[Early effect of sodium pentachlorophenate on photosynthetic activity of the alga Chlorella pyrenoidosa Chick S-39].

Early effects of 0.0001-10 mM sodium pentachlorophenate (PCP-Na) on the green alga Chlorella pyrenoidosa Chick. S-39 involves a rapid (within 1-2 min) decrease in the light-induced oxygen evolution by algal cells. The suppressed relative yield of variable chlorophyll fluorescence in C. pyrenoidosa in the presence of high PCP-Na concentrations and its dynamics provide evidence for rapid inactivation of photosystem 2, which is not observed at low concentrations of the toxicant. An analysis of the induction curve of delayed chlorophyll fluorescence in algal cells suggests that PCP-Na at low concentrations disturbs the coupling of electron transport and phosphorylation, whereas at high concentrations it inhibits electron transport and decreases the energy potential of photosynthetic membranes. The early toxic effect of PCP-Na is responsible for subsequent impairment of C. pyrenoidosa productivity.

[Activation of the chloroplast respiration increases chlorophyll fluorescence yield in Chlorella adapted to darkness at higher temperature]. / Activatsiia khloroplastnogo dykhaniia uvelichivaet vykhod fluorestsentsii khlorofilla u Chlorella, adaptirovannoi k temnote pri povyshennoi temperature.

A tenfold increase in chlororespiration during dark incubation of Chlorella perynoidosa Chick at high temperature doubled the initial chlorophyll fluorescence yield (F0). The presence of iodacetamide or unmetabolizable glucose analog 2-deoxy-D-glucose prevented increase in both chlororespiration and F0 yield. The rates of chlororespiration and F0 yield growth demonstrated a similar pattern of temperature dependence. Inhibition of electron transport between QA and plastoquinone prevented increase in F0 during dark respiration of the cells at high temperature. Apparently, a pool of plastoquinone was restored in the chlororespiratory chain during the dark incubation at 37.5-41 degrees C and plastoquinone exchanged electrons with QA. This is the cause of QA reduction and subsequent increase in F0 yield.

[Early toxic effect of zinc, cobalt, and cadmium on photosynthetic activity of green alga Chlorella pyrenoidosa Chick S-39]. / Rannie éffekty toksicheskogo deistviia tsinka, kobal'ta, kadmiia na fotosinteticheskuiu aktivnost' vodorosli Chlorella pyrenoidosa Chick S-39.

Early toxic effects of heavy metals (HMs) Zn, Co, and Cd in concentration from 0.01 to 100 mM on photosynthetic activity of the green alga Chlorella pyrenoidosa Chick S-39 were studied. The early effect of HMs was manifested as a rapid (0.5-2 h) reduction of photoinduced oxygen release by the algal cells. The suppressed relative yield of variable chlorophyll fluorescence ratio (Fv/Fm) by the metals as well as its dynamics in C. pyrenoidosa demonstrated rapid inactivation of photosystem II (PS II). Analysis of the induction curve of delayed chlorophyll fluorescence in Chlorella cells suggested that the early toxic effects of the tested concentrations of Zn, Co, and Cd included both reduced electron transport in PS II and decreased photosynthetic membrane energization. Hence, the early toxic effect of Zn, Co, and Cd was primarily related to the decreased efficiency of the light reactions of photosynthesis which further reduced the alga productivity later.

[The photodynamic inactivation of Candida guilliermondii in the presence of photodithazine]. / Fotodinamicheskaia inaktivatsiia drozhzhei Candida guilliermondii v prisutstvii fotoditazina.

Photodithazine, a glucosamine salt of chlorin e6, enhanced the inactivation of Candida guilliermondii cells by visible light. The sensitizing effect of photodithazine was found to be related to free or cell surface-bound molecules of this dye. Sodium azide (a singlet oxygen quencher) and propyl gallate (an inhibitor of lipid peroxidation) protected yeast cells from the photodithazine-enhanced photoinactivation.

[Photoinduced reactivation of photosystem II in Chlorella after prolong incubation without light]. / Svetoindutsirovannoe vosstanovlenie aktivnosti fotosistemy II u khlorelly posle dlitel'noi temnovoi inkubatsii.

The light-dependent reactivation of photosystem II in Chlorella pyrenoidosa Chick, CALU-175 cells, inactivated with supraoptimal temperatures (40-43 degrees C) in the dark or during heterotrophic growth was studied. It was shown that the inactivation of photosystem II after incubation in the dark at 41-42 degrees C, which showed up in the suppression of relative yield of variable chlorophyll fluorescence Fv due to an increase in yield F0 could be completely reversed by light. The inactivation of photosystem II at 43 degrees C in the dark could not be reversed by subsequent irradiation. In this case, the suppression of Fv/Fm was related not only to the growth of F0 but also with the decrease in Fm. The light dependences of the rate and extent of reactivation of yield Fv after heterotrophic growth or incubation of chlorella at 41 degrees C in the dark completely coincided. The full light-induced reactivation of photosystem II took place as the rate of photoinduced electron transport reached the rate of nonphotochemical reduction of plastoquinone in the dark. These results suggest that the light-reversed inactivation of photosystem II after heterotrophic growth or incubation at 41 degrees C in the dark is due to the redox-interaction of the primary quinone acceptor with plastoquinone reduced by the electron flux from the substrates of chlororespiration.