Study On Allelopathic Effects Of Invasive Plant Chenopodium Ambrosioides L.

Allelopathy means the plants release chemicals produced in subordinate metabolism to the circumstances,bringing advantage or disadvantage to neighboring plants or self. Invasive plants mean the plants are introduced outside natural distributing section and then found new groups, threatening native biology diversity,destroying species diversity and ecosystem. The allelopathy effects of invasive plants have been cognizant of, and are attached importance to as an invasion mechanism of foreign plants. Chenopodium ambrosioides L. is the annual or perennial plant of Chenopod,originally producing in tropic America,and now distributing in tropic zone and temperate zone, and being seen all the country. As invasive plants, Chenopodium ambrosioides L.is part of generic weed of farming and gardening, and brings harms to farmland and gardens.However, allelopathy effects of Chenopodium ambrosioides L.have reported rarely.This experiment is taken to research the changes of growth and physiology in the way of germination, morphological indicators of young seedlings, malondialdehyde content, antioxidant enzymes activity, morphological indicators of mature plants, and biomass allocation under the treatment of aqueous extract of fresh and dry C.ambrosioides L.in different concentration, as Triticum aestivum,Oryza sativa,Brassica chinensis, Vigna unguiculata and Capsicum annuum are the tested plants,which frequently seen in the farmland. Moreover, the experiment is also taken under different organs aqueous extract of C. ambrosioides L. This study aims at discussing the influnce of allelopathy effects of C.ambrosioides L.on the five crops above, for providing new theoretical method and practical experience for mechanism of biological invasion, prevention and utilizationg of C. ambrosioides L. The results of researches showed that:1) Studying the effects of aqueous extract of C. ambrosioides L.in different concentration on the growth and physiology of tested plants, conclusions as follows:the aqueous extract of fresh and dry C.ambrosioides L. all had allelopathy effects, the higher the concentration was, the stronger the allelopathy effects were. At low concentration, the seed germination, root growth and stem growth of young seedlings were restrained, but the stem height of Triticum aestivum,Vigna unguiculata and Brassica chinensis was stimulated at lower concentration. As the concentration was higher, malondialdehyde content had increased, but SOD,CAT and POD activity had different changes, and antioxidant enzymes activity was reduced at high concentration. The influence on the morphological indicators of mature tested plants was less than that of young seedlings under the aqueous extract's treatment in different concentration.Only at high concentration, the stem growth,stem width and root growth of mature plants were obviously restrained. For the biomass, low concentration effectively promoted biomass accumulation of Triticum aestivum and overground biomass accumulation of Brassica chinensis, but reduce that of Oryza sativa, and rarely affect that of Vigna unguiculata and Capsicum annuum; all the tested plants can't grow regularly at high concentration.2) Studying the effects of different organs aqueous extract of C. ambrosioides L.at the same concentration on the growth and physiology of tested plants, conclusions as follows:There were different effects on the same tested plant under different organs aqueous extract of C. ambrosioides L. The order of restraining effect from strong to weak was flower,leaf,root,stem.But the order was not absolute, and difference existed in different plants. Each organ aqueous extract reduced seed germination,only seed germination of Oryza sativa under the treatment of dry stem's aqueous extract increased. For the root growth and stem growth of young seedlings, they were evidently restrained under the treatment of flower and leaf's aqueous extract, but effects differed in different plants under the treatment of root and stem's aqueous extract. Malondialdehyde content of tested plants increased more under the flower and leaf's aqueous extract's treatment than under the root and stem's aqueous extract's treatment. SOD,CAT and POD activity had different changes, and antioxidant enzymes activity was also evidently reduced under the flower and leaf's aqueous extract's treatment. The influence on the morphological indicators of mature tested plants was less than that of young seedlings unde different organs aqueous extract's treatment. However, the stem growth, stem width and root growth of mature plants were still seriously affected under flower and leaf's aqueous extract's treatment. For the biomass, except fresh leaf's aqueous extract promoted root's biomass accumulation of Triticum aestivum and overground biomass accumulation of Brassica chinensis, biomass accumulation of crops all reduced, in particular, flower's aqueous extract's treatment had the obvious function.Summarizing the conclusions above, different plants have different reactions to allelopathy effects of Chenopodium ambrosioides L.; the same plant has distinct reaction to allelopathy substance in different concentration, the higher the concentration is, the stronger the allelopathy effects are; the same plant has distinct reaction to different organ treatment, and allelopathy effect of flower and leaf is remarkable. Furthermore, there is diversity between fresh and dry aqueous extract's treatment, but the two treatments have the same allelopathy effect on crops. Considering allelopathy effect of Chenopodium ambrosioides L. and its character of weed, Chenopodium ambrosioides L. is harmful, and we should get rid of it with might and main.