Vol. 69 No: 5

Title:
Manipulation of Bolting and Flowering in Celery (Apium Graveolens L. var. Dulce). III. Effects of Photoperiod and Irradiance

Authors:
A.A. RAMIN and J.G. ATHERTON

pp: 861-868

Abstract:
Photoperiods of 8 and 16 h during chilling at 5°C had no effect on bolting and macroscopic flower appearance in celery cv. New Dwarf White. Eight hour photoperiods during chilling however markedly increased the number of plants forming sessile flowers. Short photoperiods (8 h) after chilling decreased the proportion of young, but competent plants that bolted and flowered. Total darkness during chilling completely prevented any subsequent vernalization response either as bolting or as flowering. Reducing irradiance receipt by the plants during chilling from 85 to W m^-2 (PAR) had no effect on their vernalization response. After chilling, a reduction in mean daily total irradiance in the glasshouse from 4.05 to 1.57 MJ m^-2 d-¹ had no effect on bolting and flowering. Confinement of competent plants to darkness for 4–8 d at 20°C just prior to chilling resulted in a highly significant delay (P<0.001) to bolting and reduced the number of plants flowering. Two days of darkness had no significant effect. The inhibitory effects of dark treatments prior to chilling was greater in plants chilled subsequently for six weeks than for nine weeks.

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