Dormancy and Germination in Five Native Grass Species From Savannah Woodland Communities of the Northern Territory

Abstract

The dormancy and germination requirements of five native grass species (Themeda australis, Chrysopogon fallax, C. latifolius, Sorghum plumosum, S. stipoideum) from the savannah woodlands of the Northern Territory were studied under controlled conditions. Results were related to the ecology of these species in the native grasslands of the region. All species were dormant at seed fall, and dormancy was found to be broken by exposure to dry heat. Gibberellic acid was also found to have a stimulatory effect on germination of dormant seed but there was no effect on stratification. In the field, temperatures existent at the soil surface during the dry season ensure that dormancy was broken before the heavy rainfall of the following wet season. Seeds of all species studied germinated over a similar range of temperatures with optimum germination at high temperature (c. 30°C). Although seeds of all species were not adapted to germina- tion under moisture stress, the existence of sharply pointed calluses and hygroscopically active awns on the seeds ensured that they would be buried below the moisture extremes of the immediate soil surface.