接木

It has been proved by us that water ascent from stocks to scions occurs in grafts of Chamaecyparis obtusa, pine trees and Taxodiaceae, even immediately after grafting. Nonetheless, it is generally thought that water ascent does not occur until the unions may be made. For this reason, in order to clarify the mechanism about water ascent into scions and investigate the time-course translocation of photo-assimilate from scions to stocks, grafts of Chamaecyparis obtusa were used with the following new methods for tracing the movement of water and substances; use of shadowing chemical substance (Urokolin-M) applied to plants and taking photograph by radiation of super soft x-ray, and use of ^32P and ^14C. (1) On the water ascent from stocks soon after grafting: In the experiments 1-3a, it is inferred that water ascent from stocks occurs, not because each vascullar bundle of scions and stocks would be contacted closely enough to let water pass through the grafted parts, but scions, which have the strong absorbing power for water, may uptake the surplus water like bleeding fluid. Consequently, when the transpiration from stock leaves is increased and the negative pressure may become high in stems, water movement from stocks does not occur theoretically. In the experiment 3b, the experiment was made by setting two blocks; one of them, the leaves of stocks were exposed to a continuous light and, the other, each stock was covered in a black bag exposing only the scion to the light. Plants with roots removed were installed to the apparatus in order to give root pressure. The results obtained were very much in agreement with the theoretical discussion as mentioned above. That is, it was difficult for scions to absorb the water when the light was given to the leaves of stocks increasing the transpiration. But it was possible to absorb the water when the light was shut off with bags. As a result of x^2 test, this light effect was significant at 5% level. (2) On the translocation of photo-assimilate from scions: Scions of grafted plants were permitted to photo-assimilate ^14CO_2 for 14.5 hours at intervals of 2-7 days after grafting until 39 days, and the rates of the subsequent distribution of ^14C from scions to stocks were determined. Until 18 days after grafting, the rates were fairly low compared with the controls. However, it was recognized that photo-assimilate did move into stocks soon after grafting (0.10-0.17%). After 18 days, the translocation rates were increased and on the 39th day a plant translocated photo assimilate as normally as controls (26% vs. about 25%). Although the callus formation and union were observed with every individual and the final success was over 90%, some individuals remained to show low export rates. The results suggest that even after unions between parenchymatous tissue had been formed, the exchange of substances remained limited until the unions of phloem might occur.