红树植物胎生现象研究进展

Progress in the studies of vivipary in mangrove plants

植物胎生是指有性繁殖产生的后代在母体上直接萌发的现象,在红树植物中最为常见。红树植物生长在热带亚热带海岸潮间带,耐受高盐、高温、淹水缺氧和海浪冲击等复杂环境。胎生被认为是红树植物对这种特殊生境的重要适应方式。该文从形态发育、生理生化、分子水平、生态适应4个层次讨论红树植物胎生现象对复杂生境的适应性,并指出现有研究存在的不足,对将来的研究方向进行了展望。与非胎生胚胎发育相比,红树植物胎生是一个遗传的程序,在进化过程中形成了一些特殊的结构。植物激素对胎生发育起关键的调控作用,繁殖体发育过程中,其盐离子的种类与浓度的动态变化则是对海岸潮间带生境的重要适应特征。这种胎生繁殖体依靠在母体上完善的一系列功能性特征能更有效地适应落地后的滩涂环境。然而,红树植物胎生发育过程的分子机理及调控机制还有待研究。理解胎生这一特殊适应性现象的本质及其进化过程将为红树林保护繁育、适应气候变化提供理论依据。

Vivipary in plants refers to a phenomenon that sexually reproduced offsprings germinate while still attached to the maternal bodies. This is mostly manifested in mangrove plants, which occur in tropical and subtropical intertidal zones and encounter harsh environmental conditions such as high salinity, high temperatures, waterlogging, hy- poxia and tidal waves. Vivipary has long been recognized as one of the most important adaptive features under such a complex environment. Here we discuss four aspects of vivipary： morphological anatomy, physiology and biochemistry, molecular biology and ecological adaptation. We also discuss shortcomings in current studies and prospect of future directions. Differing from regular seed development, viviparous seeds in mangroves are evolved with many special structures, indicating a genetically based process. Hormones play an important role in regulating the process, whilst the dynamics of salt ion concentration during embryo and propagule development seems to be an adaptive feature. The ecological significance of vivipary is fully exhibited in the propagules that can effectively establish themselves on muddy tidal zones. Such a success heavily relies on sound functional features developed on the mother plants. However, the molecular mechanism and the regulation of viviparous seed development in mangroves remain elusive. Systematic studies of vivipary in mangroves not only help to under- stand the nature and evolutionary process of this distinct adaptive phenomenon, but also provide the foundation for mangrove forest restoration and protection in many parts of the world.