[Studies of oxygen uptake (Mehler reactions) in chloroplasts in the presence of silico-molybdic acid]. / Izuchenie reaktsii pogloshcheniia kisloroda (reaktsii melera) v khloroplastakh v prisutstvii kremnievomolibdenovoi kisloty

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.

[Localization of the Meler's reaction with ethanol catalase trap in the chain of photosynthetic electron transport]. / O lokalizatsii reaktsii Melera s etanolkatalaznoi lovushkoi v tsepi fotosinteticheskogo transporta elektronov

The common view of photosystem I as the action site of catalase and ethanol at oxygen uptake in chloroplasts are based on indirect data on this reaction. That is why the question on Mehler reaction localization in electron transport chain with ethanolcatalase trap has been investigated anew. It has been demonstrated that oxygen uptake with catalase and ethanol does not decrease in presence of dibromothymoquinone (2,5-dibromo-3-methyl-6 isopropyl-p-benzoquinone--DBTQ) which blocks electron transfer to photosystem I at plastoquinones level. The summation of oxygen uptake activities is observed on the combined action of catalase and ethanol with any of the Mehler reagents functioning in photosystem I (methylviologen,FMN, epinephrine, ferredoxin). Catalase and ethanol in contrast to methylviologen have no effect on photooxidation rate of reduced dichlorphenolindophenol in photosystem I. The quatum yield of oxygen uptake with catalase and ethanol versus wave length of actinic light shows a distinct maximum in the photosystem II absorption area and a "red drop" in the longware area. The obtained data show that the Mehler reaction with catalase and ethanol takes place in photosystem II only.