Pre- and post-harvest influences on physiological dormancy alleviation of an Australian Asteraceae species: Actinobole uliginosum (A.Gray) H.Eichler

The effects of maternal air temperature and soil moisture upon seed physiological dormancy (PD) alleviation of an Australian native Asteraceae were investigated. From the onset of flowering, Actinobole uliginosum plants growing ex situ were subjected to either a warm (mean 26 degrees C) or cool (mean 17 degrees C) temperature regime, with adequate or limited water availability. In the warm environment, the reproductive phase was accelerated, and plants yielded fewer seeds over a shorter, earlier harvest period, when compared to those in the cool environment. Initial germination of all seeds was low (< 20% at 15 degrees C) due to PD, which was gradually alleviated by a dry after-ripening (DAR) treatment (34/20 degrees C, 40% relative humidity, in darkness). Seeds from plants grown in the warm environment were more responsive to DAR than seeds from the cool environment, but maternal plant water availability had little effect on dormancy status. Germination was higher at 15 C than at 25/15 degrees C, reaching a plateau of c. 80% germination after 20 weeks DAR. Before DAR, application of GA(3) had little impact on seeds, which would consequently be classified as having deep PD if tested at the time of dispersal. However, DAR caused seeds to become increasingly responsive to GA(3), reaching 97% germination at 15 C following just 4 weeks of DAR, which would indicate non-deep PD if seeds were tested following a period of warm, dry storage. Maternal air temperature regulates PD status of A. uliginosum, such that seeds collected from a warmer environment are likely to be more responsive to DAR. Post-harvest storage in an environment suitable for DAR affects seed response to GA(3), which has implications for germination stimulation and dormancy classification