Effects of pH and deuterium oxide on the heat-inactivation temperature of chloroplasts

Heat inactivation of photosynthetic O2 evolution was studied in isolated thylakoids from spinach (Spinacia oleracea) and mangrove (Avicennia marina) leaves. Different temperatures, salt, pH and uncoupler effects were investigated. From these results and others in the literature it was concluced that chloride loss from the membrane and, more specifically, the oxygen-evolving complex of photosystem II, may be the cause of inhibition of oxygen evolution during heat inactivation.

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High-temperature damage and acclimation of the photosynthetic apparatus

Yordanov

Goltsev²,

Stoyanova³

et al. 1987

Planta

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The thermosensitivity of delayed fluorescence, the relative values of variable chlorophyll fluorescence and the degree of quenching of 9-aminoacridine fluorescene were studied in the chloroplasts from heat-acclimated and non-acclimated (treated 6 h at 52,5°C) young bean plants. The temperature sensitivity of each parameter studied was defined by that temperature at which chloroplast activity decreased by 50% (T50) of its maximum value. There was appreciable increase in the thermostability of membrane energization in chloroplasts isolated from acclimated and non-acclimated plants compared with the controls. The photosynthetic parameters differed according to the suspending medium and the preacclimation treatment. When chloroplast were suspended in phosphate buffer with the addition of stabilizing compounds (2 M sucrose or 0.5% human serum albumin) the thermostability of the thylakoid membranes increased, as was evident by the increases in T50 of about 8-10° C (sucrose) and 2-5° C (human serum albumin) for all the parameters investigated. Photoinduced quenching of 9-aminoacridine fluorescence decreased to some extent in the presence of protective compounds, but in chloroplasts from acclimated plants the T50 was practically equal to that for their long-lived luminescence under the same conditions. At the thylakoid membrane level, acclimation was clearly manifested as an increased thermostability of photoinduced proton-gradient formation.

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Effects of pH and deuterium oxide on the heat-inactivation temperature of chloroplasts

Cited by 6 publications

References 15 publications

Elevated Temperature Stress Effects on Photosystems: Characterization and evaluation of the nature of heat induced impairments

Elevated Temperature Stress Effects on Photosystems: Characterization and evaluation of the nature of heat induced impairments

Protection of photosynthetic O2 evolution against heat inactivation: the role of chloride, pH and coupling status

High-temperature damage and acclimation of the photosynthetic apparatus

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