根部の環境条件が甘藷塊根の形成におよぼす影響

抄録

To make clear the influence of environmental conditions on tuberous roots formation of sweet potato, roots were divided into the part of nutrient absorption and the part of tuberous root formation as shown in Fig. 1 and various environmental conditions, such as temperature (high and low), aeration (aerobic pearlite and non-aerobic pearlite by filled up with water) and light (roots were exposured to sunlight and roots were intercepted from light by black cover), were given only to the part of tuberous root formation. The results obtained may be summarized as follows: 1. The aerobic condition was more favorable for tuber formation than the other favorable conditions, i. e. low temperature, high temperature and non-exposure. The non-aerobic condition and the exposure to sunlight were unfavorable for tuber formation. 2. The meristematic activity of primary cambium was high and degree of lignification of stele cells was small in the roots cultured under the favorable conditions, while the contrary phenomena were observed in the unfavorable conditions. These results were in almost agreement with those of Togari, except the fact that cambium activity of the roots under the low temperature condition rather decreased compared with that under the high temperature one. 3. The concentrations of N, P₂O₅, K₂O and reducing sugar in the roots on 23 days from planting were lower under the aerobic or the high temperature than those cultured under the non-aerobic or the low temperature condition, though the concentration of starch was higher under the former. It was conceivable that cell division and starch synthesis in roots were remarkably feeble under the non-aerobic condition and the exposure to sunlight. 4. High positive correlations were recognized between the respiratory rate and the concentrations of three major nutrient elements and reducing sugar in roots on 23 days from planting, while starch showed negative correlation to respiratory rate throughout various environmental conditions except the non-aerobic condition. Moreover, it was noticed that the effects of dinitrophenol and monoiodoacetic acid on the respiration of roots under the non-aerobic condition differed from those under the other conditions. 5. There was the intimate relation between net assimilation rate and dry-weight of tuber throughout all experimental conditions. It is assumed that tuber bulking has beneficial effect on the net assimilation rate.