Biophysical studies on subcellular particles V. Effects of temperature on the ferricyanide-Hill reaction, the light-induced pH shift and the light scattering response of isolated spinach chloroplasts

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Effects of temperature on the ferricyanide-Hill reaction, the light-induced pH shift (ΔpH) and the light scattering response (ΔLS) of isolated spinach chloroplasts were studied at temperatures ranging from 5 to 60℃. Activities which produce ΔpH and ΔLS under actinic illumination decreased with a rise in the reaction temperature above 30℃ and disappeared at 50℃. The ferricyanide-Hill reaction at pH 6.0 was stimulated by raising the reaction temperature from 5 to 35℃, was slowed at higher temperatures and was inactivated at 50℃. ΔLS activity at temperatures below 20℃ depended on the activity of electron transport. With a rise in temperature of a suspension of chloroplasts which exhibited ΔLS under actinic illumination, the scattering intensity decreased. The decrease in scat-tering intensity was limited, at most, to an extent equal to ΔLS. The behavior of ΔLS which differed from that of basal scattering is discussed in connection with a mechanism of ΔLS formation other than the shrinkage-swelling cycle. Then activities were measured at 25℃ with chloroplasts warmed transiently (2 min) at various temperatures (25-60℃), the dependence of ΔLS on the warming temperature was identical with that on the reaction temperature, while the activities of both ferri-cyanide reduction and ΔpH formation were higher than those measured at the corresponding reaction temperature. This suggested that the mechanism for ΔLS formation could be irreversibly altered by a warming treatment and that it was less stable against heat than the mechanisms of ferricyanide photoreduction and ΔpH formation. That is, transiently warmed chloroplasts showed a similar behavior to alkane-treated chloroplasts. The similarity is discussed in relation to the activity change through the possible and common cause of disordering of the organized structures of lipophilic components in the lamellar membranes.
日本植物生理学会の論文

Biophysical studies on subcellular particles V. Effects of temperature on the ferricyanide-Hill reaction, the light-induced pH shift and the light scattering response of isolated spinach chloroplasts

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