This study investigated the effects of the growth chamber temperature on the germination and growth of Eustoma grandiflorum after the wet treatment of seeds at 10°C. When the dark-period temperature was 18°C, the germination rates for seeds under light-period temperatures of 22.5 and 25°C were slower than those under a light-period temperature of 30°C. The final germination rate for seeds with a light period at 35°C was significantly lower than those under the other conditions. With the light period at 32.5°C, the numbers of days to bolting, flower budding, and flowering were significantly higher than those at 27.5 or 30°C. When the dark-period temperature was 18°C, the rate and percentage of germination with a light-period temperature of 27.5°C were the same or lower than with a light period temperature at 30°C; however, when the dark-period temperature was set at 26°C, the rate and percentage of germination improved and were the same as with light/dark-period temperatures of 30/18°C. The leaf blade lengths of transplanted seedlings that had received light/dark-period temperatures of 27.5/26°C were significantly longer than those that had received light/dark-period temperatures of 30/18°C. Moreover, the numbers of days to bolting, flower budding, and flowering were significantly lower than in those with light/dark-period temperatures of 30/18°C. When the average temperature was 27.5°C, the germination rate was independent of the light/dark-period temperature under the four different conditions. However, the leaf blade lengths of the third true leaf at 32/14°C were shorter than those receiving the other three treatments. The leaf blade lengths of transplanted seedlings at 30/20°C were the same as those for 28/26°C and 27.5/27.5°C; however, the numbers of days to bolting, flower budding, and flowering at 30/20°C were significantly higher than those at 28/26°C or 27.5/27.5°C. We judged that the optimal light/dark-period temperature for producing Eustoma grandiflorum seedlings in the growth chamber was a constant 27.5°C, since changing the light/dark-period temperature requires complicated control.
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