On the Activities of the Leaf and Root of Tobacco Plants Grown at Different Solution Temperatures

Abstract

To make clear the metabolic changes which are concerened with the promortion of growth by the rise of soil temperature, following experiments were carried out. Tobacco plants for the experiment were grown for two weeks in the culture solution of a high (35°C) and a low (15°C) temperature, respectively. Within the limits of these temperatures the physhiological responses of the plant to nutrient uptake and translocation ascend, as a rule, in accord with the rise of solution temperature. Air temperature was kept at 15°C in the day-time and at l0°C at night under the artificial light condition. Physiological activities both in the leaf and root were examined in reference to the 14°C metabolism. The results obtained were as follows : 1. The growth of seedlings grown at the low solution temperature, was far less than that grown at the high solution temperature, on account of low chlorophyll content and low photo-synthetic rate. 2. The root grown at the low solution temperature was thicker and had more secondary roots in comparison with that grown at the high solution temperature. 3. As to the activities, as expressed by P uptake and CO2 exhaust from C-organic acids, the apical part of roots was higher than the basal part, being common to both solution temperatures. The activities of the root grown at high solution temperature exceeded those of the root grown at the low one, when the activities were examined by keeping it at each temperature to which the root had been exposed. It might be stressed, however, that the root grown at the low solution temperature revealed high activities, in case both kinds of roots were kept at the same temperature (30°C). Thus it was suggested that the root grown at the low solution temperature of the culture solution, was supressed in spite of their having high physiologiclal capacity. 4. Toknow the metabolism of photosynthates, C distribution was traced 6 hours after one hour's feeding. The C uptake by the leaf and its translocation into the root was higher in the same plant. 5. With respect to sugar metabolism, the contents of sugar, especially glucose and fructose in the leaf and root of plants grown at the high solution temperature were less, and the C specific activities were also lower. These facts showed that at the high solution temperature the metabolism of sugar as accelerated both in the leaf and root, and hence the C incorporation into cationic frabtion and ethanol insoluble fraction became larger. 6. From the facts that in the root grown at the high solution temperature, the sugar content, C specific activity and resbiration rate were lower, and adversely the peroxidase activity was higher, as compared with that grown at the low solution temperature, it was inferred that the decrement and aging of the root might be accelerated by high temperature around it.