Smoke plays an intriguing role in promoting the germination of seeds of many species following a fire. Recently, a bicyclic compound containing a condensed butenolide moiety, 3-methyl-2H-furo [2,3-c]pyran-2-one (1), was reported as a potent germination promoter from plant-derived smoke. In this study, a related butenolide, 3,4,5-trimethylfuran-2(5H)-one (2), which inhibits germination and significantly reduces the effect of 1 when applied simultaneously, was also isolated from plant-derived smoke. The interaction of these compounds with opposing actions on seed germination may have important ecological implications in a post-fire environment and could be useful molecules for understanding the events involved in breaking seed dormancy and promoting seed germination.Smoke from burning vegetation is recognized as an important environmental cue and promoter of germination for seeds of many species from both fire-prone and non-fire-prone environments.(1) Smoke-water, prepared by bubbling smoke through a container of water, is also highly effective in promoting seed germination of the responsive species and is a more convenient method of treatment. The major germination compound responsible for the observed germination increase was isolated and identified as 3-methyl-2H-furo[2,3-c]pyran-2-one (1, karrikinolide),(2, 3) a discovery that has revealed a class of plant bioactive compounds that are referred to as karrikins(4) and are proposed to be a new and important family of naturally occurring plant growth regulators.(5, 6) Subsequently, 1 has been shown to improve germination and improve seedling vigor of several species, including those from fire-prone environments, arable and parasitic weeds, several Australian Solanum species, and crop plants.(5) Due to the fact that it has an effect at extremely low concentrations (as low as 1 nM), it has potential as an important agronomic and horticultural chemical.(5, 7) Although the mode of action of smoke and 1 (and related karrikins) in promoting germination and vigor is currently unknown, research is progressing in this field. (4,8,9) Previous investigations of smoke-stimulated seed germination demonstrated that dilute solutions of smoke-water were highly effective in promoting the germination of light-sensitive seeds of Lactuca sativa L. cv. Grand Rapids.Thus, Grand Rapids lettuce was used as an effective model species for bioactivity-guided fractionation of smoke-water.(3, 10) Although, in general, smoke provides a positive stimulus for germination, a negative effect of high concentrations of smoke-water on germination is well demonstrated.(10-13) This effect can most likely be attributed to inhibitory compounds (i.e., compounds other than the promotory karrikins) that are present in the smoke-water. Smoke (from cigarettes or other products) is known to contain numerous compounds (estimated to be well over 4000),(14) some of which are toxic or carcinogenic. In another study, it was reported that smoke could possibly play a dual regulatory role during germination,(1...
