荒漠植物银沙槐内生菌共生抗逆生理响应研究

Adaptive strategy of stress-resistance plants for desert was closely correlated with endophytes. Some plant possesses their tolerance or resistance ability relied on endophyte absolutely. Ammodendron bifolium, an endangered species of the national grade II, was a special species for desert ecosystem for their drought tolerance and sand fixation. Our previous studies has show that the response of the plant chemicals, SOD, POD and CAT activities were significantly increased under the stresses with salinity, drought or salinity-drought mixed stresses. We also isolated a lot of bacteria from surface-sterilized root and stem of A. bifolium and identified them with 16S sequence analysis. The stress-resistance productes screening has showed that most of the strains could excrete indoleacetic acid and proline. And the effects of the isolates on seed germination were also estimated. The resultes indicated that the bacteria could enhance the germination of the seed under drought stress with PEG-6000 as stress chemical preparation. Based on the previous study, we will assessment the effectes of endophytes on physiology response related to the drought-stress tolerance. With the surface-sterilized seeds and the isolated strains, the seed germination, seedling growth, plant development and nutriants utilization would be estimated. And the physiology responses of the cell membrane, osmotic protection, such as soluble sugar, superoxide dismutase, and peroxidase, proline, nitrate reductase, abscisic acid, glycine betaine, malondialdehyde will be estimated under PEG stresses on every stages. And the nutriants utilization, such as N and P, also been estomated with or without inoculation. The results will be helpful for our understanding of the physiological responses of A. bifolium with or without inoculation with the isolates. And the adaption mechanism of the plant stress-resistance for desert would be explorated. And this will also lay a foundation for the application of microorganisms on desert ecosystems protection and restoration.

荒漠植物对逆境的适应与其内生菌密切相关。国家二级保护濒危植物银沙槐有极强的耐干旱和沙埋能力,对荒漠生态系统特别是沙漠治理有重要价值。前期研究证实银沙槐在盐、干旱及交叉胁迫时抗逆成分显著增加；已完成的内生菌分离鉴定和部分代谢产物筛选证实内生菌可产生吲哚乙酸、脯氨酸等抗逆成分，将分离株培养物接种到PEG干旱胁迫的银沙槐苗床证实可增强耐旱能力提高发芽率。为了解内生菌共生抗旱的生理机制，本项目以干旱胁迫为逆境条件，以表面灭菌银沙槐种子和分离内生菌株为材料，以银沙槐种子、幼苗和植株对接种内生菌的膜生理、渗透保护及营养利用的生理响应为指标，检验干旱条件下内生菌对银沙槐种子萌发、幼苗成活、植株生长的影响及各阶段的生理变化，通过检测植株表现型、生理生化指标、耐旱组分等抗逆成分的变化，研究银沙槐的共生抗逆生理响应，了解其抗逆机制并争取在营养利用调节方面有所突破，为内生菌应用于濒危物种保护探索新的途径。

银砂槐（Ammodendron bifolium (Pall.) Yakovl.）为一种分布于我国新疆的珍稀沙生植物。为了解荒漠环境下内生细菌共生对银砂槐种群生存的适应机制，从而为荒漠植物保护提供理论指导。本项目研究了银砂槐内生细菌对宿主植物的促生抗逆作用及生理响应，结果表明：（1）银砂槐内生细菌具有丰富多样性，45株分离株归属于13个属，即芽孢杆菌属（Busillus），不动杆菌属（Acinetobacter），欧文氏菌属（Erwinia），考克氏菌属（Kocuria），泛菌属（Pantoea），芽孢八叠球菌属（Sporosarcina），节杆菌属（Arthrobacter），纤维单胞菌属（Cellulomonas），克雷伯氏菌属（Klebsiella），海洋芽孢杆菌属（Oceanobacillus），葡萄球菌属（Staphylococcus），类芽孢杆菌属（Paenibacillus）和假单胞杆菌属（Pseudomonas），根组织内生细菌数量多于茎组织，优势菌属为芽孢杆菌属和泛菌属，二者占总内生菌数量的38%。（2）葡萄球菌属菌株AY3、AY7和AY8，芽孢杆菌属菌株AG13和AG18及考克氏菌属菌株AY9能够促进银砂槐种子萌发，胚根生长，鲜重及含水量，干旱胁迫下仅菌株AY3、AY9、AG13和AG18具有促进银砂槐种子萌发及胚根生长的作用。综合看芽孢杆菌属和葡萄球菌属菌株共同具有促生抗逆作用，其中葡萄杆菌属菌株对植物促生抗逆方面的研究鲜有报道。（3）接种内生细菌能够促进宿主植物种子内淀粉、可溶性糖、可溶性蛋白及粗脂肪的降解，同时增加了葡萄糖、果糖及游离氨基酸含量。在整个种子萌发过程中可溶性糖和可溶性蛋白降解先于淀粉和粗脂肪的降解，种子内贮藏物质的降解转化有利于萌发后幼苗的建立。（4）固氮、溶磷、生长素产生、分泌ACC脱氨酶及胞外酶产生等是植物促生细菌所具有的一些特性。银砂槐内生细菌促生特性表现为：克雷伯氏菌属、考克氏菌属和泛菌属具有较高生长素产生及ACC脱氨酶活性，欧文氏菌属、不动杆菌属和泛菌属具有较高溶磷能力，固氮和胞外酶产生能力仅限于个别菌属菌株。综上所述，本研究表明银砂槐内生细菌对其宿主植物表现出明显的促生抗逆功能。