人工湿地植物根系生长空间胁迫诱导的适应性跃变与污染物强化去除机制研究

A phenomenon of plant roots overgrowth, which is so-called redundancy in biology, usually occurs when the plant is subject to a stress from the ecological environment. It is also the ecological adaptability of plants to environmental changes. This adaptation is a new adaptive transition of plants during the stress stimulation. The overgrowth of the root system is of great significance to the efficient and stable operation of the subsurface flow constructed wetland (SSFCW). The applicant’s previous study found that when the substrate depth of SSFCW decreased dramatically, the plant root overgrew, the dissolved oxygen concentration in SSFCW increased significantly, and the pollutant removal efficiency improved significantly. However, the mechanism of the phenomenon remains unclear. The relationship between stress response and the redundancy of root and plant body will be established and the mechanism of growth redundancy will also be clarified by the limitation on the vertical growth space of roots. According to the analysis on redundancy tolerance, redundancy resistance and hereditary feature, the key stress factors will be identified; and then, a technical system of manual intervention will be established to induce the effective redundancy and configuration of roots of individual plant under a variety of stress. It will be clear by understanding the correlations between redundancy degree and changes, such as plant type, growth stage, medium type, pollutant loading, hydraulic loading, type and quantity and activity of rhizosphere microorganisms, redox conditions and dissolved oxygen in substrate, etc. Based on the above research results, the optimization of the key design and operating parameters and the investment reduction will be performed.

植物在生长受胁迫的生态系统中，根系往往出现过量增长现象，这就是生物学的冗余现象，也是植物对环境变化的生态适应性表现。这种适应性的形成是在胁迫刺激时，植物形成的新的适应性跃变，这些过量增长的根系对潜流湿地的高效稳定运行意义重大。申请人既往的研究发现：当潜流湿地床深大幅减少后植物根系过量生长，湿地中溶解氧浓度大幅升高，污染物去除效果和稳定性明显改善，但其机理尚未解明。拟通过对根系垂向生长空间的胁迫，建立应激响应与根系及植株体冗余的相关性，阐明生长冗余机理；根据多种胁迫时的冗余耐性分析、冗余抗逆性和遗传特征，识别关键胁迫因子，建立诱导植株个体根系冗余稳定发生和形成高效根构型的人工干预技术体系，构建最佳根系冗余度模型；解析冗余度与植物类型、植物不同生长阶段、填料类型、污染物及水力负荷、根圈微生物类型和数量及活性、填料床氧化还原条件和溶解氧变化的相关性，进而优化关键设计和运行参数，大幅减少工程投资。

如何在不耗能的条件下营造高溶解氧的人工湿地环境目前尚未见突破性的进展。在环境胁迫刺激时，植物根系的生态适应性与发育上的可塑性会导致新的适应性跃变，根系往往出现过量增长现象。过量增长的根系可使潜流湿地中溶解氧浓度大幅升高，污染物去除效果和稳定性明显改善，但需解明其机理。.项目主要开展了不同环境胁迫时植物根系生长冗余的机理研究和利用冗余根系强化湿地对污染物去除效果与稳定性的应用研究，阐明了各类单独或和叠加胁迫时潜流湿地中植物的应激、根系生长冗余的变化与演替规律及其对根际效应的影响，探究了胁迫对污染物净化效果影响及其相关性，确定了关键胁迫因子和胁迫最佳方法与植物生长阶段，建立了不同胁迫下强化根系生长冗余的理论与技术体系。.研究结果显示植物受到根系生长空间胁迫的应激主要是通过改变叶片捕光色素含量、增强光能的捕获效率以及通过较高的热耗散，来维持较高的光合速率，保证光合结构PS Ⅱ 正常。这种胁迫没有破坏光合效率的稳定性，也没有对叶片内的光合机构造成损害。湿地表层溶解氧的主要来源为植物根系的泌氧作用，而非大气复氧。较浅的根区生长空间能够大大加强潜流湿地中植物根际效应、根区释氧能力、根区固着能力、微生物与植物共生作用。不同的竖向根区空间的限制对湿地植物产生了非生物胁迫，根系垂向空间胁迫对湿地植物的生长特性和生理应激特性大多会产生显著的积极影响，根系竖向生长空间胁迫、氮素胁迫等多种与工程设计和运行主要参数直接相关的胁迫会引起如植物形成更发达通气组织等不可逆、全生命周期的器质性有利应激。各种叠加胁迫条件中对植物的代谢和呼吸行为产生影响最大的因子，也是实现“在不耗能的条件下营造高溶解氧的湿地环境”工程目的的最关键胁迫条件。所揭示的上述机理和现象对增强潜流湿地脱氮除磷以及固碳的效能、加强湿地植物抗逆能力及湿地运行稳定性、降低潜流人工湿地建设和运维成本等具有重要现实意义。