Under the condition of abiotic stress，how to determine or judge the changes of photosynthetic rate are caused by stomatal factors or non-stomatal factors?
Hi Cao, I am suggesting an unconventional method. I am not sure if this has been done earlier. Dissolve thermocole pieces in xylene and then paint the solution on the underside of the leaf of the crop. Once it dries, it seals the stomatas. Then measure the photosynthetic rate of such a painted leaf against a non-painted control leaf, both type of leaves UNDER stress situation. If you do find some differences, you can think of giving me credit:) If you do not find any, there could be other pragmatic solutions !! Good luck.
The most common method for assessing the relative limitation to the rate of photosynthesis (A) of leaves has been to measure A over a range of atmospheric CO2 concentrations (Ca) and at the same time measure the leaf surface (stomatal) conductance to water loss, using the calculations developed by Farquhar and von Caemmerer. From these measurements the CO2 concentration inside the leaf is calculated. The measurements are used to obtain the A/Ci curve. and these can be compared under different conditions of light, humidity and water deficits in the leaves. Using these methods has shown that water deficits decrease stomatal conductance, but also increases progressively and much more the limitation of the A caused by inhibition of metabolic processes. This resulting from slower synthesis of RuBP in the chloroplast as a consequence of inhibited synthesis of ATP. Suggestions that impaired transport of CO2 from the substomatal cavities into the chloroplast is the cause just do not explain the experimental data.
I suggest reading the papers by Lawlor and collaborators which are available on Researchgate. The papers contain references which will help understand how the evaluation is done. E.G
Photosynthetic carbon assimilation and associated metabolism in relation to water deficits in higher plants.Lawlor DW1, Cornic G.
Plant Cell and Environment, 25 275-294
Causes of decreased photosynthetic rate and metabolic capacity in water-deficient leaf cells: A critical evaluation of mechanisms and integration of processes,
Lawlor DW, Tezara Z 2009 Annals of Botany 103(4):561-79 ·
David W. Lawlor Rajesh S Patil
I exactly agree with your method. and thank you for your detailed explanation.
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