The germination of watercress (Rorippa nasturtium- aquaticum) seeds. II. The relationship between seed colour and germination

Abstract

SummaryFreshly-harvested seeds of green watercress were pale yellow, rapidly turning to pale brown under ambient laboratory conditions. Older seeds ranged from pale to very dark brown, the darker seeds losing more electrolyte than the pale ones when immersed in water. Dark seeds germinated more readily than pale ones when the seeds were freshly harvested, but with old seeds germination was generally greater with paler seeds than darker ones. The results suggested that darkening of the seed coat was associated initially with a loss in dormancy and ultimately a loss in viability. Darkening of the seeds was enhanced by moisture. It could be induced by high humidity storage at 40°C, a treatment which resulted in increased electrolyte leakage from the seeds, or by holding individual seeds dormant at 35°C, although only the former treatment reduced germination. The results suggest that the ability of the seeds to germinate and the colour of the seed coat are not directly linked but that both are influenced by RH and temperature during storage.