On the Degree of Adaptability to Spring Planting in Rape Plant

[摘要] Although a number of interesting facts have been demonstrated in connexion with the adaptability to spring planting (the ability of plants to maintain normal growm even when the sowing has been postponed until spring) in cereals, in the case of the rape plant, room still seems to be left for further investigations. As in wheat and barley, there are various degrees of adaptability to spring planting in the rape plant acoording to its variety, the differences being closely related to physiologioal factors, such for example as susceptibility to winter cold, tendency to bolting in warm climates, etc., with the result that a clear understanding of these factors is essential for breeding as well as from the standpoint of culturing technique. Experiments for the purpose just mentioned were conducted in 1940 at the Konosu Farm of the Imperial Experiment Station, using 137 varieties of rape plant preserved by that station and 94 varieties that were recommended by the various prefectural stations throughout the country. The seeds were sown every tenth day during the period from Feburuary 24 to April 14, special precautions being taken to maintain uniform moisture in the soil through the period of experiment by means of timely application of water, and to keep the plants free from diseases and insects by, frequent spraying. The degrees of adaptability to spring planting determined by a method proposed by Prof. ENOMOTO (1929), the degrees being designated by notations O-VI, as shown schematically in the Table on page 405. The results are summarised as follows: 1. Variation in abaptability to spring planting according to variety. As shown in Table 4, which is derived from Table 2 nd 3, the variation is quite striking, there being a number of classes in degrees of this character. It will be seen that the defferences in plant character hitherto recognized as a spring or a winter tybe of growth hab t are only a part of fhese wide variartions. It will also be found that compared with wheat and barley, the rape varieties, as a wbole, are of rather low degrees in this chatacter. 2. Relation between the adaptability to spring planting and early maturation. The correlation of spring adaptability (Y), with the date of maturation (X), as shown in Table 5, is very close, its coefficient being 72 percent in 113 varieties, that is, the greater the adaptability to spring planting, the earlier its time of maturation, whence the latter may be a good, though not a conclusive, index of the former. 3. Relation between the spring adaptability and the plant form. As will be seen from Table 6, spring adaptability (Y) is also closely correlated with plant form (X), the latter being classified according to Dr. U (1931), that is, the higher the form index number, the less the adaptability to spring planting, consequently higher in winter adaptability. This correlation is, however, not so great, the coefficient being 73 percent. 4. Relation between spring adaptability and stalk elongation. In certain varieties of rape, the stalk elongates to a certain extent before bolting, while in others it remains relatively short. The correlation of this character with the adaptability to spring planting is shown in Table 7, from which however it is not possible to deduce any definite relation between these two characters. 5. Relation between spring adaptability and the number of days required for bolting after sowing. From Table 8, it will be seen that the lower the variety in adaptability to spring planting, the more fhe number of days from sowing time until bolting. On the other hand, among the varieties belonging to the same class as regards spring adaptability, the number of days required for bolting varies with the season when it is sown, that is, the later the sowing date, the less, at first, and more, afterwards the number of days in consideration. It was found moreover that the lower the adaptability of the variety to spring planting, the earlier the sowing time when t

[学科分类] 农业科学（综合）