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On the relationship between the millisecond delayed light emission and licalized proton in chloroplast at different temperatures

Ren Huimiao, Wei Jiamian, Shen Yungang

Shanghi Institute of Plant Physiology,The Chinese Academy of Sciences.Shanghai 200032

Abstract

The Effects of nigericin and valinomycin on the fast phase of millisecond delayed light emission (ms-DLE) in chloroplast and the stimulation of photophosphorylation (PSP) by low concentrations of nigercin were investigated at different temperatures. The relationship between ms-DLE and PSP was also studied at low and room temperatures. The fast phase of ms-DLE decreased with increase of temperature in the range of 0-25℃, but only slightly above 8℃. At a low temperature of 0-1℃, the fast phase of ms-DLE was decreased significantly by nigericin(0.5μmol/L) or valinomycin (0.2μmol/L) and almost completely when both compounds were present. The fast phase of ms-DLE was not or only slightly affected by the same concentration of nigericin, but was almost completely demolished by the same concentration of valinomycin at 25℃. The proceeding of PSP decreased both the fast phase and slow phase of ms-DLE at 0-1℃, while the slow phase only at 25℃. Furthermore, PSP was stimulated by low concentrations of nigericin to a larger extent at 0-1℃ than at 25℃. It is suggested that at lower temperaturesthe protons from water oxidation are more likely to be localized on the thylakoid membranes. PSP can utilize the localizd protons from water oxidation in the millisecond range, which results in a decrease of the fastphase of ms-DLE. The localized proton from water oxidation may shift to thebulk phase to be delocalized protons with an increase of temperature, thereby the fast phase of ms-DLE is affected mainly by the membrane electric potentials and the effect of protons from water oxidation on the fast phase almost disapears at 25℃. When the chloroplast preparation stored in liquid nitrogen was used, the difference between the ms-DLE at different temperatures was not observed any more althrough the PSP activity remained the same as with fresh chloroplast preparation. This fact indicates that whether the protons from water oxidation are localized on the thylakoid membrane is highly dependent on the conditions of chloroplast membrane.

Key words: Chloroplast;Millisecond delayed light emission;Fast phase;Photophosphorylation;Localizedproton;Nigericin

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Citing This Article：

Ren Huimiao, Wei Jiamian, Shen Yungang. On the relationship between the millisecond delayed light emission and licalized proton in chloroplast at different temperatures. Acta Physiol Sin 1996; 48 (3): (in Chinese with English abstract).