The Vernalization and the Cotyledon of the Seedling

About the experiments on the effects of low temperature treatment with Japanese radish, race “minowase”. as the material, the following may be said:-1. The existence of cotyledons during the low temperature exposure was favorable for bolting and the order of the bolting percentage was, decreasingly, seeds with two cotyledons>those with one cotyledon>those without cotyledon; which, however, was sometimes varied under certain conditions controlling the vegetative development after the plantation of the plant.2. The presence of cotyledons during the growing period of the plant also brought about a rise in the bolting percentage. Generally speaking, the order was: materials with two cotyledons-with one-without. But also in this case disorder was sometimes seen under the influence of certain environmental conditions during the growth period of the plant.3. The portion susceptible to the effect of low temperature treatment was seemingly the plumule itself, and not the cotyledon.4. The cotyledon was supposed to play the role of a nutrition supplier in the course of vernalization.5. The soaking of the hypocotyl, from which cotyledons were removed, in a 2% or 5% glucose solution during the period of low temperature treatment or the application of a 70% glucose solution to the cut surface of the hypocotyl left by the removed cotyledon, once prior to and again in the middle of the low temperature treatment, gave a somewhat good percentage of bolting. Yet it does not follow that the external supply of glucose is absolutely necessary for vernalization of cotyledonless seedlings.6. A remarkable gap in the effect in relation to the duration of cold exposure, which causes bolting and flowering, was found between 14 days and 12 days. The same difference was also seen in the number of leaves up to the node of the primary flower stalk (primary pedicel).7. The material used in these experiments was vernalized with a 7-day period of low temperature treatment at the shortest, and with the prolongation of the period increased in the intensity of vernalization. But in this parallelism there seemed to exist a limit, and the maximum, so far as observed, was the 27-dey period.8. As to the number of leaf-primordia of the plumule of the seedling treated with low temperature, the material having cotyledons had more of them than the cotyledonless one. The writers are indebted to Ass. Prof. Y. Tajima of the Faculty of Agriculture, Kagoshima University, for his valuable suggestions in several courses of this study. The present work was supported in part by a grant out of the Fund for Scientific Research of the Ministry of Education.