of source leaves of plants grown at both ambient and elevated CO2 concentrations was
measured at saturating light and 5% CO2. Dark respiration of leaves was measured using a liquid
phase oxygen electrode with the buffer solution in equilibrium with air (21% O-2, 0.034% CO2).
Photosynthetic capacity of P. alpina was reduced by growth at 680 mu mol mol(-1) CO2 by 105 d,
and that of F. vivipara was reduced at 65 d and 189 d after CO2 enrichment began, suggesting down-
regulation or acclimation. Dark respiration of successive leaf blades of all three species was unaltered
by growth at 680 relative to 340 mu mol mol(-1) CO2. In F. vivipara, leaf respiration rate was
markedly lower at 189 d than at either 0 d or 65 d, irrespective of growth CO2 concentration. There
was a significantly lower total non- structural carbohydrate (TNC) concentration in the leaf blades
and leaf sheaths of A. capillaris grown at 680 mu mol mol(-1) CO2. TNC of roots of A. capillaris was
unaltered by CO2 treatment. TNC concentration was increased in both leaves and sheaths of P. alpina
and F. vivipara after 105 d and 65 d growth, respectively. A 4-fold increase in the water-soluble
fraction (fructan) in P. alpina and in all carbohydrate fractions in F. vivipara accounted for the
increased TNC content. In F. vivipara the relationship between leaf photosynthetic capacity and leaf
carbohydrate concentration was such that there was a strong positive correlation between
photosynthetic capacity and total leaf N concentration (expressed on a per unit structural dry weight
basis), and total nitrogen concentration of successive mature leaves reduced with time, Multiple
regression of leaf photosynthetic capacity upon leaf nitrogen and carbohydrate concentrations further
confirmed that leaf photosynthetic capacity was mainly determined by leaf N concentration. In P.
alpina, leaf photosynthetic capacity was mainly determined by leaf CHO concentration. Thus there
is evidence for downregulation of photosynthetic capacity in P. alpina resulting from increased
carbohydrate accumulation in source leaves. Leaf dark respiration and total N concentration were
positively correlated in P. alpina and F. vivipara. Leaf dark respiration and soluble carbohydrate
concentration of source leaves were positively correlated in A. capillaris. Changes in source leaf
photosynthetic capacity and carbohydrate concentration of plants grown at ambient or elevated CO,
are discussed in relation to plant growth, nutrient relations and availability of sinks for carbon.

KEYWORDS: ACCLIMATION, CALVIN CYCLE ENZYMES, CARBOHYDRATE CONTENT,
COTTON PLANTS, DIOXIDE EFFLUX, GROWTH, HIGH ATMOSPHERIC CO2,
PHOTOSYNTHETIC OXYGEN EVOLUTION, RESPIRATION, SPINACH LEAVES


     149  
Baxter, R., and J.F. Farrar. 1999. Export of carbon from leaf blades of Poa alpina L-at elevated
CO2 and two nutrient regimes. Journal of Experimental Botany 50(336):1215-1221.

The hypothesis was tested that, in plants of the alpine! meadow grass (Poa alpina L,) exposed to
elevated CO2, net photosynthesis and export from source leaves is; reduced as a result of feedback
from sinks. Nutrient supply was used as one way of reducing photosynthesis and export. Single plants
were grown in sand culture under specified controlled environmental conditions for a period of 50
d at two levels of nitrogen and phosphorus ('low': 0.2 mol m(-3) N, 0.04 mol m(-3) P;'high': 2.5 mol
m(-3) N, 0.5 mol m(-3) P). Compartmentation within, and export of carbon from, individual youngest
fully expanded leaves of acclimated plants was determined using C-14 feeding and efflux plus mass
balance calculations of carbohydrate export. Independent of treatment, the bulk of soluble
carbohydrate (65-75%) was present as fructan, with most of the remainder being sucrose. Depending
on nutrient supply, CO2 could alter export from source leaves either by a reduction in the amount of
sucrose present in a readily available pool for transport, or by altering the rate constant describing
phloem loading.

KEYWORDS: ATMOSPHERIC CO2, BARLEY, DIOXIDE, EXCISED LEAVES, GROWTH,
METABOLISM, PATTERNS, TEMPERATURE, TUSSOCK TUNDRA


     150  
Baxter, R., M. Gantley, T.W. Ashenden, and J.F. Farrar. 1994. Effects of elevated carbon-
dioxide on 3 grass species from montane pasture .2. Nutrient-uptake, allocation and efficiency of use.
Journal of Experimental Botany 45(278):1267-1278.

Agrostis capillaris L.(4), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top
chambers at either ambient (340 mu mol mol(-1) or elevated (680 mu mol mol(-1)) CO2 for periods
from 79 to 189 d. Under these conditions there is increased growth of A, capillaris and P. alpina, but
reduced growth of F. vivipara. Nutrient use efficiency, nutrient productivity (total plant dry weight
gain per unit of nutrient) and nutrient allocation of all three grass species were measured in an attempt
to understand their individual growth responses further and to determine whether altered nutrient-use
efficiencies and productivities enable plants exposed to an elevated atmospheric CO2 environment
to overcome potential limitations to growth imposed by soil fertility. Total uptake of nutrients was,
in general, greater in plants of A. capillaris and P. alpina (with the exception of N and K in the latter)
when grown at 680 mu mol mol(-1) CO2. In F. vivipara, however, uptake was considerably reduced
in plants grown at the higher CO2 concentration. Overall, a doubling of atmospheric CO2
concentration had little effect on the nutrient use efficiency or productivity of A, capillaris.
Reductions in tissue nutrient content resulted from increased plant growth and not altered nutrient
use efficiency. In P. alpina, potassium, magnesium and calcium productivities were significantly
reduced and photosynthetic nitrogen and phosphorus use efficiencies were doubled at elevated CO2
with respect to plants grown at ambient CO2. F. vivipara grown for 189 d showed the most marked
changes in nutrient use efficiency and nutrient productivity (on an extracted dry weight basis) when
grown at elevated CO2. F. vivipara grown at elevated CO2, however, showed large increases in the
ratio of nonstructural carbohydrate to nitrogen content of leaves and reproductive tissues, indicating
a substantial imbalance between the production and utilization of assimilate.

KEYWORDS: ACQUISITION, ATMOSPHERIC CO2, AVAILABILITY, CHENOPODIUM-ALBUM
L, CO2- ENRICHMENT, LEAF NITROGEN, NITROGEN CONCENTRATION,
PHOTOSYNTHETIC ACCLIMATION, PLANT GROWTH, SOURCE-SINK RELATIONS


     151  
Bazzaz, F.A. 1998. Tropical forests in a future climate: Changes in biological diversity and impact
on the global carbon cycle. Climatic Change 39(2-3):317-336.

Tropical forest ecosystems are large stores of carbon which supply millions of people with life
support requirements. Currently tropical forests are undergoing massive deforestation. Here, I
address the possible impact of global change conditions, including elevated CO2, temperature rise,
and nitrogen deposition on forest structure and dynamics. Tropical forests may be particularly
susceptible to climate change for the following reasons: (1) Phenological events (such as flowering
and fruiting) are highly tuned to climatic conditions. Thus a small change in climate can have a major
impact on the forest, its biological diversity and its role in the carbon cycle. (2) There are strong
coevolutionary interactions, such as pollination seed dispersal, with a high degree of specialization,
i.e., only certain animals can effect these activities for certain species. Global change can decouple
these tight coevolutionary interactions. (3) Because of high species diversity per unit area, species
of the tropical rain forest must have narrow niches. Thus changes in global climate can eliminate
species and therefore reduce biological diversity. (4) Deforestation and other forms of disturbance
may have significant feedback on hydrology both regionally and globally. The predicted decline in the
rainfall in the Amazon Basin and the intensification of the Indian monsoon can have a large effect on
water availability and floods which are already devastating low-lying areas. It is concluded that
tropical forests may be very sensitive to climate change. Under climatic change conditions their
structure and function may greatly change, their integrity may be violated and their services to people
may be greatly modified. Because they are large stores of great biological diversity, they require
immediate study before it is too late. The study requires the collaboration of scientists with a wide
range of backgrounds and experiences including biologists, climate modellers, atmospheric scientists,
economists, human demographers and sociologists in order to carry out holistic and urgently needed
work. Global climatic change brings a great challenge to science and to policy makers.

KEYWORDS: COOCCURRING BIRCH, DIOXIDE, ELEVATED ATMOSPHERIC CO2, GROWTH-
RESPONSE, INSECT HERBIVORE INTERACTIONS, MODEL SYSTEMS, PLANTS, RESOURCE
USE, TEMPERATURE, TREE SEEDLINGS


     152  
Bazzaz, F.A., D.D. Ackerly, F.I. Woodward, and L. Rochefort. 1992. Co2 enrichment and
dependence of reproduction on density in an annual plant and a simulation of its population-dynamics.
Journal of Ecology 80(4):643-651.

1. Populations of an annual plant, Abutilon theophrasti, were grown at four densities (100, 500, 1500
and 4000 m-2) and two CO2, concentrations (350 and 700 mul l-1) to examine the influence of CO2
environment on density-dependent patterns of demography and reproduction. Variables measured
included survivorship, proportion of plants flowering and fruiting, number of fruiting individuals,
number of seeds per individual, total seed production per population, mean seed mass, and
germination of seeds produced in each environment. 2. All variables, except the number of fruiting
individuals, declined with increasing density, and at the highest density no individuals set seed. The
number of fruiting individuals was highest at a density of 500m-2. In the elevated CO2 environment,
survivorship was significantly reduced but the proportion of plants flowering and fruiting and the
number of fruiting individuals in each population all increased. Total population seed production was
higher in the elevated CO2 environment at all densities, although the differences were not significant.
Significant effects of CO2, concentration were observed only for population-level variables, but not
for mean individual fecundity or seed size. Seed germination declined with increasing maternal
density, and no germination was recorded for seeds produced at 1500 m-2 3. Simple models of
population dynamics, utilizing difference equations, were constructed to examine potential
population-level consequences of these density and CO2 effects. In the absence of a persistent seed
pool, the simulated populations exhibited damped or stable oscillations under low germination values,
but displayed non-cyclic ('chaotic') oscillations or went extinct for higher germination due to the
complete failure of seed-set at high density. Because of its higher fecundity, the elevated- CO2
population generally exhibited greater oscillations, and the critical germination value at which the
simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2
population.

KEYWORDS: ABUTILON-THEOPHRASTI, COMPETITION, CYCLES, ELEVATED CO2,
GROWTH, NEIGHBORHOOD MODELS, SINGLE-SPECIES POPULATIONS


     153  
Bazzaz, F.A., J.S. Coleman, and S.R. Morse. 1990. Growth-responses of 7 major cooccurring tree
species of the northeastern united-states to elevated CO2. Canadian Journal of Forest Research-
Revue Canadienne De Recherche Forestiere 20(9):1479-1484.



     154  
Bazzaz, F.A., M. Jasienski, S.C. Thomas, and P. Wayne. 1995. Microevolutionary responses in
experimental populations of plants to co2-enriched environments - parallel results from 2 model
systems. Proceedings of the National Academy of Sciences of the United States of America
92(18):8161-8165.

Despite the critical role that terrestrial vegetation plays in the Earth's carbon cycle, very little is
known about the potential evolutionary responses of plants to anthropogenically induced increases
in concentrations of atmospheric CO2. We present experimental evidence that rising CO2
concentration may have a direct impact on the genetic composition and diversity of plant populations
but is unlikely to result in selection favoring genotypes that exhibit increased productivity in a CO2-
enriched atmosphere. Experimental populations of an annual plant (Abutilon theophrasti, velvetleaf)
and a temperate forest tree (Betula alleghaniensis, yellow birch) displayed responses to increased CO2
that were both strongly density-dependent and genotype-specific. In competitive stands, a higher
concentration of CO2 resulted in pronounced shifts in genetic composition, even though overall CO2-
induced productivity enhancements were small, For the annual species, quantitative estimates of
response to selection under competition were 3 times higher at the elevated CO2 level. However,
genotypes that displayed the highest growth responses to CO2 when grown in the absence of
competition did not have the highest fitness in competitive stands. We suggest that increased CO2
intensified interplant competition and that selection favored genotypes with a greater ability to
compete for resources other than CO2. Thus, while increased CO2 may enhance rates of selection
in populations of competing plants, it is unlikely to result in the evolution of increased CO2
responsiveness or to operate as an important feedback in the global carbon cycle, However, the
increased intensity of selection and drift driven by rising CO2 levels may have an impact on the
genetic diversity in plant populations.

KEYWORDS: AMBIENT, CO2- ENRICHMENT, COMPETITION, DENSITY, ECOSYSTEMS,
ELEVATED CARBON-DIOXIDE, GROWTH-RESPONSE, NITROGEN, SEEDLINGS, SELECTION


     155  
Bazzaz, F.A., and K.D.M. McConnaughay. 1992. Plant interactions in elevated CO2 environments.
Australian Journal of Botany 40(4-5):547-563.

Increasing atmospheric carbon dioxide concentrations present a novel resource condition for plant
communities. In order to understand and predict how plant community structure and function may
be altered in a high CO2 world, we need to understand how interactions among neighbouring plants
within a community will alter the growth and reproduction of component species. Because CO2 is
readily diffusible, plants have little influence on the CO2 acquisition of their neighbours, except within
particularly dense canopies. Thus, plants seldom compete directly for CO2. Rather, CO2 availability
is likely to alter plant-plant interactions indirectly through its effects on plant growth and competition
for other resources. As a consequence, competitive outcome under elevated CO2 atmospheres within
even simple systems is not easy to predict. For example, under some conditions, C4 species in
competitive assemblages have improved competitive ability relative to C3 competitors as a result of
CO2 enrichment, contrary to expectations based on their photosynthetic pathways. It is now clear that
individually grown plants can differ substantially from those within mono- or multispecific stands in
response to CO2 enrichment. At present, our understanding of how stands of interacting plants
modify the availability of CO2 and other resources is incomplete. We urgently need information about
how elevated CO2 atmospheres influence stand formation and population dynamics, specifically with
regard to the identities, numbers, sizes and reproductive fitnesses of individuals within single and
multiple species stands, if we are to make multi-generational predictions concerning the fate of
populations and communities in an elevated CO2 world.

KEYWORDS: ARCTIC TUNDRA, ATMOSPHERIC CARBON-DIOXIDE, DECIDUOUS FOREST,
ESTUARINE MARSH, OLD- FIELD PERENNIALS, QUERCUS-ALBA, SEEDLING GROWTH,
SIZE HIERARCHIES, SOIL RESPIRATION, TUSSOCK TUNDRA


     156  
Bazzaz, F.A., and S.L. Miao. 1993. Successional status, seed size, and responses of tree seedlings
to co2, light, and nutrients. Ecology 74(1):104-112.

We studied how an enriched CO2 atmosphere in a fully crossed design of light and nutrients,
influenced 1 st-yr seedling growth in six New England deciduous forest tree species. The species, in
the order of increasing shade tolerance, were gray birch (Betula populifolia), ash (Fraxinus americana
L.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), yellow birch (Betula alleghaniensis
Britton), and striped maple (Acerpensylvanicum). Elevated CO2 environments significantly stimulated
the seedling growth of all six species. Generally this was more pronounced in low light. The greatest
stimulation was found under the condition of low light and high nutrients. However, individual
species responded differently to elevated CO2 levels. Among the three early-successional species,
gray birch, ash, and red maple, a significant increase in seedling growth under elevated CO2
conditions was found only with high nutrients. The three late-successional species grown under
elevated CO2 conditions (red oak, yellow birch, and striped maple) showed a greater percentage
increase in seedling growth in low light than in high light. Thus, for the early- successional species,
the degree of enhancement of seedling growth by elevated CO2 levels was more sensitive to nutrient
levels, while in the late-successional species the enhancement was more sensitive to the level of light.
Moreover, species with large seeds (e.g., red oak) exhibited a greater response to elevated CO2 levels
under low light than species with small seeds (e.g., gray birch). The results emphasize the importance
of plant species as well as other environmental resources in modifying the response of plants to
elevated CO2. Considering the light and nutrient environment observed in forest gaps of various sizes,
the results of the present experiment suggest seedling regeneration in New England deciduous forests
may be altered in a future high CO2 environment.

KEYWORDS: ECOSYSTEMS, ELEVATED CO2, ENRICHMENT, GROWTH-RESPONSES,
LIQUIDAMBAR- STYRACIFLUA, NORTHEASTERN UNITED-STATES, PHOTOSYNTHESIS,
PINUS-TAEDA SEEDLINGS, PLANTS, TEMPERATURE


     157  
Bazzaz, F.A., S.L. Miao, and P.M. Wayne. 1993. Co2-induced growth enhancements of
cooccurring tree species decline at different rates. Oecologia 96(4):478-482.

To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence
the long-term growth of tree seedlings, six co-occurring members of temperature forest communities
including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum),
yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra
L.) were raised in a glasshouse for three years in a complete factorial design. After three years of
growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient
CO2 atmospheres, however, magnitudes of CO2-induced growth enhancements were contingent on
the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO2-
induced growth enhancements after one year of growth were greater than after three years of growth,
though species' growth enhancements over the three years declined at different rates. These results
suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods
of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence
forest productivity via long-term species compositional changes in forests.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COMMUNITIES, COOCCURRING BIRCH,
ELEVATED CO2, ENRICHMENT, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION,
RESPONSES, SEEDLINGS, SOURCE-SINK RELATIONS


     158  
Beaudry, R.M. 1999. Effect of O-2 and CO2 partial pressure on selected phenomena affecting fruit
and vegetable quality. Postharvest Biology and Technology 15(3):293-303.

It is likely that from the time of the Roman Empire and perhaps before, people involved in the storage
of plant material as food recognized that atmospheric modification can provide some benefit in
improving storability. However, active, commercial modification of the atmosphere for the
preservation of fresh fruit and vegetables dates to the early part of this century. Early successes with
apple fruit has lead to the attempt to apply modified atmospheres to a wide range of commodities.
Responses to atmospheric modification are found to vary dramatically among plant species, organ
type and developmental stage and include both unwanted and beneficial physiological responses,
Desirable responses include a reduction in respiration, a reduction in oxidative tissue damage or
discoloration, a reduction in the rate of chlorophyll degradation and a reduction in ethylene sensitivity
with the concomitant reduction in the rate of ripening and other ethylene-mediated phenomena.
Undesirable responses have included the induction of fermentation, the development of disagreeable
flavors? a reduction in aroma biosynthesis, the induction of tissue injury and an alteration in the
makeup of microbial fauna. The physiological bases for some of these responses to elevated CO2 and
reduced O-2 are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERE, BIOSYNTHESIS, BLUEBERRY FRUIT, BROCCOLI, ENERGY-
CHARGE, ETHYLENE, MAIZE ROOT-TIPS, OXYGEN PARTIAL PRESSURES, POSTHARVEST
DECAY, VOLATILE COMPOUNDS


     159  
Becker, M., T.M. Nieminen, and F. Geremia. 1994. Short-term variations and long-term changes
in oak productivity in northeastern france - the role of climate and atmospheric co2. Annales Des
Sciences Forestieres 51(5):477-492.

A dendroecological study was carried out in 2 forests in northeastern France with the aim of
identifying and quantifying possible long-term trends in the radial growth of sessile oak (Quercus
petraea (Matt) Liebl) and pedunculate oak (Q robur L). A total of 150 sites were selected to represent
the ecological diversity of these forests. An index Cd was used to correct annual ring width in order
to compensate for the effect of different competition situations. The data were standardized with
reference to the mean curve 'basal area increment vs cambial age'. The growth index curves revealed
a strong increase in sessile oak growth (+ 64% during the period 1888 to 1987) as well as in that of
peduncutate oak (+40%). The growth increase in the 'young' rings (<60 years) of sessile oak was +
87 %, and that of young rings of pedunculate oak was + 49%. The corresponding increase in the 'old'
rings (>65 years) was + 48% and 15% respectively (not significant for the latter). It would thus
appear that pedunculate oak has benefited to a lesser extent than sessile oak from the progressive
changes in its environment. Years showing a strong growth decrease are more common for
pedunculate oak than for sessile oak. These results are consistent with a recent hypothesis about a
slow but general retreat of pedunculate oak, including severe episodic declines, in favour of sessile
oak in many regions of France. A model was created using a combination of meteorological data
(monthly precipitation and temperature) starting in 1881, and increasing atmospheric CO,
concentrations. The model explains 78.3% of the variance for sessile oak and 74.3% for pedunculate
oak. This includes some monthly parameters of year y (year of ring formation), and also some
parameters of the years y-1 to y-4 for sessile oak and y-1 to y-5 for pedunculate oak. The models
satisfactorily reproduce the long-term trends and the interannual variation. The climatic variables
alone (ie excluding the CO, concentration) were insufficient to explain the trends observed. The
possible direct and indirect effects of increasing CO2 concentration on the growth of both species are
discussed.

KEYWORDS: ABIES-ALBA MILL, CARBON DIOXIDE, FOREST, GROWTH, MOUNTAINS, PAST
VITALITY, PINE, TREES, TRENDS, VEGETATION


     160  
Beckmann, K., C. Dzuibany, K. Biehler, H. Fock, R. Hell, A. Migge, and T.W. Becker. 1997.
Photosynthesis and fluorescence quenching, and the mRNA levels of plastidic glutamine synthetase
or of mitochondrial serine hydroxymethyltransferase (SHMT) in the leaves of the wild-type and of
the SHMT-deficient stm mutant of Arabidopsis thaliana in relation to the rate of photorespiration.
Planta 202(3):379-386.

The regulation by photorespiration of the transcript level corresponding to plastidic glutamine
synthetase (GS-2) was investigated in the leaves of Arabidopsis thaliana (L.) Heynh. Photorespiration
was suppressed by growing the plants in an atmosphere containing 300 Pa CO2. Suppression of
photorespiration was demonstrated by the ability of the conditionally lethal serine
hydroxymethyltransferase (SHMT)- deficient stm mutant of A. thaliana to grow normally under these
conditions. In contrast to previous studies with bean or pea that were performed at very high CO2
partial pressure (2-4 kPa; Edwards and Coruzzi, 1989, Plant Cell 1: 241-248; Cock et al., 1991, Plant
Mol Biol 17: 761-771), suppression of photorespiration during growth of A. thaliana in an
atmosphere with 300 Pa CO2 had no effect on the leaf GS-2 transcript level. In the short term, neither
suppression of photorespiration induced by the transfer of air-grown A. thaliana plants into a CO2-
enriched atmosphere, nor an increase in the rate of photorespiration achieved by the transfer of high-
CO2-grown A. thaliana plants into air resulted in a change in the GS-2 mRNA level. The absence of
photorespiratory ammonium release in leaves of the stm mutant had no effect on the GS-2 transcript
level. Overall, our data argue against a control by photorespiration of the A. thaliana leaf GS-2
mRNA pool. In contrast, regulation of the leaf SHMT mRNA level may involve a negative feedback
effect of at least one metabolite derived from the glycine/serine conversion during photorespiration,
as indicated by the overexpression of SHMT transcripts in the leaves of the stm mutant.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED CO2,
EXCHANGE, EXPRESSION, GENES, LIGHT, SUNFLOWER LEAVES, TOBACCO


     161  
Beer, S., and E. Koch. 1996. Photosynthesis of marine macroalgae and seagrasses in globally
changing CO2 environments. Marine Ecology-Progress Series 141(1-3):199-204.

Photosynthetic rates of many marine macroalgae are saturated by the present day inorganic carbon
(Ci) composition of seawater, while those of seagrasses (or marine angiosperms) are CO2- limited.
In this study we attempted to simulate the Ci conditions of near-shore seawater during the time that
seagrasses colonised the sea (in the Cretaceous), and compare the photosynthetic performance of
representatives of the 2 plant groups under those versus present day conditions. The results show that
the seagrasses have an affinity for Ci at least as high as the algae under the low pH and high
CO2/HCO3- concentration ratios simulating near-shore areas of the Cretaceous seas, indicating that
their photosynthetic capacity then matched that of macroalgae. However, in the high pH and high
CO2/HCO3- ratios of today, their affinity for Ci is lower than that of the macroalgae, and it is
suggested that this deficiency renders them a lower ability for Ci utilisation. This situation may
possibly be reversed again as global CO2 levels of the atmosphere and, consequently, of near-shore
marine habitats increase in the future.

KEYWORDS: CELLS, ULVA SP


     162  
Beerling, D.J. 1994. Modeling palaeophotosynthesis - late cretaceous to present. Philosophical
Transactions of the Royal Society of London Series B-Biological Sciences 346(1318):421-432.

This paper presents an attempt to reconstruct potential changes in the photosynthetic rates of
terrestrial C3 leaves over the past 120 Ma. The approach has been to couple palaeoatmospheric
reconstructions of O-2, CO2 and temperature from geochemical modelling, and an independent
estimate of ancient CO2 changes from fossil porphyrins, with a mechanistic biochemical model of C3
photosynthesis. The model accounts for the effect of each of these palaeoenvironmental changes, at
the biochemical level, to predict leaf photosynthesis and has been parametrized for a typical
gymnosperm and angiosperm. The results indicate clear potential for increased photosynthetic C3
fixation in the warm Cretaceous for both angiosperms and gymnosperms, despite the increased O-2
content of the atmosphere prevailing at the time. Photosynthetic rates are then predicted to
progressively decline into the Tertiary, as a result of global cooling. The model simulations also point
towards some leaf-level ecophysiological explanations for the rise in angiosperm dominance and the
concomitant decline in gymnosperms from the late Cretaceous onwards, at mid-latitudes, which have
not been considered previously. This work provides a basis for scaling up to the canopy level to
predict the primary productivity of ancient ecosystems and their possible feedback on atmospheric
composition and climate.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CLIMATE CHANGE, ELEVATED CO2,
HIGH-LATITUDES, PHANEROZOIC TIME, PHOTOSYNTHESIS, PLANTS, TEMPERATURE,
TERTIARY BOUNDARY


     163  
Beerling, D.J. 1994. Predicting leaf gas-exchange and delta-C-13 responses to the past 30000 years
of global environmental-change. New Phytologist 128(3):425-433.

Theoretical developments in our understanding of leaf gas exchange processes and carbon isotope
composition (delta(13)C) mean that it should now be possible to model their responses to global
environmental change. Such a model would be of use for process-based interpretations of historical
changes in leaf delta(13)C and for understanding the global stable carbon isotope balance. This paper
describes the development and validation of a model towards this aim. The resulting model is used
to simulate changes in leaf photosynthesis, stomatal conductance and delta(13)C of limber pine (Pinus
flexilis) in response to the past 30000 y of global environmental change. The predictions of needle
delta(13)C are in line with reported measurements of delta(13)C from fossilized Pinus flexilis needles
preserved in packrat middens in western USA. Leaf gas exchange predictions show that the increased
water use efficiency (WUE) of these trees growing in present-day environments, relative to the past,
was brought about through an increase in photosynthetic rates and a decrease in stomatal
conductance. This contrasts with the explanation of the recent (past 200 y) increase in the WUE of
temperate and Mediterranean ecosystems inferred from delta(13)C measurements which are predicted
by the model to have arisen largely by a decrease in stomatal conductance in response to increases
in the concentration of atmospheric CO2 since the pre-industrial era. The model as described offers
the potential to contribute to our understanding of vegetation effects on the global carbon isotope
balance during the glacial periods, and therefore to provide a further constraint on the carbon cycle
models used to explain the low concentrations of atmospheric CO2 at these times.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, C-13/C-12 RATIO, CARBON ISOTOPE
DISCRIMINATION, DIOXIDE, EMPIRICAL-MODEL, ICE-CORE RECORD, LEAVES,
PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, WATER-USE EFFICIENCY


     164  
Beerling, D.J. 1996. C-13 discrimination by fossil leaves during the late-glacial climate oscillation
12-10 ka BP: Measurements and physiological controls. Oecologia 108(1):29-37.

