Abstract
Half of soybean plants grown under a regime of 10h of light and 14h of darkness were placed in continuous light (CL) for 3 days. After the CL, the rate of photosynthetic CO2 fixation at 350 ppm in leaves (the fourth trifoliated leaves) of the plants (CL-plants) was about half that of control plants. Sucrose and starch contents in leaves were higher in CL-plants than in control plants. Intercellular CO2 concentration and the amounts of water, chlorophyll, soluble proteins and rubisco protein did not differ significantly between leaves of CL- and control plants. It was analyzed in leaf extracts that the activity of rubisco was lower and the amount of RuBP bound to rubisco was higher in CL-plants than in control plants. The difference in the rate of photosynthetic CO2 fixation between CL- and control plants decreased largely when the rate was determined at a high CO2 concentration.
