Abstract

Australian species germinate under the combination of environmental conditions where the potential for survival is enhanced. Most species also have dormancy mechanisms that prevent all seeds from germinating in any particular rainfall event. Immaturity of the embryo prevents some species from germinating until environmental parameters change to more favourable conditions. Seed-coat inhibitors may also delay germination, with some seed requiring ingestion and dispersal by animals or a series of rainfall cycles to facilitate germination. Adaptations to fire include germination mechanisms facilitated by impervious seed coats, seed-coat inhibitors and biochemical sensing of water-soluble components of smoke and the high soil nitrate levels found following the burning of vegetation. Germination is generally limited under saline soil conditions until rainfall dilutes concentrations to near-zero water potentials. Australian species tend to germinate under temperatures that approximate the rainfall season in their native habitat. Light sensing by Australian species ensures germination takes place only near the surface for some species or only under complete burial conditions in others. More recent research has emphasised the interaction of multiple and sequential cues to relieve dormancy and initiate germination. Knowledge of germination mechanisms provides a basis for better land management, enriched conservation, improved rehabilitation and advanced horticulture, forestry and farming practices.