Characteristics of light-induced 515-nm absorbance change in spinach chloroplasts at lower temperatures I. Participation of structural changes of thylakoid membranes in light-induced 515-nm absorbance change

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Light-induced absorbance change at 515 nm ill spinach chloroplasts was studied in the temperature range from -2℃ to 27℃. Lowering of temperature had no marked effect on the extents of initial "light-on" spike and the steady state change over the temperature range examined, whereas the rate of recovery of the 515-nm change. was significantly reduced at lower temperatures. Above 15℃, recovery of the 515-nm change after continuous illumination showed a first-order kinetics. In contrast, the recovery was composed of a fast and a slow phases at lower temperatures. The fast phase of the recovery of the 515-nm change was accelerated by carbonyl cyanide m-chlorophenylhydrazone, valinomycin plus K^+ or sodium tetraphelrylboron, while the slow phase was completely eliminated in glutaraldchyde-fixed chloroplasts. Light-induced change in absorbance at 546 nm, an indicator of structural changes of membrane, showed almost the same dependency on temperature as the slow phase of the recovery of the 515-nm change. These results suggest that not only electric field formation across the thylakoid membrane but also structural or conformational changes in the membrane participate in the 515-nm absorbance change observed under steady illumination.
日本植物生理学会の論文