Embryo dormancy in subterranean clover seeds. II. Its value relative to impermeability in field germination regulation

Abstract

Less than 20% of the viable seeds of three subterranean clover cultivars survived exposure to typical summer field environments in the absence of protection from embryo dormancy and impermeability. The survival rate of seeds was no higher when protected by embryo dormancy only. By contrast, when the seeds were protected by both embryo dormancy and impermeability the survival rate of viable seeds was 70% or higher. It is concluded that fully mature dry seeds of subterranean clover receive little protection from embryo dormancy during the summer, although the mechanism may well be important in preventing germination during the late seed maturation period. It is suggested that in breeding and selection programmes impermeability should receive priority as a germination-regulating mechanism.