The late-glacial climatic oscillation, 12-10 ka BP, is characterised in ice core oxygen isotope profiles
by a rapid and abrupt return to glacial climate. Recent work has shown that associated with this
cooling was a drop in atmospheric CO2 concentration of ca. 50 ppm. In this paper, the impact of
these environmental changes on C-13 discrimination is reported, based on measurements made on
a continuous sequence of fossil Salix herbacea leaves from a single site. The plant responses were
interpreted using an integrated model of stomatal conductance, CO2 assimilation and intercellular
CO2 concentration, influenced by external environmental factors. According to the model,
temperature exerts a marked influence on C-13 discrimination by leaves and the pattern of C-13
changes recorded by the fossil leaves is consistent with other palaeotemperature curves for 12-10 ka
BP, particularly the deuterium isotope record from Alaskan Salix woods, which generally reflects
ocean temperatures. The gas exchange model correctly accounts for these changes and so permits
the reconstruction of ancient rates of leaf CO2 uptake and loss of water vapour in response to the
abrupt late-glacial changes in global climate and CO2. The approach provides the required
physiological underpinning for extracting quantitative estimates of past temperatures and for
contributing an ecophysiological explanation for changes in C-13 discrimination in the fossil record.

KEYWORDS: ATMOSPHERIC CO2, C-13/C-12 RATIOS, C-3 PLANTS, CARBON ISOTOPE
DISCRIMINATION, ELEVATED CO2, ENVIRONMENTAL-CHANGE, STOMATAL
CONDUCTANCE, WATER-USE EFFICIENCY, WESTERN NORWAY, YOUNGER DRYAS


     165  
Beerling, D.J. 1997. Carbon isotope discrimination and stomatal responses of mature Pinus sylvestris
L trees exposed in situ for three years to elevated CO2 and temperature. Acta Oecologica-
International Journal of Ecology 18(6):697-712.

The Climate Change Experiment (CLIMEX) is a unique large scale facility in which an entire
undisturbed catchment of boreal vegetation has been exposed to elevated CO2 (560 ppm) and
temperature (+3 degrees C summer, +5 degrees C winter) for the past three years with all the soil-
plant-atmosphere linkages intact. Here, carbon isotope composition end stomatal density have been
analysed from sequential year classes of needles of mature Scots pine trees (Pinus sylvestris L.) to
investigate the response of time-integrated water-use efficiency (WUE) and stomatal density to CO2
enrichment and climate change. Cal bon isotope discrimination decreased and WUE increased in
cohorts of needles developing under increased CO2 and temperature, compared to needles on the
same trees developing in pretreatment years. Mid-season instantaneous gas exchange, measured on
the same trees for the past four pears, indicated that these responses resulted from higher needle
photosynthetic rates and reduced stomatal conductance. Needles of P. sylvestris developing under
increased CO2 and temperature had consistently lower stomatal densities than their ambient grown
counterparts on the same trees. The stomatal density of P. sylvestris needles was inversely correlated
with delta(13)C- derived WUE, implying some effect of this morphological response on leaf gas
exchange. Future atmospheric CO2 and temperature increases are therefore likely to improve the
water economy of P. sylvestris, at least at the scale of individual needles, by affecting stomatal density
and gas exchange processes.

KEYWORDS: 4-YEAR EXPOSURE, BOREAL VEGETATION, C-3 PLANTS, DENSITY,
ENRICHMENT, GAS-EXCHANGE RESPONSES, LAST 3 CENTURIES, SCOTS PINE, WATER-
USE EFFICIENCY, WHOLE-CATCHMENT


     166  
Beerling, D.J. 1997. Interpreting environmental and biological signals from the stable carbon isotope
composition of fossilized organic and inorganic carbon. Journal of the Geological Society 154:303-
309.

Stable carbon isotope studies on marine and terrestrial organic and inorganic carbon provide a means
for detecting global climate change and for reconstructing past concentrations of atmospheric CO2.
Comparison between the CO2 estimates reconstructed from carbon isotope studies for the past 150
Ma show good agreement with the predictions of a long-term carbon- cycle model based on mass-
balance studies. Further, the CO2 estimates from these sources over the entire Phanerozoic show
agreement with the fossil record of leaf stomatal density change-a feature inversely related to the
concentration of atmospheric CO2. Isotopic studies on temporal sequences of fossilized terrestrial
organic matter have contributed to palaeoecological studies on shifts in the dominance of plants with
the C-4 photosynthetic pathway in ecosystems and historical changes in the metabolic processes of
leaves of individual species. The long-term perspective offered by these studies provides critical
information for assessing the responses of biological systems to future global environmental change.

KEYWORDS: ATMOSPHERIC CO2, C-4 PLANTS, CLIMATE CHANGE, DIOXIDE, ELEVATED
CO2, ICE-CORE RECORD, LATE QUATERNARY, PERMIAN TRIASSIC BOUNDARY,
STOMATAL DENSITY, WATER-USE EFFICIENCY


     167  
Beerling, D.J. 1998. The future as the key to the past for palaeobotany? Trends in Ecology and
Evolution 13(8):311-316.

Continued increase in the concentration of atmospheric CO2 and its possible effects on global climate
has generated intense research interest on the likely responses of terrestrial plants and vegetation.
Results from this new research provide quantitative information on plant function and growth in an
environment with a high CO2 concentration, but are also relevant to understanding plant growth in
the distant past and to the techniques employed by palaeobotanists for reconstructing past climates
from fossil plant remains. Experimental CO(2)enrichment of plants has demonstrated direct effects
on leaf physiognomy, the tolerance of plants to low temperature and the relationship between tree
rings, CO(2)and climate; it therefore signals the need for caution in interpreting palaeoclimates from
fossils.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATIONS, CLIMATE, EARLY TERTIARY,
ELEVATED CO2, ENRICHMENT, FOSSIL PLANTS, FROST HARDINESS, PHOTOSYNTHESIS,
TEMPERATURE, TREE GROWTH


     168  
Beerling, D.J. 1999. Long-term responses of boreal vegetation to global change: an experimental
and modelling investigation. Global Change Biology 5(1):55-74.

The response of boreal ecosystems to future global change is an uncertain but potentially critical
component of the feedback between the terrestrial biosphere and the atmosphere. To reduce some
of the uncertainties in predicting the responses of this key ecosystem, the climate change experiment
(CLIMEX) exposed an entire undisturbed catchment of boreal vegetation to CO2 enrichment (560
ppmv) and climate change (+ 5 degrees C in winter, + 3 degrees C in summer) for three years (1994-
96). This paper describes the leaf metabolic responses of the vegetation to the experimental treatment
and model simulations of possible future changes in the hydrological and carbon balance of the site.
Randomized intervention analysis of the leaf gas exchange measurements for the dominant species
indicated Pinus sylvestris had significantly (P < 0.01) higher photosynthetic rates and Betula
pubescens and Vaccinium myrtillus had significantly (P < 0.01) lower stomatal conductances after
three years treatment compared to the controls. These responses led to sustained increases in leaf
water-use efficiency of all species of trees and ground shrubs, as determined from carbon isotope
analyses. Photosynthesis (A) vs. intercellular CO2 (c(i)) response curves (A/c(i) responses), RuBisCo
analysis and leaf nitrogen data together suggested none of the species investigated exhibited down-
regulation in photosynthetic capacity. At the whole ecosystem level, the improved water economy
of the plants did not translate into increased catchment runoff. Modelling simulations for the site
indicate this was most likely brought about by a compensatory increase in evapotranspiration. In
terms of the carbon budget of the site, the ecosystem model indicates that increased CO2 and
temperature would lead to boreal ecosystems of the type used in CLIMEX, and typical of much of
southern Norway, acting as moderate net sinks for CO2.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, ECOSYSTEM EXPERIMENTS,
ELEVATED CO2, FOREST ECOSYSTEMS, GAS-EXCHANGE RESPONSES, PHOTOSYNTHETIC
RESPONSE, RISING ATMOSPHERIC CO2, SCOTS PINE, STOMATAL CONDUCTANCE,
WATER-USE EFFICIENCY


     169  
Beerling, D.J., and W.G. Chaloner. 1993. Evolutionary responses of stomatal density to global co2
change. Biological Journal of the Linnean Society 48(4):343-353.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, FORESTS, GAS-
EXCHANGE, GROWTH, INCREASE, PLANTS, POPLAR CLONES, WATER-USE EFFICIENCY


     170  
Beerling, D.J., and W.G. Chaloner. 1993. The impact of atmospheric co2 and temperature-change
on stomatal density - observations from quercus-robur lammas leaves. Annals of Botany 71(3):231-
235.

KEYWORDS: CARBON ISOTOPES, CENTURIES, DIOXIDE, ELEVATED CO2, GROWTH,
KRAKOW REGION, PLANTS, RECORD, RESPONSES


     171  
Beerling, D.J., and W.G. Chaloner. 1993. Stomatal density responses of egyptian olea-europaea
L leaves to co2 change since 1327 bc. Annals of Botany 71(5):431-435.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, ENRICHMENT, RECORD, VOSTOK ICE-
CORE


     172  
Beerling, D.J., W.G. Chaloner, B. Huntley, A. Pearson, and M.J. Tooley. 1991. Tracking
stomatal densities through a glacial cycle - their significance for predicting the response of plants to
changing atmospheric CO2 concentrations. Global Ecology and Biogeography Letters 1(5):136-142.

Continued increases in the global atmospheric CO2 concentration have been predicted from current
and projected rates of fossil fuel burning. Understanding the response of stomatal density as an
important ecophysiological parameter controlling the productivity of vegetation is essential if the role
of plants in the global carbon budget are to be predicted. Experimental exposure of plants to elevated
CO2 regimes in controlled environment chambers can only indicate immediate, phenotypic, short-term
responses. The investigation of fossil leaves of extant species growing under the different atmospheric
conditions of the last glacial and deglacial transition, when evidence from an Antarctic ice core
(Barnola et al., 1987) indicates CO2 levels markedly different from pre-industrial levels, provides one
means for eliciting long-term plant responses to changing CO2 regimes. We have prepared cuticles
from Quaternary leaf fossils, from which stomatal density and index can be calculated. Our
preliminary results give promise of extending the record of stomatal density response back at least
10,000 years.

KEYWORDS: ENRICHMENT, ICE, RECORD


     173  
Beerling, D.J., W.G. Chaloner, B. Huntley, J.A. Pearson, M.J. Tooley, and F.I. Woodward.
1992. Variations in the stomatal density of salix-herbacea L under the changing atmospheric co2
concentrations of late-glacial and postglacial time. Philosophical Transactions of the Royal Society
of London Series B-Biological Sciences 336(1277):215-224.

The rapidly rising CO2 concentration of the past 200 years has been shown to be accompanied by a
fall in stomatal density in the leaves of temperate trees. The present study attempts to investigate the
relationship of atmospheric CO2 change and stomatal density in the arctic-alpine shrub, Salix
herbacea, over the longer time span of 11 500 years offered by fossil leaves from post-glacial
deposits. Comparisons of fossil material from Scotland and Norway are made with leaves from living
populations growing in Austria, Greenland and Scotland. The Austrian material, from an altitudinal
gradient between 2000 and 2670 m above sea level, gives added comparison of contemporary
differences of CO2 partial pressure with altitude. The results of our investigation indicate, rather
surprisingly, that the rising CO2 concentration of the past 11 500 years has been accompanied by an
increase in the stomatal density of S. herbacea in contrast to the shorter-term observations on the
herbarium material of temperate trees. The most likely explanation appears to centre on the
temperatures and water availability of the early post-glacial environment overriding the effect of the
lower CO2 regime. However, the scale of the time interval involved may also be significant. Natural
selection over the 11 500 year period concerned may have favoured a different response to what is,
in effect, an acclimatory response observed in trees within the period of rapid CO2 rise of the past
200 years.

KEYWORDS: CARBON DIOXIDE, CLIMATE, ENRICHMENT, GRADIENT, GROWTH, LEAF
ANATOMY, PHOTOSYNTHESIS, RESPONSES, TEMPERATURE, WATER-USE EFFICIENCY


     174  
Beerling, D.J., J. Heath, F.I. Woodward, and T.A. Mansfield. 1996. Drought-CO2 interactions
in trees: Observations and mechanisms. New Phytologist 134(2):235-242.

It is sometimes assumed that because increases in atmospheric CO2 concentration usually enhance
water use efficiency per unit leaf area, there will be a tendency for plants to show greater drought
tolerance as well as increased biomass in the future. A critical examination of the responses to
elevated CO2 in three temperate tree species shows that this assumption might be incorrect in the
case of two of them. Both beech (Fagus sylvatica L.) and birch (Betula pubescens Ehrh.) display
minimal stomatal closing responses to elevated CO2, and in the case of F. sylvatica the stomatal
control of transpiration per unit leaf area appears to be unable to compensate for the greater
development of leaf area. By contrast, the stomata of oak (Quercus robur L.) close appreciably in
elevated CO2, to an extent which might be sufficient to compensate for an increase in total leaf area.
A simple model for the controls on water supply and consumption for the whole tree suggests that
in F. sylvatica the potential height attainment for a given sapwood area might decrease as the
atmospheric CO2 concentration rises. The conclusions drawn from experimental data and from
modelling are supported by field observations made in the UK in 1995, when the three species
responded very differently to severe drought. We suggest that the progressive increase in the
concentration of atmospheric CO2 over the past 200 yr might have accentuated differences in drought
sensitivity between these species.

KEYWORDS: ATMOSPHERIC CO2, BETULA-PENDULA ROTH, ELEVATED CARBON-
DIOXIDE, FAGUS-SYLVATICA, GAS-EXCHANGE, GLOBAL ENVIRONMENTAL-CHANGE,
GROWTH, PHOTOSYNTHESIS, PLANT-RESPONSES, TRANSPIRATION


     175  
Beerling, D.J., B. Huntley, and J.P. Bailey. 1995. Climate and the distribution of fallopia-japonica -
use of an introduced species to test the predictive capacity of response surfaces. Journal of
Vegetation Science 6(2):269-282.

The relationship between present climate and the distribution in Europe of the aggressively invasive
exotic Fallopia japonica is described by fitting a response surface based on three bioclimatic variables:
mean temperature of the coldest month, the annual temperature sum > 5 degrees C, and the ratio of
actual to potential evapotranspiration. The close fit between the observed and simulated distributions
suggests that the species' European distribution is climatically determined. The response surface also
provides a simulation of the extent of the area of native distribution of F. japonica in Southeast Asia
that is generally accurate, confirming the robustness of the static correlative model upon which it is
based. Simulations of the potential distribution of F. japonica under two alternative 2 x CO2 climate
change scenarios indicate the likelihood of considerable spread into higher latitudes and possible
eventual exclusion of the species from central Europe. However, despite the robustness of the
response surface with present-day climate, the reliability of these simulations as forecasts is likely to
be limited because no account is taken of the direct effects of CO2 and their interaction with the
species' physiological responses to climate. Similarly, no account is taken of the potential impact of
interactions with 'new' species as ecosystems change in composition in response to climate change.
Nevertheless, the simulations indicate both the possible magnitude of the impacts of forecast climate
changes and the regions that may be susceptible to invasion by F. japonica.



     176  
Beerling, D.J., and C.K. Kelly. 1997. Stomatal density responses of temperate woodland plants
over the past seven decades of CO2 increase: A comparison of Salisbury (1927) with contemporary
data. American Journal of Botany 84(11):1572-1583.

We investigated the possible effect of recent (1927-1995) increases in the concentration of
atmospheric CO2 on the stomatal densities of leaves of a wide range of tree, shrub, and herb species
(N = 60) by making new measurements for comparison with corresponding data reported by E. J.
Salisbury in 1917-a time when ice core studies indicate CO2 concentrations similar to 55 mu L/L
lower than present. A detailed intraspecific study of the herb Mercurialis perenius showed plants of
M. perennis in a Cambridgeshire woodland in 1994 had significantly lower stomatal densities,
irrespective of leaf insertion point, compared with their 1927 counterparts. Comparisons made across
species using evolutionary comparative methods (independent contrasts revealed a significant (P <
0.01) decrease in stomatal density over the past 70 yr. The results of both the inter-and intraspecific
comparisons are consistent with the hypothesis that historical CO2 increases have influenced leaf
morphology in a manner consistent with recent experiments and the palaeoecological record. Further
analyses suggested that the strength of the stomatal density response was independent of life form
but dependent on ''exposure'' and the initial leaf stomatal density. Consequently firmer predictions for
future changes in stomatal density across all species, expected as a possible result of
authropogenically related CO2 increases, may now be possible.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, DELTA C 13, ELEVATED CO2,
ENRICHMENT, ENVIRONMENTAL-CHANGE, GAS-EXCHANGE, GROWTH, LEAF-AREA,
TAXONOMIC RELATEDNESS


     177  
Beerling, D.J., J.C. McElwain, and C.P. Osborne. 1998. Stomatal responses of the 'living fossil'
Ginkgo biloba L. to changes in atmospheric CO2 concentrations. Journal of Experimental Botany
49(326):1603-1607.

Leaf stomatal density and index of Ginkgo biloba L. were both significantly (P < 0.05) reduced after
3 years growth at elevated CO2 (560 ppm), with values comparable to those of cuticles prepared
from Triassic and Jurassic fossil Ginkgo leaves thought to have developed in the high CO2
'greenhouse world' of the Mesozoic. A reciprocal transfer experiment indicated that reductions in
stomatal density and index irreversibly reduced stomatal conductance, particularly at low leaf-to-air
vapour pressure deficits and low internal leaf CO2 concentrations (C-i). These effects probably
contributed to the high water-use efficiency of Ginkgo spp. in the Mesozoic relative to those of the
present, as determined from carbon isotope measurements of extant and fossil cuticles.

KEYWORDS: CYCLE, DENSITY, ENVIRONMENTAL-CHANGE, LEAVES, RECORD


     178  
Beerling, D.J., and W.P. Quick. 1995. A new technique for estimating rates of carboxylation and
electron-transport in leaves of C-3 plants for use in dynamic global vegetation models. Global
Change Biology 1(4):289-294.

The possible responses of the terrestrial biosphere to future CO2 increases and associated climatic
change are being investigated using dynamic global vegetation models (DGVMs) which include the
Farquhar ef al. (1980) biochemical model of leaf assimilation as the primary means of carbon capture.
This model requires representative values of the maximum rates of Rubisco activity, V-max, and
electron transport, J(max), for different vegetation types when applied at the global scale. Here, we
describe an approach for calculating these values based on measurements of the maximum rate of leaf
photosynthesis (A(max)) and C-13 discrimination. The approach is tested and validated by
comparison with measurements of Rubisco activity assayed directly on wild-type and transgenic
Nicotiana tabacum (tobacco) plants with altered Rubisco activity grown under ambient and elevated
CO2 mole fractions with high and low N-supply. V-max and J(max) values are reported for 18
different vegetation types with global coverage. Both variables were linearly related reinforcing the
idea of optimal allocation of resources to photosynthesis (light harvesting vs. Rubisco) at the global
scale. The reported figures should be of value to the further development of vegetation and ecosystem
models employing mechanistic DGVMs.

KEYWORDS: ANTISENSE GENE, CARBON ISOTOPE DISCRIMINATION, CLIMATE, CO2
CONCENTRATIONS, GROWTH, IMPACT, OXYGENASE, PHOTOSYNTHETIC RESPONSE,
RBCS


     179  
Beerling, D.J., and F.I. Woodward. 1993. Ecophysiological responses of plants to global
environmental- change since the last glacial maximum. New Phytologist 125(3):641-648.

Ecophysiological information on the responses of plants to past global environmental changes may
be obtained from Quaternary fossil leaves by measurements of (i) stomatal density, (ii) stomatal
dimensions and (iii) C-13 discrimination (DELTA C-13). The stomatal density and stomatal
dimensions of leaves can be used to calculate stomatal conductance, while leaf DELTA C-13 values
provide independent information on stomatal conductance and plant water use efficiency. In this
paper, stomatal conductance is calculated for a sequence of radiocarbon dated fossil leaves of Salix
herbacea L. which, together with herbarium and fresh material, represents a time-series spanning from
the Last Glacial Maximum (LGM) (16 500 yr BP) to the present day. The calculated values were then
tested against leaf DELTA C-13 values previously reported for the same material. Our calculations
show that stomatal conductance is negatively correlated with increases in atmospheric CO2
concentration over the last 16 500 yr. This represents the first evidence of long-term response of
stomatal conductance to increases in atmospheric CO2 concentration and confirms the response
observed in experimental systems exposing plants to lower-than-present CO2 concentrations in
controlled environments. The calculated decrease in conductance was positively correlated with leaf
DELTA C-13 values, supporting this interpretation. The mean leaf DELTA C-13 value for the 18th
and 19th centuries was significantly (P < 0.05) lower than the mean for the interval LGM-Holocene
(10000 yr BP) implying an increase in plant water-use-efficiency over this time. These two lines of
evidence, together with the stomatal density record from a glacial cycle, and experimental studies
growing C3 plants in glacial-to-present CO2 concentrations, strongly imply that the water use
efficiency of vegetation during the LGM was lower than at present and that it has increased since that
time. Further evidence in support of this conclusion comes from the pattern of world vegetation types
present during the LGM previously reconstructed using palaeoecological data. This evidence
demonstrates that the distribution of vegetation types during the LGM was significantly different from
that of the present day and showed a contraction in the area of rain forest and a major expansion of
desert areas.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, CARBON ISOTOPE DISCRIMINATION,
CLIMATE CHANGE, FORESTS, RECORD, TEMPERATURES, TRANSPIRATION, VEGETATION,
VOSTOK ICE-CORE, WATER-USE EFFICIENCY


     180  
Beerling, D.J., and F.I. Woodward. 1994. The climate-change experiment (climex) - phenology and
gas- exchange responses of boreal vegetation to global change. Global Ecology and Biogeography
Letters 4(1):17-26.

Large-scale whole ecosystem experiments will become increasingly important for predicting and
testing hypotheses of complex ecosystem responses to global change. The Climate Change
Experiment (CLIMEX) uses a site with an entire undisturbed boreal-forested catchment enclosed
within an existing very large scale (1200m2 ground area) greenhouse. In the forthcoming year
temperature will be increased stepwise to +3-degrees-C in summer, +5-degrees-C in winter and the
atmospheric CO2 concentration enriched to 560 ppm which together simulate future changes in
global climate and atmospheric composition predicted by GCMs. Plants growing within this low
nutrient ecosystem are strongly dependent upon mycorrhizal associations for nutrient uptake and rates
of nutrient uptake. Therefore it will provide an important test of current ideas concerning how
mycorrhizas might modify plant responses to global change. We describe predictions of community
phenology and gas exchange at the CLIMEX site; in the latter case the effects of including and
excluding rates of on nutrient supply are considered. The results are discussed with reference to the
opportunities presented by CLIMEX to reveal important aspects of the physiological responses of
boreal ecosystems to global change.

KEYWORDS: ASSIMILATION, ATMOSPHERIC CO2, BUDBURST, CARBON DIOXIDE,
ELEVATED CO2, PLANT-RESPONSES, PRODUCTIVITY, TREES


     181  
Beerling, D.J., and F.I. Woodward. 1995. Leaf stable carbon-isotope composition records
increased water- use efficiency of C-3 plants in response to atmospheric co2 enrichment. Functional
Ecology 9(3):394-401.

1. A total of 17 temperate C-3 grass and herb species were grown for 5 weeks at three mole fraction
treatments of atmospheric CO2 (350, 525 and 700 mu mol mol(-1)). Leaf stable carbon isotope
compositions (delta(13)C) were determined to record long-term exchange responses together with
instantaneous gas exchange measurements. The isotopic composition of the atmospheric CO2
(delta(13)C(a)) integrated over the course of the CO2 treatments was recorded biologically using the
C-4 species Zea mays. 2. We found that increases in the mole fraction of atmospheric CO2 above
current levels resulted in a sustained increase in instantaneous (photosynthesis, A/conductance, g(s))
leaf water-use efficiency (IWUE), as calculated from carbon isotope-derived p(i)/p(a) ratios. Grass
species showed a marked decline in the magnitude of WUE increase as the CO2 mole fraction was
increased from 525 to 700 mu mol mol(-1), a response which was absent in herb species. 3. Isotopic
derivation of the ratio of intercellular CO2 mole fraction (p(i)) to that in the surrounding atmosphere
(p(a)), considered as a set point of leaf metabolism, showed no significant (P = 0.06) changes in
response to increases in the mole fraction of CO2, for herb and grass species. Measurements of
p(i)/p(a) determined from measurements of leaf gas exchange differed significantly (P<0.01) from
those derived from stable isotope ratios. These differences are attributed to contrasting stomatal
behaviour between herb and grass species. 4. Leaf intercellular CO2 mole fraction and previously
reported above- ground biomass responses to CO2 increases for the same species were positively
correlated (P < 0.05). This suggests that as atmospheric CO2 levels continue to rise species showing
sustained higher rates of leaf photosynthesis, may be translated into increased productivity depending
on soil water and nutrient status.

KEYWORDS: DELTA C 13, DIOXIDE, DISCRIMINATION, LEAVES, PHOTOSYNTHETIC
ACCLIMATION, SEEDLINGS, STOMATAL CONDUCTANCE


     182  
Beerling, D.J., and F.I. Woodward. 1995. Stomatal responses of variegated leaves to co2
enrichment. Annals of Botany 75(5):507-511.

The responses of stomatal density and stomatal index of five species of ornamental plants with
variegated leaves grown at two mole fractions of atmospheric CO2 (350 and 700 mu mol mol(- 1))
were measured. The use of variegated leaves allowed any potential effects of mesophyll
photosynthetic capacity to be uncoupled from the responses of stomatal density to changes in
atmospheric CO2 concentration. There was a decrease in stomatal density and stomatal index with
CO2 enrichment on both white (unpigmented) and green (pigmented) leaf areas. A similar response
of stomatal density and index was also observed on areas of leaves with pigmentation other than
green indicating that any differences in metabolic processes associated with coloured leaves are not
influencing the responses of stomatal density to CO2 concentrations. Therefore the carboxylation
capacity of mesophyll tissue has no direct influence on stomatal density and index responses as
suggested previously (Friend and Woodward 1990 Advances in Ecological Research 20: 59-124),
instead the responses were related to leaf structure. The stomatal characteristics (density and index)
of homobaric variegated leaves showed a greater sensitivity to CO2 on green portions, whereas
heterobaric leaves showed a greater sensitivity on white areas. These results provide evidence that
leaf structure may play an important role in determining the magnitude of stomatal density and index
responses to CO2 concentrations.

KEYWORDS: CHLOROPHYLL, LEAF


     183  
Beerling, D.J., and F.I. Woodward. 1996. In situ gas exchange responses of boreal vegetation to
elevated CO2 and temperature: First season results. Global Ecology and Biogeography Letters
5(3):117-127.

The climate change experiment (CLIMEX) uses a large greenhouse to investigate the responses of
an entire undisturbed boreal forested catchment to elevated CO2 (560 ppm) and temperature (+3
degrees C in summer and +5 degrees C in winter) treatments. In July and September of the first
season of treatment the two dominant tree species, Pinus sylvestris and Betula pubescens, and the
ground shrub Vaccinium myrtillus all showed an increase in leaf photosynthetic rates relative to the
plants growing in the control section of the greenhouse and in an outside reference catchment.
Stomatal density of needles of II sylvestris, and leaves of B. pubescens and V. myrtillus decreased
under CO2 enrichment and temperature increases relative to the controls. Gas exchange and stable
carbon isotope measurements will be made in future growing seasons to investigate whether
acclimatory adjustments in plant metabolism occur-a critical issue affecting the carbon balance of
these ecosystems.

KEYWORDS: CARBON DIOXIDE, NUTRITION, PHENOLOGY, PHOTOSYNTHESIS, STOMATAL
DENSITY, WATER-USE


     184  
Beerling, D.J., and F.I. Woodward. 1996. Palaeo-ecophysiological perspectives on plant responses
to global change. Trends in Ecology and Evolution 11(1):20-23.

Taxonomic classifications of plant species, based on morphological characteristics, provide a stable
and robust approach for Inferring taxonomic and phylogenetic relationships between extant and
extinct species. This implies that, although evolution is a continuous process for a species, there is
no whole-scale change in those suites of morphological characteristics that define higher order (genus
and greater) relationships. Recent research suggests that a higher order characteristic stomatal density
- may reflect not only the atmospheric CO2 concentration during initial evolution, but may also
strongly constrain the responses of higher order plant groups to future CO2-enrichment.

KEYWORDS: CO2, EVOLUTION, RECORD, VASCULAR PLANTS


     185  
Beerling, D.J., and F.I. Woodward. 1997. Changes in land plant function over the Phanerozoic:
Reconstructions based on the fossil record. Botanical Journal of the Linnean Society 124(2):137-
153.

