Studies on the Cover-Culture of Tobacco : 2. The analysis of growth changing the durations and the materials of the cover

[摘要] Recently a large number of tobacco planters in our country make it a rule to cover the seedlings transplanted in the field with polyethylene film or melamine coated paper for several weeks, because the coverings are thought to protect tobacco from the frost and to accelerate the growth on the early period. It seems to promise excellent quality and quantity of yield, but it is not always superior. The essential cause of this fact is that the response of growth to the environmental conditions, especially temperature, affected with those coverings has not yet been made clear. This paper deals with the growth of tobacco under the cover-culture in the natural field, and the following results are obtained. (1) The growth of tobacco is dependent upon temperature affected under the coverings, and accelerated by its increase up to a certain level. At the higher temperature over it the growth is retarded by contraries. This tendency is the same to that on the rate of leaf initiation reported in our previous paper. (2) The age of leaves is influenced indirectly by temperature on the early period. Tobacco accelerated growth makes their leaves mature faster, than that grown under low temperature, but tobacco encounterd higher temperature over an optimum, as it produces many leaves and requires too many days for flower-bud initiation and blooming, delays the maturity of leaves. (3) In the duration from transplantation to the blooming, the ratio of the dry matter weight of each organ to the total is scarcely changed with temperature. This suggests that the response in growth to temperature is not localized in a particular organ but under the high temperature, the total weight per leaf area is reduced. It is thought that it is an adaption to keep the balance between production and consumption of photosynthetic products.

[学科分类] 农业科学（综合）