中文摘要：

为了了解紫花苜蓿对不同水分条件下生长的巨桉化感作用的响应，采用生物检测法研究了生长在不同水分[75％，55％，40％和30％田间持水量（FC）]条件下的巨桉幼树叶片水浸液对紫花苜蓿种子萌发和幼苗生长特征的影响。结果表明，不同水分条件下生长的巨桉均对紫花苜蓿表现出明显的化感作用。巨桉叶片水浸液显著降低了紫花苜蓿的发芽指数，且随着巨桉生长土壤水分的减少，降低作用增强。生长在较差水分（40％和30％FC）条件下的巨桉，其高浓度叶片水浸液显著抑制紫花苜蓿幼苗生长，但其低浓度叶片水浸液促进种子发芽；而生长在较好水分（75％和55％FC）条件下的巨桉，其低浓度叶片水浸液促进紫花苜蓿幼苗生长，高浓度叶片水浸液提高了种子发芽率。高浓度巨桉叶片水浸液降低了紫花苜蓿叶片叶绿素含量和根系活力。另外，紫花苜蓿对巨桉叶片水浸液处理表现出一定程度的抗性。紫花苜蓿对巨桉化感作用的这些响应特征表明紫花苜蓿可以作为巨桉林下植被优选物种。

英文摘要：

The responses of Medicago sativa to allelopathic effects of Eucalyptus grandis growing in different soil water conditions was studied using a bioassay method. The effects of E. grandis leaf extracts were examined on M. sativa seed germination and seedlings grown in different soil water conditions [75%, 55%, 40%, 30% FC （field water content）]. Regardless of water condition, E. grandis showed an obvious allelopathic effect on M. sativa. Leaf extracts of E. grandis significantly reduced the germination index of M. sativa, and the index was further reduced with a water reduction in soil used to grow E. grandis. E. grandis that grew in the lower Soil water conditions （40% and 30% FC） had a higher concentration of leaf extract that significantly inhibited seedling growth in contrast to the lower concentration of leaf extract, which enhanced the seed germination rate of M. sativa. E. grandis that grew in high soil water conditions （75% and 55% FC） produced a low concentration leaf extract that significantly improved seedling growth of M. sativa, while the high concentration extract enhanced the seed germination rate. A high concentration leaf extract of E. grandis reduced leaf chlorophyll content and root activity of M. sativa seedlings. M. sativa showed a relatively strong resistance to E. grandis leaf extract treatments and could be chosen as a priority species for tree-grass combinations in E. grandis plantations.