Major fluctuations in the concentrations of atmospheric CO2 and O-2 are predicted by historical long-
term carbon and oxygen cycle models of atmospheric evolution and will have impacted directly on
past climates, plant function and evolutionary processes. Here, palaeobotanical evidence is presented
from the stomatal density record of fossil leaves spanning the past 400 Myr supporting the predicted
changes in atsmopheric CO2. Evidence from experiments on plants exposed to long-term high CO2
environments and the newly assembled fossil data indicate the potential for genetic modification of
stomatal characters. The influence of tile changes in fossil stomatal characteristics and atmospheric
composition on the rates of leaf gas exchange over the course of land plant evolution has been
investigated through modelling. Three contrasting cras of plant water economies emerge in the
Devonian (high), Carboniferous (low) and from the Upper Jurassic to the present- day (high but
declining). These patterns of change result from structural changes of the leaves and the impact of
atmospheric CO2 and O-2 concentrations on RuBisCO function and are consistent with the fossil
evidence of sequential appearances of novel plant anatomical changes. The modelling approach is
tested by comparing predicted leaf stable carbon isotope ratios with those measured on fossil plant
and organic material. Viewed in a geological contest, current and future increases in the concentration
of atmospheric CO2 might be considered as restoring-plant function to that more typically
experienced by plants over the majority of their evolutionary history. (C) 1997 The Linnean Society
of London.

KEYWORDS: C-3 PLANTS, CARBON ISOTOPE DISCRIMINATION, CO2- ENRICHMENT,
EPIDERMAL STRUCTURE, LEAF, LEAVES, NORTH-AMERICA, PHOTOSYNTHESIS,
RESPONSES, STOMATAL DENSITY


     186  
Beerling, D.J., F.I. Woodward, M. Lomas, and A.J. Jenkins. 1997. Testing the responses of a
dynamic global vegetation model to environmental change: a comparison of observations and
predictions. Global Ecology and Biogeography Letters 6(6):439-450.

Dynamic global vegetation - biogeochemistry models are required to predict the likely responses of
the terrestrial biosphere to anticipated future global environmental change and for improved
representation of an active vegetation surface within general circulation models of the Earth's global
climate system. Testing the predictions of such models is essential to their development prior to use
in a predictive capacity. The climate change experiment (CLIMEX) has exposed an entire catchment
of boreal vegetation to elevated CO2 (560 ppmv) and temperature (+3 degrees C in summer, +5
degrees C in winter) for the past three years and has a considerable archive of pre-and posttreatment
measurements of both CO2 and water vapour fluxes of the vegetation, catchment runoff and soil
nutrient status. These data have been used to test the predictions of the University of Sheffield
dynamic global vegetation model (SDGVM) for the same site using historical records of climate as
input. Comparisons of observations and predictions at the scale of individual leaves and whole
ecosystems are generally favourable, increasing our confidence in the application of the model to
forecasting the responses of the terrestrial biosphere to various global change scenarios. The SDGVM
has been used to predict the future responses of the ecosystem at the site into the year 2003AD. The
results indicate rather small changes in leaf area index and catchment runoff but quite large increases
in net primary productivity. The model predictions are now open to testing further as the CO2 and
temperature treatments continue in the CLIMEX greenhouse.

KEYWORDS: ATMOSPHERIC CO2, BOREAL VEGETATION, CARBON BALANCE, CLIMATE
CHANGE, ELEVATED CO2, FOREST, GAS-EXCHANGE RESPONSES, SCALE, TEMPERATURE,
WHOLE-CATCHMENT


     187  
Beeson, R.C., and M.E.D. Graham. 1991. CO2 enrichment of greenhouse roses affects neither
rubisco nor carbonic-anhydrase activities. Journal of the American Society for Horticultural Science
116(6):1040-1045.

The effect of prolonged CO2 enrichment on the activities of ribulose 1,5-bisphosphate
carboxylase/oxygenase (Rubisco) and carbonic anhydrase (CA) of greenhouse roses were studied.
Plants of Rosa X hybrida 'Red Success' were grown for 2 years at ambient and 900-mu-l CO2/liter
during winter and spring with 75-mu-mol.m-2.s-1 photosynthetically active radiation supplemental
lighting for 2 years. Measurements of initial and Mg+2-Co2-activated activities of Rubisco and CA
were made during shoot development and at different positions within the plant canopy. Generally,
there were no significant differences measured in the enzyme activities between the two CO2
concentrations. The results suggest that the photosynthetic capacity did not change and that there
were no characteristic adaptations to long-term growth (up to 20 weeks) at elevated C02
concentrations. The maintenance of Rubisco and CA activities with prolonged exposure to C02-
enriched atmospheres is proposed as the reason for long-term yield increases in roses when grown
in enriched environments.

KEYWORDS: ACCLIMATION, DIOXIDE, GROWTH, LEAVES, LONG-TERM,
PHOTOSYNTHETIC REINVIGORATION, RIBULOSE BISPHOSPHATE CARBOXYLASE,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SEEDLINGS, SHOOT DECAPITATION


     188  
Behboudian, M.H., and R. Lai. 1994. Carbon-dioxide enrichment in virosa tomato plant -
responses to enrichment duration and to temperature. Hortscience 29(12):1456-1459.

Responses of the tomato (Lycopersicon esculentum Mill. cv. Virosa) plant to elevated CO2
concentrations applied throughout the photoperiod or part of it were studied under two temperature
regimes. Plants were exposed to CO2 at 340 (control), 700, and 1000 mul-liter-1. The highest
concentration was applied only at 22/16C (day/night) and 700 mul-liter-1 at 22/16C and 25/16C.
Transpiration rates were lower and photosynthetic rates were higher under elevated CO2 than at the
ambient level. Biomass production was higher only for plants grown at 700 mul-liter-1 and 25/16C.
Concentrations of macronutrients were lower in plants exposed to 1000 mul CO2/liter than in the
control plants. Intermittent CO2 was applied using two timing methods. In method 1, plants were
exposed to 4- or 8-hour high-CO2 concentrations during their 12-hour photoperiod. In method 2,
plants were exposed for 3.5 days of each week to 700 mul CO2/liter. Only two of the 8-hour
exposures resulted in greater growth than the controls. The lack of higher growth for CO2-enriched
plants at 22/16C was attributed to a higher dark respiration rate and to respiration rate and a lack of
efficient transport of photosynthates out of leaves.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, GROWTH, PHOTOSYNTHETIC ACCLIMATION,
STARCH, TRANSPIRATION, YIELD


     189  
Behboudian, M.H., and R. Lai. 1995. Partitioning of photoassimilates in virosa tomatoes under
elevated co2 concentration. Journal of Plant Physiology 147(1):43-47.

The effect of CO2 enrichment on the distribution of assimilates in tomato plants, Lycopersicon
esculentum Mill. cv. 'Virosa', was studied using C-14-label. Plants were defoliated except for leaves
8, 9, and 10 (numbered acropetally). Depending on the experiment, truss 1 or trusses 1 and 2 were
maintained on the plant. Within a 24-h period, the labelled leaf (leaf 10) retained high levels of C-14
in both control and CO2-enriched plants. Truss 1 was the dominant sink for both CO2 treatments,
drawing on a considerable supply of C-14 re-exported from leaf 8 and leaf 9. The stem and root were
transitory sinks and had the capacity to re-export C-14 at different rates during the light and dark
periods. Pattern of photoassimilate partitioning was not affected by CO2 treatment.

KEYWORDS: ENRICHMENT, LEAVES, PATTERNS, SOURCE-SINK RELATIONSHIPS,
TRANSLOCATION


     190  
Behboudian, M.H., and C. Tod. 1995. Postharvest attributes of virosa tomato fruit produced in an
enriched carbon-dioxide environment. Hortscience 30(3):490-491.

The effect of preharvest CO2 enrichment (1000 mu l . liter(-1)) on postharvest quality of tomato fruit
(Lycopersicon esculentum Mill. 'Virosa') was studied with an emphasis on soluble sugars, ripening,
and mineral composition. High-CO2 fruit had higher concentrations of sucrose, glucose, fructose, and
total soluble solids than ambient-CO2 fruit. High-CO2 fruit also ripened more slowly and was
characterized by lower respiration and ethylene production rates than ambient-CO2 fruit.
Concentrations of N, P, and K were lower in the high-CO2 fruit than in the ambient- CO2 fruit,
whereas those of S, Ca, and Mg were the same for both treatments. Preharvest CO2 enrichment of
'Virosa' tomato enhances fruit desirability in terms of slower postharvest ripening and higher
concentrations of soluble sugars and total soluble solids.

KEYWORDS: CO2


     191  
Bellisario, L.M., J.L. Bubier, T.R. Moore, and J.P. Chanton. 1999. Controls on CH4 emissions
from a northern peatland. Global Biogeochemical Cycles 13(1):81-91.

We examined the controls on summer CH4 emission from five sites in a peatland complex near
Thompson, Manitoba, Canada, representing a minerotrophic gradient from bog to rich fen at wet
sites, where the water table positions ranged from -10 to - 1 cm. Average CH4 flux, determined by
static chambers on collars, ranged from 22 to 239 mg CH4-C m(-2) d(-1) and was related to peat
temperature. There was an inverse relationship between water table position and CH4 flux: higher
water tables led to smaller fluxes. The determination of anaerobic CH4 production and aerobic CH4
consumption potentials in laboratory incubations of peat samples was unable to explain much of the
variation in CH4 flux. Average net ecosystem exchange of CO2 ranged from 1.4 to 2.5 g CO2-C m(-
2) d(-1) and was strongly correlated with CH4 flux; CH4 emission averaged 4% of CO2 uptake. End-
of-season sedge biomass was also strongly related to CH4 flux, indicating the important role that
vascular plants play in regulating CH4 flux. Determination of isotopic signatures in peat pore water
CH4 revealed average delta(13)C values of between -50 and -73 parts per thousand and delta D of
between -368 and -388 parts per thousand. Sites with large CH4 emission rates also had high CO2
exchange rates and enriched delta(13)C CH4 signatures, suggesting the importance of the acetate
fermentation pathway of methanogenesis. Comparison of delta D and delta(13)C signatures in pore
water CH4 revealed a slope shallow enough to suggest that oxidation is not an important overall
control on CH4 emissions at these sites, though it appeared to be important at one site. Analysis of
C- 14 in pore water CH4 showed that most of the CH4 was of recent origin with percent of modern
carbon values of between 112 and 128%. The study has shown the importance of vascular plant
activities in controlling CH4 emissions from these wetland sites through influences on the availability
of fresh plant material for methanogenesis, rhizospheric oxidation, and plant transport of CH4.

KEYWORDS: ATMOSPHERE, CANADA, CARBON ISOTOPIC COMPOSITION, CO2
REDUCTION, DYNAMICS, HYDROGEN, METHANE-OXIDIZING BACTERIA, ONTARIO,
WATER, WETLANDS


     192  
BenBrahim, M., D. Loustau, J.P. Gaudillere, and E. Saur. 1996. Effects of phosphate deficiency
on photosynthesis and accumulation of starch and soluble sugars in 1-year-old seedlings of maritime
pine (Pinus pinaster Ait). Annales Des Sciences Forestieres 53(4):801-810.

Maritime pine seedlings were grown in 4 L pots filled with coarse sand in a greenhouse. Seedlings
were supplied with a nutrient solution with three different concentrations of phosphorus (0, 0.125 and
0.5 mM). After 1 year of growth, gas exchange measurements were performed on mature needles.
From these measurements, the main parameters of CO2 assimilation (the carboxylation efficiency, the
apparent quantum efficiency and the maximal rate of electron transport) were estimated using the
biochemical model of photosynthesis as described by Farquhar et al (1980). Leaf nonstructural
carbohydrates were also analyzed. Phosphorus deficiency decreased the phosphorus foliar
concentration, but did not affect foliar nitrogen concentration. The maximal rate of photosynthesis,
the carboxylation efficiency and the apparent quantum efficiency decreased in phosphorus deficient
seedlings. However, the maximal rate of electron transport and stomatal conductance were not
affected by phosphorus supply. Low phosphorus nutrition caused a dramatic increase in foliar starch
level at the end of the photoperiod. These results indicate that inadequate phosphorus nutrition
principally affected the dark reactions of photosynthesis, the apparent quantum efficiency and starch
accumulation.

KEYWORDS: CARBON, ELECTRON-TRANSPORT, ELEVATED CO2, EUCALYPTUS- GRANDIS
SEEDLINGS, GAS-EXCHANGE, GROWTH, MAIZE LEAVES, PHOSPHORUS-NUTRITION,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SITKA SPRUCE


     193  
Bender, J., U. Hertstein, and C.R. Black. 1999. Growth and yield responses of spring wheat to
increasing carbon dioxide, ozone and physiological stresses: a statistical analysis 'ESPACE-wheat'
results. European Journal of Agronomy 10(3-4):185-195.

One of the major goals of the European Stress Physiology and Climate Experiment (ESPACE-wheat)
was to investigate the sensitivity of wheat growth and productivity to the combined effects of changes
in CO2 concentration, ozone and other physiological stresses. Experiments were performed at
different sites throughout Europe, over three consecutive growing-seasons using open-top chambers.
This paper summarizes the main experimental findings of the effects of CO2 enrichment and other
factors i.e. ozone (O-3), drought stress or nitrogen supply on the biomass and yield of spring wheat
(Triticum aestivum cv. Minaret). Final harvest data from different sites and seasons were statistically
analysed: (1) to identify main effects and interactions between experimentally controlled factors; and
(2) to evaluate quantitative relationships between environmental variables and biological responses.
Generally, 'Minaret' wheat did not respond significantly to O-3, suggesting that this cultivar is
relatively tolerant to the O-3 levels applied. The main effect of CO2 was a significant enhancement
of grain yield and above-ground biomass in almost all experiments. Significant interactions between
CO2 and other factors were not common, although modifications in different N- and water supplies
also led to significant effects on grain yield and biomass. In addition, climatic factors (in particular:
mean air temperature and global radiation) were identified as important co-variables affecting grain
yield or biomass, respectively. On average, the yield increase as a result of a doubling of [CO2] was
35% compared with that observed at ambient CO2 concentrations. However, linear regressions of
grain yield or above-ground biomass for individual experiments revealed a large variability in the
quantitative responses of 'Minaret' wheat to CO2 enrichment (yield increase ranging from 11 to
121%). Hence, CO2 responsiveness was shown to differ considerably when the same cultivar of
wheat was grown at different European locations. Multiple regression analyses performed to evaluate
the relative importance of the measured environmental parameters on grain yield indicated that
although yield was significantly related to five independent variables (24 h mean CO2 concentration,
12 h mean O-3 concentration, temperature, radiation, and drought stress), a large proportion of the
observed variability remained unexplained. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: CO2- ENRICHMENT, CROP RESPONSES, IMPACTS, O-3, PLANT-RESPONSES,
PROTECT, RADIATION, VEGETATION


     194  
Bender, J., U. Hertstein, A. Fangmeier, M. van Oijen, H.J. Weigel, and H.J. Jager. 1998. The
impact of climate change on yield of wheat in Europe: Results of the European stress physiology and
climate experiment (ESPACE-wheat). Journal of Applied Botany-Angewandte Botanik 72(1-2):37-
42.

The European Stress Physiology and Climate Experiment (ESPACE- wheat) was funded by the EU
from 1994-1997. Major goals of the project were 1) to investigate by means of experiments the
sensitivity of wheat growth, development and productivity to the combined effects of changes in CO2
concentration, climatic variables and other physiological stresses, 2) to use experimental data for
extension and improvement of process- based wheat growth simulation models, and 3) to apply
models to assess the influences on crops of climatic change, CO2 concentration and additional
stresses in Europe. Experimental studies were performed at different sites in Europe through three
consecutive seasons by means of open-top chambers according to a common standard protocol, and
two simulation models were used for the analysis: AFRCWHEAT2 and LINTULCC. This paper
summarizes the main findings of the effects of CO2 enrichment and other factors such as ozone,
drought stress or nitrogen supply on the yield response of spring wheat (Triticum aestivum cv.
Minaret). A comparison of the measured data with the main outputs of the LINTULCC model
simulations is are presented. Generally, Minaret wheat did not respond significantly to ozone. CO2
enrichment had a positive influence on grain yield in almost all experiments, however, significant
interactions between CO2 and other factors were not common. The average measured yield increase
due to CO2 doubling was 35 % compared to grain yield measured at ambient CO2 concentrations,
although there was a great variability in yield responses between sites and years. LINTULCC
predicted a 42 % yield increase, but a much smaller variation between individual experiments.
Although the effects of CO2 and O-2 on crop growth and yield were acceptably simulated, observed
process-rates often showed variation not related to light intensity, temperature, CO2 or O-2, ie, not
related to the main driving variables of the models. This unexplained variability in the measured
datasets suggested a role of factors which were not accounted for in the models.

KEYWORDS: CARBON DIOXIDE, CO2, FIELD, GROWTH, OZONE, PLANT-RESPONSES,
STIMULATION, TRITICUM-AESTIVUM L


     195  
Bernstson, G.M., K.D.M. McConnaughay, and F.A. Bazzaz. 1993. Elevated co2 alters
deployment of roots in small growth containers. Oecologia 94(4):558-564.

Previously we examined how limited rooting space and nutrient supply influenced plant growth under
elevated atmospheric CO2 concentrations (McConnaughay et al. 1993). We demonstrated that plant
growth enhancement under elevated CO2 was influenced more by the concentration of nutrients
added to growth containers than to either the total nutrient content per pot or amount or the
dimensions of available rooting space. To gain insight into how elevated CO2 atmospheres affect how
plants utilize available belowground space when rooting space and nutrient supply are limited we
measured the deployment of roots within pots through time. Contrary to aboveground responses,
patterns of below-ground deployment were most strongly influenced by elevated CO2 in pots of
different volume and shape. Further, elevated CO2 conditions interacted differently with limited
belowground space for the two species we studied, Abutilon theophrasti, a C3 dicot with a deep
taproot, and Setaria faberii, a C4 monocot with a shallow fibrous root system. For Setaria, elevated
CO2 increased the size of the largest region of low root density at the pot surface in larger rooting
volumes independent of nutrient content, thereby decreasing their efficiency of deployment. For
Abutilon, plants responded to elevated CO2 concentrations by equalizing the pattern of deployment
in all the pots. Nutrient concentration, and not pot size or shape, greatly influenced the density of root
growth. Root densities for Abutilon and Setaria were similar to those observed in field conditions,
for annual dicots and monocots respectively, suggesting that studies using pots may successfully
mimic natural conditions.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, FIELD, PHOTOSYNTHETIC
ACCLIMATION, PLANTS, RESTRICTION, SEEDLINGS, WATER RELATIONS, YIELD


     196  
Berntson, G.M., and F.A. Bazzaz. 1996. The allometry of root production and loss in seedlings of
Acer rubrum (Aceraceae) and Betula papyrifera (Betulaceae): Implications for root dynamics in
elevated CO2. American Journal of Botany 83(5):608-616.

Total root production (Sigma P), total root loss (Sigma L), net root production (NP), and biomass
production were determined for seedlings of Betula papyrifera and Acer rubrum in ambient and
elevated CO2 environments. Sigma P, Sigma L, and NP were calculated from sequential, independent
observations of root length production through plexiglass windows. Elevated CO2 increased Sigma
P, Sigma L, and NP in seedlings of Betula papyrifera but not Acer rubntm. Root production and loss
were qualitatively similar to whole-plant growth responses to elevated CO2. Betula showed enhanced
Sigma P. Sigma L, and biomass with elevated CO2 but Acer did not. However, the observed effects
of CO2 on root production and loss did not alter the allometric relationship between root production
and root loss for either Acer or Betula. Thus, in this experiment, elevated CO2 did not affect the
relationship between root production and root loss. The results of this study have important
implications for the potential effects of elevated CO2 on root dynamics. Elevated CO2 may lead to
increases in root production and in root loss (turnover) where the changes in root turnover are largely
a function of the magnitude of root production increases.

KEYWORDS: ATMOSPHERIC CO2, CARBON, COOCCURRING BIRCH, ECOSYSTEMS, FINE
ROOTS, GROWTH-RESPONSE, LEAF LITTER, ORGANIC-MATTER, PLANTS, SYSTEM
ARCHITECTURE


     197  
Berntson, G.M., and F.A. Bazzaz. 1996. Belowground positive and negative feedbacks on CO2
growth enhancement. Plant and Soil 187(2):119-131.

In this paper we present a conceptual model of integrated plant-soil interactions which illustrates the
importance of identifying the primary belowground feedbacks, both positive and negative, which can
simultaneously affect plant growth responses to elevated CO2. The primary negative feedbacks share
the common feature of reducing the amount of nutrients available to plants. These negative feedbacks
include increased litter C/N ratios, and therefore reduced mineralization rates, increased
immobilization of available nutrients by a larger soil microbial pool, and increased storage of nutrients
in plant biomass and detritus due to increases in net primary productivity (NPP). Most of the primary
positive feedbacks share the common feature of being plant mediated feedbacks, the only exception
being Zak et al.'s hypothesis that increased microbial biomass will be accompanied by increased
mineralization rates. Plant nutrient uptake may be increased through alterations in root architecture,
physiology, or mycorrhizal symbioses. Further, the increased C/N ratios of plant tissue mean that a
given level of NPP can be achieved with a smaller supply of nitrogen. Identification of the net plant-
soil feedbacks to enhanced productivity with elevated CO2 are a critical first step for any ecosystem.
It is necessary, however, that we first identify how universally applicable the results are from one
study or one ecosystem before ecosystem models incorporate this information. The effect of elevated
CO2 on plant growth (including NPP, tissue quality, root architecture, mycorrhizal symbioses) can
vary greatly for different species and environmental conditions. Therefore it is reasonable to expect
that different ecosystems will show different patterns of interacting positive and negative feedbacks
within the plant-soil system. This inter-ecosystem variability in the potential for long-term growth
responses to rising CO2 levels implies that we need to parameterize mechanistic models of the impact
of elevated CO2 on ecosystem productivity using a detailed understanding of each ecosystem of
interest.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DECOMPOSITION, ELEVATED CO2,
ENRICHMENT, FINE ROOTS, LONG-TERM RESPONSE, NITROGEN SATURATION, PLANT,
SOIL SYSTEM, TEMPERATE FOREST ECOSYSTEMS


     198  
Berntson, G.M., and F.A. Bazzaz. 1997. Elevated CO2 and the magnitude and seasonal dynamics
of root production and loss in Betula papyrifera. Plant and Soil 190(2):211-216.

The impact of elevated atmospheric CO2 on belowground plant growth is poorly understood relative
to its effects on aboveground growth. We carried out a study of the seasonal dynamics of gross root
production and death to determine how elevated CO2 affected the dynamics of net and gross root
production through a full growing season. We quantified gross root production and root loss from
sequential, in situ images of fine roots of Betula papyrifera in ambient (375 ppm.) and elevated (700
ppm) CO2 atmospheres from 2 weeks following germination through leaf senescence. We found that
elevated CO2 led to increases in the magnitude of cumulative gross production (Sigma P) and
cumulative gross loss (Sigma L) of roots. However, the effect of elevated CO2 on these processes
was seasonally dependent. Elevated CO2 led to greater levels of enhancement in Sigma P early in the
growing season, prior to maximum standing root length (NP). In contrast, elevated CO2 led to
greater levels of enhancement in Sigma L in the last half of the growing season, after maximum NP
had been reached. This difference in the timing of when elevated CO2 affects Sigma P and Sigma L
led to a transitory, early enhancement in NP. By the end of the growing season, there was no
significant effect of elevated CO2 on NP, and Sigma P was 87% greater than NP for ambient CO2
and 117% greater in elevated CO2. We conclude that static assessments of belowground productivity
may greatly underestimate gross fine root productivity and turnover and this bias can be exaggerated
with elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS, FINE ROOTS, LENGTH,
NITROGEN, NORTHERN HARDWOOD FOREST, RESPONSES, TURNOVER


     199  
Berntson, G.M., and F.A. Bazzaz. 1997. Nitrogen cycling in microcosms of yellow birch exposed
to elevated CO2: Simultaneous positive and negative below-ground feedbacks. Global Change
Biology 3(3):247-258.

This study investigated simultaneous plant and soil feedbacks on growth enhancement with elevated
[CO2] within microcosms of yellow birch (Betula alleghaniensis Britt.) in the second year of growth.
Understanding the integrated responses of model ecosystems may provide key insight into the
potential net nutrient feedbacks on [CO2] growth enhancements in temperate forests. We measured
the net biomass production, C:N ratios, root architecture, and mycorrhizal responses of yellow birch,
in situ rates gross nitrogen mineralization and the partitioning of available NH4+ between yellow
birch and soil microbes. Elevated atmospheric [CO2] resulted in significant alterations in the cycling
of N within the microcosms. Plant C/N ratios were significantly increased, gross mineralization and
NH4+ consumption rates were decreased, and relative microbial uptake of NH4+ was increased,
representing a suite of N cycling negative feedbacks on N availability. However, increased C/N ratios
may also be a mechanism which allows plants to maintain higher growth with a constant or reduced
N supply. Total plant N content was increased with elevated [CO2], suggesting that yellow birch had
successfully increased their ability to acquire nutrients during the first year of growth. However, plant
uptake rates of NH4+ had decreased in the second year. This discrepancy implies that, in this study,
nitrogen uptake skewed a trend through ontogeny of decreasing enhancement under elevated [CO2].
The reduced N mineralization and relatively increased N immobilization are a potential feedback
which may drive this ontogenetic trend. This study has demonstrated the importance of using an
integrated approach to exploring potential nutrient-cycling feedbacks in elevated [CO2].

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DECOMPOSITION DYNAMICS, DIRECT
EXTRACTION, FINE ROOTS, GROWTH ENHANCEMENT, HARDWOOD LEAF LITTER, LIGNIN
CONTENT, MICROBIAL BIOMASS NITROGEN, POOL DILUTION, SOIL ORGANIC MATTER


     200  
Berntson, G.M., and F.A. Bazzaz. 1998. Regenerating temperate forest mesocosms in elevated
CO2: belowground growth and nitrogen cycling. Oecologia 113(1):115-125.

The response of temperate forest ecosystems to elevated atmospheric CO2 concentrations is
important because these ecosystems represent a significant component of the global carbon cycle.
Two important but not well understood processes which elevated CO2 may substantially alter in these
systems are regeneration and nitrogen cycling. If elevated CO2 leads to changes in species
composition in regenerating forest communities then the structure and function of these ecosystems
may be affected. In most temperate forests, nitrogen appears to be a limiting nutrient. If elevated CO2
leads to reductions in nitrogen cycling through increased sequestration of nitrogen in plant biomass
or reductions in mineralization rates, long-term forest productivity may be constrained. To study
these processes, we established mesocosms of regenerating forest communities in controlled
environments maintained at either ambient (375 ppm) or elevated (700 ppm) CO2 concentrations.
Mesocosms were constructed from intact monoliths of organic forest soil. We maintained these
mesocosms for 2 years without any external inputs of nitrogen and allowed the plants naturally
present as seeds and rhizomes to regenerate. We used N-15 pool dilution techniques to quantify
nitrogen fluxes within the mesocosms at the end of the 2 years. Elevated atmospheric CO2
concentration significantly affected a number of plant and soil processes in the experimental
regenerating forest mesocosms. These changes included increases in total plant biomass production,
plant C/N ratios, ectomycorrhizal colonization of tree fine roots, changes in tree fine root
architecture, and decreases in plant NH4+ uptake rates, gross NH4+ mineralization rates, and gross
NH4+ consumption rates. In addition, there was a shift in the relative biomass contribution of the two
dominant regenerating tree species; the proportion of total biomass contributed by white birch (Betula
papyrifera) decreased and the proportion of total biomass contributed by yellow birch (B.
alleghaniensis) increased. However, elevated CO2 had no significant effect on the total amount of
nitrogen in plant and soil microbial biomass. In this study we observed a suite of effects due to
elevated CO2, some of which could lead to increases in potential long term growth responses to
elevated CO2, other to decreases. The reduced plant NH4+ uptake rates we observed are consistent
with reduced NH4+ availability due to reduced gross mineralization rates. Reduced NH4+
mineralization rates are consistent with the increases in C/N ratios we observed for leaf and fine root
material. Together, these data suggest the positive increases in plant root architectural parameters and
mycorrhizal colonization may not be as important as the potential negative effects of reduced nitrogen
availability through decreased decomposition rates in a future atmosphere with elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DIRECT EXTRACTION, LEAF LITTER,
MICROBIAL BIOMASS NITROGEN, PLANT, POOL DILUTION, RESPONSES, SEEDLINGS,
SOIL, TERRESTRIAL ECOSYSTEMS


     201  
Berntson, G.M., N. Rajakaruna, and F.A. Bazzaz. 1998. Growth and nitrogen uptake in an
experimental community of annuals exposed to elevated atmospheric CO2. Global Change Biology
4(6):607-626.

