荒漠植物沙冬青对不饱和水汽的吸收利用机制和生理生态适应性研究

The ability of desert plants to absorb and utilize unsaturated water vapor has been confirmed. But correlative research has just begun. This study belongs to the new field about ecological hydrology of desert plants and is a leading subject. Unsaturated water vapor is of great ecological and physiological significance to desert plants, and plays an important role to maintain stability and the existence of desert ecosystem. Lack of understanding of this scientific issue, we cannot fully and deeply understand the mechanism of drought resistance of desert plants. In this project, we will chose the desert extreme xerophytes shrub, Ammopiptanthus mongolicus(Maxim.)Cheng F., which has been confirmed with the ability to absorb unsaturated water vapor, as the research object. This project intends to comprehensively study on the absorption and utilization mechanism of unsaturated water vapor through the methods of isotopic tracing, fluorescence staining tracing, photosynthesis monitoring, sap flow monitoring and water potential monitoring. It will explore the absorption process and transportation process of unsaturated water vapor, and reveal the mechanism of water vapor absorption, generally analyze the physiological and ecological adaptation mechanism of the plant after the absorption of unsaturated water vapor from the point of view of morphology, photosynthesis, water physiology and metabolic physiology under the control experiments of unsaturated vapor humidification. Our goal is to provide theoretical support for drought-resistant mechanism, ecological and physiological adaptation mechanisms and water use strategies of desert plants under water stress. It also has important theoretical significance for management of natural desert vegetation, restoration work of degraded desert vegetation and evaluation of stability of desert ecosystem.

荒漠植物具有吸收和利用不饱和水汽的能力已被证实，但相关研究刚刚开展，属于荒漠植物生态水文的新辟领域，立足于学科前沿。不饱和水汽对荒漠植物的生存具有非常重要的生理生态学意义，对荒漠生态系统维持稳定和存续也起着不可估量的作用，缺乏对这个科学问题的认识，使得我们不能全面深入的理解荒漠植物的抗旱机制。本项目选择具有吸收不饱和水汽能力的荒漠超旱生灌木沙冬青为研究对象，通过加湿控制实验，利用同位素示踪、荧光染色示踪、光合监测、液流监测、水势分析等方法和手段综合研究沙冬青对不饱和水汽的吸收利用机制，认识不饱和水汽的吸收运输过程，揭示水汽吸收的机理，从形态、光合、水分、代谢等生理角度上全面分析沙冬青吸收不饱和水汽后的生理生态响应。拟为荒漠植物在水分胁迫下的抗旱机制和生理生态适应机制以及水分利用策略研究提供理论支持，对于荒漠天然植被管理、退化植被恢复、荒漠生态系统稳定评价等工作具有重要的理论指导意义。

本研究以典型荒漠常绿阔叶灌木沙冬青为研究对象，通过野外和室内加湿实验的共同对比、验证和完善，形成了对沙冬青大气水汽利用机制及适应机理较为系统的认识和深入理解。室内加湿控制实验分析得到沙冬青叶片水汽吸收发生的边界条件是：土壤湿度≤田间持水量的58%（即轻度干旱），空气相对湿度≥80%（轻度干旱）或≥70%（中度干旱）或≥60%（重度干旱）或≥50%（极度干旱）。水汽从叶片逆向传导到一级茎的时间尺度是6～8h。采用同位素多源线性方法对不同程度干旱胁迫的叶片水汽吸收量进行了估算，发现只有极度干旱胁迫时加湿水汽才成为沙冬青的主要水分来源。通过同步观测液流、水势、光合、荧光等多项指标和分析多项理化指标，从形态生理、光合生理、水分生理和代谢生理角度上揭示了水汽吸收的生理促进作用。另外，野外加湿控制实验发现干旱胁迫较小的月份叶片吸收的不饱和水汽仅仅是对沙冬青缺水状态的水分补充，植物更多利用的是中、深层的土壤水。在遭受严重干旱胁迫的月份叶片吸收的不饱和水汽才成为沙冬青的主要利用水源。本研究验证了沙冬青具有特殊的叶片吸收不饱和水汽的利用方式，研究结果有助于我们理解荒漠植物在干旱胁迫下的生理生态适应机制和水分利用策略，并可以丰富和充实具有吸收不饱和水汽能力的荒漠植物库。