生物进化的重大事件——陆地植物的起源及其研究的新进展

ORIGIN OF LAND PLANTS IS AN IMPORTANT EVENT OF LIFE EVOLUTION

植物由水生向陆生发展是生物进化的重大事件。陆地植物起源的研究是植物学基础理论的重要内容。必须综合生物学和地学的研究,才能正确认识陆地植物起源的问题。目前认为陆地植物起源的时间在中奥陶世至晚奥陶世(距今4.7亿年至4.5亿年)之间。当时新的陆生环境对植物造成很强的选择压力。植物在累代延续中发生结构和生理的改变,逐步适应新环境。认识当时的全球环境有助于理解植物登陆的过程。现代植物性状的研究认为陆地植物起源于轮藻类植物。推断陆地植物世代交替的起源是由于合子的减数分裂推迟发生所致。早期陆地植物配子体的发现倾向于陆地植物世代交替是同源起源。

Origin of land plants is an important event in the history of life on earth. The evidence of microfossils indicates that the land-adapted plants appeared about 450 to 470 million years ago, during the period from mid to late Ordovician. It is several ten million years earlier than the appearance of Cooksonia, the oldest vascular plant living in Wenlock time. The comparison of living plants suggests that land plants derived from the algae ancestor which belongs to charaphytes and looks like Coleochaete. Antithetic theory, origin of alternation of generation in land plants by delay in zygotic meiosis, is strongly supported by the research on living plants. But the evidence of Early Devonian gametophytes is more or less in favour of the homological theory.