Rising levels of atmospheric CO2 may alter patterns of plant biomass production. These changes will
be dependent on the ability of plants to acquire sufficient nutrients to maintain enhanced growth.
Species-specific differences in responsiveness to CO2 may lead to changes in plant community
composition and biodiversity. Differences in species-level growth responses to CO2 may be, in a large
part, driven by differences in the ability to acquire nutrients. To understand the mechanisms of how
elevated CO2 leads to changes in community-level productivity, we need to study the growth
responses and patterns of nutrient acquisition for each of the species that comprise the community.
In this paper, we present a study of how elevated CO2 affects community-level and species-level
patterns of nitrogen uptake and biomass production. As an experimental system we use experimental
communities of 11 co- occurring annuals common to disturbed seasonal grasslands in south-western
U.S.A. We established experimental communities with approximately even numbers of each species
in three different atmospheric CO2 concentrations (375, 550, and 700 ppm). We maintained these
communities for 1, 1.5, and 2 months at which times we applied a N-15 tracer ((NH4NO3)-N-15-N-
15) to quantify the nitrogen uptake and then measured plant biomass, nitrogen content, and nitrogen
uptake rates for the entire communities as well as for each species. Overall, community- level
responses to elevated CO2 were consistent with the majority of other studies of individual- and
multispecies assemblages, where elevated CO2 leads to enhanced biomass production early on, but
this enhancement declines through time. In contrast, the responses of the individual species within the
communities was highly variable, showing the full range of responses from positive to negative. Due
to the large variation in size between the different species, community- level responses were generally
determined by the responses of only one or a few species. Thus, while several of the smaller species
showed trends of increased biomass and nitrogen uptake in elevated CO2 at the end of the
experiment, community-level patterns showed a decrease in these parameters due to the significant
reduction in biomass and nitrogen content in the single largest species. The relationship between
enhancement of nitrogen uptake and biomass production in elevated CO2 was highly significant for
both 550 ppm and 700 ppm CO2. This relationship strongly suggests that the ability of plants to
increase nitrogen uptake (through changes in physiology, morphology, architecture, or mycorrhizal
symbionts) may be an important determinant of which species in a community will be able to respond
to increased CO2 levels with increased biomass production. The fact that the most dominant species
within the community showed reduced enhancement and the smaller species showed increased
enhancement suggest that through time, elevated CO2 may lead to significant changes in community
composition. At the community level, nitrogen uptake rates relative to plant nitrogen content were
invariable between the three different CO2 levels at each hardest. This was in contrast to significant
reductions in total plant nitrogen uptake and nitrogen uptake relative to total plant biomass. These
patterns support the hypothesis that plant nitrogen uptake is largely regulated by physiological
activity, assuming that physiological activity is controlled by nitrogen content and thus protein and
enzyme content.

KEYWORDS: ARCHITECTURE, BIODIVERSITY, CARBON DIOXIDE, ECOSYSTEMS,
ENRICHMENT, GAILLARDIA-PULCHELLA, LOBLOLLY-PINE, PHLOX, PLANTS, RESPONSES


     202  
Berntson, G.M., P.M. Wayne, and F.A. Bazzaz. 1997. Below-ground architectural and
mycorrhizal responses to elevated CO2 in Betula alleghaniensis populations. Functional Ecology
11(6):684-695.

1. Replicate populations of crowded, regenerating stands of Betula alleghaniensis were grown in
ambient and elevated (700 p.p.m.) atmospheric CO2 concentrations in monoliths of forest soil. Early
in the second year the seedlings were harvested and detailed measurements of individual plant root
architectural parameters and ectomycorrhizal colonization were made. 2. Comparing the average
responses of individual plants within the populations, elevated CO2 had no significant effects on
architectural parameters that improve a plant's ability to forage for and acquire soil resources. In
contrast, the intensity and magnitude of mycorrhizal colonization, and whole plant C/N ratios were
significantly enhanced with elevated CO2. 3. The allometric scaling relationship between total plant
biomass and root biomass was not affected by CO2, suggesting that relative allocation between roots
and shoots was not affected. However, the allometric scaling relationships between root architectural
parameters and plant biomass, and between fine root biomass and woody root biomass were
significantly altered by elevated CO2. For all of these relationships, elevated CO2 reduced the 'size
bias' of architectural components in relation to plant size within the populations; in elevated CO2 root
architectural size (e.g. root length) per unit biomass was more similar between the smallest and largest
individuals within the population than was the case for ambient CO2. 4. Overall, the results of this
study suggest that the average individual seedling biomass and architectural growth responses within
populations of plants exposed to elevated atmospheric CO2 levels may be unresponsive, but that
mycorrhizal responses and interactions among plants within populations may be altered significantly.
These findings have important implications for how we make predictions about plant growth
responses to elevated CO2 in natural ecosystems. Significant increases in mycorrhizal infection rates
and architecture-biomass allometries suggest that below-ground competitive interactions within plant
populations may be reduced in elevated CO2. Alterations in competitive interactions may lead to
shifts in productivity and plant population structure.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COMPETITION, ENRICHMENT, FOREST
ECOSYSTEMS, GROWTH, PLANT-ROOT SYSTEMS, QUERCUS-ALBA, SEEDLINGS, SIZE
HIERARCHIES, SOIL


     203  
Berntson, G.M., and F.I. Woodward. 1992. The root-system architecture and development of
senecio- vulgaris in elevated co2 and drought. Functional Ecology 6(3):324-333.

1. The impact of elevated CO2 and drought on the architecture and development of root systems of
Senecio vulgaris was examined and implications for water and nutrient uptake discussed. Plants were
grown in miniature rhizotrons to non- destructively monitor the development of roots in situ at both
an elevated (700-mu-mol mol-1) and ambient (350-mu-mol mol-1) atmospheric CO2 concentration
and a high or a low supply of water. 2. CO2 and water had a significant impact on the way that S.
vulgaris root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root
systems that foraged through larger volumes of soil. Under elevated CO2 and a low water supply,
root systems had branching and foraging patterns and root length similar to those grown under
ambient CO2 with a high water supply. 3. Overall, water had a more pronounced impact on the
growth rate of S. vulgaris roots than did CO2. The density of rooting remained unchanged across all
treatments. Thus, under elevated CO2 the intensity of foraging S. vulgaris root systems might be
unchanged while the extent of foraging by these root systems, as indicated by the horizontal spread
of roots, may be increased.



     204  
Berry, S.C., G.T. Varney, and L.B. Flanagan. 1997. Leaf delta C-13 in Pinus resinosa trees and
understory plants: Variation associated with light and CO2 gradients. Oecologia 109(4):499-506.

Our objective was to evaluate the relative importance of gradients in light intensity and the isotopic
composition of atmospheric CO2 for variation in leaf carbon isotope ratios within a Pinus resinosa
forest. In addition, we measured photosynthetic gas exchange and leaf carbon isotope ratios on four
understory species (Dryopteris carthusiana, Epipactus helleborine, Hieracium floribundum, Rhamnus
frangula), in order to estimate the consequence of the variation in the understory light microclimate
for carbon gain in these plants. During midday, CO2 concentration was relatively constant at vertical
positions ranging from 15 m to 3 m above ground. Only at positions below 3 m was CO2
concentration significantly elevated above that measured at 15 m. Based on the strong linear
relationship between chan in CO2 concentration and delta(13)C values for air samples collected
during a diurnal cycle, we calculated the expected vertical profile for the carbon isotope ratio of
atmospheric CO2 within the forest. These calculations indicated that leaves at 3 m height and above
were exposed to CO2 of approximately the same isotopic composition during daylight periods. There
was no significant difference between the daily mean delta(13)C values at 15 m (- 7.77 parts per
thousand) and 3 m (-7.89 parts per thousand), but atmospheric CO2 was significantly depleted in C-
13 closer to the ground surface, with daily average delta(13)C values of -8.85 parts per thousand at
5 cm above ground. The light intensity gradient in the forest was substantial, with average
photosynthetically active radiation (PAR) on the forest floor approximately 6% of that received at
the top of the canopy. In contrast, there were only minor changes in air temperature, and so it is likely
that the leaf-air vapour pressure difference was relatively constant from the top of the canopy to the
forest floor. For red pine and elm tree samples, there was a significant correlation between leaf
delta(13)C value and the height at which the leaf sample was collected. Leaf tissue sampled near the
forest floor, on average, had lower delta(13)C values than samples collected near the top of the
canopy. We suggest that the average light intensity gradient through the canopy was the major factor
influencing vertical changes in tree leaf delta(13)C values. In addition, there was a wide range of
variation (greater than 4 parts per thousand) among the four understory plant species for average leaf
delta(13)C values. Measurements of leaf gas exchange, under natural light conditions and with
supplemental light, were used to estimate the influence of the light microclimate on the observed
variation in leaf carbon isotope ratios in the understory plants. Our data suggest that one species,
Epipactus helleborine, gained a substantial fraction of carbon during sunflecks.

KEYWORDS: AMAZONIAN RAIN FORESTS, ATMOSPHERIC CO2, C 13/C 12, CANOPIES,
CARBON ISOTOPE DISCRIMINATION, LEAVES, PHOTOSYNTHESIS, STRATIFICATION,
SUNFLECKS, VALUES


     205  
Berryman, C.A., D. Eamus, and G.A. Duff. 1993. The influence of co2 enrichment on growth,
nutrient content and biomass allocation of maranthes-corymbosa. Australian Journal of Botany
41(2):195-209.

Seedlings of Maranthes corymbosa Blume, an evergreen tree of tropical Australia and Indonesia were
grown for 32 weeks under conditions of ambient and elevated (700 mumol CO2 mol-1) CO2 in
tropical northern Australia. Seedlings were exposed to ambient temperature, vapour pressure deficit
and photon flux density fluctuations. Rates of germination and percentage germination were not
affected by elevated CO2.Total plant biomass, height growth, total plant leaf area, numbers of leaves
and branches and specific leaf weight were significantly increased by elevated CO2. Root:shoot ratio
and foliar P, K, Mg, Mn and Ca levels were unaffected but foliar nitrogen levels were decreased by
elevated CO2, Nutrient-use-efficiency was unaffected for phosphorus, magnesium, manganese,
calcium and potassium but nitrogen-use-efficiency increased in response to elevated CO2.

KEYWORDS: ACCLIMATION, CARBON-DIOXIDE ENRICHMENT, CARBOXYLASE, ECOLOGY,
ELEVATED CO2, FOREST, LIRIODENDRON-TULIPIFERA L, NITROGEN, PHOTOSYNTHESIS,
SEEDLING GROWTH


     206  
Berryman, C.A., D. Eamus, and G.A. Duff. 1994. Stomatal responses to a range of variables in
2 tropical tree species grown with co2, enrichment. Journal of Experimental Botany 45(274):539-
546.

Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F. Muell) were grown with
or without CO2 enrichment (700 mu mol CO2 mol(-1)). The response of stomatal conductance (g(s))
to leaf drying, exogenous abscisic acid and calcium ions was investigated in M. corymbosa.
Reciprocal transfer experiments were also conducted whereby plants were grown in one treatment
and then transferred to the other before g(s) was measured. Stomatal conductance in M. corymbosa
was more sensitive (a greater percentage decline in g(s) per unit percentage decline in leaf fresh
weight) to leaf water status under conditions of CO2 enrichment compared to ambient conditions.
However, the rate of reduction of g(s) in response to exogenous abscisic acid was not influenced by
CO2 treatment. In contrast, the rate of reduction of g(s) in response to exogenous CaCl2 was
decreased under conditions of CO2 enrichment. Reciprocal transfer experiments showed that
exposure to CO2 enrichment results in a short-term, reversible decline in g(s) as a result of decreased
stomatal aperture and a long-term, irreversible decline in g(s) as a result of a decreased stomatal
density. Seedlings of E. tetrodonta were used to investigate the response of g(s) to light flux density,
leaf-to-air vapour pressure difference (LAVPD), leaf internal CO2 concentration (C-i) and
temperature. Reciprocal transfer experiments were also conducted. CO2 enrichment did not influence
the pattern or sensitivity of response of g(s) to LAVPD and C-i in E. tetrodonta. In contrast, the
slope of the response of g(s) to temperature decreased for trees grown under elevated [CO2](a)
conditions and the equilibrium g(s) attained at saturating light was also decreased for plants grown
under elevated [CO2](a) conditions.

KEYWORDS: ABSCISIC- ACID, ATMOSPHERIC CO2, BEHAVIOR, CALCIUM, HUMIDITY,
LEAVES, PRESSURE, SOLANUM-MELONGENA, WATER-STRESS


     207  
Bertani, A., I. Brambilla, S. Mapelli, and R. Reggiani. 1997. Elongation growth in the absence
of oxygen: The rice coleoptile. Russian Journal of Plant Physiology 44(4):543-547.

Rice, one of the few plant species adapted to growth in wetland conditions, is able to germinate in
waterlogged soils promoting only the growth of a white coleoptile in order to reach the surface of
the water, contact the atmosphere, and transfer oxygen to the seed, allowing subsequent growth of
the radicle and leaf. In the anoxic cells of rice coleoptiles, an efficient alcoholic fermentation allows
an elevated energy charge to be maintained. Significant RNA and protein syntheses including
phosphorylation and glycosylation occur too. The cytoplasmic pH is maintained at a level far from
acidosis. The anoxic growth of rice coleoptiles, essentially an elongation growth, is sustained by a
high turgor pressure, with free amino acids and potassium as main components. Among the metabolic
processes involved in the regulation of the elongation of rice coleoptiles, a crucial role is played by
amino acid metabolism and the accumulation of putrescine, which is able to stimulate plasmalemma
ATPase activity. Anaerobic elongation is also stimulated in the presence of 20% CO2 in the growth
medium, inhibited by light and abscisic acid, unaffected by ethylene, and slightly promoted by auxin.
The role of both metabolites and hormones along with environmental factors in maintaining cellular
homeostasis and coleoptile elongation are reconsidered and discussed in Light of new data.

KEYWORDS: ACCUMULATION, ANAEROBIOSIS, ANOXIA, GERMINATION, METABOLIC-
RATE, ORYZA SATIVA L, PH, POLYAMINES, PROTEIN-SYNTHESIS, SEEDLINGS


     208  
Bertin, N., and C. Gary. 1993. Evaluation of tomgro, a dynamic-model of growth and development
of tomato (lycopersicon-esculentum mill) at various levels of assimilate supply-and-demand.
Agronomie 13(5):395-405.

TOMGRO, a tomato growth and development model, has been examined under different levels of
assimilate source and sink activities, induced by CO2 enrichment and truss thinning. The main
purpose was the evaluation of the assumptions on dry matter partitioning and fruit setting. The
photosynthesis submodel has been calibrated to fit the daily dry matter production. The main input
parameters to the development and growth submodels have been experimentally measured. The
calibrated model provides good simulations of the leaf area expansion, but it takes no account of the
variations in the assimilates stored in leaf blades. Total fruit growth is well simulated in spite of a
small underestimation for of development and simulations of source/sink balance leads to good
simulations of the number of set fruits. This result confirms the hypothesis that fruit set depends on
the ratio between assimilate source and sink activities. This calibration with a beef tomato cultivar
proves the robustness of the model and permits some improvements to be suggested. The surplus
assimilates should be stored in a pool, which could exert a buffer effect during low supply periods.
Sink strength of reproductive and vegetative parts should be measured for different cultivars, and
under various climatic conditions. Finally, whether the functions of assimilate distribution and fruit
set are still valid under very low supply conditions or whether some organs have priority over the
others remains to be determined.



     209  
Bertin, N., and C. Gary. 1998. Short and long term fluctuations of the leaf mass per area of tomato
plants - Implications for growth models. Annals of Botany 82(1):71-81.

The leaf mass per unit leaf area (LMA) is a key variable in many growth models, since it is often used
to predict leaf area expansion from leaf dry weight increase, or vice versa. Influences of source-sink
balance on leaf area, leaf dry weight, LMA, and leaf content in non-structural carbohydrates were
investigated in glasshouse tomato crops. The source-sink balance was manipulated by artificial
shading, CO2 enrichment or fruit removal using different tomato cultivars. Leaf area was hardly
affected by competition for assimilates except under extreme conditions. Iri contrast, leaf dry weight,
and consequently LMA, underwent large and rapid fluctuations in response to any factor that changed
source and sink activities. A 60% reduction of photosynthetically active radiation involved a 24%
decrease in LMA after 10 d. Carbon dioxide enrichment and fruit removal induced about a 45% and
15% increase in LMA, respectively, on plants with two fruiting trusses, but hardly affected LMA of
producing plants. No significant cultivar effect could be identified. Changes in starch and soluble
sugar content in leaves accounted for only 29% of diurnal variations in LMA, suggesting regular
fluctuations of other components. We propose that structural LMA varies between a maximum and
a minimum value according to the ratio of assimilate supply and demand during leaf development.
Leaf area is independent of the supply of assimilates when the minimum structural LMA is realised.
When the maximum structural LMA is attained, a storage pool of assimilates may accumulate in
leaves during periods of high supply and low demand. We present a model including these
hypotheses, which predicts structural and non- structural LMA variations of plants with different
source-sink ratios. (C) 1998 Annals of Botany Company.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CROP, LEAVES, PHOTOSYNTHESIS,
SOURCE-SINK RELATIONSHIPS


     210  
Bertin, N., and E. Heuvelink. 1993. Dry-matter production in a tomato crop - comparison of 2
simulation-models. Journal of Horticultural Science 68(6):995-1011.

TOMSIM(1.0) and TOMGRO(1.0) are two dynamic models for tomato growth and development.
Their submodels for dry matter production are compared and discussed. In TOMSIM(1.0), dry matter
production is simulated by a modified version of SUCROS87 (Spitters et al., 1989). Single leaf
photosynthesis rates are calculated separately for shaded and sunlit leaf area at different depths in the
canopy, according to the direct and diffuse components of light; daily crop gross assimilation rate (A)
is computed by integration of these rates over the different depths and over the day. In TOMSIM(1.0)
leaf photochemical efficiency (epsilon) and potential leaf gross photosynthesis rate at saturating light
level (P(g,max)) both depend on temperature and CO2 level. In TOMGRO(1.0) crop gross
photosynthesis rate is calculated by the equation of Acock et al. (1978); epsilon is a constant and
P(g,max) is a linear function of CO2. In both models leaf photosynthesis characteristics are assumed
to be identical in the whole canopy. Maintenance respiration (R(m)) and conversion efficiency (C(f))
are taken into account in the same way, except that root maintenance respiration is neglected in
TOMGRO(1.0). For both models a sensitivity analysis was performed on the input variables (light
intensity, temperature, CO2 and leaf area index (LAI)) and on some of the model parameters. Under
most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(1.0) than in
TOMGRO(1.0). At temperatures above 18-degrees-C R(m) was also higher in TOMSIM(1.0), and
C(f) was 4% higher in TOMGRO(1.0). The two models were very sensitive to changes in epsilon and
to a lesser extent to changes in the light extinction coefficient, whereas the scattering coefficient of
leaves had hardly any effect on the simulated A. TOMGRO(1.0) appeared to be rather sensitive to
the CO2 use efficiency, whereas at ambient CO2 level mesophyll resistance was quite important in
TOMSIM(1.0). Four sets of experimental data (differences in cultivar, CO2 enrichment and planting
date) from Wageningen (The Netherlands) and Montfavet (southern France) were used to validate
the models. Average 24 h temperature and average daily CO2 concentration values were used as
input to the models. For the Wageningen experiments, hourly PAR values were calculated from the
daily global radiation sum by TOMSIM(1.0) and used as input in both models. For the Montfavet
experiment, average hourly PAR measurements were used. Also measured LAI, dry matter
distribution and organ dry weights (for calculation of R(m)) were input to the simulation. In the
Wageningen experiments, total dry matter production was simulated reasonably well by both models,
whereas in the Montfavet experiment an under- estimation of about 35% occurred. TOMGRO(1.0)
and TOMSIM(1.0) simulated almost identical curves in all four experiments. Strong and weak points
of both models are discussed.

KEYWORDS: CANOPY, CO2, GAS-EXCHANGE, GROWTH, LEAVES, LIGHT,
PHOTOSYNTHESIS, YIELD


     211  
Bertoni, G.P., and W.M. Becker. 1996. Expression of the cucumber hydroxypyruvate reductase
gene is down-regulated by elevated CO2. Plant Physiology 112(2):599-605.

We examined the effects of CO2 concentration on the white- light-stimulated expression of the
cucumber (Cucumis sativus L.) Hpr gene. Hpr encodes hydroxypyruvate reductase, an enzyme
important in the photorespiratory glycolate pathway, which plays an integral role in carbon allocation
in C-3 plants. Because CO2 is an end product of this pathway and because increased CO2
concentrations lessen the need for photorespiration, we tested whether exposure of plants to elevated
CO2 would affect white-light-stimulated Hpr gene expression. Exposure of dark-adapted cucumber
seedlings to elevated CO2 (2 to 3 times ambient) during a 4-h white-light irradiation significantly
inhibited the accumulation of Hpr mRNA. Increasing the CO2 concentration during irradiation to 6
or 9 times ambient did not further inhibit Hpr mRNA accumulation. The depressing effect of high
CO2 on Hpr mRNA accumulation was seen in both high and low light, but was more pronounced in
higher light. These results suggest that maximum sensitivity to CO2 occurs in conditions near those
normally encountered by the plant (high light, CO2 concentration near ambient) and support a model
in which white-light-regulated Hpr expression is modulated in part by environmental CO2
concentration.

KEYWORDS: COTYLEDONS, PHOTORESPIRATION, PLANT, SEQUENCE


     212  
Besford, R.T. 1993. Photosynthetic acclimation in tomato plants grown in high co2. Vegetatio
104:441-448.

The effects of prolonged CO2 enrichment of tomato plants on photosynthetic performance and Calvin
cycle enzymes, including the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco),
were determined. Also the light-saturated rate of photosynthesis (P(max)) of the 5th leaf throughout
leaf development was predicted based on the amount and kinetics of RuBPco. With short-term CO2
enrichment, i.e. only during the photosynthesis measurements, P(max) of the young leaves did not
increase while the leaves reaching full expansion more than doubled their net rate of CO2 fixation.
However, with longer- term CO2 enrichment, i.e. growing the crop in high CO2, the plants did not
maintain this photosynthetic gain. Compared with leaves of plants grown in normal ambient CO2 the
high CO2-grown leaves, when almost fully expanded, contained only about half as much RuBPco
protein and P(max) in 300 and 1000 vpm CO2 was similarly reduced. The loss of RuBPco protein
may be a factor associated with the accelerated fall in P(max) since P(max) was close to that
predicted from the amount and kinetics of RuBPco assuming RuBP saturation. Acclimation to high
CO2 is fundamentally different from acclimation to high light. In contrast to acclimation to high light,
acclimation to high CO2 does not usually involve an increase in photosynthetic machinery so the
synthesis and maintenance costs (as indicated by the dark respiration rate) are generally lower.

KEYWORDS: ACTIVATION, CALVIN CYCLE ENZYMES, ENRICHMENT, HIGH ATMOSPHERIC
CO2, LEAVES, NITROGEN, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE,
RICE, WHEAT


     213  
Betsche, T. 1994. Atmospheric co2 enrichment - kinetics of chlorophyll a fluorescence and
photosynthetic co2 uptake in individual, attached cotton leaves. Environmental and Experimental
Botany 34(1):75-86.

Chl fluorescence and gas exchange of attached cotton leaves (Gossypium hirsutum L.) were measured
in ambient air and in a highly CO2-enriched atmosphere (4000 mu l l(-1) CO2; photosynthetic
saturation). In the shore term (hours to one day), net CO2 uptake approximately doubled in all leaves
examined. Photochemical (q(P)) and nonphotochemical (q(NP)) quenching of chlorophyll
fluorescence, and calculated linear photosynthetic electron Row, did not change significantly when
CO2 rose from 250 to 4000 mu l l(-1) CO2. These results show that high CO2 concentration did not
inhibit photosynthesis in any leaf. In contrast, the long-term response of leaves to atmospheric CO2-
enrichment was variable, Some leaves sustained the initial high level of photosynthetic stimulation for
more than a week while in others photosynthetic CO2-uptake declined more or less. These leaves
turned yellowish-green although chlorophyll content declined little. Variance in the degree of leaf
yellowing was also encountered in experiments with clover when sets of plants were CO2-enriched.
Gas exchange and chi fluorescence results suggest that yellowing of cotton leaves in high CO2 was
not equivalent to 'natural' senescence although some chlorophyll fluorescence parameters changed
similarly. During extended high CO2 treatment the level of q(NP) increased notably in the yellowing
leaves. The high levels of q(NP) and relaxation kinetics of chi fluorescence quenching recorded upon
darkening demonstrate that thylakoid energization increased during the decline of photosynthetic CO2
uptake in high CO2. This shows that the photosynthetic decline was not caused by decreasing
thylakoid energization because of physical damage by oversized starch grains. Calculated
photosynthetic electron flow declined little suggesting that CO2 at ribulosebisphosphate carboxylase-
oxygenase fell and thus photorespiration rose. With regard to growth limitation in high CO2
concentration, these results support the concept that high CO2 concentration tends to induce low
inorganic phosphate concentrations (Morin et al. Plant Physiol. 99, 89-95, 1992; Duchein et al. J.
Exp. Bet. 44, 17-22, 1993) which can limit chloroplast ATP synthase and thus increase thylakoid
energization. It is proposed that the different responses of individual leaves to atmospheric CO2
enrichment reflects variety among leaves in the phosphate status or in the capacity for Pi-recycling
(assimilate utilization).

KEYWORDS: CARBON DIOXIDE, CROP RESPONSES, DROUGHT STRESS, ELECTRON-
TRANSPORT, ELEVATED CO2, GROWTH, INORGANIC- PHOSPHATE, PHASEOLUS-
VULGARIS L, PLANT NUTRITION, STARCH


     214  
Bettarini, I., G. Calderoni, F. Miglietta, A. Raschi, and J. Ehleringer. 1995. Isotopic carbon
discrimination and leaf nitrogen-content of erica-arborea L along a co2 concentration gradient in a
co2 spring in italy. Tree Physiology 15(5):327-332.

We studied a Mediterranean species (Erica arborea L.) growing in a CO2 spring in Italy that was
naturally exposed for generations to a gradient of atmospheric CO2 concentrations. The CO2
concentration gradient to which different individual plants were exposed was determined by an
indirect method based on radioisotope analysis. The stable carbon isotope ratio of sampled leaves was
determined by mass spectrometry, and isotopic discrimination was then calculated. Leaf nitrogen,
specific leaf area, total soil nitrogen, soil organic matter content and soil pH were also measured. In
one group of plants, grown on a homogeneous soil and exposed to moderate CO2 enrichment,
isotopic discrimination was significantly reduced in response to increasing CO2 concentrations,
whereas the intercellular CO2 concentration and leaf nitrogen content were almost unaffected. In a
second group of plants, grown along a gradient of CO2 concentration and soil nitrogen content, leaf
nitrogen content was reduced when nitrogen availability was limiting. However, when soil nitrogen
was available in excess, even very high CO2 concentrations did not result in increased discrimination
or reduced leaf nitrogen content in the long term. The results are discussed with respect to current
theories about the long-term CO2 response of plants based on several years of experimentation with
elevated atmospheric CO2 concentrations under controlled conditions.

KEYWORDS: ELEVATED CO2, ENVIRONMENT, LEAVES, PHOTOSYNTHESIS, PLANT-
RESPONSES, STOMATAL DENSITY


     215  
Bettarini, I., F.P. Vaccari, and F. Miglietta. 1998. Elevated CO2 concentrations and stomatal
density: observations from 17 plant species growing in a CO2 spring in central Italy. Global Change
Biology 4(1):17-22.

