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 preferenc