燃烧植物产生烟与热的生理生态效应

燃烧植物产生的烟与热对植物的生理生态功能有重要的影响，相关研究已成为生态学研究的热点之一。植物源烟对一些植物种子的萌发和幼苗生长有促进作用，这种促进作用与GA和细胞分裂素的作用相似。在植物烟水溶液中分离得到了具有促进植物种子萌发作用的化合物丁烯羟酸内酯，该物质具有热稳定性、挥发性和有效浓度范围广等特点。丁烯羟酸内酯可以通过纤维素加热产生，因而几乎所有的植物燃烧产生的烟中都可以产生丁烯羟酸内酯。热因子对植物种子萌发有利作用表现为打破种子休眠、清除限制种子萌发的物理、化学因素和减轻种子病原体等方面。大量研究显示，不同植物对烟与热的响应机理存在显著的差异，这是植物群落过火后物种组成改变的重要原因之一。烟与热因子对植物生理生态作用的研究我国开展较少．这与我国是一个森林、草原火灾频繁的国家是不相称的，加强这方面的研究很有必要。另外，今后我国可以在烟与热因子对植物作用的机理，揭示传统用烟火处理土壤促进农林业植物生长的物理和化学本质，以及这些机理在发展有机农业中运用等方面开展深入的研究。

Ecophysiological effects of plant-derived smoke and heat on plants

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-furo2,3-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 from 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.