[Structural-functional organization of the cells of Brc-1 mutant Chlamydomonas reinhardtii, supplying protoporphyrin IX in the dark].

The structural-functional characteristics of the cells of wild type CC-124 and Brc-1 mutant of the unicellular green algae Chlamydomonas reinhardtii while growing in the dark and light were studied. It has been shown that the cells of the wild type in heterotrophic and mixotrophic growth conditions had a well developed structure and high functional activity due to the ability of the cells to synthesize chlorophyll both in the light and in the dark. The cells of Brc-1 mutant lost their ability to synthesize chlorophyll in the dark and the cells' color was orange due to brc-1 mutation in the nuclear gene LTS3 that regulated the activity of Mg-chelatase enzyme. In the dark the mutant cells accumulated protoporphyrin IX and had a weakly developed structure with low functional activity. It has been ascertained that due to high content of protoporphyrin IX even a short-term exposure of the cells of Brc-1 mutant to the light was accompanied by very strong destructive changes in all the membranes in a cell: plasmalemma, chloroplast, mitochondrion, shells of the nucleus and vacuoles. The reasons of these significant damages of the membrane components and O2-gas exchange in the cells of Brc-1 mutant are discussed.

[NaCl-induced photoinhibition and the recovery of the photosynthetic activity of katG- mutant of the cyanobacterium Synechocystis sp. PCC 6803].

The joint effects of 0.5 M NaCI and light of different intensities on the activity of the photosynthetic apparatus and ATP contents in cells of the katG- mutant of cyanobacterium Synechocystis sp. PCC 6803 have been studied. The mutant demonstrated a higher photoinhibition rate and a slower rate of recovery compared to the wild type, as it was shown by measurements of the CO2-dependent O2 production and delayed light emission of Chl a. The presence of 0.5 M NaCl in incubation medium induced the equal photoinhibition of the photosynthetic apparatus at I = 1200 microE m(-2) x (-1) in the mutant and wild-type cells. At I = 2400 microE m(-2) x c(-1), a stronger inhibition and a slower recovery of the photosynthetic apparatus activity in the kat- mutant than in wild-type cells was observed. The data obtained evidence an important role of catalase-peroxidase in the system of reparation of the photosynthetic apparatus damaged by high-intensty light, especially against the background of NaCI stress.

[Effect of oxidative stress inductors on the photosynthetic apparatus in cyanobacterium Synechocystis sp. PCC 6803 Prq20 mutant resistant to methyl viologen].

The damaging effect of oxidative stress inductors: methyl viologen, benzyl viologen, cumene hydroperoxide, H2O2, menadion, and high irradiance on the photosynthetic apparatus of cyanobacterium Synechocystis sp. PCC 6803 in cells of the wild type strain and the methyl viologen-resistant Prq20 mutant with the disrupted function of the regulatory gene prqR has been investigated by measuring the delayed fluorescence of chlorophyll a and the rate of CO2dependent -O2 gas exchange. It has been shown that the damage to the photosynthetic apparatus in the Prq20 mutant as compared with the wild type was less in the presence of methyl viologen and benzyl viologen. Reasons for the enhanced resistance of the photosynthetic apparatus in the mutant Prq20 to methyl viologen and benzyl viologen are discussed.

[Sugar beet photosynthesis under conditions of increasing water deficiency in soil and protective effects of a low-molecular-weight alcohol]. / Fotosintez sakharnoi svekly pri narastaiushchem defitsite vody v pochve i protektornoe vliianie nizkomolekuliarnogo spirta.

The rate of CO2 gas exchange, transpiration, stomatal conductivity, and efficiency of the use of water were assessed in leaves of the sugar beet (Beta vulgaris var. Saccharifera (Alef) Krass.) sprayed with 40% methanol, against the background of increasing water deficiency in soil. A decrease in the negative impact of water deficiency in experimental plants was shown to be due to the larger stress-resistance of the photosynthetic apparatus, higher rate of photosynthesis, and more effective use of water.

[Low radiance in the region of wavelengths 620-660 nm reduces the UV-B-induced damage to photosystem II in spinach leaves]. / Nizkoénergeticheskii svet v oblasti dlin voln 620-660 nm umen'shaet UF-B-indutsirovannoe povrezhdenie fotosistemy II v list'iakh shpinata.

The effect of monochromatic preirradiation in the region of wavelengths 550-730 nm on the parameters of variable and delayed fluorescence in primary spinach leaves irradiated with UV-B was investigated. It was shown that irradiation of leaves with UV-B at lambda(M) = 300 nm reduced photoinduced changes in variable and delayed fluorescence as well as increased the half rise-time of maximum fluorescence. Preirradiation in the region of 620-660 nm (I = 2-4 W x m(-2)) reduced partly the damage to photosystem II induced by UV-B, whereas preirradiation at lambda(m) = 550, 600, 700, and 730 nm had no significant influence. Potential receptors of red light that take part in the protection of photosystem II against UV-B are discussed.