短命植物抱茎独行菜内生菌多样性与共生抗旱研究

Ephemeral plant, a kind of plant that has a very short life cycle, was a special species for desert ecosystems with their highly on growth rate, photosynthetic and reproduction efficiency. Endophytes, a specific group of microorganisms that colonize healthy plant tissue intercellularly and/or intracellularly without causing any apparent symptoms of disease, has been shown to increase resistance against biotic and abiotic stresses, growth enhancing and health promoting in most plants. The endophytes also play significance effects on seed production and vigour. The results of our previous study indicated that the strains isolated from surface-sterilized desert plants have higher tolerance on salt and pH than others. The microbial communities of each plant were different but some strains, based on molecular analysis, appeared in other plants. Another study has also showed that the drought stress have been released or removed when endobacteria has been inoculated. For the purpose to understand the species specificity, symbiotic tolerance on drought, and the diversity of the endophyte in desert plant, Lepidium perfoliatum L. of genus Lepidium, family Cruciferae, one important traditional chinese medicine and wildly spread ephemeral specie, be selected to analyses the distribution and community of the endopgytes and symbiosis resistance. The samples, including seed, leaves, stems and roots from the southern edge of the Gurbantunggut desert, will be surface sterilized and grinded with PBS by sterilizated mortar and pestle and series diluted. The dilution will be spraided on medium plate and the endophytic bacterial would be isolated and purified. Then the surface and /or deep sterilized seeds would germinate with or without inoculation with the isolates. The influence with or without inoculation on seed germination would be estimated. The resultes will indicated that the endophytes, differentiate with cultured or uncultured, has mutualistic effects on resistance against environment stresses or the life cycle mediation. That will helpful for our understanding the adaptation of the plants on the desert. And this will also lay a foundation for the application of microorganisms on desert ecosystems protection and restoration.

短命植物环境适应性强且是荒漠生态恢复中的先锋物种。植物内生菌通过代谢调节和产生抗逆成分等对宿主环境适应有协助甚至决定作用。前期研究显示，荒漠植物内生菌可耐受盐碱并有部位分布特异性，且可缓解或解除干旱胁迫促进种子萌发。由抱茎独行菜的不同部位共分离到内生细菌60株，其中芽孢杆菌占57%且主要源于叶片；而30株可分泌胞外多糖的菌株主要来自于根部，显著区别于其它植物内生菌并具有部位代谢多样性，推测各自具有相应共生抗逆功能。为了解抱茎独行菜内生菌的多样性及空间分布，及其与环境适应的关系，本研究在此基础上以非培养方法检测内生菌空间分布，以分离株接种经深层灭菌的种子及幼苗,以PEG为胁迫剂对不同发育阶段施加干旱胁迫,试验内生细菌对干旱条件下种子萌发的作用，探索短命植物共生微生物多样性与共生抗干旱。研究结果对揭示内生菌与短命植物共生抗逆机制有重要科学意义并对荒漠环境保护有重要价值。

短命植物抱茎独行菜对荒漠生态系统有重要价值。为了解其内生菌对宿主环境适应的价值，本项目对前期分离到的内生细菌的生物学特性、在干旱胁迫下对种子萌发的促进作用，以及抱茎独行菜种子的自然萌发特性等进行了研究。结果表明，分离自荒漠短命植物抱茎独行菜的内生菌具有耐受盐碱的特性，分别有100.00%、98.39%、96.77%、93.55%、88.71%和25.81%的菌株在2%、5%、7%、10%、12%和15%的NaCl浓度下仍可生长；61.61%的菌株可产生淀粉酶；在已完成的酸碱耐受性检验中，大多数菌株的pH耐受范围为5-10；为去除种子表面粘液层对萌发的影响，试验采用浓硫酸浸泡5分钟可使粘液层去除率达到 84.81 %，并使萌发率由 18 %上升到 25 %；在种子萌发实验中，首次发现抱茎独行菜的种子自然萌发需要一定强度的干旱胁迫，5%和10%的PEG 6000的模拟干旱条件下种子萌发率由25%分别提高到78%和50%；内生菌缓解干旱胁迫筛选表明，在5%的PEG 6000的模拟干旱条件下，有39株可比对照促进种子的萌发，其中最高比对照组提高44%。实验阶段性成果为了解荒漠植物抗逆机制和进一步研究荒漠植物与微生物的共生抗逆提供了基础。