Stimulation of Germination of Quandong (Santalum acuminatum) and Other Australian Native Plant Seeds

Abstract

Intact seeds of quandong (Santalum acuminatum), Ixodia achillaeoides, Ptilotus exaltatus, Codonocaupus pyramidalis and Exocarpos aphyllus which are normally difficult to germinate responded to vacuum infiltration with gibberellins. In most cases GA₄ was far more effective than GA₃. Cytokinins, ethylene and silver ions did not affect quandong germination but abscisic acid (ABA) was inhibitory. If imbibed quandong seeds were subject to a rapid drying and re-wetting cycle, subsequent germination was inhibited. This transient drying was associated with a rise in endogenous ABA and the effect of the drying could be overcome by gibberellin. There was no correlation between ABA level and state of dormancy in recently imbibed seed suggesting that ABA was not necessary for the maintenance of dormancy. These results suggest that the mechanisms controlling quandong seed germination are hormonally based although the mechanical constraints imposed by the rigid shell may also be important.