Chen, Y., Yu, J. and Huang, B. 2015. Effects of elevated CO2 concentration on water relations and photosynthetic responses to drought stress and recovery during re-watering in tall fescue. Journal of the American Society of Horticultural Science 140: 19-26.
Introducing their study, Chen et al. (2015) write that "drought stress is one of the most detrimental abiotic stresses for plant growth," in that it "leads to stomatal closure and reduces photosynthesis resulting from restricted CO2 diffusion through leaf stomata and inhibition of carboxylation activity," as described by Flexas et al. (2004). And they thus note that "minimizing cellular dehydration and maintaining active photosynthesis are key strategies for plant survival or persistence through dry-down periods," as is described in more detail by Nilsen and Orcutt (1996).The researchers wondered if these problems might be reversed by CO2 enrichment...
This work revealed, in the words of the three scientists, that (1) "elevated CO2 reduced stomatal conductance and transpiration rate of leaves during both drought stress and re-watering," that (2) "osmotic adjustment and soluble sugar content were enhanced by elevated CO2," and that (3) the "elevated CO2enhanced net photosynthetic rate with lower stomatal conductance but higher Rubisco and Rubisco activase activities during both drought and re-watering." And what was the end result of these several changes?
Chen et al. conclude that "the mitigating effects of elevated CO2 on drought inhibition of photosynthesis and the enhanced recovery in photosynthesis on re-watering were mainly the result of the elimination of metabolic limitation from drought damages associated with increased enzyme activities for carboxylation."