丛枝菌根对桑树雌雄植株邻间关系的影响机制

Arbuscular mycorrhiza plays an important role in plant growth and development, mineral nutrition and water metabolism. However, the knowledge about the effects of arbuscular mycorrhizal fungi on the relationship between plants is still limited, especially between two sexes in dioecious plants. To explore the effects of arbuscular mycorrhiza on the neighbor interactions between male and female individuals, mulberry (Morus alba) is selected as a model tree in our study. During the experiment, nitrogen absorption, morphological characteristcs, gas exchange, mineral nutrition, phytohormones levels, as well as the root exudates of male and female plants, which subjected to three neighbor interactions (female vs female, male vs male and female vs male), would be investigated by using the method of 15N labeling and inoculating with an arbuscular mycorrhizal fungi. Our aims are (1) to detemine different effects on root exudates between male and femlae plants caused by arbuscular mycorrhiza, (2) to investigate the variations of utilization and transfer of nitrogen caused by arbuscular mycorrhiza, and (3) to explore the important role of arbuscular mycorrhiza acts on neighbor interactions in dioecious plant. Our study may contribute to broadening the research scale of neighbor interactions between different plants, providing new evidences for studing sex-related adaptive ability between the sexes, and developing a scientific technology for regulating neighbor interactions of trees in the plantation and silviculture.

丛枝菌根对植物的生长发育、矿质营养和水分代谢等具有重要的作用，但有关其改变植株邻间关系的研究极少，尤其是雌雄异株植物的两性个体间。我们以桑树为研究对象，采用接种丛枝菌根真菌和氮稳定性同位素标记方法相结合的方法，对桑树雌雄植株在3种不同邻间关系（雌-雌、雄-雄、雌-雄）下的氮素吸收、形态发育、气体交换、元素含量、激素水平和根系分泌物组成进行比较分析。验证丛枝菌根对雌雄植株根系分泌物产生的不同影响，探究接种丛枝菌根真菌后雌雄植株间氮素利用方式和转移途径的变化，阐明丛枝菌根在雌雄植株邻间关系中的重要作用。研究结果可以完善植物间相互作用的研究内容，进一步为揭示雌雄植株间的适应差异提供证据，同时也为林业生产中植株的邻间关系调节的提供理论参考。

本项目以桑树为研究对象，采用接种丛枝菌根真菌和氮稳定性同位素标记方法相结合的方法，对桑树雌雄植株在3种不同邻间关系（雌-雌、雄-雄、雌-雄）下的氮素吸收、形态发育、气体交换、元素含量、激素水平和根系分泌物组成进行比较分析。通过研究发现：1）相邻植株的性别影响了雌雄桑树根系解剖结构和形态。同时，雌雄植株对相邻植株性别改变的响应呈现性别二态性，这种二态性响应影响了雌雄植株水分利用效率和营养吸收。2) 接种AMF显著提高了3种性别合栽模式植物的总叶面积和总叶片数、生物量、气体交换、叶绿素含量和侵染率。侵染率的增加更有利于异性合栽模式的桑树光合能力的增加，并促进地上部分生物量的积累。3) 接种AMF显著促进了雌雄桑树的生长，并影响了雌雄植株间氮素转移的方向和力度。当雌株为N供体时，接种AMF降低了氮素向雌性邻株的转移量，而显著增加了向雄性邻株的转移量。4）接种丛枝菌根真菌对桑树根系分泌物成分有显著影响。接种AMF后，雌株和雄株的根系分泌物的种类表现出不同变化，反映了桑树植株对AMF共生的性别差异。5) 低氮环境显著降低了雌株向雄株的氮转移量、氮转移率和%NDFT，同时异性合种之间的%NDFT显著低于同性合栽，而雌雄株之间的双向氮素转移没有显著性差异。上述研究结果将完善植物间相互作用的研究内容，进一步为揭示雌雄植株间的适应差异提供证据，同时也为林业生产中植株的邻间关系调节的提供理论参考。