ウリ科植物の接ぎ木活着機構に関する研究

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From the experiments which were performed in order to observe the histological developmental states of the scions and stocks in grafting among the various species and varieties of Cucurbitaceae, the following results were obtained. (1) A number of practical experiments on the grafting among those mentioned above showed that the scions, when the cotyledons unfolded entirely (leaf age 1.0) in the watermelon (Citrullus vulgaris) or the first leaf half unfolded (leaf age 1.5) in the oriental melon (Cucumis Melo var. Makuwa,) could be most successfully united with the stocks. On the other hand, the squash and pumpkin (Cucurbita maxima, C. moschata and C. pepo) and the calabash (Lagenaria leucantha), which were used as the stocks, so with the scions, when the first leaves unfolded from half to entirety (leaf age 2.0), respectively. (2) Though the basic number of the longitudinal vascular bundles in the hypocotyl of Cucurbitaceae was six or ten, they were collected into two groupes just under the cotyledonary node, and took an annular appearance at the node. Then the bundles were again devided into ten in the epicotyl over the cotyledons. The bicollateral vascular bundle in the hypocotyl of Cucurbita spp. were often accompanied by the connective phloems. On several occasions, the interfascicular phloems, the intraxylary ones and the cortex ones were differentiated. (3) At the optimum stages for grafting, there were found the additional bundles and the anastomosis to have been deveboped between the longitudinal bundles in both scions and stocks. In some cases, besides the medullary bundles and the cortical bundles, some other abnormal vascular bundles were observed, for instance, conical bundles, cylindrical bundles, loop bundles and abnormally segmented bundle etc. (4) Although insert-grafting is more reasonable in the histological situation of both members after grfting and the economy of grafting labour, cleft-grafting, in fact, was more advantageous than that because the scions cleft-grafted, in general, grew more uniformly in contrast to those inserトgrafted. But the scions insert-grafted with very good skill were most vigorous throughout the growing period.(5) After grafting, in common, the calluses formedon thecut or injured surfaces of the stock and the scion made each of the wounds heal. They filled up the gap between the components of the graft to connect with each other, if their surfaces were not in complete contact. But in some cases where those were in complete contact, it was found that the intact parenchymatous cells on the cut surfaces of both members, without forming any callus tissue between them, directly adhered to each other to proliferate themselves. At last, blended into a tissue undistinguishable. The real union of the scion with the stock is achieved when the primordia of vascular strands which had been differentiated in both of them parallelly with the above-mentioned proliferation have developed into the combiniting vascular bundles between both members oJ the graft. (6) Some of the cells near the boundary of the graft were divided further excessively to be metamorphose into the linkage tissue which looked like strings, braids, or sticking things and caused the stok and the scion to connect more strongly, in which the cellmembranes showing such a devided appearance as the "dendrite" of a neuron were found. (7) Abreast with the abov-mentioned phenomena, in many cases, it was found that the followings developed as the compensative organs for the damage of grafting, namely, adventitious and latent buds from the stock and adventitous roots from the scion, as those were suppressing phenomena for the graft union. Especially, they were sprouted more abundantly in the case where the graft union did not go sufficiently. (8) It may be concluded that the grafted Cucurbitaceae are really united with each other through the following four stages. They are (1) contact stage of both members of the graft at their cut surfaces, (2) adhesion stage, in which both members have been really connected by the callus tissue or their own cells, but be able to distinguish the one tissue from the other, (3) fusion stage, where the tissue consisting in the cells multiplied excessively on the boundary of both components of the graft can not be distinguishable from each other, and (4) union stage, in which the longitudinal vascular bundles have been formed between the stock and the scion.

ウリ科植物の接ぎ木活着機構に関する研究

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