Journal of the Japanese Society for Horticultural Science
Online ISSN : 1880-358X
Print ISSN : 0013-7626
ISSN-L : 0013-7626
Studies on Thermal Conditions of Curd Formation and Development in Cauliflower and Broccoli
II. Effects of Diurnal Variation of Temperature on Curd Formation
Yukihiro FUJIMETadahiko HIROSE
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1980 Volume 49 Issue 2 Pages 217-227

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Abstract

Effects of diurnal variation of temperature on the curd formation of′Nozaki-wase′ cauliflower and′Wase-midori′broccoli were investigated in temperature-controlled conditions, using platns with the 7th or 8th unfolded leaf.
1. The plants were grown for 35 days at various temperatures in the 1st period of a day (8 hours from 9:00a.m. to 5:00p.m. ) and at 10°C in the 2nd period of a day (16 hours from 5:00p.m. to 9:00a.m.). Curds of cauliflower were formed when the plants were grown at 15° and 20°C in the 1st period, but not when grown at 10°, 25° and 30°C. The number of nodes to the curd was larger at 20°C than at 15°C. Flower heads of broccoli were formed when the plants were grown at 15°, 20°, 25° and 30°C in the 1st period, and the number of nodes to the flower head was larger as the temperature increased.
2. Curds were formed on cauliflower plants, when the plants were grown for 45 days at 10° and 15°C in the 2nd period (15 hours from 5:30p.m. to 8:30a.m.) in combination with the temperatures of 15° and 20°C in the 1st period, but not when grown in combination with the temperatures of 25° and 30°C in the 1st period. Flower heads were formed on broccoli plants, when the plants were grown for 45 days at 20°C in the 2nd period in combination with the temperatures of 15° and 20°C in the 1st period, but not when grown in combination with the temperatures of 25° and 30°C in the 1st period.
3. Curds were not formed on cauliflower plants when they were grown for 6 weeks at 25°C in the 1st period (12 hours from 7:00a.m. to 7:00p.m.) in combination with the temperatures of 15° and 25°C in the 2nd period. The plants of cauliflower grown at 15°C in the 2nd period for 6 weeks formed curds earlier than those grown at 25°C in the 2nd period when they were exposed to natural outdoor temperatures.
4. The plants of cauliflower were kept for 10 weeks at 25°C in the 1st period (12 hours from 7:00a.m. to 7:00p.m. ) and at 15° and 25°C in the 2nd period. Both the plants grown at 15° and 25°C in the 2nd period did not form curds by the 7th week. Plants grown at 15°C in the 2nd period eventually formed curds in the 10th week.
5. From these results, it is deduced that the stimulus of low temperature given in a certain period of a day is reduced but not nullified by subsequent high temperature in a day under the condition with diurnal temperature variations. And the plants form curds when the stimulus of low temperature is accumulated day by day and reaches a certain level.

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