中文摘要：

选用互花米草根、茎、叶5个浓度梯度（0．065、0．130、0．195、0．260、0．325g·mL^-1）的水浸液为处理液，研究其对莴苣种子萌发及幼苗生长的影响．结果表明：互花米草根水浸液在浓度大于0．260g·mL-1时会显著抑制莴苣种子的萌发，而茎、叶水浸液产生显著抑制作用的起始浓度分别为0．130g·mL^-1和0．195g·mL^-1；互花米草根、茎、叶水浸液对莴苣种子萌发的抑制，不仅表现为降低种子的最终萌发率，还表现为延长种子的平均萌发周期；茎、叶水浸液对幼苗生长的影响比较显著，而根水浸液浓度低于0．195g·mL^-1时对幼苗胚轴的生长产生促进作用（敏感指数RI〉0）．不同构件水浸液化感效应强度由大到小依次为：茎〉叶〉根，并且化感效应强度随水浸液浓度的增加而增强．

英文摘要：

Aqueous extracts of the root, stem and leaf of smooth cordgrass （Spartina alterniflora Loisel）, at concentrations of 0. 065, 0. 130, 0. 195, 0. 260 and 0. 325 g·mL^-1, were used as treatment solutions to study their allelopathic effects on seed germination and early seedling growth of （Lactuca sativa L. ）. Seed germination was significantly inhibited by the root aqueous extract at concentrations ≥ 0. 260 g· mL^ -1 ; or by stem and leaf extracts at concentrations ≥ 0. 130 g·mL^-1 and ≥ 0. 195 g· mL^-1, respectively. All the aqueous extracts of the root, stem and leaf inhibit seed germination of lettuce, which not only reduced the rate of germination but also prolonged the mean period of ultimate germination. The stem and leaf aqueous extracts had more significant inhibitory effects on seedling growth, while the root aqueous extract actually promoted the growth of the seedling hypocotyl at low concentrations （ 〈 0. 195 g·mL^-1, RI 〉 0）. The allelopathic effect of the aqueous extracts is in the sequence of stem 〉 leaf 〉 root. This study suggests that the root, stem and leaf of smooth cordgrass contain water - soluble allelochemicals which can inhibit both seed germination and seedling growth of lettuce. The allelopathic effects are intensified at higher extract concentrations.