EFFECT OF PHOTOPERIOD AND LIGHT INTENSITY ON BOLTING AND FLOWERING IN CELERY

Expriments under controlled environments were carried out to examine the responses of celery cv. New Dwarf White to photoperiod and light intensity, during and following vernalization, on the flowering process. Photoperiods of 8 and 16 .h during vernalization at 5^(degree)ffect on bolting and flowering. Short photoperiods (8 h) after vaenalization markedly decreased the proportion of plants bolting and flowering in young mature plants. Light intensity in the range of 6 to 85 Wm^-2 (PAR) at plant height during chilling (5^degreeC) had no effect on vernalization. After vernalization a reduction in mean daily irradiance from 1.57 to 4.05 MJ m^-2 d^-1 had no effect on bolting and flowering. Exposing competent plants to darkness just prior to chilling resulted in a highly significant delay in bolting and reduced the number of flowering plants (P<0.001). Two days of darkness had no significant influence, but 4 and 8 days of darkness at 20 C caused a very significant inhibition of bolting and flowering (P<0.001). The in plants chilled for 6 weeks than those chilled for 9 weeks, effectiveness of dark -treatments prior to vernalization was greater in plants chilled for 6 weeks than those chilled for 9 weeks.