Stomatal density (SD) and stomatal conductance (g(s)) can be affected by an increase of atmospheric
CO2 concentration. This study was conducted on 17 species growing in a naturally enriched CO2
spring and belonging to three plant communities. Stomatal conductance, stomatal density and
stomatal index (SI) of plants from the spring, which were assumed to have been exposed for
generations to elevated [CO2], and of plants of the same species collected in a nearby control site,
were compared. Stomatal conductance was significantly lower in most of the species collected in the
CO2 spring and this indicated that CO2 effects on g, are not of a transitory nature but persist in the
long term and through plant generations. Such a decrease was, however, not associated with changes
in the anatomy of leaves: SD was unaffected in the majority of species (the decrease was only
significant in three out of the 17 species examined), and also SI values did not vary between the two
sites with the exception of two species that showed increased SI in plants grown in the CO2-enriched
area. These results did not support the hypothesis that long-term exposure to elevated [CO2] may
cause adaptive modification in stomatal number and in their distribution.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CONDUCTANCE, EXPOSURE, GAS-
EXCHANGE, GRASSLAND, INCREASE, LEAVES, RESPONSES, TREES


     216  
Betts, R.A., P.M. Cox, S.E. Lee, and F.I. Woodward. 1997. Contrasting physiological and
structural vegetation feedbacks in climate change simulations. Nature 387(6635):796-799.

Anthropogenic increases in the atmospheric concentration of carbon dioxide and other greenhouse
gases are predicted to cause a warming of the global climate by modifying radiative forcing(1).
Carbon dioxide concentration increases may make a further contribution to warming by inducing a
physiological response of the global vegetation-a reduced stomatal conductance, which suppresses
transpiration(2). Moreover, a CO2-enriched atmosphere and the corresponding change in climate may
also alter the density of vegetation cover, thus modifying the physical characteristics of the land
surface to provide yet another climate feedback(3-6). But such feedbacks from changes in vegetation
structure have not yet been incorporated into general circulation model predictions of future climate
change. Here we use a general circulation model iteratively coupled to an equilibrium vegetation
model to quantify the effects of both physiological and structural vegetation feedbacks on a doubled-
CO2 climate. On a global scale, changes in vegetation structure are found to partially offset
physiological vegetation-climate feedbacks in the long term, but overall vegetation feedbacks provide
significant regional-scale effects.

KEYWORDS: CANOPY, EUROPE, FOREST, IMPACT, LAND, MODEL, SENSITIVITY


     217  
Bezemer, T.M., and T.H. Jones. 1998. Plant-insect herbivore interactions in elevated atmospheric
CO2: quantitative analyses and guild effects. Oikos 82(2):212-222.

Interactions between insect herbivores and plants grown under conditions of ambient and elevated
CO2 were investigated by analysing data on 43 herbivores, representing 61 plant- herbivore
interactions. Changes in herbivore performance in enhanced CO2 environments were correlated with
changes in the quality of the host plants, measured as nitrogen content, water content, carbohydrate
content and secondary plant compounds. The data were analysed to determine whether CO2 mediated
effects on insect performance differed between feeding guilds (leaf-chewers, leaf miners, phloem-
feeders (root and shoot), xylem-feeders, whole-cell-feeders and seed-eaters) or instar stage. Host-
plant quality changed in elevated CO2; leaf nitrogen content decreased, on average, by 15% while
carbohydrates increased by 47% and secondary plant compounds (phenolics) by 31%. Water content
did not change. Of the variables measured, changes in nitrogen and carbohydrate levels only were
found to be correlated with changes in food consumption. No differences were found in CO2-
mediated herbivore responses on woody plant compared with non-woody plants. Insects from
different feeding guilds respond to CO2 mediated changes in host-plant quality in various ways. Leaf-
chewers generally seem able to compensate for the decreased nitrogen levels in the plant tissues by
increasing their food consumption (by 30%) and with no adverse effects on pupal weights. Leaf-
miners only slightly increase their food consumption. The negative effect on pupal weight suggests
that their population dynamics may change over several generations. Limited data on seed-eaters
suggest that enhanced CO2 conditions have no effect on these insects. Phloem-feeders and whole-
cell-feeders are the only insects to show a positive CO2 response. Population sizes generally increased
in elevated CO2 and development lime of phloem-feeders was reduced by 17%. Early instar larvae
are restricted more by CO2 enhancement than late instars. Although changes in food consumption
are similar, changes in development times are much more pronounced in young instars (18% vs 6%).

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, CLIMATE CHANGE, GROWTH, JUNONIA-
COENIA, LEPIDOPTERA, NOCTUIDAE, NUTRIENT BALANCE, PAPER BIRCH,
PERFORMANCE, RESPONSES


     218  
Bezemer, T.M., T.H. Jones, and K.J. Knight. 1998. Long-term effects of elevated CO2 and
temperature on populations of the peach potato aphid Myzus persicae and its parasitoid Aphidius
matricariae. Oecologia 116(1-2):128-135.

Model terrestrial ecosystems were set-up in the Ecotron controlled environment facility. The effects
of elevated CO2 (ambient + 200 mu mol/mol) and temperature (ambient + 2.0 degrees C) on plant
chemistry, the abundance of the peach potato aphid Myzus persicae, and on the performance of one
of its parasitoids Aphidius matricariae, were studied. Total above-ground plant biomass at the end
of the experiment was not affected by elevated atmospheric CO2, nor were foliar nitrogen and carbon
concentrations. Elevated temperature decreased final plant biomass while leaf nitrogen concentrations
increased. Aphid abundance was enhanced by both the CO2 and temperature treatment. Parasitism
rates remained unchanged in elevated CO2, but showed an increasing trend in conditions of elevated
temperature. Our results suggest that M. persicae, an important pest of many crops, might increase
its abundance under conditions of climate change.

KEYWORDS: ATMOSPHERIC CO2, CLIMATE CHANGE, DECOMPOSITION, DYNAMICS,
ECOSYSTEMS, HERBIVORY, HOMOPTERA, INSECT PERFORMANCE, PHYTOCHEMISTRY,
RESPONSES


     219  
Bezemer, T.M., K.J. Knight, J.E. Newington, and T.H. Jones. 1999. How general are aphid
responses to elevated atmospheric CO2? Annals of the Entomological Society of America 92(5):724-
730.

We studied the impact of elevated CO2 on 2 aphid pest species, Myzus persicae and Brevicoryne
brassicae (Homoptera: Aphididae), on a series of host plants in 3 independent studies each differing
in experimental complexity. Measurements on individual aphids showed that host plant and aphid
species significantly influenced the response to elevated CO2. These differences occurred not only
in the level of responsiveness but also directionally. B. brassicae reared on Brassica oleracea produced
significantly less offspring at elevated CO2, whereas the opposite was found for M. persicae on the
same host. No response was found for M. persicae on Senecio vulgaris. When populations of B.
brassicae and M. persicae were followed for a longer period, no differences were observed in
population sizes, Comparisons between different experimental systems show that long-term
population responses to elevated CO2 can not be reliably predicted from detailed measurements on
individual aphids. The consequences of these findings for climate change research are discussed.

KEYWORDS: BREVICORYNE-BRASSICAE, CARBON DIOXIDE, CLIMATE CHANGE,
DECIDUOUS TREES, HERBIVORE INTERACTIONS, INSECT PERFORMANCE, MYZUS-
PERSICAE, PLANT, POPULATION-DYNAMICS, TERRESTRIAL ECOSYSTEMS


     220  
Bezemer, T.M., L.J. Thompson, and T.H. Jones. 1998. Poa annua shows inter-generational
differences in response to elevated CO2. Global Change Biology 4(6):687-691.

Inter-generational effects on the growth of Poa annua (L.) in ambient and elevated atmospheric CO2
conditions (350 and 550 mu l l(-1), respectively) were studied in two different experiments. Both
experiments showed similar results. In a greenhouse experiment growth, measured as the numbers
of tillers produced per week, was compared for plants grown from first and second generation seeds.
Second generation seeds were obtained from plants grown for one whole generation in either ambient
or elevated atmospheric CO2 ('ambient' and 'elevated' seeds, respectively). First generation plants and
second generation 'ambient' plants did not respond to elevated CO2. Second generation 'elevated'
plants produced significantly more tillers in elevated CO2. In the second experiment model terrestrial
ecosystems growing in the Ecotron and which included Poa annua were used. Above-ground biomass
after one and two generations of growth were compared. At the end of Generation 1 no difference
was found in biomass production while at the end of Generation 2 biomass increased in elevated CO2
by 50%. The implications for climate change research are discussed.

KEYWORDS: ECOTRON, ENVIRONMENTS, FACILITY, GROWTH, PLANTS, POPULATION


     221  
Bhattacharya, N.C., D.R. Hileman, P.P. Ghosh, R.L. Musser, S. Bhattacharya, and P.K.
Biswas. 1990. Interaction of enriched CO2 and water-stress on the physiology of and biomass
production in sweet-potato grown in open-top chambers. Plant, Cell and Environment 13(9):933-
940.

The objective of this study was to investigate the effects of water stress in sweet potato (Ipomoea
batatas L. [Lam] 'Georgia Jet') on biomass production and plant-water relationships in an enriched
CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two
concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first
12 d of water stress, leaf xylem potentials were higher in plants grown in a CO2 concentration of 438
and 666-mu-mol mol-1 than in plants grown at 364-mu-mol mol-1. The 364-mu-mol mol-1 CO2
grown plants had to be rewatered 2d earlier than the high CO2-grown plants in response to water
stress. For plants grown under water stress, the yield of storage roots and root:shoot ratio were
greater at high CO2 than at 364-mu-mol mol-1; the increase, however, was not linear with increasing
CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at
elevated CO2, and these were greater as compared to water-stressed plants grown at the same CO2
concentration.

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CARBON-DIOXIDE, FIELD,
PHOTOSYNTHESIS, SOYBEANS, YIELD


     222  
Bhattacharya, N.C., J.W. Radin, B.A. Kimball, J.R. Mauney, G.R. Hendrey, J. Nagy, K.F.
Lewin, and D.C. Ponce. 1994. Leaf water relations of cotton in a free-air co2-enriched environment.
Agricultural and Forest Meteorology 70(1-4):171-182.

As part of an intensive study of crop response to CO2 enrichment in a free-air CO2 enrichment
(FACE) experiment in the field, we determined aspects of the water relations of a cotton crop on
selected dates in 1991. The atmosphere was enriched from 370 mumol CO2 mol-1 (control) to about
550 mumol mol-1 in free air during daylight hours. Under full irrigation, CO2 enrichment decreased
stomatal conductance and single-leaf transpiration only toward the end of the season, and these
changes led to increased leaf water potentials only at that time of year. Under water-stressed (deficit
irrigation) conditions, CO2 enrichment decreased conductance throughout the season but there was
no corresponding consistent effect on leaf water potentials. As with the fully irrigated controls, CO2
enrichment increased leaf water potentials only at the end of the season. CO2 enrichment increased
season-long biomass accumulation 39% under full irrigation and 34% under deficit irrigation. These
results are consistent with previous studies of cotton in open-top chambers that found only small
effects of CO2 enrichment on internal water relations of cotton, and no water stress-induced increase
in crop responsiveness to elevated CO2.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CO2- ENRICHMENT, CONDUCTANCE,
GROWTH, PHOSPHORUS, PHOTOSYNTHESIS, RESPONSES, SEEDLINGS, STRESS, YIELD


     223  
Bialczyk, J., Z. Lechowski, and A. Libik. 1998. Modification of tannin concentration by abiotic
factors in Lycopersicon esculentum Mill. seedlings. Zeitschrift Fur Pflanzenkrankheiten Und
Pflanzenschutz-Journal of Plant Diseases and Protection 105(3):264-273.

Results of the study on the effect of some abiotic factors on the modification of Leaf tannin
concentration of greenhouse tomato seedlings are discussed in the work. The total content of soluble
and insoluble tannins was calculated as tannic acid equivalent x g(-1) dry matter. The cultivars of
tomato were characterized by the differentiated tannin content in leaves, stems; and roots, the
proportion being 1 : 1/2 and 1/3, respectively. Two of the investigated cultivars were characterized
by extreme values of che natural tannin content (cv. 'Baron' with the greatest content and cv. 'Perkoz'
with the smallest one), the differences between them reaching about 240 %. A partial defoliation-or
mechanical wounding of leaf blades increased the content of tannins in these organs, In relation to
the effect of the partial defoliation (about 50 % of leaves being cut oft), the content of tannins was
higher in the case of pricking the leaves with needles. Depending on the number of pricks per cm(2)
of the leaf blade (8, 20 or; 40), associated with a different degree of its wounding (1 %, 2.5 %, and
5 %, respectively), a maximum increase in tannin content was 180 % with 20 pricks x cm(-2) as
compared with the control. The intensity of photosynthetically active radiation (PAR) significantly
affected the kinetics of tannin synthesis. In the case of a 90 % reduction of daily PAR intensity, the
content of tannins was reduced by about 50 % after a 2-week experiment with the two cultivars.
Changes in CO2 concentration in the environment of seedlings differently modified the level of leaf
tannins. With CO2 concentration reduced to 170 mu mol x mol(-1) air, the content of tannins
decreased to about 76 % of the value evidenced in atmospheric air. CO, elevated to 680 mu mol x
mol(-1) air induced an increase in leaf tannins to about 112- 121 % in, relation to the control. The
enrichment of soil solution with phosphorus or nitrogen compounds had different and opposing
effects on tannin content. With phosphorus enrichment of the substrate, the content of tannins in
leaves increased to about 120 % in relation to the control. The elevated nitrogen concentration
reduced the content of tannins by about 30 % after a 2-week experiment. The results concerning the
effect of abiotic factors on the tannin level in the leaves of greenhouse tomato seedlings could lead
to the development of control measures based-on the activation of the natural defense system of
planes against herbivores.

KEYWORDS: CARBON NUTRIENT BALANCE, CO2, PATHWAY, PHYTOCHEMISTRY,
POLYPHENOL OXIDASE, RESPONSES


     224  
Bialczyk, J., Z. Lechowski, and A. Libik. 1999. The protective action of tannins against glasshouse
whitefly in tomato seedlings. Journal of Agricultural Science 133:197-201.

The synthesis and accumulation of tannins on tomato seedlings are regulated by environmental
factors. The variation in the content of tannins was sufficiently important to bring about the
occurrence of significant differences in the numbers of glasshouse whitefly on the seedlings. During
a 2-week experiment, the treatments included mechanical wounding (20 prickings per cm(2)),
spraying with kinetin solutions of 10(-4) mol/dm(3), plant growth regulators, and the atmosphere
enrichment to 680 mu mol CO2/mol air, the content of tannins being increased by c. 40, 70, 10-45
and 25 % above the values obtained in the control. These results were correlated with a decrease in
the numbers of insects occurring on the seedlings by c. 35, 45, 8-29 and 18 %, respectively. Contrary
to the above results the spraying with solutions of abscisic acid, gibberellic acid, and the incubation
of plants in an atmosphere containing 170 mu mol CO2/mol air, reduced the content of tannins by c.
69, 22 and 25 %, respectively. This was reflected in the respective increases by c. 70, 40 and 35%
in the numbers of insects occurring on the seedlings. The obtained results suggest that tannins seem
to have a dosage-dependent effect on glasshouse whitefly. Decreasing the host plant quality by
increasing tannin content may act as an important selective agent limiting the losses brought about
by glasshouse whitefly in tomato cultivation.

KEYWORDS: CHEMICAL DEFENSE, CO2, GROWTH, METABOLISM, NUTRIENT, PLANT
POLYPHENOLS, RESPONSES, TREE


     225  
Billes, G., H. Rouhier, and P. Bottner. 1993. Modifications of the carbon and nitrogen allocations
in the plant (triticum-aestivum L) soil system in response to increased atmospheric co2 concentration.
Plant and Soil 157(2):215-225.

The aim of this work was to examine the response of wheat plants to a doubling of the atmospheric
CO2 concentration on: (1) carbon and nitrogen partitioning in the plant, (2) carbon release by the
roots; and (3) the subsequent N uptake by the plants. The experiment was performed in controlled
laboratory conditions by exposing fast-growing spring wheat plants, during 28 days, to a (CO2)-C-14
concentration of 350 or 700 muL L-1 at two levels of soil nitrogen fertilization. Doubling CO2
availability increased total plant production by 34% for both N treatment. In the N-fertilized soil, the
CO2 enrichment resulted in an increase in dry mass production of 41% in the shoots and 23% in the
roots; without N fertilization this figure was 33% and 37%, respectively. In the N-fertilized soil, the
CO2 increase enhanced the total N uptake by 14% and lowered the N concentration in the shoots by
23%. The N concentration in the roots was unchanged. In the N-fertilized soil, doubling CO2
availability increased N uptake by 32% but did not change the N concentrations, in either shoots or
roots. The CO2 enrichment increased total root-derived carbon by 12% with N fertilization, and by
24% without N fertilization. Between 85 and 90% of the total root derived-C-14 came from
respiration, leaving only 10 to 15% in the soil as organic C-14. However, when total root-derived C-
14 was expressed as a function of root dry weight, these differences were only slightly significant.
Thus, it appears that the enhanced carbon release from the living roots in response to increased
atmospheric CO2, is not due to a modification of the activity of the roots, but is a result of the
increased size of the root system. The increase of root dry mass also resulted in a stimulation of the
soil N mineralization related to the doubling atmospheric CO2 concentration. The discussion is
focused on the interactions between the carbon and nitrogen allocation, especially to the root system,
and the implications for the acquisition of nutrients by plants in response to CO2 increase.

KEYWORDS: DIOXIDE, DRY-MATTER, ELEVATED CO2, ENRICHMENT, GROWTH,
METABOLISM, MICROBIAL BIOMASS, MINERAL NUTRITION, RESPIRATION, ROOT-
DERIVED MATERIAL


     226  
Bindi, M., L. Fibbi, B. Gozzini, S. Orlandini, and F. Miglietta. 1996. Modelling the impact of
future climate scenarios on yield and yield variability of grapevine. Climate Research 7(3):213-224.

A mechanistic growth model was used to evaluate the mean yield and yield variability of grapevine
Vitis vinifera L. under current and future climates. The model used was previously validated using
field experiment data. The effect of elevated CO2 on grapevine growth was also considered.
Adaptation of 2 varieties (Sangiovese and Cabernet Sauvignon) to scenarios of increased CO2 and
climate change, and potential changes in agricultural risk (i.e. inter-seasonal variability), were
examined. Before testing the effect of climate scenarios, we analysed the sensitivity of modelled
grapevine yield to arbitrary changes in the 3 driving variables (temperature, solar radiation and CO2).
The results showed the model to be more sensitive to changes in CO2 concentration and temperature
than to changes in radiation. Analyses made using transient GCM (general circulation model)
scenarios (UKTR and GFDL) showed different changes in mean fruit dry matter for the different
scenarios, whereas mean total dry matter, and fruit and total dry matter variability, were predicted
to increase under almost all the scenarios. Predictions based on equilibrium scenarios (UKLO and
UKHI) gave similar results. For Sangiovese, variety adaptation analysis suggested a better adaptation
in terms of mean production, but a worse adaptation in terms of yield variability.

KEYWORDS: CO2, RADIATION, TEMPERATURE


     227  
Biondi, F., and J.E. Fessenden. 1999. Response of lodgepole pine growth to CO2 degassing at
Mammoth Mountain, California. Ecology 80(7):2420-2426.

We conducted dendroclimatic and stable isotope analyses of lodgepole pines (Pinus contorta) located
in high-mortality sites at Mammoth Mountain (California, USA) to test for tree responses to
magmatic degassing. Existing climatic and tree- ring data from nearby Yellowstone National Park
were used for comparison. Sampled trees were scarcely sensitive to climate, and their growth showed
an overall decline during the 20th century. Past growth rates of currently dead and stressed pines
plummeted after 1990, when degassing of magmatic CO2 was first reported in the area. No consistent
or strong correlation was found with monthly and seasonal climatic parameters. Stable carbon
isotopes were measured on holocellulose extracted from annual rings of a dead pine, a stressed pine,
and a live pine. The delta(13)C signature of the dead and stressed pines showed enrichment in heavy
carbon beginning in 1990, which could be related to stomatal closure following impairment of root
systems by high levels of magmatic CO2 in the soil.

KEYWORDS: CARBON, EMISSION, ISOTOPE, LONG VALLEY CALDERA, RATIOS, RINGS,
UNREST


     228  
Bishop, D.L., and B.G. Bugbee. 1998. Photosynthetic capacity and dry mass partitioning in dwarf
and semi-dwarf wheat (Triticum aestivum L.). Journal of Plant Physiology 153(5-6):558-565.

Efficient use of space and high yields are critical for long- term food production aboard the
International Space Station. The selection of a full dwarf wheat (less than 30 cm tall) with high
photosynthetic and yield potential is a necessary prerequisite for growing wheat in the controlled,
volume- limited environments available aboard long-term spaceflight missions. This study evaluated
the photosynthetic capacity and carbon partitioning of a full-dwarf wheat cultivar, Super Dwarf,
which is routinely used in spaceflight studies aboard U.S. space shuttle and NASA/Mir missions and
made comparisons with other dwarf and semidwarf wheat cultivars utilized in other ground-based
studies in plant space biology. Photosynthetic capacity of the flag leaf in two dwarf (Super Dwarf,
BB-19), and three semi-dwarf (Veery-10, Yecora Rojo, IBWSN 199) wheat cultivars (Triticum
aestivum L.) was assessed by measuring: net maximum photosynthet ic rate, RuBP carboxylation
efficiency, chlorophyll concentration and flag leaf area. Dry mass partitioning of carbohydrates to the
leaves, sheaths, stems and ear was also assessed. Plants were grown under controlled environmental
conditions in three replicate studies: slightly enriched CO2 (370 mu mol mol(-1)), high photosynthetic
photon flux (1000 mu mol m(-2) s(-1); 58 mol m(-2) d(-1)) for a 16 h photoperiod, 22/15 degrees
C day/night temperatures, ample nutrients and water provided by one-half strength Hoagland's
nutrient solution (Hoagland and Amen, 1950). Photosynthetic capacity of the flag leaf was determined
at anthesis using net CO2 exchange rate versus internal CO2 concentration curves measured under
saturating light (2000 mu mol m(-2) s(-1)) and CO2 (1000 mu mol mol(-1)). Dwarf wheat cultivars
had greater photosynthetic capacities than the taller semi-dwarfs, they averaged 20 % higher
maximum net photosynthetic rates compared to the taller semi-dwarfs, but these higher rates occurred
only at anthesis, had slightly greater carboxylation efficiencies and significantly increased chlorophyll
concentrations per unit leaf area. The reduced- height wheat had significantly less dry mass fraction
in the stem but greater dry mass partitioned to the ear than the taller semi-dwarfs (Yecora rojo,
IBWSN-199). Studies with detached heads confirm that the head is a significant sink in the shorter
wheat cultivars.

KEYWORDS: BIOCHEMISTRY, CANOPY, FLAG LEAF, GAS-EXCHANGE, HEIGHT, LEAVES,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SPRING WHEAT, SUCROSE METABOLISM,
WINTER-WHEAT


     229  
Biswas, P.K., D.R. Hileman, P.P. Ghosh, N.C. Bhattacharya, and J.N. McCrimmon. 1996.
Growth and yield responses of field-grown sweetpotato to elevated carbon dioxide. Crop Science
36(5):1234-1239.

Root crops are important in developing countries, where food supplies are frequently marginal.
Increases in atmospheric CO2 usually lead to increases in plant growth and yield, but little is known
about the response of root crops to CO2 enrichment under field conditions, This experiment was
conducted to investigate the effects of CO2 enrichment on growth and yield of field-grown
sweetpotato [Ipomoea batatas (L.) Lam.]. Plants were grown in open-top chambers in the field at
four CO2 levels ranging from 354 (ambient) to 665 mu mol mol(-1) in two growing seasons, Shoot
growth was not affected significantly by elevated CO2. Yield of storage roots increased 46 and 75%
at the highest CO2 level in the 2 yr, The yield enhancement occurred through increases in the number
of storage roots in the first year and through increases in both the number and size of the storage
roots in the second year, Storage- root/shoot ratios increased 44% and leaf nitrogen concentrations
decreased by 24% at the highest CO2 level, A comparison of plants grown in the open field to plants
grown in open-top chambers at ambient CO2 concentrations indicated that open-top chambers
reduced shoot growth in the first year and storage-root yield in both years, These results are
consistent with the majority of CO2-enrichment studies done on pot-grown sweetpotato.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, COTTON, ENVIRONMENT, IRRIGATION,
NITROGEN, OPEN-TOP CHAMBERS, PHYSIOLOGY, PLANT-RESPONSES, SWEET-POTATO,
WATER-STRESS


     230  
Bjorn, L.O., T.V. Callaghan, I. Johnsen, J.A. Lee, Y. Manetas, N.D. Paul, M. Sonesson, A.R.
Wellburn, D. Coops, H.S. HeideJorgensen, C. Gehrke, D. GwynnJones, U. Johanson, A.
Kyparissis, E. Levizou, D. Nikolopoulos, Y. Petropoulou, and M. Stephanou. 1997. The effects
of UV-B radiation on European heathland species. Plant Ecology 128(1-2):252-264.

The effects of enhanced UV-B radiation on three examples of European shrub-dominated vegetation
were studied in situ. The experiments were in High Arctic Greenland, northern Sweden and Greece,
and at all sites investigated the interaction of enhanced UV-B radiation (simulating a 15% reduction
in the ozone layer) with artificially increased precipitation, The Swedish experiment also involved a
study of the interaction between enhanced UV-B radiation and elevated CO2 (600 ppm). These field
studies were supported by an outdoor controlled environment study in the United Kingdom involving
modulated enhancement of UV-B radiation in combination with elevated CO2 (700 ppm). Effects of
the treatments on plant growth, morphology, phenology and physiology were measured. The effects
observed were species specific, and included both positive and negative responses to the treatments.
In general the negative responses to UV-B treatments of up to three growing seasons were small, but
included reductions in shoot growth and premature leaf senescence. Positive responses included a
marked increase in flowering in some species and a stimulation of some photosynthetic processes.
UV-B treatment enhanced the drought tolerance of Pinus pinea and Pinus halepensis by increasing
leaf cuticle thickness. In general, there were few interactions between the elevated CO2 and enhanced
UV-B treatments. There was evidence to suggest that although the negative responses to the
treatments were small, damage may be increasing with time in some long-lived woody perennials.
There was also evidence in the third year of treatments for effects of UV-B on insect herbivory in
Vaccinium species. The experiments point to the necessity for long-term field investigations to predict
the likely ecological consequences of increasing UV-B radiation.

KEYWORDS: ACTION SPECTRA, DROUGHT, FIELD CONDITIONS, GROWTH, LEAVES,
PHOTOSYNTHESIS, SOLAR ULTRAVIOLET-RADIATION, STOMATAL CLOSURE, SURFACE,
TERRESTRIAL PLANTS


     231  
Bladier, C., and P. Chagvardieff. 1993. Growth and photosynthesis of photoautotrophic callus
derived from protoplasts of solanum-tuberosum L. Plant Cell Reports 12(6):307-311.

We describe a photoautotrophic culture procedure of potato (cvs Kennebec, Haig, DTO-33) callus
derived from mesophyll protoplasts. The protoplast culture was initiated at very low concentration
of glucose (down to 0.25 g l-1). Callus was subcultured under CO2 enriched air and glucose was
suppressed by the successive dilutions with glucose free media. Regeneration was successfully
obtained under photoautotrophic conditions. The characterization of oxygen exchange and of some
enzymes and metabolites of carbon assimilation indicated that chlorophyllous callus, grown on
carbohydrate free medium, developed the photosynthetic pathway typical of C3 plants. By comparing
the fresh weight of callus cultivated in the light or in non-photosynthetic conditions (in darkness or
in the light +3-(3,4-Dichlorophenyl)-1,1-dimethylurea) we concluded that growth depended to about
70 to 88 % on photosynthesis.

KEYWORDS: CELL-SUSPENSION CULTURES, CO2, LIGHT, METABOLISM, MUTANTS,
NICOTIANA-PLUMBAGINIFOLIA, OXYGEN- EXCHANGE, PLANTS, RESPIRATION, SUCROSE


     232  
Blobner, M., R. Bogdanski, E. Kochs, J. Henke, A. Findeis, and S. Jelen-Esselborn. 1998.
Effects of intraabdominally insufflated carbon dioxide and elevated intraabdominal pressure on
splanchnic circulation - An experimental study in pigs. Anesthesiology 89(2):475-482.

