Sinapis alba, a Plant requiring a Single Long Day or a Single Short Day for Flowering

Abstract

Sinapis alba (white mustard) will flower only in a regime of long days and short nights when the temperature is kept at 20° C, the relative humidity is 80% and illumination is provided by fluorescent white light (Phytor C.R.H.Lg. tubes) providing an intensity of 22,000 to 28,000 ergs cm⁻² s⁻¹ at the top of the plants¹. In these conditions, 65 day old plants subjected from sowing to 8 h days (0830 h to 1630 h) can be induced to flower by exposure to a single long day beginning at 0830 h¹. The longer the photoperiod, the more complete is flower induction, with a maximal response after 18 h; in photoperiods shorter than 10 h flowering does not occur.