洪水条件下湿地植物的生存策略

Survival strategies of wetland plants in flooding environments

洪水是自然界存在的一种普遍现象。湿地植物由于所处生境的特殊性,会经常受到周期性或永久性的洪水胁迫。在长期的适应进化过程中,湿地植物形成了一些特殊的生存策略,以适应水文条件的大幅度变化。主要的生存策略如下:1)生活史方面,植物可通过改变生长时间、繁殖方式、种子特征等避免洪水的直接伤害或利用洪水的流动起到传播扩散的作用;2)形态学特征方面,植物可通过调整根系形态、分布等将根系生长到氧气相对充足的土壤表层或形成不定根增强根系通气功能;3)解剖学方面,植物可通过改善组织孔隙度形成通气组织等改善空气传导到根系的"气体通道";4)生理生化方面,植物可通过增加碳水化合物含量以延长生存时间,释放出一些生长激素(乙烯等)以调节植物缺氧条件下的生理活动或形态、解剖方面的变化。在今后的研究中,不定根的形成机理、乙烯在通气组织形成中的作用及其过程、放射氧损失(ROL)的形成机理及其释放速率的调控等一些机理性的工作还需进一步加强。

Flooding is a common phenomenon in the nature. Wetland plants, due to their special habitats, are usually stressed by periodical or permanent flooding. !n the process of long-time adaptive evolution, wetland plants adopted a series of special survival strategies to fit the wide range changes of hydrological conditions, and the main strategies are ： 1 ） adjusting their life history, e.g. , changing growth time to escape direct damage and taking use of the movability of flooding to diffuse their seeds into new regions; 2） adjusting their root morphology and distribution depth of root into the top soil with relatively abundant oxygen content or grow adventitious roots to enhance the capacity of oxygen transportation; 3） changing their anatomical characteristics, e.g. , the enhanced porosity and the formation of aerenchyma to ameliorate the ＂gas channels＂ from air to root system; and 4） changing their physiological and biochemical characteristics via enhancing the carbohydrate content to prolong survival time or releasing hormone （ethylene etc. ） to regulate physiological activity or morphological and anatomical variations. In the further, the researches on the formation mechanisms of adventitious roots, the roles of ethylene in the formation of aerenchyma, the mechanisms of radial oxygen loss （ROL）, and the regulation of ROL release should be strengthened.