水、钙胁迫下外生菌根调控樟子松钙吸收的效应和机制研究

Water shortage and soil calcium heterogeneity (high calcium / low calcium) are the main characteristics of the natural environment in semi-arid areas of North China. Calcium, as a tree growth stress factor, also plays a key role in plant adaptation to drought stress. Ectomycorrhiza can have an influence on the uptake of calcium, but its effect and mechanisms of regulating the calcium uptake of trees under different water and calcium conditions is have not been identified. This project intends to take Pinus sylvestris var. Mongolica as the research object, which is the main afforestation tree species in semi-arid areas, (1) investigate the influence of ectomycorrhiza on calcium uptake and the growth of Pinus sylvestris var. mongolica under different water and calcium gradients, to expound the regulating effect of ectomycorrhizal plants on the absorption of calcium through. (2) Study the responses of mycorrhizal mycelium biomass, exogenous calcium activated and calcium transport capacity to different water and calcium conditions, in order to explore the mechanism in which ectomycorrhiza regulates the calcium uptake. This study can improve the understanding of environmental adaptability of plantation growth in semi-arid areas, and provide theoretical guidance for the plantation construction and management in the studied area.

缺水和土壤钙异质性（高钙/低钙）是我国北方半干旱区自然环境的主要特点，其中钙在成为树木生长胁迫因子的同时，在植物适应干旱胁迫过程中发挥核心调控的作用。外生菌根具有影响钙吸收的能力，但在不同水、钙条件下外生菌根调控树木钙吸收的效应和机制尚不明确。本项目拟以半干旱区主要造林树种樟子松为研究对象，（1）通过研究在不同水分和钙梯度下，外生菌根对樟子松钙吸收的调控作用及对生长的影响，阐明外生菌根对植物钙吸收的调控效应；（2）研究外生菌根菌丝生物量、钙活化能力以及钙运移量，对不同水、钙条件的响应，探索其对钙吸收的调控机制。本研究可完善对半干旱区人工林生长的环境适应性问题的理解，为科学指导该区域人工林建设和经营提供理论支撑。

钙在干旱胁迫适应中起着核心调控作用，但同时过量钙又会影响植物光合和磷代谢。外生菌根（EM）在植物适应干旱胁迫过程中发挥重要调控，但不同水、钙条件下EM调控树木钙吸收的效应尚不明确。本项目通过盆栽模拟控制试验发现，干旱降低土壤钙有效性并减少植株钙吸收，而EM能够显著活化土壤钙、促进钙吸收并提高水分利用效率，表明在低钙土和正常钙土壤中，EM活化土壤钙并促进钙吸收是EM提高树木抗旱性的重要机制。在高钙土中，钙能够显著抑制光合产生的非结构性碳向根和茎中运输，从而加重树木在干旱条件下的碳负平衡。EM能够调节非结构性碳的分配，但是不同菌根菌株对树木碳平衡的调节效果不同。我们通过根系分隔试验进一步探讨EM调控树木适应不同钙环境的机理。我们发现低钙和中钙土中，菌丝拓展空间显著增加根、茎、叶钙吸收量，表明菌丝能够帮助树木吸收钙。高钙土中，菌丝则通过提高菌根侵染率并提高植株磷和钾的吸收量，促进植株生长。