Abstract: Plants may beneficially or adversely affect other plants and microorganism through allelochemical compounds and cause allelopathic and phytotoxic effects by directly or indirectly release of live or dead parts. The allelopathy of the aqueous extracts of Kochia sieversiana leaves and stems on Lactuca sativa (lettuce) was evaluated in his study compared with a NaCl solution of the same conductivity. The germination rate, germination index,vigor index and mitotic index of lettuce seeds were analyzed. Results showed that the germination rates and indices of lettuce were decreased with an increasing of treated concentration. There was no obvious variation at lower concentrations, while there was significant difference at higher concentrations (P<0.05). The vigor index of lettuce had significant variation (P<0.05). The analysis of meristematic tissue showed that the mitotic index of lettuce root tip was decreased significantly with treated concentration increasing (P<0.05). The numbers of cells that participated in cell division were decreased during metaphase, anaphase, and telophase. In the presence of allelochemical compounds, the process of cell division was stopped in the prophase. Root elongation was inhibited. Thus K. sieversiana shoots have an allelopathic potential that could influence the other plants, the inhibitory effects of leaves extracts were more intense than those of stems. The vigor index of lettuce was more sensitive to allelopathic effect of K. sieversiana than the germination rate and index.

Key words: Allelopathy, Kochia sieversiana, Lactuca sativa, Mitotic index

摘要： 植物体内的化感物质通过淋溶、根系分泌物等途径进入环境,对周围植物、微生物产生有益或有害的影响。通过不同浓度碱地肤(Kochia sieversiana)叶部、茎部水浸提液及其相同电导率NaCl溶液处理莴苣(Lactuca sativa)种子及幼苗,比较发芽率、发芽指数、活力指数、有丝分裂指数等指标,旨在采用生物鉴定法评估碱地肤叶、茎中化感物质的效应。结果表明:随着碱地肤叶片、茎部浸提液浓度的增加,莴苣发芽率、发芽指数逐步降低;在低浓度处数值变化不明显;在最高浓度处(2 mg·mL^-1),叶片浸提液使莴苣发芽率、发芽指数分别降低26.5%(P<0.05,RI=-0.27)和40.7%(P<0.05,RI=-0.41),茎部浸提液使莴苣发芽率、发芽指数分别降低36.7%(P<0.05,RI=-0.37)和27.8%(P<0.05,RI=-0.28)。莴苣幼苗活力指数随浸提液浓度增加而明显降低(P<0.05),在最高浓度处,叶片、茎部浸提液使莴苣幼苗活力指数分别降低82.6%(P<0.05,RI=-0.82)和70%(P<0.05,RI=-0.7)。莴苣根尖分生组织细胞观察结果表明:随着浸提液浓度的增加,有丝分裂指数明显降低(P<0.05),在最高浓度处(2 mg·mL^-1),叶片、茎部浸提液使莴苣根尖有丝分裂指数分别降低33.7%和17%;在有丝分裂前期,参与分裂的细胞数目随着处理浓度的增加而增加,在中期、后期和末期细胞数目变化趋势则相反;这表明,碱地肤中化感物质的存在使得大部分细胞都停滞于有丝分裂前期,从而导致根尖细胞的伸长生长受到抑制。与浸提液电导率相同的NaCl处理对莴苣发芽率、发芽指数、活力指数等指标影响不大。碱地肤地上部分确实存在对其他植物产生一定效应的化感物质,其中叶片中化感物质的抑制作用大于茎部;与发芽率、发芽指数相比,莴苣活力指数对化感效应更为敏感。

关键词: 化感效应, 碱地肤, 莴苣, 有丝分裂指数