Red and Far-Red Action on Oxidative Phosphorylation

Abstract

The rate of oxidative phosphorylation by isolated mitochondria was found to be affected by red (650 m mu ) and far-red (725 m mu ) light. Esterification of adenosine diphosphate to adenosine tripliosphate by rat liver mitochondria is decreased by concomitant or prior irradiation with far-red and increased by red light. The effect of far-red is reversible by red in an alternating sequence. An analogous sensitivity was not found when isolated mitochondria of the Avena seedling were irradiated. However, irradiation of the intact seedling significantly affected the phosphorylative capacity of the mitochondria subsequently isolated. Whether enhancement or inhibition of activity took place depended on the time at which the seedlings were irradiated in the post germinative period. There is apparently no direct correlation between radiationinduced changes in phosphorylative rate and either mitochondrial protein or volume. Impairment of ATP generation is suggested as the biochemical basis for the far-red potentiation of x-ray-induced chromatid aberrations. The photosensitivity of this phosphorylation also suggests its consideration as a metabolic determinart of the photomorphogeneses controlled by red and far-red light. (auth)