SENSITIVITY OF PHOTOSYNTHESIS TO OXYGEN AT LOW-TEMPERATURES IN SOYBEAN LEAF - EFFECT OF GROWTH TEMPERATURE

Sensitivity of photosynthesis to oxygen at low temperatures was investigated in leaves of soybean (Glycine max (L.) Merr.) plants grown at 15, 20, 25, and 30-degrees-C. Leaves expanded at 15-degrees-C showed a sensitivity of photosynthesis to oxygen at low temperatures while those expanded at high temperatures lost the sensitivity. Labelling pattern of the photosynthates produced from (CO2)-C-14 at 17.5-degrees-C showed that the photorespiratory metabolism at a low temperature proceeded in the same way in leaves expanded at 25-degrees-C and at 15-degrees-C. Leaves expanded at low temperatures relative to those at high temperatures contained a larger amount of inorganic phosphate, indicating that the leaf inorganic phosphate status is more favorable for photosynthesis at low temperatures in leaves grown under cold than warm conditions.