Smoke and heat are the simultaneous byproducts from the combusting plant materials, these byproducts of fire have a lot of physiological and ecological effects on seeds germination, seedling growth, flowering and other parts of plants that distribute near the fire fields. Many researchers reported that exposure of seeds to airborne smoke or crude smoke extracts stimulated the germination and seedling growth of a lot of fire-prone and fire-independent plant species in controlled and natural conditions in the world. Furthermore, the act of smoke or smoke extracts on plants seeds or seedlings revealed to be in a similar way to cytokinins, by enhancing gibberellin activity in plant seed system. The response of seeds to smoke was deduced in the signal-mediated mechanism.
A germination-promoting compound present in plant and cellulose-derived smoke was identified in the latest study. The structure of this compound was confirmed by spectroscopy and synthesis, all methods showed the compound was butenolide (3-methyl-2H-furo[2,3-c]pyran-2-one). The butenolide conforms to the ecological needs very well. For instance, the butenolide is water soluble, active at a wide range of concentrations, and a more high stability in heat condition. Particularly, the butenolide is derived from combustion of cellulose, which is the main component of nearly all plant, suggests any plant combustion could produce the butenolide.
The role of heat shock in stimulating the germination of soil-stored hard seeds and canopy-stored seeds from fire-following species is well known. Thus, various researches exploited the fire heat on postfire plants in the following ways: (1) a potentially elevated nutrient supply, especially for nitrogen and phosphorus, (2) an allelochemical-free germination site, (3) reduced rates of attack fr om herbivores, and (4) obviously decreased the pathogens. It was often ignored that the heat effect on seed, which produced with combusting. In fact, heat shock was a very important factor on breaking some dormant seeds.
Out of question, the heat shock and smoke were occurring simultaneously, seeds germinated post-fire were obviously affected by these both factors almost in the same period. However, there were few reports combining these two factors until recently, and showed that the interaction between smoke and heat shock may play an important role in alleviating dormancy in natural recruitment, the interactive effects of smoke and heat were most pronounced and resulted in germination in response to higher temperatures without smoke or, alternatively, lower temperatures enhanced germination with smoke. It varied significantly that different species of plant seeds and seedlings responded to heat shock and smoke in natural conditions, these differentiations came from these species adaptive abilities on fire.
Fire was frequent in China, but the fire associated by-products (smoke and heat) effects on plant ecological and physiological processing were not paid attentions at all. We suggested the following aspects of smoke and heat on plants in ecosystems should be further investigated: (1) mechanisms of smoke and heat on plants recovering around and in fire fields, (2) the chemical and physical nature of burned soil benefits on plant growths, which has been used in China for thousands years, and (3) more bioactive chemicals in smoke identifying and isolating.