通过剪除部分颖花和部分功能叶片以及~(14)CO_2标记光合产物等处理,探讨了亚种组合结实率偏低的生理原因。结果证明:光合产物供给水平是制约亚种组合结实率的一个十分重要的因素。虽然亚种组合的叶面积指数和单株叶面积比常规籼稻大得多,但由于每穗颖花数多。以至每朵颖花占有的叶面积并无明显优势,且其光合速率低于常规籼稻,因而分配给每朵颖花的光合产物量相对减少,限制了部分颖花的发育。~(14)C光合产物分配到穗部的比率不但不低于常规籼稻,而且比其略高,说明亚种组合输导组织的运输能力不是结实率偏低的限制因素。 By cutting off some of the spikelets and some functional leaves and ~ (14) CO_2 labeled photosynthetic products and other treatments, we discussed the physiological reasons for the low seed setting rate of subspecies. The results showed that the supply level of photosynthate was a very important factor to restrict the seed setting rate of subspecies. Although the leaf area index and leaf area per plant of the subspecies are much larger than that of conventional indica rice, the number of spikes per spike is large. As a result, the leaf area occupied by each spikelet had no obvious advantage and its photosynthetic rate was lower than that of conventional indica rice. Therefore, the amount of photosynthate allocated to each spikelet was relatively reduced, which limited the development of some spikelets. The ratio of ~ (14) C photosynthate to spike was not only not lower than that of conventional indica rice, but slightly higher than that of conventional indica rice, indicating that transport ability of subspecies combination guide tissue was not the limiting factor of low seed setting rate.