Abstract:

Extracellular polysaccharides （EPS） produced by microorganisms， as an environmentally friendly green agent， have broad application prospects in promoting plant growth. The EPS produced by Sphingomonas sp. CX7 fermentation was used as the research object to analyze its primary structure， and explore its promoting and stress resistance effects on barley seedlings. The results showed that EPS produced by CX7 was a heteropolysaccharide composed of glucose， mannose， rhamnose， fucose， ribose， glucuronic acid， galactose， galacturonic acid， arabinose and xylose， with a mass ratio of 5.68∶3.25∶1.99∶1.62∶1.00∶0.81∶0.27∶0.06∶0.02∶0.01. By spraying barley leaf， the optimal EPS dosage for barley growth was 2 g·L^-1. At 2 g·L^-1 EPS， the root length， plant height， fresh weight and dry weight of barley increased by 47.45%， 19.28%， 18.15% and 37.88%， respectively， the contents of chlorophyll， soluble sugar， soluble protein， proline and the activities of peroxidase， catalase increased by 52.47%， 25.55%， 27.36%， 94.44% and 82.81%， 97.91%， respectively. In summary， the EPS produced by Sphingomonas sp. could promote plant growth and enhance plant stress resistance， which provided a certain reference basis for green biological agents to replace traditional agricultural foliar fertilizers.

Key words: Sphingomonas sp., extracellular polysaccharides, composition and structure, barley seedlings, promoting effects

摘要：

微生物所产的胞外多糖（extracellular polysaccharides，EPS）作为一种对环境友好的绿色制剂，在促生植物方面具有广阔的应用前景。以鞘氨醇单胞菌（Sphingomonas sp.）CX7发酵所产的EPS为研究对象，分析其一级结构，并探究其对大麦幼苗的促生和抗逆性作用。结果显示，CX7所产EPS是一种由葡萄糖、甘露糖、鼠李糖、岩藻糖、核糖、葡萄糖醛酸、半乳糖、半乳糖醛酸、阿拉伯糖、木糖组成的杂多糖，质量比为5.68∶3.25∶1.99∶1.62∶1.00∶0.81∶0.27∶0.06∶0.02∶0.01。配制不同剂量的EPS喷施大麦叶片，结果表明，大麦生长最适的EPS剂量为2 g·L^-1，在此剂量下大麦的根长、株高、鲜重和干重分别增加47.45%、19.28%、18.15%和37.88%；叶片的叶绿素、可溶性糖、可溶性蛋白和脯氨酸含量及过氧化物酶、过氧化氢酶活性分别增加52.47%、25.55%、27.36%、94.44%、82.81%、97.91%。综上所述，鞘氨醇单胞菌所产EPS对植物生长具有一定的促生作用，提高植物抗逆性，为绿色生物制剂替代传统农用叶面肥提供一定的参考依据。

关键词: 鞘氨醇单胞菌, 胞外多糖, 组成结构, 大麦幼苗, 促生作用