.ALPHA.-Azohydroperoxide, A New Photosynthetic Reaction Inhibitor.

Abstract

The azo-compound, 1-(p-bromophenylazo)-1-phenyl-1-hydroperoxymethane, is also called α-azohydroperoxide or AHPO. AHPO differs in structure from other herbicides, and at 10-50μM inhibites O2 evolution and photoreduction of ferricyanide, NADP+ and methyl viologen (O2) which represent photosystem II (PS II), cytochrome-b6/f complex and photosystem I (PS I) reactions. But PS II specific O2 evolution and PS I specific reactions (NADP+ and methyl viologen (O2) photoreduction, cytochrome-f photooxidation and cyclic photophosphorylation), however, were not inhibited. The AHPO inhibition site was presumed to be the electron transport system between PS II and PS I, perhaps at the plastoquinone or the cytochrome-b6/f complex site. Photosynthesis of chloroplasts, green algae and leaf cells were easily inhibited by AHPO. Thus AHPO is an unique inhibitor possibly applicable as a new type of herbicide.