All Scientists are Sceptics ~Professor Bob Carter

Whenever someone asserts that a scientific question is “settled,” they tell me immediately that they don’t understand the first thing about science. Science is never settled. Dr David Deming

Perhaps the most frustrating aspect of the science of climate change is the lack of any real substance in attempts to justify the hypothesis ~Professor Stewart Franks

A lie told often enough becomes the truth.
-- Vladimir Ilyich Lenin - See more at: http://thepeoplescube.com/lenin/lenin-s-own-20-monster-quotes-t185.html#sthash.aTrSI3tG.dpuf
A lie told often enough becomes the truth.
-- Vladimir Ilyich Lenin - See more at: http://thepeoplescube.com/lenin/lenin-s-own-20-monster-quotes-t185.html#sthash.aTrSI3tG.dpuf
A lie told often enough becomes the truth.
-- Vladimir Ilyich Lenin - See more at: http://thepeoplescube.com/lenin/lenin-s-own-20-monster-quotes-t185.html#sthash.aTrSI3tG.dpuf

Thursday, 14 January 2016

Increased atmospheric CO2 help plants recover from droughts (peer-reviewed paper)

CO2 Science reviewed the following paper:

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.

Abstract

Water availability for plant growth is becoming increasingly limited, whereas rising atmospheric carbon dioxide concentration may have interactive effects with drought stress. The objectives of this study were to determine whether elevated CO2 would mitigate drought-induced water deficit and photosynthesis inhibition and enhance recovery from drought damages on rewatering and to determine whether the mitigating effects during drought stress and the recovery in photosynthesis during rewatering by elevated CO2 were the result of the regulation of stomatal movement or carboxylation activities in tall fescue (Festuca arundinacea Schreb. cv. Rembrandt). Plants were grown in controlled-environment chambers with ambient CO2 concentration (400 μmol·mol−1) or elevated CO2 concentration (800 μmol·mol−1) and maintained well watered (control) or subjected to drought stress and subsequently rewatered. Elevated CO2 reduced stomatal conductance (gS) and transpiration rate of leaves during both drought stress and rewatering. Osmotic adjustment and soluble sugar content were enhanced by elevated CO2. Elevated CO2 enhanced net photosynthetic rate with lower gS but higher Rubisco and Rubisco activase activities during both drought and rewatering. The results demonstrated that elevated CO2 could improve leaf hydration status and photosynthesis during both drought stress and rewatering, and the recovery in photosynthesis from drought damages on rewatering was mainly the result of the elimination of metabolic limitation from drought damages associated with carboxylation enzyme activities. (bold added)

CO2 Science Review:
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."

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