[Studies of oxygen uptake (Mehler reactions) in chloroplasts in the presence of silico-molybdic acid].

Silico-molybdic acid (SiMo) alone or in combination with diurone is known to provide for the functioning of various sites of electron transport within photosystem II (PS-II). Using SiMo, the ability of PS-II to competitive reduction of O2 with SiMo in the presence of some activators of O2 uptake (e. g. catalase"ethanol, malonate, oxalate and glyoxalate) was shown. Oxygen uptake (Mehler reaction) with those compounds may be accomplished against the diurone block. The Mehler reactions studied occur in PS-II at the site, uncoupled with phosphorylation, up to the primary acceptor Q, The Mehler reactions with FMN and ferredoxin confirm the fact that PS-II functioning in the presence of SiMo is possible only after its reduction. Photoreduction of NADP is inhibited irrespective of whether the oxidized or reduced form of SiMo is added.