Abstract
Climatic change may bring about increased aridity to large areas of Europe. Higher temperatures, larger water deficits and high light stress are likely to occur in conjunction with elevated atmospheric C02. This raises the question whether a high C02 concentration in the atmosphere can compensate for the decrease in carbon gain in water-stressed plants. The processes which determine dry matter production and the ways they are affected by soil water deficits are discussed. It is now well established that in most species and under most circumstances stomata are the main limiting factor to carbon uptake under water deficit, the photosynthetic machinery being highly resistant to dehydration. However, when other stresses are superimposed, a decline in photosynthetic capacity may be observed. In the short term, under drought conditions, the increase in C02 in the atmosphere may diminish the importance of stomatal limitation for carbon assimilation, inhibit photorespiration, stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent evidence seems to indicate that under conditions of high irradiance, plants growing at elevated C02 may develop protection towards photoinhibition, which might otherwise result in significant losses in plant production under stress conditions. In the longer term though, a negative acclimation of photosynthesis appears to occur in many species, an explanation for which still needs to be clearly identified. Similarly, the effects of extended exposure to elevated C02 under arid conditions are not known. Plant production is more closely related to the integral of photosynthesis over time and total foliage area than to the instantaneous rates of the photosynthetic process. Water deficits result in a decrease in foliage area biomass and, therefore, in productivity. On the other hand, the increase in air temperature may result in more respiratory losses. However, experimental as well as simulatory evidence suggests that doubling C02 concentration in the air may improve carbon assimilation and compensate partially for the negative effects of water stress even if we assume a down regulation of the photosynthetic process as a result of acclimation to elevated C02.
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Claims 10
Claim · model-written summary
Stomata are described as the main limitation to carbon uptake during water deficit in most species.
Verbatim
e0“in most species and under most circumstances stomata are the main limiting factor to carbon uptake under water deficit”
Claim · model-written summary
Additional stresses can reduce photosynthetic capacity.
- Taxon
- plantsViridiplantaet0
- Outcome
- photosynthetic capacitye0
- Direction
- declinee0
Verbatim
e0“when other stresses are superimposed, a decline in photosynthetic capacity may be observed”
t0“water-stressed plants”
Claim · model-written summary
Under drought, higher atmospheric CO2 may reduce stomatal limitation of carbon assimilation.
- Taxon
- plantsViridiplantaet0
- Treatment
- increase in C02e0
- Outcome
- stomatal limitation for carbon assimilatione0
- Direction
- diminishe0
Verbatim
e0“under drought conditions, the increase in C02 in the atmosphere may diminish the importance of stomatal limitation for carbon assimilation”
t0“water-stressed plants”
Claim · model-written summary
Under drought, elevated CO2 may inhibit photorespiration.
- Taxon
- plantsViridiplantaet0
- Outcome
- photorespiratione0
- Direction
- inhibite0
Verbatim
e0“inhibit photorespiration”
t0“water-stressed plants”
Claim · model-written summary
Under drought, elevated CO2 may stimulate carbon partitioning to soluble sugars.
- Taxon
- plantsViridiplantaet0
- Outcome
- carbon partitioning to soluble sugarse0
- Direction
- stimulatee0
Verbatim
e0“stimulate carbon partitioning to soluble sugars”
t0“water-stressed plants”
Claim · model-written summary
Under drought, elevated CO2 may increase water-use efficiency.
- Taxon
- plantsViridiplantaet0
- Outcome
- water-use efficiencye0
- Direction
- increasee0
Verbatim
e0“increase water-use efficiency”
t0“water-stressed plants”
Claim · model-written summary
Elevated CO2 may protect plants under high irradiance from photoinhibition.
- Taxon
- plantsViridiplantaee0
- Treatment
- elevated C02e0
- Outcome
- protection towards photoinhibitione0
Verbatim
e0“plants growing at elevated C02 may develop protection towards photoinhibition”
Claim · model-written summary
Many species appear to acclimate photosynthesis negatively over longer exposure to elevated CO2.
Verbatim
e0“a negative acclimation of photosynthesis appears to occur in many species”
Claim · model-written summary
Water deficits decrease foliage area biomass and productivity.
- Taxon
- plantsViridiplantaet0
- Treatment
- Water deficitse0
- Outcome
- foliage area biomass and, therefore, in productivitye0
- Direction
- decreasee0
Verbatim
e0“Water deficits result in a decrease in foliage area biomass and, therefore, in productivity.”
t0“water-stressed plants”
Claim · model-written summary
Doubling atmospheric CO2 may improve carbon assimilation despite acclimation and partially offset water stress.
- Taxon
- plantsViridiplantaet0
- Treatment
- doubling C02 concentration in the aire0
- Outcome
- carbon assimilatione0
- Direction
- improvee0
Verbatim
e0“doubling C02 concentration in the air may improve carbon assimilation and compensate partially for the negative effects of water stress”
t0“water-stressed plants”