Abstract:

Endogenous Rhizobia existed widely in the whole body and seeds of leguminous plants, but the specific migrational pathway, migrational pattern and the factors that influencing endogenous Rhizobia migration were not clear. 3-indole acetic acid (IAA), lanthanum chloride (LaCl₃) and extra-cellular polysaccharides from other Rhizobia were used in this study to conduct root immersion on the bud seedlings of Medicago sativa cv. ‘Gannong 5’, in order to compare the migrational dynamic and quantitative distribution of the marked Rhizobia containing CFP (Cyan fluorescent protein) under the action of the 3 exogenous substances, and to further explore the influence of endogenous rhizobia strain (isolated from host plant) and exogenous strain (purchased from strain conservation center, Chinese academy of sciences) Rhizobia. The results showed that Rhizobium meliloti. GNf (endogenous marked strain) cells were11.43 and 1.71 times of CK in root and stem under the action of extra-cellular polysaccharides, respectively. The LaCl₃ of 50 mg·L^-1 increased the number of R.meliloti. GNf and S.meliloti.12531f (exogenous marked strain) in the root by 656.83 % and 303.19 %, and decreased the number of S.12531f in stem to the 3.64 % of CK. IAA increased R.GNf and S. 12531 cells in the seedling root by 18.34 and 12.11 times, respectively, while for the number in stem, S.12531 had increased to 163.09 %, while R.GNf decreased to 75.45 %. IAA could significantly decrease R.GNf cells in cotyledon to the 4.13 % of CK, indicating that all the 3 exogenous substances increased the cells of marked Rhizobia in root. The quantity difference of marked rhizobia cell numbers in different parts of bud seedlings under exogenous substance free conditions indicated that the migrational pathway of Rhizobium among root-stem-cotyledon in the bud seedlings had the selective barriers of only allowing endogenous Rhizobia to pass.

Key words: Endogenous rhizobia, Medicago sativa.L, Migrational dynamic, 3-IAA, Exopolysaccharides

摘要：

内生根瘤菌普遍存在于豆科植物的种子及植株体内,但其在苜蓿体内的运移通道、运移规律及运移的影响因素尚不明确。本研究用菌液中分别混合3-吲哚乙酸、LaCl₃和其他根瘤菌的胞外聚合物(EPS)(过滤除去活菌菌体)对‘甘农5号’紫花苜蓿(Medicago sativa ‘Gan Nong 5’)芽苗浸根处理,比较青色荧光蛋白(CFP, cyan fluorescent protein)标记根瘤菌在芽苗体内的运移动态及数量分布,探明内源根瘤菌(分离自宿主植株根瘤)与外源根瘤菌(购自中科院菌种保存中心)在宿主体内的运移差异。结果表明:胞外聚合物使Rhizobium meliloti.GNf (内源标记菌)在芽苗根和茎内的数量为对照(未添加外源物质的菌液处理)的11.43和1.71倍。50 mg·L^-1的LaCl₃使根内R.meliloti GNf和S.meliloti 12531f(外源标记菌)的菌体增加656.83%和303.19%,且使S.12531f在茎内的菌体仅为对照的3.64%。IAA处理使芽苗根内R.GNf和S.12531菌体增加18.34和12.11倍,使茎中S.12531增加163.09%,但R.GNf降低为对照的75.45%。IAA处理能降低芽苗子叶内R.GNf数量至对照的4.13%,表明三种外源物均能增加标记菌在芽苗根系中的数量。无外源物时,标记菌在芽苗各部位的数量差异表明,根瘤菌由根系向茎和子叶的运移通道存在仅允许内源菌通过的选择性屏障。

关键词: 内生根瘤菌, 紫花苜蓿, 迁移动态, 3-IAA, 胞外聚合物