THE EFFECTS OF SOME INHIBITORS OF PHOTOSYNTHESIS UPON THE PHOTOCHEMICAL REDUCTION OF A DYE BY ISOLATED CHLOROPLASTS

Abstract

The reduction of phenol indophenol in air was detd. photometrically using chloroplasts from the leaves of Beta vulgaris. HgCl2, CuSO4, o-phenan-throline, hydroxylamine and dinitrophenol inhibit the action of isolated chloroplasts specifically, as they do photosynthesis, whereas cyanide, pyrophosphate, thiourea, and iodoacetate do not and are probably primarily concerned with the inhibition of the utilization of CO2 in photosynthesis. CUSO4, hydroxylamine, o-phenanthroline, dinitrophenol. phenylurethane, chloroform, thymol, resorcinol and formaldehyde inhibit a photochemical reaction. A few other inhibiting reagents were tested. Inhibiting concns. of the important inhibitors do no affect the spectral absorption maxima of chlorophyll in the chloroplasts. The toxicity of Hg+ and Cu++ indicates the presence of enzymatically essential, or perhaps active, sulfhydryl groups. The results are compared on the basis of the homology, the evidence for which is reviewed, between the photoreducing system of chloroplasts in dye reduction and in photosynthesis.