采用不同质量浓度的杨树根系水浸提液处理草决明种子，同时以不同质量浓度的草决明种子水浸提液处理杨树插穗，探讨相互间的他感作用。结果表明，杨树草决明复合经营时存在一定的他感作用。总体上，两个参试杨树无性系(南林-95杨和NL-80351杨)根系浸提液质量浓度在3~10 mg/mL时对草决明种子的发芽率、幼苗高生长、根长生长及简化活力指数有一定的促进作用，但质量浓度为30 mg/mL时有明显的抑制作用。较低浓度的草决明种子浸提液可促进杨树根系的生长，而在较高浓度下则对根系生长有明显抑制作用，但对扦插苗地上部分生长影响不显著；随着处理浓度的增加，杨树根系活力呈现先增大后减小的抛物线形变化趋势，其中当浸提液在3~12 mg/mL的质量浓度范围内对根系活力有一定的促进作用，6 mg/mL时根系活力达到最大，而24 mg/mL时则表现为明显的抑制作用。

Using the water extracts of the poplar roots to treat the seeds of Cassia tora (L.), and the water extracts of C.tora seeds to treat the poplar cuttings, the allelopathy between the two species was studied. The results showed that some allelopathy existed in poplar-Juemingzi agroforestry system. The water extraction of the roots of two poplar clones with 3—10 mg/mL concentrations could promote seed germination, seedling height, root growth and simplify the vigor index of C.tora, while the water extracts with 30 mg/mL concentrations suppressed seed germination and seedling growth. The root growth of poplar cuttings was improved under treatment with relatively low concentration of water extracts of C.tora seeds, while the root growth was suppressed at a high concentration. However, no significant difference in young seedling biomass was observed among the treatments. With increase of water extraction concentrations of C.tora seeds, the root vigor of poplar cuttings showed a hyperbola pattern, e.g., at the concentration of 3—12 mg/mL, the root vigor was improved, and reached the highest at 6 mg/mL. However, the root vigor was lowered at the concentration of 24 mg/mL.