不同盐渍和光热条件下胡杨水盐吸收转运的过程和机理

Populus euphratica has been widely used to restore saline land for many years in the arid Northwestern China. The afforestation by P. euphratica has profoundly influenced the distribution and movement of water and salt in local soil. Pot-investigation on the planted forest of P. euphratica in different conditions (salt, water, temperature and air humidity) will be proceeded to clarify the influence on soil water/salt distribution patter in saline region by P. euphratica afforestation. Also, the growth of P. euphratica is always accompanying with high light (or high temperature in some region), therefore the light and temperature not only influence the movement of water and salt in the soil, but also modify the salt tolerance in the P. euphratica. The plants of P. euphratica will be treated by different salt treatment under controlled condition, accompanying by different light and temperature condition. We would analyse the physiological process of water/salt movement, water transpiration and salt accumulation characteristics, salt distribution in the organ, tissue, cellular and subcellular levels. The cooperation function of different transmembrane and aquadrin proteins will be also analysed, as well as the photosynthesis and antioxidation processes. The proposal aims to clarify the functions of light/temperature on the process and mechanism of absorption and translocation of water/salt, and aims to reveal the survival mechanism of P. euphratica under salt and high light stresses. This investigation is helpful for the afforestation by P. euphratica and the restoration of saline region.

胡杨在西北干旱地区用于盐碱地治理已经有几十年的时间，胡杨造林深刻影响了盐渍地水盐分布和运动，本项目通过不同生境条件（盐分、水分和温度）下人工胡杨林的定点调查，旨在明确胡杨造林对盐渍地土壤/植被（胡杨）水盐分布格局的影响。另一方面，干旱区盐碱地的胡杨在生长期内总是伴随着强光影响（部分还遭受高温影响）；因此光热条件不仅影响到盐渍地水盐运动过程，而且对胡杨的抗盐性可能起着重要调控作用；本项目拟采用控制实验方法，将胡杨置于不同光照强度或者温度下进行不同水平的盐胁迫处理，分析胡杨水分盐分转运的生理过程、水分耗散和积盐特征、盐分在器官组织亚细胞水平的分配、各种跨膜转运蛋白和水孔蛋白对水盐转运的协同驱动作用、光合生产和抗氧化机制，明确不同光热和盐渍条件下胡杨水盐吸收转运的过程和机理，揭示胡杨在盐渍和光热条件下的生存机制；研究结果对于胡杨造林、盐碱地修复和生态重建都具有指导意义。

本项目采用野外调查试验和控制实验相结合的方法，研究不同光热、盐分条件对胡杨水盐转运的影响。样地调查发现干旱导致胡杨林顶部/上部枝条叶片干枯脱落；盐分则导致下部枝条出现干枯死亡现象，随盐分加重向低矮灌木方向演变和柽柳\芦苇方向演替；较低生长温度下的胡杨林其叶片加厚明显。样地胡杨林叶片维持了良好的离子和营养平衡。胡杨林叶片Na+与叶片相对含水量RWC成显著正相关，显示Na+提高了其叶片肉质化程度；但是RWC、Na+、Mg2+、N/P比值与叶片含碳量C%成显著负相关，显示盐分仍然影响了胡杨固碳功能和碳氮平衡。控制试验表明胡杨根系有较强的排盐或阻盐吸收功能；胡杨叶片能将Na+离子高效地区隔在液泡内或者质膜外。胡杨能较好地保持Na+/K+离子平衡。弱光照改善了盐敏感树种及中等抗性树种的生长和耐盐能力，对胡杨则有相反作用；对于前者，遮阴阻遏了盐分运输、通过叶黄素/谷胱甘肽循环的提升对光合作用/光化学功能提供了保护，并降低了单位叶面积负担；但是对于胡杨没有发现这些作用，反而使胡杨的合成/消耗平衡严重破坏；我们研究发现胡杨作为一种光补偿点和光饱和点很高的植物也具有很强的耐受高温能力。