Influence of 2 degC increase under controlled air temperature on physiological fruit drop in Citrus
2010
Sato, K., National Inst. of Fruit Tree Science, Minamishimabara, Nagasaki (Japan). Kuchinotsu Citrus Research Station | Okuda, H. | Iwasaki, M. | Yonemoto, Y. | Fukamachi, H. | Takahara, T.
We studied the influence of a 2degC increase in air temperature on physiological fruit drop in Citrus using a growth chamber for two months after full bloom. One room of the growth chamber was maintained at the standard temperature (control), while the other was maintained at 2degC higher than the control (+2degC treatment). The average temperature was changed every ten days. In 'Okitsu wase', 'Ishiji', 'Shirakawa' Satsuma mandarin (Citrus unshiu Marcow.), and 'Shiranui' [(Citrus unshiu Marcow. x C. sinensis Osbeck) x C. reticulate Blanco], physiological fruit drop occurred more intensively in +2degC treatment than in the control after 10-20 days of full bloom. At the end of the experimental period, the physiological fruit drop ratio in plants receiving +2degC treatment was higher (5%) than that in controls for 'Okitsu wase' and 'Ishiji'. In 'Miyagawa wase' and 'Sasebo unshiu' Satsuma mandarin, in which number of fruit was controlled by artificial fruit thinning, physiological fruit drop also occurred more intensively in plants receiving +2degC treatment than in controls after 10-20 days of full bloom. Especially in 'Sasebo unshiu' at the end of the experimental period, the difference in the physiological fruit drop ratio between plants receiving +2degC treatment and controls was larger (26%) than that in 'Miyagawa wase'. In 'Miyagawa wase' and 'Sasebo unshiu' fruit diameter of plants receiving +2degC treatment was larger than that of controls. These findings suggested that with acceleration of fruit enlargement, and physiological fruit drop were both promoted by a 2degC increase in air temperature after full bloom.
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