Increased CO_2 fixation by Pisum sativum chloroplasts in vitro reflecting a change in coupling caused by illuminating the plants

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Illumination of pea plants caused a doubling in the rate of CO_2 fixation by the subsequently isolated chloroplasts compared with the rate obtained for chloroplasts from plants in the dark. This enhancement in the CO_2 fixation rate was half-maximal for 800 lux incident on the plants and was 90% Iight saturated at 2000 lux. The half-time for the enhancement of the CO_2 fixation rate following illumination of the plants was about 4 min and the half-time for its reversal when the plants were placed back in the dark was 5 min. Illuminating the plants had relatively little effect on the 02 evolution rate of the subsequently isolated chloroplasts. Moreover, the ferricyanide reduction rate by the isolated chloroplasts was also essentially unaffected by the illumination condition of the plants from which the chloroplasts were isolated. Consequently, ligllt on the plant apparently causes a doubling in the CO_2 fixed per electron moving in the photosynthetic electron transport pathway. This enhanced coupling is discussed in terms of a concomitant increase in endogenous photophosphorylation and flattening of the chloroplasts in vivo, other changes caused by light incident on the plant.
日本植物生理学会の論文