叶表盐分对荒漠泌盐植物水汽吸收的影响机制

Atmospheric water vapor absorbed by leaves or tender stems become important sources of water for the growth of plants or for drought avoidance by plants. Whether the salts secreted by the leaves of saline plants, which are widely distributed in northwest arid region of China, is beneficial to the absorption and utilization of atmospheric water have not been studied. In this project, we take three typical saline desert plants Tamarix ramosissima, Reaumuria soongorica, Haloxylon ammodendron as the subjects. The research work will be carried out to test the surface characteristics of leaves and to do multiple sets of atmospheric wetting experiments on the washed and unwashed leaves of the sample plants in different saline environments, and to monitor the process of atmospheric water from the adsorption on the leaf surface to the absorption into the mesophyll cells by the fluorescent tracer and the environmental scanning electron microscope (ESEM). Its purpose is to compare and analysis on the process and the characteristics of adsorbing and absorbing atmospheric water of salts (different composition, content and structure) on the leaves surface and to monitor the changes of leaf water potential and leaf water content during the absorption process of atmospheric water. Its purpose is to clarify the relationship of three factors of leaf surface salts, the capacity of leaf surface to adsorb atmospheric water and the ability of leaves to absorb the atmospheric water into plant cells and to reveal the effect mechanism of the salts on leaf surface to absorb the atmospheric water. This protect will provide a scientific basis for knowing the role of salts on leaf surface in leaves to absorb the atmospheric water and in ecological adaptability of drought resistance.

植物叶片（包含嫩茎）吸收利用大气水汽已成为干旱区植物生长或逃避干旱的重要水源。干旱区广泛分布的泌盐植物其叶表析出的盐分是否有利于叶片吸收利用大气水汽尚无研究。以干旱区典型泌盐植物柽柳、红砂、梭梭为研究对象，采用对不同盐渍环境的样本植株的清洗和未清洗叶片进行叶面特性检测和多种大气水汽加湿实验，通过荧光染色示踪检测和环境扫描仪来监测大气水汽从吸附于叶表至吸收进入叶肉细胞的全过程，比较分析不同盐分（组成、含量、结构）的叶面吸附和吸水过程及特征，监测水汽吸收过程中叶水势和叶片含水量的变化差异，明确叶表盐分、叶面吸附性能、叶片吸收大气水汽能力三者之间的关系，揭示泌盐植物叶表盐分对其叶片吸收大气水汽的影响机制，为认识干旱区泌盐植物叶表盐分对其叶片吸收大气水汽的作用和抗旱生态适应性奠定坚实基础。

干旱区植物对大气水汽的利用正被日益重视。越来越多的研究认为植物地上部分直接吸收的大气水汽、雾、露和凝结水已经成为干旱植物生长或逃避干旱的重要水源。我国西北干旱区广泛分布着不同类型的泌盐盐生植物，其叶表所泌盐分是否具有吸附大气水汽于叶表进而被吸入叶肉细胞而被植物利用呢？荒漠泌盐植物叶表盐分这些方面的作用与机理一直未被重视。.本项目以典型盐渍区植物多枝柽柳、红砂、梭梭为研究对象，开展不同盐渍生境梯度、不同生长时期泌盐植物洗和未洗叶表泌盐特征、叶表润湿性、叶水势、叶含水量及叶片大气水汽吸收荧光示踪实验的研究，取得了以下重要研究成果：.1..随着样地盐渍浓度的增加，红砂和多枝柽柳叶表盐分各种离子浓度依次增加。红砂和多枝柽柳上叶表盐分主要为NaCl，部分Na2SO4，和少量的MgCl2和CaCl2。叶表盐分对叶片亲水性影响显著。.2..叶表盐分能增强叶片对大气水汽的吸附，包括饱和水和非饱和水。叶表上盐粒越多，盐粒越大，叶片吸附大气水汽的能力越强。叶表粒子吸附水分子体积与盐粒大小成指数倍增加。.3..叶表盐分中含有极易潮解的MgCl2和CaCl2，叶表盐粒在外界大气相对湿度达49%的情况下，就开始潮解，当外界大气相对湿度达到69%就完全潮解变成水珠状液滴。潮解后的叶表盐分的风化点是49%，没有滞后现象。.4..叶表少量盐分或薄的盐层有利于叶片对非饱和大气水汽的吸附和吸收，叶表未溶化的大的盐粒对降雨或湿度大持续时间长的情况下有利于大气水汽的吸附和吸收。.5..梭梭同化枝上未检测盐腺结构，也未见叶表上有大量盐分。在水分条件极差的极端干旱区夏末8月底，梭梭同化枝表皮上开始长白色细丝。这种细丝能促进梭梭同化枝对大气水汽的吸收。未长细丝的梭梭主要靠活化的气孔吸收大气水汽。.6..幼嫩叶片或同化枝吸水能力比老的叶片吸水能力更强。.这些研究成果为深入认识泌盐植物的生态水文响应过程和生态适应性意义具有重要价值，也为探索干旱区荒漠植物叶或同化枝吸收大气水汽机制和机理研究奠定基础。