Role of the Hull in the Ripening of Rice Plant : VI. Translocation of carbohydrates into fertile and sterile grains

[摘要] The distribution of 14C in panicles assimilated through leaves and stems at heading stage was investigated in plants with completely and partially sterile panicles, with focusing on hulls of grains. The results are as follows. 1. Photosynthetic activity was much lower in hulls than in rachis and rachis-branches. 2. In the completely sterile panicles, 14C translocated from the grains on the lower branches to those on upper branches, and from the grains in the lowest position to those in highest position on the same branches. When all the grains became sterile and kernels were not formed, 14C assimilated through leaves and stems translocated and accumulated from the grains in the lowest position to those in the highest position. These results suggest strongly that the translocation of carbohydrates proceeds through the gradient of sugars4) content in the plant organs. 3. On the other hand, impartially sterile panicles, there was a great difference in the ammount of 14C translocated from leaves and stems to the hulls between sterile and fertile grains. Namely, in hulls of fertile grains 14C amount increased rapidly one day after flowering (i.e. the day after 14C assimilation treatment) and there was a peak in the amount of 14C in hulls (9490 dpm/grain) 4 days after flowering. Thereafter the value was almost constant until 17 days after flowering, and then it decreased. In contrast, in the hulls of sterile grains the amount of 14C translocated was much smaller, with a peak (2684 dpm/grain) one day after flowering. Thereafter 14C flowed out of the hulls. 4. In fertile grains, at the very early stage of ripening when the development of kernel was very small, 14C translocated much more in hulls than in kernels. From these results, it was concluded that the hulls of fertile grains absorb carbohydrates much more actively than those of sterile grains after flowering, that this function takes place through fertilization, and that hulls play an important role in pooling the carbohydrates to be translocated into kernels at the very early stages of ripening.

[学科分类] 农业科学（综合）