Allelopathy Of An Invasive Plant, Alternanthera Philoxeroides Griseb

A perennial herbaceous species,alligator weed(Alternanthera philoxeroides Griseb ) that is classified family Amaranthaceae belongs to Alternanthera genus. It is a invasive plant that has spread thoughout our country and has been harm to agriculture economy, entironment and biodiversity. It is important significance that studied the mechanism of the allelopathy and heredity toxicity of this species to effectively control the invasive plant.In this study, we tested the allelopathic effects of different concentrations aqueous upground organ and underground organ extracts of A. philoxeroides on seed germination, seedling growth and some physiological process of three receptor plants such as lettuce (Lactuca sactiva L.), whea(tTriticum aestivum L.)and rape (Brassica. napus L)by biassay. The result showed that the aqueous extract of A. philoxeroides observably inhibited the final germination and germination speed of lettuce and rape. The allelopathic effect of A. philoxeroide on seed germination of receptors mainly exhibited that delayed seed germination. And the aqueous extracts of A. philoxeroides markedly promoted growth the upground growth of lettuce, but have no significant effect to underground growth of lettuce. Low concentration aqueous extract of A. philoxeroides promoted seedling growth of wheat ,and high concentration aqueous underground organ extract inhibited seedling growth of wheat. The aqueous extract of A.philoxeroides commonly promoted seedling growth of rape. MDA content of receptors increased and the SOD active and POD active observably changed by aqueous extract s of A. philoxeroides showed that receptors were stressed and their structure and function of membranes were damaged in a certain extent by water-solubility allelopathic matter of A. philoxeroides. The water-solubility allelopathic matter affected the photosynthesis of receptors by influencing content of chlorophyla, chlorophylb and carotinoid. The allelopathy of A.philoxeroides was concentration dependent, increasing with the increase of concentration. The allelopathy of the underground organ was biger than that of upground organ. The sensitivity of the receptors to the allelopathy of A.philoxeroides changed with species and were rapeï¹¥lettuceï¹¥wheat.The micronucleus test technique of Vicia fabra cells was first applied to study the allelopathic effect of A. philoxeroides. The results showed that t aqueous extract s of A. philoxeroides significant inhibited mitosis,disturbed the DNA repaired of receptors cells and damaged structure and function of spindle. So the rate of micronuclei rised and Bhromosome Bridge, chromosome break and chromosome lag appeared. The results of this present indicated that water-solubility Allelopathic matter of A.philoxeroides was genotoxic.As a result, A. philoxeroides had very strong allelopathy. It could influence the photosynthesis process, changed the cell membrane's permeability and function, inhibited the mitosis and disturb the DNA repaired, more affected seed germination and seedling growth. So allelopathy of A.philoxeroides Griseb was one of potential causes of successful invasion.