Testing the influence of night length on the anthesis of staminate flowers of Halophila engelmannii aschers. (Hydrocharitaceae)

Abstract

Staminate flowers of Halophila engelmannii Aschers. Studied under varied night lengths had the same pattern of bud opening. During nights of either 4 1/2 or 6 h duration, the staminate flowers opened and released pollen during a 9 1/2-h light period that extended from the commencement of light at 06:00 h until mid-afternoon, 15:30 h. Flowers that had not opened by 15:30 h and that were subsequently monitored in light from 15:30 h until the time of darkness at either 24:00 or 01:30 h did not reach anthesis until the following light period. Although a previous study using 9-h nights had indicated that night length was a possible determinant of the timing of anthesis, the present study suggests that bud opening is initiated by the onset of light and that subsequently buds continue to open during a 9 1/2-h period.