Flower opening in Asiatic lily is a rapid process controlled by dark-light cycling

In commerce, Asiatic lilies are picked in bud, each stem holding several buds. We found flower opening was rapid, taking less than 4 h both on the stem and for excised buds. Opening was also strongly synchronous. For a 12 h day-night cycle, opening began late in the dark period, reaching a mid-point after 11 h of darkness. This was equally true of buds that were excised when nearly ready to open, and those with 3-4 d of development to complete. Reversing day and night reversed the time of opening, and red light was as effective as white light in providing 'day' conditions. A 15 min light break during the night did not affect the opening. Lengthening the night (8, 12, 16 h) and shortening the day delayed opening from 9, to 11, to 13 h after the start of darkness, respectively. In continuous light and continuous dark, synchronicity was lost. If opening flowers were held in extended darkness, two phases of opening could be discriminated. In a 'dark phase', petals opened to approx. 40 degrees, and anthers remained intact. When such flowers were returned to light, there was a 'light phase', where petals opened further, became more pigmented and began to recurve, and the anthers dehisced. these events taking only 2-3 h. The net result was that flowers became fully open and anthers dehisced approx. 2 h after dawn, regardless of daylength. (C) 2000 Annals of Botany Company.