THOMAS, T.H., National Vegetable Research Station, Wellesbourne, Warwick, CV35 9EF, United Kingdom
PALEVITCH, D., National Vegetable Research Station, Wellesbourne, Warwick, CV35 9EF, United Kingdom
BIDDINGTON, N.L., National Vegetable Research Station, Wellesbourne, Warwick, CV35 9EF, United Kingdom
AUSTIN, R.B., National Vegetable Research Station, Wellesbourne, Warwick, CV35 9EF, United Kingdom

Seeds of five celery (Apium graveolens L.) cultivars germinated at 15°C in the light or dark but at 22°C only in the light. This light requirement was overcome by treatment with a mixture of the gibberellins GA4 and GA7 (GA4/7) but interactions of cytokinins, daminozide, ethephon, EDTA and N‐phenyl‐N′‐4‐pyridylurea (NC5392) with GA4/7 were observed. Varietal differences in response to GA4/7 concentration and the requirement for cytokinins were related to the upper temperature limits for germination of the different cultivars. Seeds of cultivars responding to low concentrations of GA4/7 appeared to contain less natural inhibitor than those requiring either high concentrations of GA4/7 or cytokinin in addition to low GA4/7. The cytokinin requirement for germination was partially removed by leaching the seeds with water. Interaction studies with applied hormones indicated that in seeds incubated in the light inhibition by abscisic acid was partially alleviated by N6‐benzyladenine but not by GA4/7 application. The implications of these results are discussed in relation to the involvement of natural plant hormones in the dormancy mechanism of celery seeds. Copyright © 1975, Wiley Blackwell. All rights reserved