Light-induced inhibition of respiration in DCMU-poisoned Chlorella caused by photosystem I activity

Abstract

We have demonstrated that the reduced net rate of oxygen uptake observed when DCMU-poisoned Chlorella are illuminated is a result of an inhibition of respiration rather than residual photosynthetic oxygen evolution. The action spectrum of the effect demonstrates that chlorophyll a is the main photoreceptor, implicating system I of photosynthesis. Studies using PMS, which is known to stimulate cyclic photophosphorylation by photosystem I, show that the respiratory inhibition is caused by a change in the intracellular ATP/ADP balance as a result of cyclic photophosphorylation.