Background Intraabdominally insufflated carbon dioxide (CO2) during laparoscopy may have a
specific effect on splanchnic circulation that may be unrelated to the effects of increased
intraabdominal pressure alone. Therefore, the influences of insufflation with CO2 versus air on
splanchnic circulation were compared. Methods: Pigs were chronically instrumented for continuous
recording of mesenteric artery, portal venous, inferior vena cava, and pulmonary arterial blood flow
and portal venous pressure. After induction of anesthesia, CO2 or air was insufflated in 14 and 10
pigs, respectively. with the pigs in the supine position, intraabdominal pressure was increased in steps
of 4 mmHg up to 24 mmHg by graded gas insufflation, Results: During air insufflation, mesenteric
artery vascular resistance was unchanged, whereas mesenteric arterial blood flow decreased with
increasing intraabdominal pressure. Shortly after CO2 insufflation to an intraabdominal pressure of
4 mmHg, mean arterial pressure, mesenteric arterial blood flow, and mesenteric arterial vascular
resistance were increased by 21%, 12% and 9%, respectively. Subsequently, with the onset of CO2
resorption in the third minute, mean arterial pressure declined to baseline values and mesenteric
arterial vascular resistance declined to 85% of baseline values, whereas mesenteric arterial blood flow
continued to increase to a maximum of 24% higher than baseline values. At steady-state conditions
during CO2 insufflation, mesenteric arterial blood flow was increased up to an intraabdominal
pressure less than or equal to 16 mmHg but decreased at higher intraabdominal pressures.
Conclusions: in contrast to air insufflation, intraabdominal insufflation of CO2 resulted in a moderate
splanchnic hyperemia at an intraabdominal pressure less than or equal to 12 mmHg. At higher
intraabdominal pressure values, pressure-induced changes became more important than the type of
gas used.

KEYWORDS: BLOOD-FLOW, DOGS, HALOTHANE ANESTHESIA, INTRA-ABDOMINAL
PRESSURE, LAPAROSCOPIC CHOLECYSTECTOMY, PNEUMOPERITONEUM, RESPONSES,
TENSION, VASOPRESSIN RELEASE


     233  
Blum, H., G. Hendrey, and J. Nosberger. 1997. Effects of elevated CO2, N fertilization, and
cutting regime on the production and quality of Lolium perenne L. shoot necromass. Acta
Oecologica-International Journal of Ecology 18(3):291-295.

In the Swiss grassland FACE experiment, we measured the effect of elevated CO2 on the shoot
necromass production and quality of Lolium perenne in 1995. Dead stubble of reproductive tillers and
dead leaf sheaths were the main components of necromass. Elevated CO2 did not significantly change
the amount and the nitrogen concentration of necromass. Significantly more necromass was produced
and the N concentration was lower in the low N supply treatments. Total necromass amounted to
250-500 g m(-2). Necromass N content was in the order of 5-6 g m(-2) This underscores the
importance of the carbon and nitrogen fluxes included in necromass and their importance for soil
biology and fertility.



     234  
Blumenthal, C., H.M. Rawson, E. McKenzie, P.W. Gras, E.W.R. Barlow, and C.W. Wrigley.
1996. Changes in wheat grain quality due to doubling the level of atmospheric CO2. Cereal
Chemistry 73(6):762-766.

Elevated levels of atmospheric CO2 have been shown to increase grain yield and reduce grain
nitrogen concentration. The object of this study was to determine whether elevated CO2 levels would
modify other aspects of grain quality relevant to processing, particularly protein and starch quality.
Wheat of two genotypes (Hartog and Late Hartog) was grown in the field in controlled-atmosphere
tunnels at either the ambient level of CO2 (350 mu l/L) or an elevated level (700 mu l/L). This
elevated level of CO2 produced significant increases in grain yield, but decreases in 1,000-kernel
weight. Grain grown in the elevated CO2 atmosphere produced poorer dough and decreased loaf
volume, farinograph development time, and dough extensibility. These changes were largely
attributable to the lower protein content of the grain grown at elevated CO2. There did not appear
to be major changes in protein composition or in the functional properties of the protein. Grain
produced at elevated CO2 yielded starch with a significantly higher proportion of large (A-type)
starch granules but no overall change in amylose-to-amylopectin ratio. These studies indicate that
elevated levels of CO2 may result in decreased quality of bread wheats largely due to lowered protein
content.

KEYWORDS: CARBON DIOXIDE, CLIMATE, GENOTYPES, GROWTH, NITROGEN
APPLICATION, NUTRITION, SPRING WHEAT, TEMPERATURE, YIELD


     235  
Boerner, R.E.J., and J. Rebbeck. 1995. Decomposition and nitrogen release from leaves of 3
hardwood species grown under elevated o-3 and/or co2. Plant and Soil 170(1):149-157.

Elevated concentrations of O-3 and CO2 have both been shown to affect structure, nutrient status,
and deposition of secondary metabolites in leaves of forest trees. While such studies have produced
robust models of the effects of such air pollutants on tree ecophysiology and growth, few have
considered the potential for broader, ecosystem-level effects after these chemically and structurally
altered leaves fall as leaf litter and decay. To determine the effects of elevated O-3 and/or CO2 on
the subsequent decomposition and nutrient release from the leaves grown in such altered
atmospheres, we grew seedlings of three widespread North American forest trees, black cherry
(Prunus serotina) (BC), sugar maple (Acer saccharum) (SM), and yellow-poplar (Liriodendron
tulipifera) (YP) for two growing seasons in charcoal-filtered air (CF-air=approximately 25% ambient
O-3), ambient O-3 (1X) or twice-ambient O-3 (2X) in outdoor open-top chambers. We then assayed
the loss of mass and N from the litter derived from those seedlings through one year litterbag
incubations in the forest floor of a neighboring forest stand. Mass loss followed linear functions and
was not affected by the O-3 regime in which the leaves were grown. Instantaneous decay rates (i.e.
k values) averaged SM:-0.707 y(-1), BC:-0.613 y(-1), and YP:-0.859 y(-1). N loss from ambient (1X)
O-3-grown SM leaves was significantly greater than from CF-air leaves; N loss from BC leaves did
not differ among treatments. Significantly less N was released from CF-air-grown YP leaves than
from 1X or 2X O-3-treated leaves. YP leaves from plants grown in pots at 2X O-3 and 350 ppm
supplemental CO2 in indoor pollutant fumigation chambers (CSTRs or Continuously Stirred Tank
Reactors) loss 40% as much mass and 27% as much N over one year as did leaves from YP grown
in CF-air or 2X O-3. Thus, for leaves from plants grown in pots in controlled environment fumigation
chambers, the concentrations of both O-3 and CO2 can affect N release from litter incubated in the
field whereas mass loss rate was affected only by CO2. Because both mass loss and N release from
leaves grown at elevated CO2 were reduced significantly (at least for yellow-poplar), forests exposed
to elevated CO2 may have significantly reduced N turnover rates, thereby resulting in increased N
limitation of tree growth, especially in forests which are already N-limited.

KEYWORDS: ACIDIC RAIN, ATMOSPHERIC CO2, CARBON DIOXIDE, OZONE,
PHOTOSYNTHESIS, QUALITY, RESPONSES, SEEDLINGS, SULFUR-DIOXIDE, TREE


     236  
Boese, S.R., and D.W. Wolfe. 1995. Elevated-temperatures limit sink development and
photosynthetic benefit from elevated co2. Plant Physiology 108(2):26.



     237  
Boese, S.R., D.W. Wolfe, and J.J. Melkonian. 1997. Elevated CO2 mitigates chilling-induced
water stress and photosynthetic reduction during chilling. Plant, Cell and Environment 20(5):625-
632.

Bean, cucumber and corn plants were grown in controlled- environment chambers at 25/18 degrees
C day/night temperature and either ambient (350 mu mol mol(-1)) or elevated (700 mu mol mol(-1))
CO2 concentration, and at 20-30 d after emergence they were exposed to a 24 h chilling treatment
(6.5 +/- 1.5 degrees C) at their growth CO2 concentration. Whole-plant transpiration rates (per unit
leaf area basis) during the first 3 h of chilling were about 26, 28 and 13% lower at elevated than at
ambient CO2 for bean, cucumber and corn, respectively. The decline in leaf water potential (Psi(L))
and visible wilting of bean and cucumber during chilling were significantly less at elevated than at
ambient CO2. Corn Psi(L) was not significantly affected by chilling, and corn did not exhibit any
other symptoms of chilling-induced water stress. Leaf osmotic potentials (measured before chilling
only) of bean and cucumber were more negative at elevated than at ambient CO2, and the
corresponding calculated leaf turgor potentials were significantly higher at elevated than at ambient
CO2. Leaf relative water content (RWC) during chilling at ambient CO2 fell to 62 and 48% for bean
and cucumber, respectively, RWC during chilling at elevated CO2 was never below 79% for bean or
63% for cucumber. Corn RWC was not measured, After 24 h of chilling at ambient CO2, net
photosynthetic rate (PN) reductions were 83, 89 and 24% for bean, cucumber and corn, respectively.
P-N reductions during chilling were less at elevated CO2: 53, 40 and 4% for bean, cucumber and
corn, respectively. At ambient CO2, none of the species fully recovered to pre-chilling P-N, but at
elevated CO2 both bean and corn recovered fully. The average percentage leaf area with visible leaf
damage due to chilling was 20.6 and 9.6% at ambient and elevated CO2, respectively, for bean, and
32.4 and 23.6% at ambient and elevated CO2, respectively, for cucumber. Corn showed no significant
permanent leaf damage from chilling at either CO2 concentration. These results indicate that
cucumber was most sensitive to chilling as imposed in this study, followed by bean and corn. The
results support the hypothesis that, at least in young plants under controlled- environment conditions,
elevated CO2 improves plant water relations during chilling and can mitigate photosynthetic
depression and chilling damage. The implications for long-term growth and reproductive success in
managed and natural ecosystems will require testing of this hypothesis under field conditions.

KEYWORDS: ABSCISIC- ACID, LEAF GAS- EXCHANGE, LIGHT, LOW-TEMPERATURE,
PHASEOLUS-VULGARIS L, PHOTOINHIBITION, PISUM SATIVUM L, SENSITIVE PLANTS,
STOMATAL BEHAVIOR, ZEA-MAYS


     238  
Boetsch, J., J. Chin, M. Ling, and J. Croxdale. 1996. Elevated carbon dioxide affects the
patterning of subsidiary cells in Tradescantia stomatal complexes. Journal of Experimental Botany
47(300):925-931.

The influence of elevated CO2 concentration (670 ppm) on the structure, distribution, and patterning
of stomata in Tradescantia leaves was studied by making comparisons with plants grown at ambient
CO2. Extra subsidiary cells, beyond the normal complement of four per stoma, were associated with
nearly half the stomatal complexes on leaves grown in elevated CO2. The extra cells shared
characteristics, such as pigmentation and expansion, with the typical subsidiary cells, The position and
shape of the extra subsidiary cells in face view differed in the green and purple varieties of
Tradescantia. Substomatal cavities of complexes with extra subsidiary cells appeared larger than those
found in control leaves, Stomatal frequency expressed on the basis of leaf area did not differ from the
control. Stomatal frequency based on cell counts (stomatal index) was greater in leaves grown in
CO,enriched air when all subsidiary cells were counted as part of the stomatal complex. This
difference was eliminated when subsidiary cells were included in the count of epidermal cells, thereby
evaluating the frequency of guard cell pairs, The extra subsidiary cells were, therefore, recruited from
the epidermal cell population during development, Stomatal frequency in plants grown at elevated
temperature (29 degrees C) was not significantly different from that of the control (24 degrees C).
The linear aggregations of stomata were similar in plants grown in ambient and elevated CO2. Since
enriched CO2 had no effect on the structure or patterning of guard cells, but resulted in the formation
of additional subsidiary cells, it is likely that separate and independent events pattern the two cell
types. Plants grown at enriched CO2 levels had significantly greater internode lengths, but leaf area
and the time interval between the appearance of successive leaves were similar to that of control
plants. Porometric measurements revealed that stomatal conductance of plants grown under elevated
CO2 was lower than that of control leaves and those grown at elevated temperature, Tradescantia
was capable of regulating stomatal conductance in response to elevated CO2 without changing the
relative number of stomata present on the leaf.

KEYWORDS: ARABIDOPSIS, CO2- ENRICHMENT, DIFFERENTIATION, LEAF
DEVELOPMENT, MORPHOLOGY, PHASEOLUS-VULGARIS L, PHOTOSYNTHESIS, PLANTS,
RESPONSES, SEEDLINGS


     239  
Bolin, B. 1999. Effect on the biosphere of elevated atmospheric CO2 (pg 1851). Science
286(5440):684.



     240  
Bolin, B., J. Canadell, B. Moore, I. Noble, and W. Steffen. 1999. Effect on the biosphere of
elevated atmospheric CO2. Science 285(5435):1851-1852.



     241  
Bolker, B.M., S.W. Pacala, F.A. Bazzaz, C.D. Canham, and S.A. Levin. 1995. Species-diversity
and ecosystem response to carbon-dioxide fertilization - conclusions from a temperate forest model.
Global Change Biology 1(5):373-381.

This paper explores how the response of a temperate forest ecosystem to climate change might
depend on species diversity and community change. In particular, we look at the dynamics of a model
of temperate forest growth under doubled CO2. We combine a detailed, field-calibrated model of
forest dynamics (Pacala et al. 1993) with greenhouse data on the range of seedling biomass growth
response to doubled CO2 concentrations (Bazzaz et al. 1990; Bazzaz & Miao 1993). Because total
ecosystem response to climate change depends delicately on many environmental variables other than
CO2, we isolate the effects of community change by comparing runs of the regular model, allowing
dynamic community change, with runs of a reduced model that holds species composition static by
using a single tree species with average parameters. Simulations that allowed community change
instead of holding species composition constant showed a roughly 30% additional increase in total
basal area over time scales of 50-150 years. Although the model omits many possible feedbacks and
mechanisms associated with climate change, it suggests the large potential effects that species
differences and feedbacks can have in ecosystem models and reinforces the possible importance of
diversity to ecosystem function (Naeem et al. 1994; Tilman & Downing 1994) over time scales within
the planning horizon for global change policy.

KEYWORDS: ATMOSPHERIC CO2, CANOPY, CO2-INDUCED CLIMATE CHANGE,
ENRICHMENT, GROWTH, LIGHT, LIQUIDAMBAR- STYRACIFLUA, PINUS-TAEDA
SEEDLINGS, STORAGE, TERRESTRIAL ECOSYSTEMS


     242  
Bonghi, C., A. Ramina, B. Ruperti, R. Vidrih, and P. Tonutti. 1999. Peach fruit ripening and
quality in relation to picking time, and hypoxic and high CO2 short-term postharvest treatments.
Postharvest Biology and Technology 16(3):213-222.

Peach fruits (Prunus persica L. Batsch, cv Springcrest) were harvested at two ripening stages (flesh
firmness of 60 N, first harvest, and 45 N, second harvest) and maintained at 20 degrees C in air
(control) or for 24 and 48 h in streams of ultra low(<l%) oxygen (ULO) or high (30%) CO2
concentration and then transferred to air for up to 8 days. The decline in flesh firmness was strongly
reduced by ULO and CO2 treatments in fruits of both harvests, although the effect was stronger in
fruits picked earlier in which ethylene biosynthesis remained at the basal level. In fruits of the second
harvest, endo beta- 1,4-glucanase (EGase) activity was lower in ULO- and CO2- treated fruits than
in control fruits at the end of the 24 h treatment and the following two days in air. Acetaldehyde (AA)
gradually accumulated in control fruit and the highest concentrations were detected during late
ripening. Both treatments induced a strong accumulation of AA but, with the exception of the 24 and
48 h CO2 treatments performed on fruits of the second harvest, a decrease in AA content was
observed when the fruits were transferred to air. A slight increase in ethanol (EtOH) was found
throughout the ripening process in control fruits; ULO and CO2 strongly stimulated EtOH
production. When fruits were transferred to air, EtOH concentration declined rapidly. Alcohol
dehydrogenase (ADH) activity significantly increased in control fruit only in the late stages of
ripening. Greater ADH activity was found throughout the experimental period in fruits of the first
harvest treated for 24 h in ULO and CO2, whereas, at day 8, control and treated fruits of the second
harvest showed similar ADH activity values. Hypoxic and, to a lesser extent, CO2- enriched
atmospheres stimulated Adh gene expression. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ETHYLENE, EXPRESSION, LOW-OXYGEN ATMOSPHERES, NECTARINES,
RESPONSES, STORAGE


     243  
Booker, F.L. 1997. Effects of elevated CO2 and nitrogen on proanthocyanidins in cotton. Plant
Physiology 114(3):489.



     244  
Booker, F.L., C.D. Reid, S. BrunschonHarti, E.L. Fiscus, and J.E. Miller. 1997. Photosynthesis
and photorespiration in soybean [Glycine max (L.) Merr.] chronically exposed to elevated carbon
dioxide and ozone. Journal of Experimental Botany 48(315):1843-1852.

The effects of elevated carbon dioxide (CO2) and ozone (O-3) on soybean [Glycine max (L.) Merr.]
photosynthesis and photorespiration-related parameters were determined periodically during the
growing season by measurements of gas exchange, photorespiratory enzyme activities and amino acid
levels, Plants were treated in open-top field chambers from emergence to harvest maturity with
seasonal mean concentrations of either 364 or 726 mu mol mol(-1) CO2 in combination with either
19 or 13 nmol mol(-1) O-3 (12 h daily averages). On average at growth CO2 concentrations, net
photosynthesis (A) increased 56% and photorespiration decreased 36% in terminal mainstem leaves
with CO2-enrichment. Net photosynthesis and photorespiration were suppressed 30% and 41%,
respectively, by elevated O-3 during late reproductive growth in the ambient CO2 treatment, but not
in the elevated CO2 treatment. The ratio of photorespiration to A at growth CO2 was decreased 61%
by elevated CO2. There was no statistically significant effect of elevated O-3 in the ratio of
photorespiration to A. Activities of glycolate oxidase, hydroxypyruvate reductase and catalase were
decreased 10-25% by elevated CO2, and by 46-66% by elevated O-3 at late reproductive growth.
The treatments had no significant effect on total amino acid or glycine levels, although serine
concentration was lower in the elevated CO2 and O-3 treatments at several sampling dates. The
inhibitory effects of elevated O-3 on photorespiration-related parameters were generally
commensurate with the O-3-induced decline in A. The results suggest that elevated CO2 could
promote productivity both through increased photoassimilation and suppressed photorespiration.

KEYWORDS: ARABIDOPSIS-THALIANA, ATMOSPHERIC CO2, CARBOXYLASE ACTIVITY,
GAS-EXCHANGE, L LEAVES, PHASEOLUS-VULGARIS L, PLANT-RESPONSES, SPRING
WHEAT, SUPEROXIDE-DISMUTASE, ULTRAVIOLET-B


     245  
Boone, R.D., K.J. Nadelhoffer, J.D. Canary, and J.P. Kaye. 1998. Roots exert a strong influence
on the temperature sensitivity of soil respiration. Nature 396(6711):570-572.

The temperature sensitivity of soil respiration will largely determine the effects of a warmer world
on net carbon flux from soils to the atmosphere. CO2 flux from soils to the atmosphere is estimated
to be 50-70 petagrams of carbon per year and makes up 20-38% of annual inputs of carbon (in the
form of CO2) to the atmosphere from terrestrial and marine sources(1,2). Here we show that, for a
mixed temperate forest, respiration by roots plus oxidation of rhizosphere carbon, which together
produce a large portion of total effluxed soil CO2, is more temperature-sensitive than the respiration
of bulk soil. We determine that the Q(10) value (the coefficient for the exponential relationship
between soil respiration and temperature, multiplied by ten) is 4.6 for autotrophic root respiration
plus rhizosphere decomposition, 2.5 for respiration by soil lacking roots and 3.5 for respiration by
bulk soil. If plants in a higher-CO2 atmosphere increase their allocation of photosynthate to roots(3-
6), these findings suggest that soil respiration should be more sensitive to elevated temperatures, thus
limiting carbon sequestration by soils.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE, CO2, EXCHANGE, FLUXES,
FOREST, LITTER, VEGETATION


     246  
Boote, K.J., and N.B. Pickering. 1994. Modeling photosynthesis of row crop canopies. Hortscience
29(12):1423-1434.

KEYWORDS: CARBON DIOXIDE, CARBOXYLASE-OXYGENASE, CO2/O2 SPECIFICITY,
DIRECT COMPONENT, ELEVATED CO2, GLOBAL RADIATION, LEAF NITROGEN, NET
PHOTOSYNTHESIS, SOYBEAN CANOPIES, USE EFFICIENCY


     247  
Borkhsenious, O.N., C.B. Mason, and J.V. Moroney. 1998. The intracellular localization of
ribulose-1,5-bisphosphate carboxylase/oxygenase in Chlamydomonas reinhardtii. Plant Physiology
116(4):1585-1591.

The pyrenoid is a proteinaceous structure round in the chloroplast of most unicellular algae. Various
studies indicate that ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is present in the
pyrenoid, although the fraction of Rubisco localized there remains controversial. Estimates of the
amount of Rubisco in the pyrenoid of Chlamydomonas reinhardtii range from 5% to nearly 100%.
Using immunolocalization, the amount of Rubisco localized to the pyrenoid or to the chloroplast
stroma was estimated for C. reinhardtii cells grown under different conditions. It was observed that
the amount of Rubisco in the pyrenoid varied with growth condition; about 40% was in the pyrenoid
when the cells were grown under elevated CO2 and about 90% with ambient CO2. In addition, it is
likely that pyrenoidal Rubisco is active in CO2 fixation because in vitro activity measurements showed
that most of the Rubisco must be active to account for CO2-fixation rates observed in whole cells.
These results are consistent with the idea that the pyrenoid is the site of CO2 fixation in C. reinhardtii
and other unicellular algae containing CO2-concentrating mechanisms.

KEYWORDS: CARBONIC-ANHYDRASE, CHLOROPLAST, MECHANISM, OXYGENASE,
PHOTOSYNTHESIS


     248  
Borodin, V.B. 1995. Photosynthetic o-2 exchange in chlorella cells adapted to low co2 concentration
under blue or red-light. Russian Journal of Plant Physiology 42(1):31-36.

The effect of light quality on the adaptation to low atmospheric CO2 concentration was studied on
the cells of unicellular green al,oa Chlorella pyrenoidosa 82T grown under 2% CO2 concentration
and white light. The adaptation of Chlorella cells was more successful under blue than under red light.
Thus, the air-adapted cells under blue light showed a higher affinity for CO2, a higher quantum
efficiency of apparent photosynthesis at CO2 limitation, and acceleration of O-2 evolution at light
saturation, as compared to the red- light-adapted cells. In air-adapted cells, the photosynthetic rates
at low CO2 concentration were enhanced with increased intensities of both blue and red light, but the
differences between the two treatments were retained. It was inferred that Chlorella cell adaptation
depended on both light intensity and its spectral composition. The light intensity exerts its action via
photosynthetic apparatus while spectral composition of light exerts its effect via a system of
photoreception, which absorbs blue light. This additional blue light absorption is considered favorable
for Chlorella cell adaptation to low CO2 concentration.

KEYWORDS: ACETABULARIA- MEDITERRANEA, CARBONIC-ANHYDRASE,
CHLAMYDOMONAS-REINHARDTII, INDUCTION, PROTEIN


     249  
Bosac, C., S.D.L. Gardner, G. Taylor, and D. Wilkins. 1995. Elevated co2 and hybrid poplar -
a detailed investigation of root and shoot growth and physiology of populus-euramericana, primo.
Forest Ecology and Management 74(1-3):103-116.

Exposure of the hybrid poplar clone 'Primo' (Populus deltoides X Populus nigra) to 580 mu l 1(-1)
carbon dioxide for just 68 days significantly (P less than or equal to 0.05) increased stem height by
13% compared with trees grown in ambient CO2 concentrations. The stem diameter was significantly
(P less than or equal to 0.05) increased and both total biomass and woody stem biomass also showed
higher values (38% and 31% increases respectively) in elevated CO2. Trees in elevated CO2 had
more leaves and a greater total leaf area, whilst the specific leaf area was decreased in elevated CO2
on four out of five occasions and was significantly (P less than or equal to 0.05) lower after 68 days,
an effect indicating that leaves were thicker and/or heavier. Rates of photosynthesis (A) measured
after 49 and 67 days of exposure revealed that trees in the elevated CO2 treatment had lower values
of A when measured at either 350 or 580 mu l 1(-1) CO2. Sequential harvests at intervals during the
study in which the root and shoot components were analysed separately allowed the construction of
root:shoot ratios and allometric coefficients; there was no significant effect on the allometric
coefficient and the root:shoot ratio was significantly increased on only one occasion. However,
measurements of the 'apparent' root length suggested that root lengths were greater in the CO2
treatment. There was a significant increase in the number of fine root tips visible down the surface
of specially designed rooting tubes (P less than or equal to 0.05), indicating more fine roots or an
increase in fine root branching. The growth rates of individual fine or large roots over 24 h were
unaffected, again suggesting that increases in biomass may be due to more root segments rather than
longer individual roots. Root water relations were also examined and showed a tendency towards
solute accumulation and increases in turgor pressure (P) and effective tugor (P-e) at times when root
growth was stimulated, although these were not consistent. Cell wall plasticity of the tips of large
roots was significantly (P less than or equal to 0.01) reduced in elevated CO2, possibly indicating a
greater tendency to divert resources to the formation of root branches. The results of the study are
discussed in the light of the possible consequences of changes in poplar growth and physiology for
forestry practice in an increased CO2 environment.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, CELL-WALLS, CLONES,
CONDUCTANCE, DROUGHT, ENRICHMENT, LEAF GROWTH, PHOTOSYNTHESIS, SOURCE-
SINK RELATIONS


     250  
Bottomley, P.A., H.H. Rogers, and S.A. Prior. 1993. Nmr imaging of root water distribution in
intact vicia-faba L plants in elevated atmospheric co2. Plant, Cell and Environment 16(3):335-338.

The effect of elevated atmospheric CO2 on water distribution in the intact roots of Vicia faba L. bean
seedlings grown in natural soil was studied noninvasively with proton (H-1) nuclear magnetic
resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric Co2-enriched air at 650 cm3
m-3 produced significant increases in water imaged in upper roots, hypogeal cotyledons and lower
stems in response to a short-term drying- stress cycle. Above ground, drying produced negligible stem
shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused
significant depletion of water imaged in the same upper root structures in control plants subject to
ambient CO2 (350 m3 m-3), and stem shrinkage and increased stomatal resistance. The results
suggest that inhibition of transpiration caused by elevated CO2 does not necessarily result in
attenuation of water transport from lower root structures. Inhibition of water loss from upper roots
and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious
effects of greenhouse changes on crops during periods of dry climate.

KEYWORDS: CARBON DIOXIDE, INSITU, MAGNETIC-RESONANCE MICROSCOPY,
TRANSPORT


     251  
Bouma, T.J., K.L. Nielsen, D.M. Eissenstat, and J.P. Lynch. 1997. Estimating respiration of roots
in soil: Interactions with soil CO2, soil temperature and soil water content. Plant and Soil
195(2):221-232.

Little information is available on the variability of the dynamics of the actual and observed root
respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil
CO2 concentration, temperature, soil water content and root respiration, and II) the effect of short-
term fluctuations of these three environmental factors on the relation between actual and observed
root respiration rates. We designed an automated, open gas-exchange system that allows continuous
measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with
each a different path for the air flow, we were able to measure root respiration over a 50-fold range
of soil CO2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed
vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus
seedlings in sterilized sandy soil with minimal organic material. Root respiration was strongly affected
by diurnal fluctuations in temperature (Q(10) = 2), which agrees well with the literature. In contrast
to earlier findings for Douglas-fir (Qi et al., 1994), root respiration rates of citrus were not affected
by soil CO2 concentrations (400 to 25000 ppm CO2; pH around 6). Soil CO2 was strongly affected
by soil water content but not by respiration measurements, unless the air flow for root respiration
measurements was directed through the soil. The latter method of measuring root respiration reduced
soil CO2 concentration to that of incoming air. Irrigation caused a temporary reduction in CO2
diffusion, decreasing the observed respiration rates obtained by techniques that depended on
diffusion. This apparent drop in respiration rate did not occur if the air flow was directed through the
soil. Our dynamic data are used to indicate the optimal method of measuring root respiration in soil,
in relation to the objectives and limitations of the experimental conditions.

