中国桫椤科植物生殖障碍的比较研究

Cyatheaceae, relicted ferns of Jurassic Period, are the rare species for studying on ecological environmental change and ecological adaptation. By reason of the destruction of habitat, species from Cyatheaceae in China have been endangered. After decades of environmental restoration, the endangered situation have improved significantly. However, the number of seedings heavily declined with the intensified enviromental pollution in recent years, and then the endangered situation is getting severer. The intrinsic relationship between reproductive barriers and environmental pollution was scarce. Sperms of ferns, haploid without cytoderm, have to swim into archegonium by the way of perceiving the concentration of inductors in water in order to completing fertilization. Meanwhile, the development of embryo is also highly dependent on natural environment. We have found that the slight contamination would make sperms of Alsophila costularis got lost, and the differentiation of embryos confused. With the breakthrough success of reproductive barriers of Isoetaceae, this project would choose one representatives from all genera of Cyatheaceae. Referring to the pollution of local environment, gradient polluted-culture mediums would be prepared, and then the gamobium of species would be cultivated contrastly. The reproductive parameters, reproductive structure, the feature of cellular regulation and the ability of reproductive compensatory would be analyzed by software SPSS. It is expected to illuminate the basic reproductive regularity of different genera and species, to reveal the intrinsic relationship of Cyatheaceae between reproductive barriers and environmental pollution. This project would provide the theoretical basis and technical support for the scientific protection and the endangered prediction, and the stable and original embryonic basis for the researches of controversial core leptosporangiates.

桫椤科是侏罗纪孑遗的唯一乔木状濒危蕨类，是研究系统演化和生态适应的珍贵材料。国产桫椤类曾因生境破碎化而高度濒危，经数十年的生境修复，长势都有明显改善。近年随着环境污染的加剧，幼苗数量不断下降，生殖障碍日趋严重。而相关研究十分匮乏。我们初步发现桫椤类的精子必须依靠自然水体中雌性物质的诱导，才能游进颈卵器，轻微的水体污染就能导致精子迷失方向、胚胎分化紊乱。本项目在成功破解国产古老而濒危蕨类水韭科生殖障碍的基础上，选取桫椤科全部三属中的各1种，结合污染实际，分别配制梯度污染培养基，对照培养有性世代；用SPSS软件辅助分析各对照组的配子体发育、精子行为、胚胎发生等环节的生殖参数、生殖结构、细胞调控特点和生殖代偿能力，阐明不同属种的基本生殖规律，揭示我国桫椤类生殖障碍与环境污染间的内在关系，为预测和保护提供理论依据和技术支撑，也为颇具争议的“核心薄囊蕨类” 提供胚胎遡祖依据。

桫椤科是侏罗纪孑遗的唯一乔木状濒危蕨类，是研究系统演化和生态适应的珍贵材料。国产桫椤类曾因生境破碎化而高度濒危，经过数十年的生境修复，尽管长势都有明显改善，但随着环境污染的加剧，幼苗数量不断下降，生殖障碍日趋严重。本项目以国产桫椤多数种的孢子为材料，经分组胁迫培养，发现有性世代的生殖结构容易发生畸变，畸变的发生率与胁迫类型、胁迫程度都存在稳定的相关性，共观察到4类17种结构性畸变的生殖障碍；胁迫对配子体生殖生理指标、根际土壤酶活性、根际土壤微生物，都能造成显著的破坏，即使轻微的污染，也能对配子体造成严重的生理生态干扰，而且干扰的程度因胁迫因素、胁迫强度和种属的不同而不同；精子的发生、寿命、游动速度、游动方向等，是各项生殖障碍中最严重的环节；配子体单倍体细胞的DNA更容易发生甲基化而导致性别紊乱或降低成苗率。本项目还利用GBS简化基因组测序技术获得的单核苷酸变异位点（SNPs），对国产桫椤科植物进行了种属间遗传结构的分析、种间杂交生殖及杂交种的评估；首次报道了桫椤等多个类群的颈卵器都是多细胞起源，发现了核心薄囊蕨类系统演化的保守溯祖形态。与姊妹项目极危古老蕨类水韭科生殖障碍研究的成果相比，本项目不仅拓宽了研究领域、提升了理论水平，人工繁殖技术也获得了较大突破，已批量培养出全部供试桫椤的幼孢苗，并捐赠给数十家科研单位。