抄録
The purpose of this study is to make clear the effects of sink on the translocation process of 14C-photosynthates from the leaves of several leaf plastochron indices (LPI) at different stages of development in Ipomoea grafts. 1. Two combination grafts were obtained by grafting the scion of improved variety (I. batatas POIRET var. Okinawa No. 100) on the stock of the wild type plant (I. trfida (H.B.K.) Don.·T-15) and the stock of Okinawa No. 100. 2. The leaves of LPI 4, 7, l2 and 19 in the respective grafts were exposed to 14CO2 gas for 30 minutes. The distinctions of leaves in each LPI were as follows: LPI 4, the leaves reached the beginning stage of rapid leaf expansion; LPI 7, the leaf areas were found about 65% of matured leaves; LPI 12 and 19, the leaves reached in full expansion stage. The plants were harvested in the lapse of 1 hour after the beginning of the exposure to 14CO2 gas. 3. In case where the leaves of LPI 4 were exposed to 14CO2 gas, 14C-photosynthates translocated slightly in upward and downward direction. In case of the leaves at LPI 7, downward translocation of 14C-photosynthates was more predominant in the grafts of Okinawa No. 100 stock than that in the grafts of T-15 stocks. On the other hand, the differences of upward translocation were not recognized between grafts. At LPI 12 leaves, downward translocation increased more than that of LPI 7 in the grafts of T-15 stocks. In case of the leaves at LPI 19, the differences of translocation pattern of 14C-photosynthates were not found between the grafts, and then the translocation of 14C-photosynthates was found predominantly in downward direction at both stock grafts. 4. From the above mentioned results, it may be considered that the translocations of 14C-photosynthatcs from the leaves of LPI 4 are not liable to be affected by the stock types, that those of the leaves at LPI 7 are apt to be affected remarkably in downward translocation by the stock type, and that those of the LPI 19 are not liable to be affected in upward and downward translocation by the stock types.
