内蒙古荒漠珍稀复苏植物绵刺的生态适应性研究

Potaninia mongolica Maxim comes from tertiary and it is one of ancient and survivor species in ancient Mediterrnaena region, belonging to single species Potaninia genus of Rosace family. It has been classified as second degree national priority protective plant in 1980's. The P. mongolica is super-xerophytic shrublet and has peculiar classification status, morphological and propagative characteristics. The P. mongolica has strong capability of enduring dry, salt and infertility and against wind-erosion, so it can well adapted to the cruel envirenment. Form. Potaninia mongolica Maxim is one of the endemic formation of East Alashan-West Ordos Region in Inner Mongolia. The study of P. mongolica about morphological and anatomical structure，physiology characters，ecological adaptation was made，because the mostly characteristics of its fighting drought is avoiding drought by summer dormancy, resuscitating after absorbing water. In all of ecological factors, it is of most susceptibility and dependence to soil moisture. The P. mongolica has the characteristies of dormancy and leaf abscission under desiccation. So it is a resurrection plant in desert zones and a good material in study plnats on drouhgt tolerance. However, its drought resistance researched mostly in the artificial conditions, drought resistance index was relatively single and not comprehensive explanation of a particular issue. The study on ecological adaptation has not been reported about the resurrection plant P. mongolica. In this study, through three phase of normal growth, dormant state, and rewatering revival under the natural conditions, we study the changes of biological characteristics and the relationship between the environment change, the biological changes involving plant tissue water potential, photosynthesis efficiency, water use efficiency, endogenous hormone, protective enzyme and non-enzyme defense system. The sutdies are analyzed and discussed to elucidate further the ecological adaptation and self regulation mechanisms of adaptation to summer dormancy and resuscitation in P. mongolica. It will be to provide the theory foundation for conservation and restoration of P. mongolica vegetation. It also will provide new theoretical basis for study on desert plants adapation to extreme environment and conservation rare and endangered plant .

绵刺是阿拉善荒漠古老的单种属残遗特有种，强旱生小灌木，具有独特的分类地位、形态特征、繁殖特性，属国家二级保护的珍稀濒危植物，绵刺荒漠是阿拉善荒漠的特有群系。绵刺具有干旱季节性休眠，遇雨后复苏的特有现象,在学术界备受关注，在形态解剖、生理特性和生态适应方面进行了研究，但对绵刺的抗旱性研究指标都较为单一，不能综合说明问题。且抗旱性研究大多在人工实验条件下进行，对分布在自然干旱条件下的荒漠植物缺乏普遍的解释意义，绵刺休眠-复苏现象提出的多,深入研究的很少,尤其在自然条件下。本研究通过对野外自然条件下正常生长、持续干旱休眠期间以及降雨复苏后三个阶段植物组织水势、光合效率和水分利用效率、内源激素及保护酶和非酶性防御系统变化与环境变化的关系，探讨绵刺干旱休眠、降雨复苏的生态适应和自我调控机理。为绵刺植被的保护和重建提供理论基础，也为荒漠植物对极端环境的适应研究和珍稀植物保护提供新的理论依据。

绵刺是蒙古高原特有的单种属植物，古地中海孓遗植物，在极端干热的夏季具落叶休眠的特征，因此为温带荒漠的一种复苏植物，是研究植物抗旱机制的好材料。本项目通过对原生自然条件下，绵刺生长、休眠、复苏阶段的光合特征变化，生理指标的变化及转录组测序，探索绵刺忍耐极端干早的适应机理，以期为绵刺植被的保护和珍稀植物对极端环境的适应研究提供新的理论依据。1.土壤含水量不足3.5%时，绵刺进入休眠；土壤含水量达到8.8%，绵刺即可复苏生长。反映了绵刺对水分的依赖和敏感。2.绵刺净光合速率Pn与环境因子响应具“光合下调”现象。最大 Pn为16.89μmol·m-2s-1；光补偿点和饱和点为124.31 和2178.31μmol·m-2s-1。CO2补偿点和饱和点为82.92和616.75μmol·mol-1。生长期和休眠期Pn为双峰曲线；各阶段蒸腾速率呈单峰曲线；水分利用效率变化差异大。休眠期净光合速率、蒸腾速率及气孔导度明显减少。光抑制导致“光合下调”是绵刺对水分胁迫的保护性机制，反映了荒漠植物与环境协同进化中的生态适应性。3.干旱胁迫的休眠期，绵刺叶绿素含量显著下降（1.33mg/g）、丙二醛含量上升（38.86nmol/g），抗氧化酶类活性下降，绵刺通过积累脯氨酸（高达1130.23ng/n）增加抗氧化性。抗坏血酸ASA和谷胱甘肽GSH显著升高（1.05mg/g和274.94μmol/g），ASA-GSH系统对清除活性氧起主要作用。4.在干旱胁迫下，绵刺叶片生长促进型激素IAA、GA和ZR的含量下降，抑制型激素脱落酸显著升高（88.44ng/g）。各激素协同作用，使绵刺迅速降低生长速率，加快叶片衰老，抑制生长，促进了休眠。在干旱缓减时，生长型激素增加，脱落酸下降，有助于提高生长速率，促进茎的生长和开花，保障绵刺复苏。这是绵刺在生理生化过程中和生理应答方面对荒漠干旱胁迫的适应机理。5.转录组测序得到75.63Gb clean data， 各样品Q30的碱基百分比大于92.84%。组装后，得到 141,608个平均长 703bp的 Unigene，87,707 个 Unigene有注释信息。其中33,305个Unigene被注释到KEGG数据库的118个代谢通路中。差异表达基因中，复苏期有更多的基因参与了调控。数据分析正在进行中。这些研究将揭示植物适应干旱的分子机制。