Embryo dormancy in subterranean clover seeds. I. Environmental control

Abstract

Embryo dormancy in seeds of subterranean clover (Trifolium subterraneum) is at a maximum at field maturity in the spring. High summer temperatures are the causative agent in the subsequent breakdown of embryo dormancy, the germination inhibitors in the seeds apparently being susceptible to heat. There is no evidence for germination inhibitors in the pod and burr material, nor is there any evidence to support the hypothesis of an environmentally imposed dormancy, for germination is relatively fast at 15 ? 25¦C, a temperature regime equivalent to the daily temperature change of summer moist soil. There are differences between cultivars in the initial level of embryo dormancy and in the subsequent rate of breakdown.