Germination of the Salt-Tolerant Grass Diplachne fusca. I. Dormancy and Temperature Responses

Abstract

The germination of the salt-tolerant grass Diplachne fusca (L.) Beauv. was investigated because of its potential as a pasture species to be used in the reclamation of salt-affected land. Fresh seed was dor- mant. Dormancy was not broken by stratification, but gradually broke down during air-dry storage, indicating an after-ripening period of at least 1 year. The germination of germinable stored seeds at various temperature regimes (combinations of day and night temperatures between 11 and 31°C) was assessed on a thermogradient plate. The germination after 21 days was greatest at high temperatures (40-90% when both day and night temperatures were between 24 and 31°C, either constant or alter- nating). Germination was completely inhibited when both day and night temperatures were 5 18.5°C. Germination percentage was more strongly correlated with night than with day temperature. Seeds for which dormancy had been broken by scarification were capable of germinating at lower temperatures (19% germination at 11°C) than stored seeds. From the observed temperature dependence of germination and the mean daily maximum and minimum temperatures recorded at Tatura and Deniliquin (latitudes 36° 26̸2S. and 35° 32̸2S. respectively), it is expected that germination in the field, in the Riverine Plain of south-eastern Australia, would be limited to the summer months (December-February).