盐胁迫下沙枣的离子转运机制研究

Ion absorption, transportation and compartmentalization play decisive roles in plant adaptation and tolerance to salt stress. Therefore, it is of great scientific significance to research and clarify the ion transport rules for analyzing plant salt adaptation mechanisms. However, until to now, the understanding and awareness of researchers to ion transport mechanisms are majorly based on findings from grasses, seldom involved in woody plants, and more less related to salt-tolerant forest trees..Based on the formerly accumulated research work, a salt-tolerant and predominant tree species, Elaeagnus angustifolia, which is widely distributed and planted in many marginal lands or environmentally harsh conditions in northern China, was selected as materials in this project. Firstly, we investigated the growth performance of NaCl-stressed seedlings under nutrient culture conditions. Then, the ion compartmentalization at levels of tissue, cell and sub-cell, and the changes in ion fluxes of roots under the conditions of steady state, instantaneous salt stress and pharmacological responses were systematically investigated by a series of instruments and techniques, such as Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), Scanning Electron Microscope - Energy Disperse Spectroscopy (SEM-EDS), Laser Scanning Confocal Microscopy (LSCM) and Scanning Ion-selective Electrode Technique (SIET). The ion transport mechanisms of Elaeagnus angustifolia were preliminarily discussed by a combination of long-term static accumulation and real-time dynamic exchange. This to-be executed project will be great significance to compare the similarities and differences in ion transport mechanisms between woody halophytes and grasses, and between halophytes and glycophytes, and to enrich the basic theory on plant ion transport. The compound research methods used will provide reference for related research in the future, and the obtained achievements will found theoretical basis for the large-scale promotion and application of Elaeagnus angustifolia.

离子的吸收、运输和区隔化对于植物适应和忍耐盐胁迫具有决定性作用。因此，研究并阐明植物的离子转运规律，对于解析植物盐适应机制进而揭示其耐盐性具有重要科学意义。然而，目前人们对于离子转运机制的理解和认识绝大多数是基于草本得出的，鲜有涉及木本植物，真正耐盐的林木更少。本项目以北方生态脆弱区内广域分布的盐生树种沙枣（Elaeagnus angustifolia）为材料，在掌握生长基础前提下，采用电感耦合等离子体光谱仪（ICP-OES）、扫描电子显微镜-能谱仪（SEM-EDS）、激光扫描共聚焦显微镜（LSCM）和扫描离子选择电极技术（SIET）研究离子的组织、细胞和亚细胞区隔化特征以及根系稳态经时、瞬时胁迫和药理学响应离子流变化，将长期静态累积和实时动态交换相结合，阐明沙枣的离子转运机制。这对于比较木本盐生植物与草本和甜土植物转运矿质离子的异同、丰富植物离子转运的基础理论具有重要意义，这种复合型研究方法将为今后相关研究提供参考与借鉴，取得的成果将为沙枣的规模化推广与应用奠定理论基础。

离子的吸收、运输和区隔化对于植物适应和忍耐盐胁迫具有决定性作用。因此，研究并阐明植物的离子转运规律，对于解析植物盐适应机制进而揭示其耐盐性具有重要科学意义。然而，目前人们对于离子转运机制的理解和认识绝大多数是基于草本得出的，鲜有涉及木本植物，真正耐盐的林木更少。本项目以北方生态脆弱区内广域分布的盐生树种沙枣（Elaeagnus angustifolia）为材料，联合运用ICP-OES、SEM-EDS、LSCM、SIET等仪器、技术和试剂，研究了盐胁迫幼苗的生长表现与耐盐性、矿质离子的区隔化特征以及根系的离子交换特性。结果表明：（1）盐胁迫下沙枣生长表现良好、耐盐性强，是开展盐渍逆境下离子转运机制研究的理想模式乔木树种。盐胁迫改变了植株生物量分配格局，根系补偿生长效应对于维持植株地上部分的正常生长和水分需求具有重要意义。（2）沙枣耐盐主要是通过根系对Na和Cl的聚积与限制作用以及茎有效限制Na向功能叶片运输来实现的，也与其具有较强的K、Ca和Mn转移能力有关，这对于揭示沙枣盐适应机制具有重要的理论价值。（3）盐胁迫沙枣幼苗不同类型细胞始终维持较高的K含量，但不同器官不同类型细胞内矿质离子含量差异较大。盐处理1 d时，根细胞中Na和Cl含量最高。100 mM盐处理7 d时，茎细胞内Na和Cl含量最高，而处理14 d时叶细胞内含量最高。（4）在10 min测定时间域内，不同盐处理幼苗根系的稳态K、Na、H均为外流。经不同化学试剂或试剂组合瞬时胁迫后的初始5 min以及约25 min时间域内，K均为外流且流量较大，而H则为微弱的内流或外流，2种离子流均具有明显离子交互效应。沙枣根系Na外排和K保留能力与质膜Na/H逆向转运体活性、K运输和通道蛋白活性以及H-ATPase活性密切相关。本项目的实施对于比较木本盐生植物与草本、甜土植物转运矿质离子的异同、丰富植物离子转运的基础理论具有重要意义，采用的研究方法可为今后相关研究提供参考与借鉴，取得的成果可为沙枣的规模化推广与应用奠定理论基础。