KEYWORDS: CARBON DIOXIDE, DARK RESPIRATION, ELEVATED CO2, ENRICHMENT,
FIELD, GROWTH, PLANTS, RESPONSES, SEEDLINGS, SOUR ORANGE TREES


     252  
Bowden, R.D., K.M. Newkirk, and G.M. Rullo. 1998. Carbon dioxide and methane fluxes by a
forest soil under laboratory-controlled moisture and temperature conditions. Soil Biology and
Biochemistry 30(12):1591-1597.

Carbon dioxide and methane are important greenhouse gases whose exchange rates between soils and
the atmosphere are controlled strongly by soil temperature and moisture. We made a laboratory
investigation to quantify the relative importance of soil moisture and temperature on fluxes of CO2
and CH4 between forest soils and the atmosphere. Forest floor and mineral soil material were
collected from a mixed hardwood forest at the Harvard Forest. Long-Term Ecological Research Site
(MA) and were incubated in the laboratory under a range of moisture (air-dry to nearly saturated) and
temperature conditions (5-25 degrees C). Carbon dioxide emissions increased exponentially with
increasing temperature in forest floor material, with emissions reduced at the lowest and highest soil
moisture contents. The forest floor Q(10) of 2.03 (from 15-25 degrees C) suggests that CO2
emissions were controlled primarily by soil biological activity. Forest floor CO2 emissions were
predicted with a multiple polynomial regression model (r(2) = 0.88) of temperature and moisture, but
the fit predicting mineral soil respiration was weaker (r(2) = 0.59). Methane uptake was controlled
strongly by soil moisture, with reduced fluxes under conditions of very low or very high soil moisture
contents. A multiple polynomial model accurately described CH4 uptake by mineral soil material (r(2)
= 0.81), but only weakly (r(2) = 0.45) predicted uptake by forest floor material. The mineral soil
Q(10) of 1.11 for CH4 uptake indicates that methane uptake is controlled primarily by physical
processes. Our work suggests that inclusion of both moisture and temperature can improve
predictions of soil CO2 and CH4 exchanges between soils and the atmosphere. Additionally, global
change models need to consider interactions of temperature and moisture in evaluating effects of
global climate change on trace gas fluxes. (C) 1998 Elsevier Science Ltd. All rights reserved.

KEYWORDS: ATMOSPHERIC METHANE, CONSUMPTION, DYNAMICS, ECOSYSTEMS,
NITROGEN, OXIDATION, RESPIRATION, RESPONSES, WATER


     253  
Bowes, G. 1991. Growth at elevated CO2 - photosynthetic responses mediated through rubisco.
Plant, Cell and Environment 14(8):795-806.

The global uptake of CO2 in photosynthesis is about 120 gigatons (Gt) of carbon per year. Virtually
all passes through one enzyme, ribulose bisphosphate carboxylase/oxygenase (rubisco). which initiates
both the photosynthetic carbon reduction, and photorespiratory carbon oxidation, cycles. Both CO2
and O2 are substrates; CO2 also activates the enzyme. In C3 plants, rubisco has a low catalytic
activity, operates below its K(m) (CO2), and is inhibited by O2. Consequently, increases in the
CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually
enhances the productivity of C3 plants, but the effect is marginal in C4 species. It also causes
acclimation in various ways: anatomically. morphologically, physiologically or biochemically. So,
CO2 exerts secondary effects in growth regulation, probably at the molecular level, that are not
predictable from its primary biochemical role in carboxylation. After an initial increase with CO2
enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in
field studies, that is ultimately mediated by a decline in rubisco activity, though the RuBP/P(i)-
regeneration capacities of the plant may play a role. The decline is due to decreased rubisco protein,
activation state, and/or specific activity, and it maintains the rubisco fixation and RuBP/P(i)-
regeneration capacities in balance. Carbohydrate accumulation is sometimes associated with reduced
net photosynthesis, possibly causing feedback inhibition of the RuBP/P(i)-regeneration capacities, or
chloroplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction
in net photosynthesis and rubisco activity is not inevitable under CO2 enrichment. Strong sinks or
rapid translocation may avoid such acclimation responses. Over geological time, aquatic autotrophs
and terrestrial C4 and CAM plants have genetically adapted to a decline in the external CO2/O2 ratio,
by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibition
of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation
compatible with a high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating
mechanisms acclimate to the external CO2, being suppressed at high-CO2. It is unclear, whether a
doubling in atmospheric CO2 will be sufficient to cause a de-adaptive trend in the rubisco kinetics
of future C3 plants, producing higher catalytic activities.

KEYWORDS: 1,5-DIPHOSPHATE CARBOXYLASE, CARBON-DIOXIDE CONCENTRATIONS,
CO2-ENRICHED ATMOSPHERE, ECHINOCHLOA CRUS GALLI, HIGH ATMOSPHERIC CO2,
KINETIC-PROPERTIES, LONG-TERM EXPOSURE, MONOECIOUS CUCUMBERS,
PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE BISPHOSPHATE CARBOXYLASE


     254  
Bowes, G. 1993. Facing the inevitable - plants and increasing atmospheric co(2). Annual Review of
Plant Physiology and Plant Molecular Biology 44:309-332.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CO2- ENRICHMENT, ELEVATED CO2,
INORGANIC CARBON, PHASEOLUS-VULGARIS L, RIBULOSE BISPHOSPHATE
CARBOXYLASE, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SHORT- TERM, SOURCE-
SINK RELATIONS, SOYBEAN LEAVES


     255  
Bowes, G., J.C.V. Vu, M.W. Hussain, A.H. Pennanen, and L.H. Allen. 1996. An overview of
how rubisco and carbohydrate metabolism may be regulated at elevated atmospheric [CO2] and
temperature. Agricultural and Food Science in Finland 5(3):261-270.

Although atmospheric CO2 concentration ([CO2]) has been up to 16-fold higher than at present, the
past several million years have seen atypically low values. Thus, modern-day plants are adapted to
cope with a low [CO2]/[O-2] ratio. The present [CO2] does nor saturate C-3 photosynthesis, so its
doubling produces an ''efficiency effect'', but it is not always fully realized. Acclimation to high [CO2]
during growth can down-regulate photosynthesis, presumably to optimize carbon acquisition and
utilization. A primary factor in acclimation is a reduction in rubisco. Two crops, rice and soybean,
were used to study this phenomenon. Rice photosynthesis and growth peaked at 500 mu mol mol(-1),
whereas soybean responded up to 990 mu mol mol(-1) Rubisco concentration declined under CO2-
enrichment and increasing temperatures, more so in rice than soybean. The rubisco k(cat) Of rice was
unaffected by growth [CO2] or temperature, but that from soybean was increased by both. In rice the
capacity to handle carbohydrate, as measured by sucrose phosphate synthase activity was up-
regulated by CO2- enrichment, but not by temperature. Leaf carbohydrates were increased by [CO2],
but decreased by higher temperatures, starch more so than sucrose. Even though C-3 species differ
in response to [CO2] and temperature, CO2-enrichment can moderate adverse effects of temperature
extremes.

KEYWORDS: ACCLIMATION, CARBON-DIOXIDE CONCENTRATION, CARBOXYLASE,
EXPRESSION, GROWTH, LEAVES, PHOTOSYNTHESIS, PLANT-RESPONSES, RICE, SOURCE-
SINK RELATIONS


     256  
Bowler, J.M., and M.C. Press. 1993. Growth-responses of 2 contrasting upland grass species to
elevated co2 and nitrogen concentration. New Phytologist 124(3):515-522.

Growth parameters of Agrostis capillaris L. and Nardus stricta L. were measured in relation to
ambient and elevated concentrations of CO2 (340 and 550 mul CO2 l-1, respectively) and at low and
high concentrations of nitrogen (0.8 and 3 mm NH4NO3, respectively). After 60 d of growth A.
capillaris had attained approx. four times the total dry weight of N. stricta in all treatments, which was
attributed to the greater leaf area ratio of the former. A. capillaris grown at the low nitrogen
concentration attained 30% of the total dry weight of plants grown at high nitrogen. Over the 60 d
period, destructive harvests (seven in total) showed the growth of N. stricta to be less sensitive than
that of A. capillaris to the concentration of nitrogen, but in both species growth analysis showed the
lower total dry weight at low nitrogen to be attributable to lower unit leaf rate. There was a
differential response of both species to elevated concentrations of CO2 which was nitrogen
dependent. A. capillaris grown at elevated CO2 attained a greater total dry weight than at ambient
CO2 and this response was proportionately greater at low nitrogen (78% increase) than at high
nitrogen (58% increase). In contrast, in N. stricta there was no effect of CO2 concentration on the
total dry weight at low nitrogen whilst at high nitrogen plants grown at elevated CO2 had a greater
total dry weight after 48 d of growth. Calculation of the allometric coefficient (K) relating root
growth to shoot growth indicated that the effect of the lower nitrogen concentration was to increase
partitioning to the roots while the higher CO2 concentration did not alter partitioning.

KEYWORDS: AVAILABILITY, CARBON-DIOXIDE ENRICHMENT, IRRADIANCE, MINERAL
NUTRITION, PHOTOSYNTHESIS, PLANTS, SEEDLINGS, SOURCE-SINK RELATIONS,
TEMPERATURE, WHEAT


     257  
Bowler, J.M., and M.C. Press. 1996. Effects of elevated CO2, nitrogen form and concentration on
growth and photosynthesis of a fast- and slow-growing grass. New Phytologist 132(3):391-401.

Growth and photosynthesis of Agrostis capillaris L. and Nardus stricta L. were measured for plants
grown under ambient and elevated concentrations of CO2 (340 and 550 mu l CO2 l(-1) respectively)
and a range of nitrogen concentrations (0.01, 0.1, 1 and 5 mg N l(-1)) supplied as either ammonium
sulphate or sodium nitrate. After 42 d of growth for A. capillaris and 49 d of growth for N. stricta,
the higher nitrogen concentrations resulted in stimulation of growth. The form of nitrogen did not
affect the total dry weight attained by A. capillaris. However, ammonium-grown N. stricta attained
a greater total dry weight than did nitrate-grown plants. Nitrogen form influenced leaf area ratio,
which was greater in nitrate-grown A. capillaris and in ammonium-grown N. stricta. At the two
lowest nitrogen concentrations there was no effect of elevated CO2 on total dry weight in either
species, whilst at the two highest nitrogen concentrations positive growth responses to elevated CO2
were observed. Photosynthetic capacity and carboxylation efficiency were lower in plants grown in
elevated CO2 at the two lowest nitrogen concentrations, and were associated with greater leaf soluble
carbohydrate content and lower foliar nitrogen concentrations. By contrast, the CO2 treatment did
not affect these parameters at the two highest nitrogen concentrations employed.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, ENRICHMENT, EXPOSURE, GAS-
EXCHANGE, HIGH ATMOSPHERIC CO2, LEAVES, NUTRITION, PLANTS, RIBULOSE-1;5-
BISPHOSPHATE CARBOXYLASE-OXYGENASE


     258  
Brailsford, R.W., L.A.C.J. Voesenek, C.W.P.M. Blom, A.R. Smith, M.A. Hall, and M.B.
Jackson. 1993. Enhanced ethylene production by primary roots of zea-mays L in response to sub-
ambient partial pressures of oxygen. Plant, Cell and Environment 16(9):1071-1080.

Ethylene production by primary roots of 72-h-old intact seedlings of Zea mays L. cv. LG11 was
studied under ambient and sub-ambient oxygen partial pressures (pO(2)) using a gas how- through
system linked to a photoacoustic laser detector. Despite precautions to minimize physical perturbation
to seedlings while setting-up, ethylene production in air was faster during the first 6h than later, in
association with a small temporary swelling of the roots. When roots were switched from air (20.8kPa
O-2) to 3 or 5kPa O-2 after 6h, ethylene production increased within 2-3h. When, the roots were
returned to air 16h later, ethylene production decreased within 2-3h. The presence of 1OkPa CO2
did not interfere with the effect of 3kPa O-2. Transferring roots from air to 12.5kPa did not change
ethylene production, while a reduction to 1kPa O-2 induced a small increase. The extra ethylene
formed in 3 and 5kPa O-2 was associated with plagiotropism, swelling, root hair production, and
after 72h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension
was also slowed down, but the pattern of response to oxygen shortage did not always match that of
ethylene production. On return to air, subsequent growth patterns became normal within a few hours.
In the complete absence of oxygen, no ethylene production was detected, even when anaerobic roots
were returned to air after 16h.

KEYWORDS: ANOXIA, BIOSYNTHESIS, DEEP-WATER RICE, FORMING ENZYME, GROWTH,
PLANTS, STIMULATION, SUBMERGENCE


     259  
Brakke, M., and L.H. Allen. 1995. Gas-exchange of citrus seedlings at different temperatures,
vapor-pressure deficits, and soil-water contents. Journal of the American Society for Horticultural
Science 120(3):497-504.

Midday reductions of stomatal conductance and carbon dioxide assimilation rates (A(CO2)) in Citrus
are typically attributed to large leaf-to-air vapor-pressure differences or high atmospheric vapor-
pressure deficits (VPD). This study investigated air temperature (T-a) and available soil water (ASW)
level as corollary factors of atmospheric VPD that influence midday reduction of net gas exchange
in citrus leaves. The influence of elevated atmospheric CO2 under conditions that inhibit net canopy
A(CO2) was also investigated. Net canopy A(CO2) and evapotranspiration rates of Carrizo citrange
[Poncirus trifoliata Raf x Citrus sinensis (L.) Osbeck] and Swingle citrumelo (P. trifoliata Raf x C.
paradisii Macf.) seedlings grown in outdoor controlled- environment growth chambers were
measured under two levels of T-a with concomitant changes in VPD and two levels of atmospheric
CO2 concentration, which were changed in steps over time. Cyclical depletion of ASW was allowed
to occur at each set of T-a/VPD and CO2 combinations. Highest net canopy A(CO2) rates at ambient
CO2 concentration (330 mu mol . mol(-1)) were obtained at the low T-a/VPD level (29C/2.4 kPa)
and ASW >50%. Diurnal canopy CO2 uptake rates decreased at the high T-a/VPD level (37C/3.6
kPa), and midday depression of canopy A(CO2) was observed at ASW levels <50%. Net canopy
A(CO2) decreased at higher levels of ASW under the high T-a/VPD treatment than at the low T-
a/VPD treatment. At the elevated CO2 concentration (840 mu mol . mol(-1)) net canopy CO2 uptake
rates were double those that occurred at ambient CO2 levels and they did not exhibit midday
reduction. Our data indicate that, when soil water is not readily available, citrus seedlings are more
sensitive to high levels of T-a and VPD which results in reduction of CO2 uptake. The inhibitory
effects of elevated VPD and reduced ASW on citrus net A(CO2) were lessened at the elevated
atmospheric CO2 level.

KEYWORDS: CARBON DIOXIDE, GROWTH, HUMIDITY, LEAVES, PHOTOSYNTHESIS,
RESPONSES, TRANSPIRATION, TREES, VALENCIA ORANGE


     260  
Brandrud, T.E., and J.G.M. Roelofs. 1995. Enhanced growth of the macrophyte Juncus bulbosus
in S Norwegian limed lakes. A regional survey. Water, Air, and Soil Pollution 85(2):913-918.

The effects of liming on the aquatic macrophyte vegetation have been investigated in S and SW
Norway. In the western part of the study area, Juncus bulbosus was considerably more frequent in
the limed than in the unlimed lakes, whilst in the eastern part there were no such differences, and the
J. bulbosus populations were generally not so vital. In some southwestern areas a luxuriant and
massiv nuisance growth of Juncus bulbosus in the depth zone 0-4 m was recorded. The most vital
plants produced up to 1 m long annual shoots, and developed extensive, dense and vital surface mats
in shallow areas (depth zone 0-3 m) after 4-5 years. The original isoetid vegetation had disappeared
in the areas of dense J. bulbosus populations, and this development seems to be more or less
irreversible. The massive J. bulbosus expansion is seen mainly in directly limed lakes with a sometimes
visible layer of calcium carbonate on the sediment surface, but enhanched growth has been observed
also in lakes downstream liming. The massive expansion is believed to be due to an increase of CO2
and ammonium in the sediment pore water, combined with a mild climate with a very high
precipitation. In many areas the liming has led to an increase in species diversity, and a (re-
)establishment of some acid-intolerant species such as Myriophyllum alterniflorum and Potamogeton
spp.

KEYWORDS: ACIDIFICATION


     261  
Bransby, D.I., S.B. McLaughlin, and D.J. Parrish. 1998. A review of carbon and nitrogen
balances in switchgrass grown for energy. Biomass & Bioenergy 14(4):379-384.

Increased atmospheric CO2, caused partly by burning fossil fuels, is assumed to elevate the risk of
global warming, while nitrate contamination of surface runoff and groundwater from fertilizer and
agricultural wastes constitutes a serious environmental hazard on a regional scale. Switchgrass
(Panicum virgatum L.) grown as an energy crop could reduce atmospheric CO2 accumulation by
replacing fossil fuels and sequestering C. It could also improve soil productivity by C sequestration,
and reduce NO3-1 contamination of water by absorbing N lost from fertilizer and agricultural waste
if planted in filter strips on adjacent land. The objective of this study was to assess potential impacts
of switchgrass on C and N balances by reviewing and synthesizing information from current literature,
unpublished data and on-going research. Replacing fossil fuels with switchgrass, or any other
biomass, will have a much greater effect on atmospheric CO2 than C sequestration. This is because
replacing fossil fuels provides a cumulative effect, while C sequestration offers only a one-time
benefit. Furthermore, switchgrass will provide net gains in C sequestration only if it replaces annual
row crops, but not if it replaces grazed pasture. Nitrogen recovery by switchgrass in an Alabama
study was 65.6%, which compares favorably with the 50% recovery frequently quoted as the norm
for wheal (Triticum aestivum L.) and corn (Zea mays L). (C) 1998 Elsevier Science Ltd. All rights
reserved.



     262  
Brearley, J., M.A. Venis, and M.R. Blatt. 1997. The effect of elevated CO2 concentrations on K+
and anion channels of Vicia faba L. guard cells. Planta 203(2):145-154.

The effects of elevated CO2 concentrations on stomatal movement, anion-and K+-channel activities
were examined in guard cells from epidermal strips of Vicia faba. Membrane voltage was measured
using intracellular, double-barrelled microelectrodes and ion-channel currents were recorded under
voltage clamp during exposure to media equilibrated with ambient (350 mu l . l(-1)), 1000 mu l . l(-1)
and 10 000 mu l . l(-1) CO2 in 20% O-2 and 80% N-2. The addition of 1000 mu l . l(-1) CO2 to the
bathing solution caused stomata to close with a halftime of approx. 40 min, and with 10 000 mu l .
l(-1) CO2 closure occurred with a similar time course. Under voltage clamp, exposure to 1000 mu
l . l(-1) and 10 000 mu l . l(-1) CO2 resulted in a rapid increase (mean, 1.5 +/- 0.2-fold, n = 8; range
1.3- to 2.5-fold) in the magnitude of current carried by outward-rectifying K+ channels (I-K,I-out).
The effect of CO2 on I-K,I-out was essentially complete within 30 s and was independent of clamp
voltage, but was associated with 25-40% (mean, 30 +/- 4%) decrease in the halftime for current
activation. Exposure to CO2 also resulted in a four-fold increase in background current near the free-
running membrane voltage, recorded as the instantaneous current at the start of depolarising and
hyperpolarising voltage steps, and a decrease in the magnitude of current carried by inward-rectifying
K+ channels (I-K,I-in). The effect of CO2 on I-K,I-in was generally slower than on I-K,I-out; it was
allied with a transient acceleration of its activation kinetics during the first 60-120 s of treatment; and
it was associated with a negative shift in the voltage-sensitivity of gating over a period of 3-5 min.
Measurements carried out to isolate the background currents attributable to anion channels (I-Cl),
using tetraethylammonium chloride and CsCl, showed that CO2 also stimulated I-CL and dramatically
altered its relaxation kinetics. Within the timeframe of CO2 action at the membrane, no significant
effect was observed on cytosolic pH, measured using the fluorescent dye 2',7'-bis-(2-carboxyethyl)-
5,6- carboxyflourescein (BCECF) and ratio fluorescence microphotometry. These results are broadly
consistent with the pattern of guard-cell response to abscisic acid, and indicate that guard cells control
both anion and K+ channels to achieve net solute loss in CO2. By contrast with the effects of abscisic
acid, however, the data indicate that CO2 action is not mediated through changes in cytosolic pH and
thereby implicate new and, as yet, unidentified pathway(s) for channel regulation in the guard cells.

KEYWORDS: ABSCISIC- ACID, CYTOSOLIC-FREE CALCIUM, ELECTRICAL
CHARACTERISTICS, FUSICOCCIN ACTION, PLASMA-MEMBRANE, PROTEIN
PHOSPHATASE, SIGNAL-TRANSDUCTION, STOMATAL CLOSURE, TRANSPORT, VOLTAGE


     263  
Bremer, D.J., J.M. Ham, and C.E. Owensby. 1996. Effect of elevated atmospheric carbon dioxide
and open-top chambers on transpiration in a tallgrass prairie. Journal of Environmental Quality
25(4):691-701.

Increasing concentrations of atmospheric carbon dioxide (CO2) may influence plant-water relations
in natural and agricultural ecosystems. A tallgrass prairie near Manhattan, KS, was exposed to
elevated atmospheric CO2 using open-top chambers (OTCs). Heat balance sap Bow gauges were
used to measure transpiration in ironweed [Vernonia baldwini var. interior (Small) Schub.], a C-3
forb, and on individual grass culms of big bluestem (Andropogon gerardii Vitman) and indiangrass
[Sorghastrum nutans (L.) Nash], both C-4 grasses, in each of three treatments: (i) CE (chamber
enriched, 2x ambient CO2); (ii) CA (chamber ambient, no CO2 enrichment); and (iii) NC (no
chamber, no CO2 enrichment). Sap Bow data were coupled with measurements of stomatal
conductance, plant/canopy resistance, and whole- chamber evapotranspiration (ET) to determine the
effect of elevated CO2 on water use at different scales. Because of frequent rainfall during the study,
all data were collected under well-watered conditions, Comparisons of CE and CA showed that sap
Bow was reduced by 33% in ironweed, 18% in big bluestem, and 22% in indiangrass under CO2
enrichment. Whole- chamber ET was reduced by 23 to 27% under CO2 enrichment. Comparisons
of CA and NC showed that the environmental effect of the OTCs caused a 21 to 24% reduction in
transpiration, Stomatal conductance decreased from 7.9 to 3.6 mm s(-1) in big bluestem and from 5.3
to 3.2 mm s(-1) in indiangrass under CO2 enrichment. Soil water was consistently highest under
elevated CO2, reflecting the large reductions in transpiration, During sap flow measurements, whole-
plant stomatal resistance to water vapor Bur in big bluestem increased from 103 to 194 s m(-1) under
elevated CO2.

KEYWORDS: CO2, FLOW, PHOTOSYNTHESIS, RESPONSES, WATER RELATIONS


     264  
Bremer, D.J., J.M. Ham, C.E. Owensby, and A.K. Knapp. 1998. Responses of soil respiration
to clipping and grazing in a tallgrass prairie. Journal of Environmental Quality 27(6):1539-1548.

Soil-surface CO2 flux (F-s) is an important component in prairie C budgets. Although grazing Is
common in grasslands, its effects on F-s have not been well documented. Three clipping treatments:
(i) early-season clipping (EC); (ii) full- season clipping (FC); and (iii) no clipping (NC); which
represented two grazing strategies and a control, were applied to plots in a tallgrass prairie in
northeastern Kansas, USA. Measurements of F-s were made with a portable gas-exchange system
at weekly to monthly intervals for 1 yr. Concurrent measurements of soil temperature and volumetric
soil water content at 0.1 m were obtained with dual-probe heat-rapacity sensors. Measurements of
F-s also were obtained in grazed pastures. F-s ranged annually from 8.8 x 10(-3) mg m(-2) s(-1)
during the winter to 0.51 mg m(-2) s(-1) during the summer, following the patterns of soil
temperature and canopy growth and phenology. Clipping typically reduced F-s 21 to 49% by the
second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual F-s
were 4.94 4.04, and 4.11 kg m(-2) yr(-1) in NC, EC, and FC treatments, respectively; thus, clipping
reduced annual F-s by 17.5%. Differences in F-s between EC and FC were minimal, suggesting that
different grazing strategies had little additional impact on annual F-s. Daily F-s in grazed pastures was
20 to 37% less than F-s in ungrazed pastures. Results suggest that grazing moderates F-s during the
growing season by reducing canopy photosynthesis and slowing translocation of carbon to the
rhizosphere.

KEYWORDS: ANDROPOGON-GERARDII, ATMOSPHERIC CO2, CARBON, ELEVATED CO2,
EXCHANGE, FLUXES, PANICUM-VIRGATUM, PLANT, ROOT RESPIRATION, TEMPERATE
GRASSLAND


     265  
Briones, G.L., P. Varoquaux, Y. Chambroy, J. Bouquant, G. Bureau, and B. Pascat. 1992.
Storage of common mushroom under controlled atmospheres. International Journal of Food Science
and Technology 27(5):493-505.

The effect of controlled atmosphere (CA) on the shelf-life of the common mushroom (Agaricus
bisporus) was assessed using six parameters correlated with its commerical qualities. Low CO2
concentrations (up to 2.5%) reduced brown discolouration compared to the control in air. Higher
CO2 concentrations enhanced both internal and external browning. Low O2 concentrations reduced
growth of micro-organisms, including pseudomonads. Respiration rate, when the mushrooms are
placed again in normal air, is proportional to CO2 concentration during storage suggesting that CO2
exhibits a phytotoxic effect on mushrooms. A lower mannitol content was noted in mushrooms stored
under CA than those stored in air (control). Mushrooms stored in a 5% CO2 atmosphere for 7 days
did not break their veil but their texture was very soft and spongy. Texture losses decreased when
CO2 concentrations increased.

KEYWORDS: AGARICUS-BISPORUS


     266  
Brioua, A.H., and C.T. Wheeler. 1994. Growth and nitrogen-fixation in alnus-glutinosa (L) gaertn
under carbon-dioxide enrichment of the root atmosphere. Plant and Soil 162(2):183-191.

The effects of aeration of the N-free rooting medium with elevated CO2 on (a) acetylene reduction
by perlite-grown plants and (b) N-2-fixation and long-term growth of nutrient solution- grown plants
were determined for nodulated Alnus glutinosa (L.) Gaertn. In the former experiments, roots of intact
plants were incubated in acetylene in air in darkened glass jars for 3 hr, followed by a further 3 hr
incubation period in air enriched with CO2 (0-5%). During incubation, the CO2 content of the jars
increased by 0.17% per hour due to respiration of the root system, so that the CO2 content at 3 hr
was 0.5%. Additional enrichment of the rooting medium gas-phase with CO2 equivalent to 1.1% and
1.75% CO2 of the gas volume significantly increased nitrogenase activity (ethylene production) by
55% and 50% respectively, while enrichment with greater than 2.5% CO2 decreased activity. In
contrast, ethylene production by control plants, where CO2 was not added to the assay jars,
decreased by 8% over the assay period. In long-term growth experiments, nodulated roots of intact
Alnus glutinosa plants were sealed into jars containing N-free nutrient solution (pH 6.3) and aerated
with air, or air containing elevated levels of CO2 (1.5% and 5%). Comparison of the appearance of
CO2-treated with air treated plants suggested that 1.5% CO2 stimulated plant growth. However, at
harvest after 5 or 6 weeks variability between plants masked the significance of differences in plant
dry weight. A significant increase of 33% in total nitrogen of plants aerated with 1.5% CO2,
compared with air-treated plants, was demonstrated, broadly in line with the short-term increase in
acetylene reducing activity observed following incubations with similar CO2 concentrations. Shoot
dry weight was not affected significantly by long-term exposure to 5% CO2, the main effect on
growth being a 20% reduction in dry weight of the root system, possibly through inhibition of root
system respiration. However, in contrast to the inhibitory effects of high CO2 on acetylene reduction
there was no significant effect on the amounts of N-2 fixed.

