Abstract
The purpose of this study is to clarify the interrelationship between the translocation of 14C-photo-synthate and 14CO2 exposed leaf positions on the grafts of Ipomoea. Four combinations of grafts were brought about by grafting the stocks and scions of improved variety Okinawa No. 100 (I. batatas Poiret) upon the kindred wild type plant (I. trifida (H.B.K.) Don.) T-15 clone. The third or the thirtieth leaf blade counting from the top was exposed to 14CO2 for thirty minutes in August, 1973. The sample materials were harvested in the lapse of twenty four hours after 14CO2 exposure. (1) In case of 0-100/0-100 (scion/stock) graft, the dry matter distribution ratio to the underground organ at the time of treatment reached a maximum. In cases of 0-100/T-15 graft and T-15/0-100 graft, the ratios reduced to a medium, in case of T-15/T-15 graft, the ratios reduced to a minimum. (2) In case where the third leaf blade was exposed to 14CO2, and where the scions used as samples were of the same types, the volume of the 14C-photosynthate translocated from the third leaf blade on the grafts of Okinawa No. 100 stock was larger than that on the grafts of T-15 stocks. The rate of 14C-photosynthate translocated to each organ varied with scion type, i.e., in case of Okinawa No. 100 scion grafts, the rate was high in the organs lower in position than the third leaf blade as well as in the underground organs. While in base of T-15 scion grafts, the rate was high in the parts of organs higher in position than third leaf blade. (3) In case where the thirtieth leaf blade was exposed to 14CO2, the gross activity of the 14C-photosynthate translocated from the thirtieth leaf blade was almost alike in every graft, excepting T-15/T-15 grafts. The high translocation rate of 14C-photosynthate was found in the parts of stems lower in position than the treated leaf on the grafts of T-15 scion, while in the underground organs in case of grafts of Okinawa No. 100 scions. (4) From the above mentioned results, the following facts may be pointed out: 1) 14C-photosynthate translocated from the treated leaf blade to the sinks is liable to be affected remarkably by the combinations of leaf blade positions and the graft types. 2) In case of grafts of T-15 scions, 14C-photosynthate of upper leaf blade is translocated mainly upward, while those of lower leaf blade mainly downward. 3) In case of grafts of Okinawa No. 100 scions, the 14C-photosynthates are apt to be translocated to the underground organs, irrespective of the fact that either the upper leaf blade or lower one is exposed to 14CO2.
