Physiological studies on the tobacco seeding : IV. Growth responses of tobacco seeding to differential soil and air temperature

Abstract

l) By applying high temperature H (20°∼30°C) and low temperature L (5°∼20°C) to the aerial and root portions respectively, four plots (H/H, H/L, L/H, L/L) were provided in order to study the effect of temperature upon the nature of tobacco seedling only for twenty days at the end of seed-ded period. 2) At high air temperature (H/H and H/L), the plants showed elongated appearance, while the highest dry weights of top and root were obtained at high root temperature (H/H and L/H). There was scarcely striking difference in final number of leaves among them. 3) Some chemical analysis indicated that carbohydrate content was highest at L/H, and that above all starch accumulation was remarkably high and reversely total nitrogen content was very low in that Plot. The H/H plants came next to this. In general, high root temperature showed high carbohydrate content. 4) Comparing their rooting ability, L/H was highest, H/H was next to it, and H/L and L/L were lower. This suggests that the above facts had close relation to high carbohydrate content and high dry weights of top and root. 5) It seems that root temperature is an important factor to obtain good tobacco seedlings suitable for transplanting.