空心莲子草浸提液对苜蓿、菊苣和燕麦的潜在化感效应

空心莲子草(Alternanthera philoxeroides)是全球难以根除的恶性杂草,遍布我国20多个省(市)的陆地和水域,造成巨大的生态灾难和经济损失,研究它对牧草的化感作用可为有效防除和选种牧草提供科学依据。本研究以苜蓿(Medicago sativa)、菊苣(Cichorium intybus)和燕麦(Avena sativa)为受体植物材料,采用培养和盆栽试验,研究了空心莲子草地上部(ESA)和根系浸提液(ERA)对牧草种子发芽和幼苗生长的影响。结果表明,用ESA和ERA浸种,抑制牧草胚乳蛋白质、淀粉和肌醇磷酸盐水解,降低种子游离氨基酸、可溶性糖和水溶性无机磷含量,破坏种子细胞膜结构,从而抑制牧草种子萌发,其发芽率、发芽指数和活力指数的最大降幅依次为95.66%、96.15%和98.63%。用ESA和ERA浇灌幼苗,会降低牧草根系活力、硝酸还原酶活性和叶绿素含量,减少植株氮、磷、钾吸收,抑制幼苗生长,生物量的最大降幅分别为52.27%(ESA)和63.74%(ERA)。此外,ESA和ERA对3种牧草的化感指数和化感综合效应均为负值,其绝对值随浸提液浓度增加而增大,且表现为ERA大于ESA,燕麦大于苜蓿和菊苣。因此,空心莲子草浸提液对3种牧草均有化感抑制作用,ERA的化感效应大于ESA,燕麦种子发芽和幼苗生长受到的抑制程度大于苜蓿和菊苣。在牧草栽培中,选种较不敏感的菊苣和苜蓿有益于减轻危害和减少损失。

Allelopathic effects of Alternanthera philoxeroides extract on Medicago sativa,Cichorium intybus,and Avena sativa

Alternanthera philoxeroides,a noxious weed whose removal is difficult,is widely distributed over land and water surface in more than 20 provinces (or municipalities)of China,and leads to devastating ecologi-cal disasters and considerable economical loss.Investigation of the allelopathic effects of this noxious weed on pasture grass would provide useful information on the elimination of A.philoxeroides and selection of pasture grass species for cultivation.Therefore,pure culture and greenhouse pot experiment were conducted to evaluate the allelopathic effects of extracts of both shoot regions (ESA)and roots (ERA)of A.philoxeroides on seed germination and growth of Medicago sativa,Cichorium intybus,and Avena sativa seedlings.The results showed that seed soak in ESA and ERA inhibited the hydrolysis of proteins,starch,and inositol phosphates in the endosperm,and reduced the levels of free amino acids,soluble sugars,and soluble inorganic phosphates in seeds;it even damaged the seed cell membrane.The results showed that seed germination rate,germination in-dex,and seed vigor index were reduced by 95.66%,96.15%,and 98.63%,respectively.Irrigation of pasture grass seedlings with A.philoxeroides extracts reduced root vigor,nitrate reductase activity,chlorophyll con-tent,and uptake of nitrogen,phosphorus,and potassium,resulting in the inhibition of seedling growth.The highest rate of seedling biomass reduction ranged from 52.27% (ESA)to 63.74% (ERA).Furthermore,the al-lelopathic response index and allelopathic synthetic effect of A.philoxeroides on the three grasses,whose ab-solute values increased with increase in A.philoxeroides extract concentrations,were negative;the allelopathic inhibitory effect was stronger for Avena sativa than for Cichorium intybus and Medicago sativa,and the intensi-ty of the allelopathic effect of ERA was higher than that of ESA.Therefore,the extracts exerted allelopathic effects on the three pasture grasses,with ERA showing a stronger effect than ESA.Seed germination and growth of A.sativa seedlings were more sensitive than those of C.intybus and M.sativa.The selection of in-sensitive M.sativa and C.intybus for pasture grass cultivation could reduce harm and economic loss.