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 treatment for seed of four native plant species from south-western Western Australia. Many Australian native species demonstrate low germination responses using conventional nursery propagation methods. Smoke water, prepared from burning 6 kg of fresh and dry foliage of Eucalyptus, Adenanthos and Banksia species and bubbling the smoke through water (20 L) for 1 h was found to substantially improve germination of Stylidium affine Sender., Stylidium brunonianum Benth. (Stylidiaceae) and Conostylis setigera R.Br. (Haemodoraceae), whereas Actinotus leucocephalus Benth. (Apiaceae) retained a high level of dormancy despite prolonged exposure to smoke water. Diluted and full strength smoke water was found to significantly increase germination of S. brunonianum, C. setigera and A. leucocephalus over water alone. Seeds retained the smoke cue after imbibition in smoke water, whether incubated continuously with smoke water or imbibed in smoke water and dehydrated or dehydrated, stored for 3 weeks. Species varied in their germination response to changes in imbibing time in diluted smoke water. A. leucocephalus required longer periods of smoke water imbibition (24-48 h) to elevate germination irrespective of the three treatments following imbibition. All imbibition periods were effective in enhancing germinability of S, affine and S. brunonianum regardless of subsequent treatments. However, S. affine required shorter imbibition exposure times (3-12 h) for optimal germination for the dehydrated and stored treated seeds. C. setigera required shorter exposure to smoke water of 3 and 6 h, when germinated immediately, whereas longer exposure to 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 reside 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 mechanisms in S. affine and A. leucocephalus whereas gibberellic acid (GA) and zeatin 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 seeds in the horticulture and land restoration activities.