Prolongation of photosynthetic induction as a consequence of interference with mitochondrial oxidative metabolism in mesophyll protoplasts of the pea (Pisum sativum L.)

Abstract

The restriction of mitochondrial oxidative metabolism by metabolic inhibitors caused a prolongation of induction of photosynthetic O₂ evolution in mesophyll protoplasts of the pea (Pisum sativum L.) at both optimal and limiting CO₂. There was a significant increase in the lag period of photosynthesis in the presence of oligomycin (an inhibitor of oxidative phosphorylation) or antimycin A (an inhibitor of cytochrome pathway), while the increase in lag was marginal in presence of salicylhydroxamic acid (SHAM) or propyl gallate (inhibitors of alternative oxidase (AOX) pathway). There was a pronounced decrease in steady-state levels of ribulose-1,5-bisphosphate (RuBP) in the presence of oligomycin or antimycin A, but not in the presence of SHAM or propyl gallate. Our results suggest that the restriction of the cytochrome pathway of mitochondrial electron transport or oxidative phosphorylation, leads to a prolongation of the photosynthetic induction period and a marked decrease in the steady state levels of RuBP.