The study of oxygen reduction in photosystem I of higher plants using electron donors for this photosystem in intact thylakoids

Abstract

Oxygen uptake in the light was investigated in suspensions of isolated pea thylakoids upon inhibition of electron transport from photosystem II by diuron and delivery of electrons to photosystem I by means of artificial donors in the presence of ascorbate. The effects of ascorbate and donors on the process of the reduction of O2 molecules by the components of acceptor side of photosystem I was analyzed. It was shown that DCPIP cannot be used as the donor for photosystem I in the study of this process. Apparently, TMPD applied as a donor does not affect immediately the reaction of the O2 reduction, since an increase in its concentration did not lead to an increase in the oxygen uptake rate in the light. In the experiments with TMPD, an increase in light intensity led to an increase in the oxygen uptake rate, and this fact was interpreted as a consequence of the increase in the apparent rate constant of the reaction of the O2 reduction by the components of the acceptor side of photosystem I.