内生真菌与禾本科植物的共生机制研究进展

本文从物种的起源进化、生理学、化学生态学等角度阐述了内生真菌与禾本科植物的共生机制。此类共生体起源于植物致病真菌的一个分支，即生活史具有高度可塑性的有性型Epichloё属真菌经过种间杂交、失去有性生殖能力后的Neotyphodium属真菌与禾本科植物形成了专一性、互利共生程度更高的共生形式。Neotyphodium真菌获得了宿主植物更有效的保护和传播，同时产生更多的生物碱，使得植物抗性增加，竞争能力更强；内生真菌可作为一种生物异源物质在植物内部诱导某种胁迫预警机制，使得植物在环境胁迫来临时更快、更有效的进行气孔调节、渗透调节，同时真菌释放的激素和生物碱可保持植物较高的水分利用效率、维持根系生长以及保证植物的生长不受影响。长期来看，内生真菌-禾草共生体将改变土壤的营养元素水平，降低植物群落的生物多样性，改变食草动物的取食行为，进而影响食物链的能量流动和食物网结构，进而对生态系统产生不可低估的作用。

A study on mechanism of grass-endophytes symbiosis

The purpose of this article is to discuss the mutualistic mechanism of grass/endophyte. Studies on Epichloe species and the asexual anamorphicNeotyphodium species indicates that life histories of Epicbloe species have higher plasticity and Neotypbodium species derived from interspecific hybridization of Epichloe species and consequently evolving higher specifity symbiosis. The symbionts have a series of physiological adaptive characters such as enhanced drought tolerance （osmotic adjustment.）, induction of plant hormone and endophyt-deriving alkaloids. Benefits of the endophytes are efficient protection by plant and vertical transmission via host seeds. Endophyte enhance water use efficiency, growth and productivity of plant. Endophyte, meanwhile, as a xenobiotie component of a grass, may induce a permanent internal stress in the host grass. This may precondition or sensitize the plant to drought and other stresses. Alkaloids protect host plants against herbivores, insects, nematodes and other pathogenic fungi. The symbionts may change soil nutriment level in a long time and can alter competitive interactions with other plants, reducing biodiversity in ecosystems.