Department of Agronomy, Purdue University, West Lafayette, Indiana 47907.
Plant Physiol. 1976 Apr;57(4):560-3. doi: 10.1104/pp.57.4.560.
Net photosynthetic rate, CO(2) compensation concentration, and starch and soluble sugar concentrations were measured in soybean (Glycine max [L.] Merrill) leaves in an attempt to evaluate the effect of carbohydrate concentration on rate of CO(2) assimilation.Plants were grown in a controlled environment room at 23.5 C, 50% relative humidity, 16-hour photoperiod, and quantum flux (400-700 nm) of 510 mueinsteins/m(2).sec (30,090 lux) at plant level. On the 21st day after seeding, plants were subjected for 12.5 hours to one of three CO(2) concentrations (50, 300, or 2000 mul/l) in an attempt to alter leaf carbohydrate levels. Following the CO(2) treatment, gas exchange measurements were made at a CO(2) concentration of 300 mul/l on the lowermost trifoliolate leaf. Immediately after measurement, the leaf was removed and stored at -20 C until carbohydrate analyses were performed.Increasing the CO(2) concentration for 12.5 hours significantly increased leaf starch concentration but not soluble sugar concentration. There was a strong negative correlation between net photosynthetic rate and starch concentration. Net photosynthetic rate declined from approximately 38 to 22 mg CO(2)/dm(2) leaf area.hr as starch concentration increased from 0.5 to 3 mg/cm(2) leaf area. Carbohydrate concentrations had no effect on compensation concentration.The decrease in net photosynthetic rate as starch concentration increased resulted from an increase in mesophyll (liquid phase) CO(2) diffusion resistance. This suggests that starch accumulation may reduce net photosynthetic rate by impeding intracellular CO(2) transport.
测定了大豆（Glycine max [L.] Merrill）叶片的净光合速率、CO2 补偿浓度以及淀粉和可溶性糖浓度，以评估碳水化合物浓度对 CO2 同化速率的影响。在 23.5°C、50%相对湿度、16 小时光周期和量子通量（400-700nm）为 510 μeinsteins/m²·sec（30,090lux）的控制环境室内种植植物。在播种后的第 21 天，将植物暴露于三种 CO2 浓度（50、300 或 2000μl/l）中的一种 12.5 小时，以改变叶片碳水化合物水平。在 CO2 处理后，在 CO2 浓度为 300μl/l 的条件下对最底层三叶复叶进行气体交换测量。测量后立即将叶片取出并储存在-20°C，直到进行碳水化合物分析。将 CO2 浓度增加 12.5 小时可显著增加叶片淀粉浓度，但不会增加可溶性糖浓度。净光合速率与淀粉浓度之间存在强烈的负相关关系。随着淀粉浓度从 0.5 增加到 3mg/cm²叶片面积，净光合速率从约 38 下降到 22mg CO2/dm²叶片面积·小时。碳水化合物浓度对补偿浓度没有影响。随着淀粉浓度的增加，净光合速率的下降是由于叶肉（液相）CO2 扩散阻力的增加所致。这表明淀粉积累可能通过阻碍细胞内 CO2 运输来降低净光合速率。
