You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Article
Title:
Limitation to Photosynthesis in Water-stressed Leaves: Stomata vs. Metabolism and the Role of ATP
Contributor:
LAWLOR, DAVID W.
imprint:
Oxford University Press, 2002
Published in:Annals of Botany
Language:
English
ISSN:
1095-8290;
0305-7364
Origination:
Footnote:
Description:
<p>Decreasing relative water content (RWC) of leaves progressively decreases stomatal conductance (gs), slowing CO₂ assimilation (A) which eventually stops, after which CO₂ is evolved. In some studies, photosynthetic potential (Apot), measured under saturating CO₂, is unaffected by a small loss of RWC but becomes progressively more inhibited, and less stimulated by elevated CO₂, below a threshold RWC (Type 1 response). In other studies, Apot and the stimulation of A by elevated CO₂ decreases progressively as RWC falls (Type 2 response). Decreased Apot is caused by impaired metabolism. Consequently, as RWC declines, the relative limitation of A by gs decreases, and metabolic limitation increases. Causes of decreased Apot are considered. Limitation of ribulose bisphosphate (RuBP) synthesis is the likely cause of decreased Apot at low RWC, not inhibition or loss of photosynthetic carbon reduction cycle enzymes, including RuBP carboxylase/oxygenase (Rubisco). Limitation of RuBP synthesis is probably caused by inhibition of ATP synthesis, due to progressive inactivation or loss of Coupling Factor resulting from increasing ionic (Mg²⁺) concentration, not to reduced capacity for electron or proton transport, or inadequate trans-thylakoid proton gradient (△pH). Inhibition of Apot by accumulation of assimilates or inadequate inorganic phosphate is not considered significant. Decreased ATP content and imbalance with reductant status affect cell metabolism substantially: possible consequences are discussed with reference to accumulation of amino acids and alterations in protein complement under water stress.</p>