Studies of the Effect of High Temperature on Growth and Developmental Response of Tobacco Plants : 1. Effect of various high temperatures on the flowering of tobacco plants

[摘要] Two varieties of flue cured tobacco plants (var. Bright Yellow and var. Hicks) were exposed to various high temperatures for 2 hours in daytime for 2 weeks. Plants were grown in the growth room maintained at 18°C in the experiment 1, and in the uncontrolled greenhouse in the experiment 2 during the treatments, respectively. Heat treatments were conducted in each growth chamber at temperatures of 18 (check), 33, 38, 43, 45 and 48°C respectively in the experiment 1, and of 26 (check), 48, 53 and 58°C in the experiment 2. After these treatments plants were transferred to greenhouse and grown to bloom. Total number of leaves and days to flowering increased with increasing temperatures. Plants of var. Hicks showed somewhat similar responses of flowering at the temperatures between 48 and 53°C. There were similar modal curves of the rate of leaf emergence in both varieties during the treatments. The rate increased with temperature up to about 33-38°C and declined at higher temperatures than 38°C. It was obtained that the rate of incresed total number of leaves per unit degree °C (an index of thermal sensitivity) increased with temperature up to about 38°C in var. Hicks and 45°C var. Bright Yellow, then declined at higher temperatures than those in both varieties. Thus, var. Hicks was less sensitive to thermal exposure than that of var. Bright Yellow. Another index of thermal sensitivity expressed on the rate of retarded days to flowering was increased with temperature at any plot of exposures in experiment 2. The area of the largest leaf at flowering stage was reduced with temperature in both varieties, specially, it was seriously decreased at the exposures to higher temperatures over 43°C. Plant height at flowering stage increased with temperature in both varieties, even in the 48°C plot. From this fact, together with the result of leaf area, it was suggested that the effects of high temperatures upon the growth of tobacco plants might be different between each organ of the plant.

[学科分类] 农业科学（综合）