[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.

[Pigment degradation in Synechocystis aquatilis under nitrogen starvation with varying illumination]. / Degradatsiia pigmentov u Synechochystis aquatilis v usloviiakh azotnogo golodanii pri razlichnoi osveshchennosti.

When the cells of Synechocystis aquatilis are incubated in a medium without nitrogen, the degradation of pigments in the conditions of illumination occurs in two stages: (i) during the first day and (ii) after three days of the incubation. The degree of degradation increases with the intensity of illumination and correlates with the rate of cell death. The pigments are not degraded in the dark. When chlorotic cells are transferred to a medium containing nitrogen, their number increases stepwise by a factor of 1.2 after 7--8 hours and rises exponentially after 14 hours; the synthesis of phycocyanin starts after 7 hours and the synthesis of chlorophyll only after 12 hours when the chlorophyll-to-phycocyanin ratio reaches its normal value (1. 1).