Analysis of products formed inChlorella vulgaris11 h cells during photosynthesis in air containing 3,000 ppm14CO2at various temperatures revealed that the level of14C-starch was maximum around 20–24°C and decreased with further rise in temperature until 40°C, while14C-sucrose greatly increased at temperatures above about 28°C. Elevating the temperature from 20 to 38°C during photosynthetic14CO2fixation resulted in a remarkable decrease in14C in starch and a concomitant increase in14C in sucrose. This conversion of starch to sucrose when shifting the temperature from 20 to 38°C proceeded even in the dark. Hydrolysis of sucrose by rβ-fructosidase showed that, irrespective of the experimental conditions, the radioactivities in sucrose were equally distributed between glucose and fructose. The enhancement of starch degradation with temperature rise was more remarkable than that of the activity of ribulose bisphosphate carboxylase from the same cells. WhenChlorellacells which had been preloaded with14C-starch after photosynthesis for 30 min at 20°C were incubated in the dark for an additional 30 min at 20°C,14C-starch was degraded by only about 4%. However, the values after 30-min dark incubation at 28, 32, 36 and 40°C were increased by about 10, 19, 36 and 50%, respectively. During the temperature-dependent conversion of starch to sucrose, no significant amount of radioactivity accumulated in free glucose a
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