Successful seed germination of the nickel hyperaccumulator Stackhousia tryonii

Background and Aims Stackhousia tryonii, a rare nickel hyperaccumulating herb, is endemic to ultramafic (serpentine) soils of central Queensland, Australia. The effects of eight dormancy-relieving treatments on germination of stored seeds of Stackhousia tryonii were investigated under controlled light and temperature conditions. Methods The treatments were: untreated (control i), leached and dehydrated (primed control ii), treating with gibberellic acid (150 and 300 uM), smoke extract (5 and 10 %, v/v) and potassium cyanide (40 and 80 mM). Key Results Freshly harvested seeds did not germinate. Germination percentage increased with time of storage for up to 18 months (38.3 %). Gibberellin, smoke extract and cyanide treatments did not significantly improve germination. Light did not affect seed germination and there was no interaction between dormancy-relieving treatments and light. A significant inhibition of germination occurred in seeds treated with 5 % (but not 10 %) aqueous smoke extract. Saturated fatty acids, predominantly tridecanoic (C13:0), constituted about 90 % of the total fatty acids in the oil of freshly harvested seeds. In contrast, there was increased accumulation (>75 %) of monounsaturated (oleic, C18:1) and poly-unsaturated (linoleic, C18:2; linolenic, C18:3) fatty acids in the oil of stored seeds. Conclusions Seeds of S. tryonii require an after-ripening period for germination.