Germination of four species of native western Australian plants using plant-derived smoke

Plant-derived smoke was investigated in this study as a pre-germination tre atment for seed of four native plant species from south-western Western Aus tralia. Many Australian native species demonstrate low germination response s using conventional nursery propagation methods. Smoke water, prepared fro m burning 6 kg of fresh and dry foliage of Eucalyptus, Adenanthos and Banks ia species and bubbling the smoke through water (20 L) for 1 h was found to substantially improve germination of Stylidium affine Sender., Stylidium b runonianum Benth. (Stylidiaceae) and Conostylis setigera R.Br. (Haemodorace ae), whereas Actinotus leucocephalus Benth. (Apiaceae) retained a high leve l of dormancy despite prolonged exposure to smoke water. Diluted and full s trength smoke water was found to significantly increase germination of S. b runonianum, C. setigera and A. leucocephalus over water alone. Seeds retain ed the smoke cue after imbibition in smoke water, whether incubated continu ously with smoke water or imbibed in smoke water and dehydrated or dehydrat ed, stored for 3 weeks. Species varied in their germination response to cha nges in imbibing time in diluted smoke water. A. leucocephalus required lon ger periods of smoke water imbibition (24-48 h) to elevate germination irre spective of the three treatments following imbibition. All imbibition perio ds were effective in enhancing germinability of S, affine and S. brunonianu m regardless of subsequent treatments. However, S. affine required shorter imbibition exposure times (3-12 h) for optimal germination for the dehydrat ed and stored treated seeds. C. setigera required shorter exposure to smoke water of 3 and 6 h, when germinated immediately, whereas longer exposure t o smoke water was necessary for effective germination in dehydrated (24-48 h) and dehydrated and stored (48 h) treated seeds. The site of action of smoke water in seed was investigated and found to res ide in part in the seed coat in S. affine, and the embryo and/or endosperm in A. leucocephalus. The smoke chemical(s) overcame multiple dormancy mecha nisms in S. affine and A. leucocephalus whereas gibberellic acid (GA) and z eatin were unable to break dormancy. Mechanism of dormancy relief by smoke water was not the same as GA and zeatin. These data indicate that there are good prospects using imbibition with smoke water as a pre-treatment for se eds in the horticulture and land restoration activities.