The effects of temperature and 'night-break' lighting on the development of glasshouse celery.

Daylit, controlled environment cabinets were used in an experiment to investigate the developmental responses of November-sown celery to three temperatures (10, 14 and 18°C) combined factorily with two daylength regimes (natural days or natural days plus night-break lighting). At 10°C flower initiation and ‘bolting’ occurred eventually in both daylength treatments, whereas plants grown at 18° remained vegetative. At 14°C some plants initiated and developed an inflorescence while others remained vegetative to the end of the experiment. It appeared that the average critical temperature for vernalization in celery (at least in cv. Celebrity) is about 14°C. Vegetative growth was generally more vigorous with increasing temperature, but fewer side-shoots developed when the temperature was too high for flower initiation. Night-break lighting produced plants with a more erect habit, a lower total left number, longer leaves (petiole + lamina) and fewer side- shoots. Developmental responses were only modifed by day...