Dark starvation and plant metabolism : II. CO2 fixation in isolated chloroplasts.

The fixation pattern of radioactive labelled photosynthetic intermediates was followed under steady state conditions during prolonged dark starvation of spinach plants (Spinacia oleracea L.). It is suggested that the considerable increase of radioactive dihydroxyacetonephosphate is correlated with a specific leakage of the outer chloroplast envelope induced by dark starvation. The primary fixation product, phosphoglyceric acid, followed the same decreasing tendency as observed for the net CO2 fixation. In contrast, the relative label in other intermediates is the same as in the controls. When after several days of dark starvation the plants were again transferred into light, a regeneration of the CO2 fixation accompanied by the appearance of a normal fixation pattern was observed. Since the regeneration was prevented by the addition of lincomycin, the net increase is considered to be due to a new protein synthesis rather than a reactivation.