[Changes in the ultrastructures of Anacystis nidulans cells at different temperatures]

If the cells of the blue-green alga Anacystis nidulans are put in the unfavourable conditions, the pairs of photosynthetic membranes separate, vacuoles are formed within thylakoids, and degradation of the photosynthetic apparatus occurs the earlier the sooner photosynthetic electron transport stops functioning: after 7--9 days in the dark, after 7--10 days in the light at 5 degrees C, after 5--7 days at 45 degrees C. If the cells are incubated at 5 and 45 degrees C, they become longer and form rods upto 10--12 mcm in length; at 45 degrees C, degradation takes place and the cell contents separate. The stationary phase of growth in the optimal conditions at 37 degrees C takes more time and the cells are degraded only after 45 days. If the temperature is lowered to 20 degrees C in the light, the cells remain viable for a long time and are degraded only after 60 days. In these conditions, invaginations of photosynthetic lamellae appear in the living cells, and the activity of TTC reduction in the light remains high for a long period of time. The cell wall remains intact upon degradation in remains high for a long period of time. The cell wall remains intact upon degradation in all the variants. Pigments are not destroyed both at a high (45 degrees C) and low (5 degrees C) temperature longer in the dark than in the light; therefore, photodestruction is involved in degradation of the lamellar apparatus in the light. The order in which pigments decompose differs depending on the conditions: chlorophyll is the first to be destroyed at 5 degrees C, phycocyanin at 45 degrees C, chlorophyll and phycocyanin at 37 degrees C; the rate of degradation of all pigments is almost the same at 20 degrees C. Apparently, additional pigments play different role in the processes of degradation occurring in the light.