KEYWORDS: ACETYLENE-REDUCTION, CO2- ENRICHMENT, METABOLISM, N2 FIXATION,
NODULATION, NODULE DEVELOPMENT, PHOSPHOENOLPYRUVATE CARBOXYLASE,
PHYSIOLOGY, PISUM-SATIVUM, RESPIRATION


     267  
Britz, S.J., D.T. Krizek, D.R. Lee, W.G. Harris, W.E. Hungerford, and W.A. Bailey. 1993.
Soybean growth under microwave-powered lamps, high-irradiance- discharge lamps, or solar-
radiation at ambient or elevated co2. Plant Physiology 102(1):141.



     268  
Brklacich, M., P. Curran, and D. Brunt. 1996. The application of agricultural land rating and crop
models to CO2 and climate change issues in Northern regions: The Mackenzie Basin case study.
Agricultural and Food Science in Finland 5(3):351-365.

The Mackenzie Basin in northwestern Canada covers approximately 1.8 million km(2) and extends
from 52 degrees N to 70 degrees N. Much of the Basin is currently too cool and remote from markets
to support a viable agricultural sector, but the southern portion of the Basin has the physical potential
to support commercial agriculture. This case study employed agricultural land rating and crop models
to estimate the degree to which a CO2-induced global warming might alter the physical potential for
commercial agriculture throughout the Basin. The two climate change scenarios considered in this
analysis would relax the current constraints imposed by a short and cool frost-free season, but
without adaptive measures, drier conditions and accelerated crop development rates were estimated
to offset potential gains stemming from elevated CO2 levels and warmer temperatures. In addition
to striving for a better understanding of the extent to which physical constraints on agriculture might
be modified by climate change, there is a need to expand the research context and to consider the
capacity of agriculture to adapt to altered climates.

KEYWORDS: CANADA


     269  
Broadmeadow, M.S.J., J. Heath, and T.J. Randle. 1999. Environmental limitations to O-3 uptake
- Some key results from young trees growing at elevated CO2 concentrations. Water, Air, and Soil
Pollution 116(1-2):299-310.

Elevated carbon dioxide concentrations and limited water supply have been shown to reduce the
impact of ozone pollution on the growth and physiology of Quercus petraea in a long-term factorial
experiment. These responses can be explained by observed reductions in stomatal conductance, and
thus potential ozone exposure of 28% and 40% for CO2 and drought treatments respectively.
However, parameterisation of a stomatal conductance model for Quercus robur and Fagus sylvatica
grown under ambient and elevated CO2 concentrations in a separate experiment has demonstrated
that elevated CO2 also reduces the responsiveness of stomata to both saturation deficit (LAVPD) and
soil moisture deficit (psi) in beech, and to a lesser extent, in oak. Season-long model simulations of
ozone fluxes suggest that LAVPD and psi conductance parameters derived at ambient CO2
concentrations will lead to these fluxes being underestimated by 24% and 2% for beech and oak
respectively at 615 ppm CO2.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, FOREST TREES, GAS-
EXCHANGE, OZONE UPTAKE, PLANTS, SENSITIVITY, SITCHENSIS BONG CARR, STOMATAL
RESPONSE


     270  
Brooks, G.L., and J.B. Whittaker. 1998. Responses of multiple generations of Gastrophysa
viridula, feeding on Rumex obtusifolius, to elevated CO2. Global Change Biology 4(1):63-75.

Rumex obtusifolius plants and three generations of the tri- voltine leaf beetle Gastrophysa viridula
were simultaneously exposed to elevated CO2 (600 ppm) to determine its effect on plant quality and
insect performance. This exposure resulted in a reduction in leaf nitrogen, an increase in the C/N ratio
and lower concentrations of oxalate in the leaves than in ambient air (350 ppm). Despite these
changes in food quality, the effect of elevated CO2 on larvae of Gastrophysa viridula over three
generations was minimal. However, the effect of CO2 did differ slightly between the generations of
the insect. For the first generation, the results obtained were different from many of the published
results in that elevated CO2 had no measurable effects on performance, except that third instar larvae
showed compensatory feeding. Food quality, including leaf nitrogen content, declined over time in
material grown in both ambient and elevated CO2. The results obtained for the second generation
were similar to the first except that first instar larvae showed reduced relative growth rate in elevated
CO2. Development time from hatching to pupation decreased over each generation, probably as a
result of increasing temperatures. Measurements of adult performance showed that fecundity at the
end of the second generation was reduced relative to the first, in line with the reduction in food
quality. In addition at the end of the second generation, but not at the end of the first generation, adult
females in elevated CO2 laid 30% fewer eggs per day and the eggs laid were 15% lighter than those
in ambient conditions. These lighter eggs, coupled with no effect of elevated CO2 on growth during
the third generation, meant that the larvae were consistently smaller in elevated CO2 during this
generation. These results offer further insights into the effect that elevated CO2 will have on insect
herbivores and provide a more detailed basis for population predictions.

KEYWORDS: CARBON DIOXIDE, DIETARY NITROGEN, GAS-EXCHANGE, GROWTH,
JUNONIA-COENIA, LARVAE, LEPIDOPTERA, MANDUCA-SEXTA CATERPILLARS,
NUTRITIONAL ECOLOGY, PERFORMANCE


     271  
Brooks, G.L., and J.B. Whittaker. 1999. Responses of three generations of a xylem-feeding insect,
Neophilaenus lineatus (Homoptera), to elevated CO2. Global Change Biology 5(4):395-401.

A population of the xylem-feeding spittlebug, Neophilaenus lineatus, on blocks of natural vegetation
transferred to large hemispherical chambers was studied over two generations with continuous
exposure to elevated CO2 (600 ppm). The third generation was transferred from the blocks to potted
Juncus squarrosus to enable measurements of fecundity. The principal food plant throughout was
Juncus squarrosus. Survival of the nymphs was reduced by more than 20% in elevated CO2 relative
to ambient (350 ppm) in both years of the main experiment. Elevated CO2 also delayed development
by one or more nymphal instars in each year. Fecundity was not significantly affected. The C/N ratio
of whole Juncus leaves was increased in elevated CO2 and the transpiration rates of the plants were
reduced. These changes may have been responsible for the effect of elevated CO2 on spittlebug
performance. However, other factors such as plant architecture and microclimate may also be
important.

KEYWORDS: CICADELLIDAE, FLUID, GROWTH, HOMALODISCA-COAGULATA,
LEAFHOPPER, PERFORMANCE, PREFERENCE, RUMEX, SAP, SPITTLEBUG


     272  
Brooks, J.R., L.B. Flanagan, N. Buchmann, and J.R. Ehleringer. 1997. Carbon isotope
composition of boreal plants: Functional grouping of life forms. Oecologia 110(3):301-311.

We tested the hypothesis that life forms (trees, shrubs, forbs, and mosses; deciduous or evergreen)
can be used to group plants with similar physiological characteristics. Carbon isotope ratios
(delta(13)C) and carbon isotope discrimination (Delta) were used as functional characteristics because
delta(13)C and Delta integrate information about CO2 and water fluxes, and so are useful in global
change and scaling studies. We examined delta(13)C values of the dominant species in three boreal
forest ecosystems: wet Picea mariana stands, mesic Populus tremuloides stands, and dry Pinus
banksiana stands. Life form groups explained a significant fraction of the variation in leaf carbon
isotope composition; seven life-form categories explained 50% of the variation in delta(13)C and 42%
of the variation in Delta and 52% of the variance not due to intraspecific genetic differences (n=335).
The life forms were ranked in the following order based on their values: evergreen trees<deciduous
trees=evergreen and deciduous shrubs=evergreen forbs<deciduous forbs=mosses. This ranking of the
life forms differed between deciduous (Populus) and evergreen (Pinus and Picea) ecosystems.
Furthermore, life forms in the Populus ecosystem had higher discrimination values than life forms in
the dry Pinus ecosystem; the Picea ecosystem had intermediate Delta values. These correlations
between Delta and life form were related to differences in plant stature and leaf longevity. Shorter
plants had lower Delta values than taller plants, resulting from reduced light intensity at lower levels
in the forest. After height differences were accounted for, deciduous leaves had higher discrimination
values than evergreen leaves, indicating that deciduous leaves maintained higher ratios of intracellular
to ambient CO2 (c(i)/c(a)) than did evergreen leaves in a similar environment within these boreal
ecosystems. We found the same pattern of carbon isotope discrimination in a year with above-average
precipitation as in a year with below-average precipitation, indicating that environmental fluctuations
did not affect the ranking of life forms. Furthermore, plants from sites near the northern and southern
boundaries of the boreal forest had similar patterns of discrimination. We concluded that life forms
are robust indicators of functional groups that are related to carbon and water fluxes within boreal
ecosystems.

KEYWORDS: C-13, COMMUNITIES, CONSEQUENCES, DISCRIMINATION, FOREST, MODEL,
PHOTOSYNTHESIS, TEMPERATURE, TRANSPIRATION, WATER-USE EFFICIENCY


     273  
Brooks, J.R., L.B. Flanagan, G.T. Varney, and J.R. Ehleringer. 1997. Vertical gradients in
photosynthetic gas exchange characteristics and refixation of respired CO2 within boreal forest
canopies. Tree Physiology 17(1):1-12.

We compared vertical gradients in leaf gas exchange, CO2 concentrations, and refixation of respired
CO2 in stands of Populus tremuloides Michx., Pinus banksiana Lamb. and Picea mariana (Mill.)
B.S.P. at the northern and southern boundaries of the central Canadian boreal forest. Midsummer gas
exchange rates in Populus tremuloides were over twice those of the two conifer species, and Pinus
banksiana rates were greater than Picea mariana rates. Gas exchange differences among the species
were attributed to variation in leaf nitrogen concentration. Despite these differences, ratios of
intercellular CO2 to ambient CO2 (c(i)/c(a)) were similar among species, indicating a common
balance between photosynthesis and stomatal conductance in boreal trees. At night, CO2
concentrations were high and vertically stratified within the canopy, with maximum concentrations
near the soil surface. Daytime CO2 gradients were reduced and concentrations throughout the canopy
were similar to the CO2 concentration in the well-mixed atmosphere above the canopy space.
Photosynthesis had a diurnal pattern opposite to the CO2 profile, with the highest rates of
photosynthesis occurring when CO2 concentrations and gradients were lowest. After accounting for
this diurnal interaction, we determined that photosynthesizing leaves in the understory experienced
greater daily CO2 concentrations than leaves at the top of the canopy. These elevated CO2
concentrations were the result of plant and soil respiration. We estimated that understory leaves in
the Picea mariana and Pinus banksiana stands gained approximately 5 to 6% of their carbon from
respired CO2.

KEYWORDS: ATMOSPHERE, CARBON ISOTOPE DISCRIMINATION, DIOXIDE, PLANTS,
RATIOS, SEEDLINGS, SPATIAL VARIATION, STOMATAL CONDUCTANCE, TEMPERATURE,
USE EFFICIENCY


     274  
Brooks, P.D., D.H. Campbell, K.A. Tonnessen, and K. Heuer. 1999. Natural variability in N
export from headwater catchments: snow cover controls on ecosystem N retention. Hydrological
Processes 13(14-15):2191-2201.

The causes of natural variability in catchment scale N export need to be understood and quantified
before the effects of increased N deposition in high elevation catchments can be evaluated. This study
evaluates controls on the size of the leachable soil N pool concurrent with the spring hydrologic flush
that is primarily responsible for the transport of N to surface water. In high elevation catchments in
the western United States, sources of N during this snowmelt flush include both atmospheric N
deposition stored in the snowpack until melt and mobile soil N pools, and sinks are dominated by
biogeochemical processes that occur in soil under snow cover. Because soil processes may serve
either as a source or sink for N, controls on the amount of inorganic N leached from soil during the
snowmelt period were evaluated in the major landscape types in four catchments in Colorado.
Measurements of leached N were inversely related to measurements of over-winter CO2 flux at all
sites, indicating that N was immobilized in soil heterotrophic biomass. Because over-winter soil
heterotrophic activity is controlled primarily by the depth and timing of snow accumulation, the
importance of these plot scale measurements to catchment scale N export were evaluated using a
long-term record of winter precipitation, N deposition, and N export from Loch Vale in Rocky
Mountain National Park. This data set identified a strong, linear relationship (r(2) = 0.68) between
catchment scale N retention and winter snow cover, consistent with subnivean, soil based controls
on the mobile N pool identified at the plot scale. These results indicate that the winter snow pack is
the major control both on hydrologic N export and on soil source/sink relationships for N concurrent
with this transport mechanism. The effect of winter snow cover on the fate of both atmospheric and
soil N needs to be considered when evaluating potential the effects of increased N deposition on
either terrestrial or aquatic ecosystems in seasonally snow-covered watersheds. In these systems,
changes in surface water chemistry are likely to occur in high deposition, snow-covered sites during
low snow years before terrestrial vegetation is affected. Copyright (C) 1999 John Wiley & Sons, Ltd.

KEYWORDS: ALPINE TUNDRA, CO2, COLORADO, FLUX, FOREST, FRONT RANGE,
INORGANIC NITROGEN, NITROGEN MINERALIZATION, NIWOT RIDGE, SATURATION


     275  
Brown, K.R. 1991. Carbon-dioxide enrichment accelerates the decline in nutrient status and relative
growth-rate of Populus tremuloides Michx seedlings. Tree Physiology 8(2):161-173.

Changes in growth dynamics and mineral nutrient concentrations were measured in Populus
tremuloides Michx., trembling aspen, grown for 100 days following germination in atmospheres
containing 350 or 750-mu-l l-1 CO2. Seedlings were fertilized with nitrogen (N) at concentrations
of 15.5 mM (high-N), 1.55 mM (medium-N), or 0.155 mM (low-N). Initially, relative growth rates
were enhanced by CO2 enrichment in each N regime, but the effects did not persist. In plants grown
in high-N or medium-N, foliar concentrations of Ca and Mg decreased in response to CO2
enrichment. During the 100-day study, whole-plant concentrations of N and P decreased in all
treatments. The decreases in mineral nutrient concentrations over time were accelerated in CO2-
enriched plants and accompanied the disappearance of the CO2-induced growth enhancement. It is
concluded that the depression of relative growth rates often associated with long-term CO2
enrichment of plants may result from decreases in plant nutrient status.



     276  
Brown, R.A., and N.J. Rosenberg. 1999. Climate change impacts on the potential productivity of
corn and winter wheat in their primary United States growing regions. Climatic Change 41(1):73-
107.

We calculate the impacts of climate effects inferred from three atmospheric general circulation models
(GCMs) at three levels of climate change severity associated with change in global mean temperature
(GMT) of 1.0, 2.5 and 5.0 degrees C and three levels of atmospheric CO2 concentration ([CO2]) -
365 (no CO2 fertilization effect), 560 and 750 ppm - on the potential production of dryland winter
wheat (Triticum aestivum L.) and corn (Zea mays L.) for the primary (current) U.S. growing regions
of each crop. This analysis is a subset of the Global Change Assessment Model (GCAM) which has
the goal of integrating the linkages and feedbacks among human activities and resulting greenhouse
gas emissions, changes in atmospheric composition and resulting climate change, and impacts on
terrestrial systems. A set of representative farms was designed for each of the primary production
regions studied and the Erosion Productivity Impact Calculator (EPIC) was used to simulate crop
response to climate change. The GCMs applied were the Goddard Institute of Space Studies (GISS),
the United Kingdom Meteorological Transient (UKTR) and the Australian Bureau of Meteorological
Research Center (BMRC), each regionalized by means of a scenario generator (SCENGEN). The
GISS scenarios have the least impact on corn and wheat production, reducing national potential
production for corn by 6% and wheat by 7% at a GMT of 2.5 degrees C and no CO2 fertilization
effect, the UKTR scenario had the most severe impact on wheat, reducing production by 18% under
the same conditions; BMRC had the greatest negative impact on corn, reducing produc tion by 20%.
A GMT increase of 1.0 degrees marginally decreased corn and wheat production. Increasing GMT
had a detrimental impact on both corn and wheat production, with wheat production suffering the
greatest losses. Decreases for wheat production at GMT 5.0 and [CO2] = 365 ppm range from 36%
for the GISS to 76% for the UKTR scenario. Increases in atmospheric [CO2] had a positive impact
on both corn and wheat production. AT GMT 1.0, an increase in [CO2] to 560 ppm resulted in a net
increase in corn and wheat production above baseline levels (from 18 to 29% for wheat and 2 to 5%
for corn). Increases in [CO2] help to offset yield reductions at higher GMT levels; in most cases,
however, these increases are not sufficient to return crop production to baseline levels.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CO2, EPIC MODEL, EROSION,
METHODOLOGY, RESPONSES, SENSITIVITY, SIMULATION, VARIABILITY, YIELD


     277  
Brown, S., C.A.S. Hall, W. Knabe, J. Raich, M.C. Trexler, and P. Woomer. 1993. Tropical
forests - their past, present, and potential future- role in the terrestrial carbon budget. Water, Air, and
Soil Pollution 70(1-4):71-94.

In this paper we review results of research to summarize the state-of-knowledge of the past, present,
and potential future roles of tropical forests in the global C cycle. In the pre- industrial period (ca.
1850), the flux from changes in tropical land use amounted to a small C source of about 0.06 Pg yr-1.
By 1990, the C source had increased to 1.7 +/- 0.5 Pg yr-1. The C pools in forest vegetation and soils
in 1990 was estimated to be 159 Pg and 216 Pg, respectively. No concrete evidence is available for
predicting how tropical forest ecosystems am likely to respond to CO2 enrichment and/or climate
change. However, C sources from continuing deforestation are likely to overwhelm any change in C
fluxes unless land management efforts become more aggressive. Future changes in land use under a
''business as usual'' scenario could release 41-77 Pg C over the next 60 yr. Carbon fluxes from losses
in tropical forests may be lessened by aggressively pursued agricultural and forestry measures. These
measures could reduce the magnitude of the tropical C source by 50 Pg by the year 2050. Policies
to mitigate C losses must be multiple and concurrent, including reform of forestry, land tenure, arid
agricultural policies, forest protection, promotion of on-farm forestry, and establishment of
plantations on non-forested lands. Policies should support improved agricultural productivity,
especially replacing non-traditional slash-and-burn agriculture with more sustainable and approaches.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS, CYCLE, DIOXIDE, LAND-USE CHANGE,
MODEL, NET, ORGANIC-MATTER, PRIMARY PRODUCTIVITY, SINKS


     278  
Bryant, J., G. Taylor, and M. Frehner. 1998. Photosynthetic acclimation to elevated CO2 is
modified by source : sink balance in three component species of chalk grassland swards grown in a
free air carbon dioxide enrichment (FACE) experiment. Plant, Cell and Environment 21(2):159-168.

Artificial chalk grassland swards were exposed to either ambient air or air enriched to 600 mu mol
mol(-1) CO2, using free-air CO2 enrichment technology, and subjected to an 8 week simulated
grazing regime. After 14 months of treatment, ribulose-1,5-bisphosphate carboxylase (Rubisco)
activity (V- c,V-max) and electron transport mediated ribulose-1,5- bisphosphate (RuBP)
regeneration capacity (J(max)), estimated from leaf gas exchange, were significantly lower in fully
expanded leaves of Anthyllis vulneraria L. (a legume) and Sanguisorba minor Scop, grown in elevated
CO2. After a change in source:sink balance brought about by defoliation, photosynthetic capacity was
fully restored in A. vulneraria and S. minor, but acclimation continued in the grass Bromopsis erecta
(Hudson) Fourr. Changes in net photosynthesis (P-n) with growth at elevated CO2 ranged from a
1.6% reduction in precut leaves of A. vulneraria to a 47.1% stimulation in postcut leaves of S. minor.
Stomatal acclimation was observed in leaves of A. vulneraria (reduced stomatal density) and B. erecta
(reduced stomatal conductance). The results are discussed in terms of whole-plant resource-use
optimization and chalk grassland community competitive interactions at elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, BIOCHEMISTRY, C-3, GAS-EXCHANGE, LEAVES,
METABOLISM, PLANT GROWTH, STOMATAL DENSITY


     279  
Bucher, J.B., D.P. Tarjan, R.T.W. Siegwolf, M. Saurer, H. Blum, and G.R. Hendrey. 1998.
Growth of a deciduous tree seedling community in response to elevated CO2 and nutrient supply.
Chemosphere 36(4-5):777-782.

In a FACE experiment, one year old alder, ash, beech, and oak seedlings were planted together in
tubs containing calcareous sandy alluvial soil with or without a slow release NPK- fertilizer, and
exposed to ambient and elevated CO2 concentrations (360 and 600 mu l mol(-1)) for 20 weeks. In
addition to the fertilizer, all tubs received N-15-ammonium nitrate as a marker. Elevated CO2
significantly increased biomass production in alder, but had no effect on oak and ash. In beech, due
to disease and mortality in all treatments, any possible effects were obscured. The addition of fertilizer
had no effect on biomass production in alder, but increased production in oak and ash significantly.
In oak a treatment synergism may be present. The non-appearance of a synergistic CO2 and fertilizer
effect in alder may be explained by a fertilizer induced reduction of the N-fixing root-nodule biomass
concurrent with a switch of the N-assimilation from atmospheric N to soil N supply, as the delta(15)N
measurements in the leaves of alder as opposed to oak indicate. Although elevated CO2 resulted in
a significant biomass increase in alder, it did not lead to an appreciable increase in the proportional
presence of the species as measured on total plant biomass in the tub. Increasing the nutrient supply
in the soil, however, did lead to appreciable gains in the proportional presence of oak and ash.

KEYWORDS: ATMOSPHERE, ECOSYSTEMS, ENRICHMENT


     280  
Buchi, R., M. Bachmann, and F. Keller. 1998. Carbohydrate metabolism in source leaves of sweet
basil (Ocimum basilicum L.), a starch-storing and stachyose-translocating labiate. Journal of Plant
Physiology 153(3-4):308-315.

Sweet basil (Ocimum basilicum L.) is an annual aromatic herb that grows in temperate to tropical
regions. During ontogeny, the predominant non-structural carbohydrate of mature leaves of plants
older than 2 months after sowing was starch (up to 66 mg.g fresh weight(-1)), followed by the
raffinose family oligosaccharides (RFO) and galactinol (metabolic RFO precursor) (both up to 1.0
mg.g fresh weight(-1)). Sucrose was only a minor component (up to 0.5 mg.g fresh weight(-1)). All
of these carbohydrates displayed distinct diurnal patterns with an increase during the day and a
decrease during the night. Starch concentrations showed the most pronounced diurnal change, with
an almost tenfold increase during the day. A treatment combining leaf excision, continuous
illumination, and high CO2 levels was aimed at elevating the leaf carbohydrate status and resulted in
an increase of the concentrations of starch and soluble carbohydrates (mainly glucose and fructose)
of 60- and 12-fold, respectively. We conclude that sweet basil leaves use starch as their main storage
carbohydrate, and nor RFO or sucrose. Phloem exudates were collected by the classical EDTA-
method and analyzed by HPLC. More than 85 % of the translocated sugars were RFO (mainly
stachyose) and only 5 % sucrose. To study the tissue compartmentation of stachyose synthesis in
source leaves, leaf pieces and mesophyll protoplasts isolated from them were compared. Stachyose
and its anabolic enzyme, stachyose synthase, were totally absent from mesophyll protoplasts.
Likewise, isolated mesophyll protoplasts were not capable of photosynthesizing [C-14]stachyose from
(CO2)-C-14, even after GO min, whereas osmotically stressed leaf pieces were. These results are in
support of the current polymer tray model of symplastic phloem loading of stachyose, which states
that stachyose is synthesized in the intermediary cells of minor vein phloem.

KEYWORDS: ACCUMULATION, AJUGA- REPTANS L, CELL, COMPARTMENTATION,
CUCUMIS-MELO L, DIURNAL PATTERN, MESOPHYLL, MINOR-VEIN ANATOMY,
PROTOPLASTS, RAFFINOSE FAMILY OLIGOSACCHARIDES


     281  
Buchmann, N., J.R. Brooks, K.D. Rapp, and J.R. Ehleringer. 1996. Carbon isotope composition
of C-4 grasses is influenced by light and water supply. Plant, Cell and Environment 19(4):392-402.

The carbon isotope composition of C-4 grasses has the potential to be used as an indicator of changes
in the isotopic composition and concentration of atmospheric CO2, especially for climate
reconstruction. The usefulness of C-4 grasses far this purpose hinges on the assumption that their
photosynthetic discrimination against C-13 remains constant in a wide range of environmental
conditions. We tested this assumption by examining the effects of light and water stress on the carbon
isotope composition of C-4 grasses using different biochemical subtypes (NADP-ME, NAD-ME,
PCK) in glasshouse experiments. We grew 14 different C-4 grass species in four treatments: sun-
watered, sun-drought, shade-watered and shade-drought. Carbon isotope discrimination (Delta) rarely
remained constant. In general, Delta values were lowest in sun-watered grasses, greater for sun-
drought plants and even higher for plants of the shade-watered treatment. The highest Delta values
were generally found in the most stressed grasses, the shade-drought plants. Grasses of the NADP-
ME subtype were the least influenced by a change in environmental variables, followed by PCK and
NAD-ME subtypes. Water availability affected the carbon isotope discrimination less than light
limitation in PCK and NAB-ME subtypes, but similarly in NADP-ME subtypes. In another
experiment, we studied the effect of increasing light levels (150 to 1500 mu mol photons m(-2) s(-1))
on the Delta values of 18 well-watered C-4 grass species. Carbon isotope discrimination remained
constant until photon flux density (PFD) was less than 700 mu mol photons m(-2) s(-1). Below this
light level, Delta values increased with decreasing irradiance for all biochemical subtypes. The change
in Delta was less pronounced in NADP-ME and PCK than in NAD-ME grasses. Grasses grown in
the field and in the glasshouse showed a similar pattern. Thus, caution should be exercised when using
C-4 plants under varying environmental conditions to monitor the concentration or carbon isotopic
composition of atmospheric CO2 in field/glasshouse studies or climate reconstruction.

KEYWORDS: ATMOSPHERIC CO2, C-4 PLANTS, CO2 ASSIMILATION, DISCRIMINATION,
IRRADIANCE, LEAF CONDUCTANCE, LEAVES, NUTRITION, PARTIAL-PRESSURE,
PHOTOSYNTHESIS


     282  
Buddendorfjoosten, J.M.C., and E.J. Woltering. 1994. Components of the gaseous environment
and their effects on plant-growth and development in-vitro. Plant Growth Regulation 15(1):1-16.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, CONTROLLED INVITRO
ENVIRONMENT, DENOVO SHOOT REGENERATION, ETHYLENE INHIBITORS,
PHOTOSYNTHETIC CHARACTERISTICS, STAGE-II MICROPROPAGATION, STRAWBERRY
PLANTLETS, TISSUE-CULTURE, VOLATILE EMISSIONS


     283  
Bugbee, B., B. Spanarkel, S. Johnson, O. Monje, and G. Koerner. 1994. Co2 crop growth
enhancement and toxicity in wheat and rice. Life Sciences and Space Research XXV (3) 14(11):257-
267.

The effects of elevated CO2 on plant growth are reviewed and the implications for crop yields in
regenerative systems are discussed. There is considerable theoretical and experimental evidence
indicating that the beneficial effects of CO2 are saturated at about 0.12% CO2 in air. However, CO2
can easily rise above 1% of the total gas in a closed system, and we have thus studied continuous
exposure to CO2 levels as high as 2%. Elevating CO2 from 340 to 1200 mu mol mol(-1) can increase
the seed yield of wheat and rice by 30 to 40%; unfortunately, further CO2 elevation to 2500 mu mol
mol(-1) (0.25%) has consistently reduced yield by 25% compared to plants grown at 1200 mu mol
mol(-1); fortunately, there was only an additional 10% decrease in yield as the CO2 level was further
elevated to 2% (20,000 mu mol mol(-1)). Yield increases in both rice and wheat were primarily the
result of increased number of heads per m(2), with minor effects on seed number per head and seed
size. Yield increases were greatest in the highest photosynthetic photon flux. We us