Growth Regulators and the Phytochrome‐Mediated Dormancy of Celery Seeds

Abstract

Abstract 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 GA 4 and GA 7 (GA 4/7 ) but interactions of cytokinins, daminozide, ethephon, EDTA and N‐phenyl‐N′‐4‐pyridylurea (NC5392) with GA 4/7 were observed. Varietal differences in response to GA 4/7 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 GA 4/7 appeared to contain less natural inhibitor than those requiring either high concentrations of GA 4/7 or cytokinin in addition to low GA 4/7 . 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 N 6 ‐benzyladenine but not by GA 4/7 application. The implications of these results are discussed in relation to the involvement of natural plant hormones in the dormancy mechanism of celery seeds.