Annals of Botany 82: 67-70, 1998
© 1998 Annals of Botany Company
Environmental Factors Controlling Flower Opening and Closing in aPortulacaHybrid
National Research Institute of Vegetables, Ornamental Plants and Tea, Ano, Mie, 514-2392, Japan
December 12, 1997 ; January 26, 1998 . March 26, 1998 .
To examine flower opening and closing of aPortulacahybrid, flower buds were placed in darkness for 12 h (2030–0830 h) at 20 °C and then exposed to various light-temperature conditions. Flower buds exposed to light at 25, 30 or 35 °C opened within 1 h, and wilted 10–14 h later. Flower buds exposed to light at 20 °C started to open after 4 h but opened slowly and not completely. Flower buds subjected to 25, 30 or 35 °C in darkness also opened rapidly, but did not reach full opening. Flowers opened at 30 °C in light, and partially closed and opened repeatedly in response to cycles of a 2-h exposure to 20 °C and a 2-h exposure to 30 °C at any time between 1000 to 1600 h. Similar phenomena were observed when the flowers opened at 30 °C in light and then were subjected to darkness and light alternately at 30 °C, although the effect of light was less obvious than that of alternating temperature. Flower opening and closing were not affected by relative humidity. These results indicate that a rise in temperature is required for rapid flower opening in the buds kept at 20 °C, and that light intensifies the effect of high temperature. Exposure to light without a temperature change delayed and slowed flower opening which was never complete. The involvement of an endogenous rhythm in flower opening byPortulacais indicated.
Portulacahybrid, flower opening, flower closing, temperature shift, endogenous rhythm.
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