白三叶草/根瘤菌共生固氮潜力及干旱限制因素

为了探讨白三叶草生物固氮与土壤水分供应和菌种基因型的关系,采用温室盆栽试验方法,对9个基因型的三叶草根瘤菌固氮效率和与土壤含水量的关系进行了研究。结果发现,根瘤菌接种后,白三叶草叶片含氮量明显增加,有3个基因型的根瘤菌接种植株后叶片氮含量达到对照的3倍以上,据此可根据根瘤菌的基因型来预测其固氮效率,共生固氮效率与根瘤菌基因型的关系较与分离宿主的关系更加密切。在中度干旱胁迫下,白三叶草植株地上部生物量积累所受影响较地下部所受影响更大,在白三叶草与根瘤菌共生体系建立过程中,当根瘤菌固定的氮素可以满足植株生长需要时,干旱胁迫可能成为生长的限制因子。

Potential Capacity of Symbiosis Nitrogen Fixation of White Clover-Rhizobium Interaction and Drought Limiting Factor

The interactions between white clover（ Trifolium repens L. ）and Rhizobium strains were tested in order to identify the effectiveness of biological nitrogen fixation in relation to water supply, as well as the possibility to predict strain effectiveness according to genotype. Nine Rhizobium strains of R. trifolii were isolated from Trifolium repens L. and Trifolium fragiferum L. from different areas in southern China. White clover（ cv Reventel ）was planted in pots, nodulated with the nine strains, and grown in a greenhouse with the same amount of irrigation water. Foliage was harvested 8 and 12 weeks after sowing. Significant increases in foliar nitrogen, up to three-fold those of the control, were observed in plants inoculated with the three most effective strains. It was possible to predict the effectiveness of a rhizobial strain from its genotype. Symbiotic nitrogen fixation was more related to the genotype of the rhizobial strain than to host-specific. Once nitrogen was no longer a limiting factor, foliar biomass of all treatments was growing rapidly, leading to increased depletion of soil water. After cyclic moderate drought stress, white clover foliar biomass accumulation was more affected than foliar nitrogen content. The feedback of drought stress on foliar growth may be a new limiting factor when nitrogen demand is met satisfied in plants with the clover-Rhizobium interactions by N2 fixation.