Biological Characteristics On The Invasive Plant, Alternanthera Philoxeroides (Mart.) Griseb

The invasion of exotic harmful plants has been receiving more and more attention of scholars and the governments of all worlds, which have affected on the agricultural production and the health of residents. Alternanthera philoxeroides (Mart.) Griseb, is one of the most notorious invasive weeds and has been introduced to the regions with warm to subtropical humid climates worldwide. This host plant was listed on “the first alien biological list of China" in2003.The success of the invasive plant is benefited from its special vegetative propagation and its tolerance to environment. This article through field investigation, indoor Petri dish bioassay (ability of vegetative propagation and the effect of allelopathy), analyzes the invasive mechanism of the host plant. According to this research, we can explore the mechanism of its invasion, manage the invasive plant and recovery the ecological functions of the invaded habitat. According to the experiments, we found four results:1. To ascertain the effect of the invasive species on plant community in different habitats, field surveys of species diversity of plant community and morphological traits associated with the host plant were investigated. The species was found to have good growth in wetland, the morphological traits, including stem length, leaf area and node length of A. philoxeroides, showed(as road side and cultivated land) and the other habitats. The two morphological characteristics were related to adapt the host plants to human activities and heat-drought stresses. Based on the sample plot survey, the results indicated the variation of the relative coverage, frequency and densities, and showed a certain pattern in different invaded habitats. As the important value of the species over60.96%, the plant species diversity of community showed decreased tendency. A. philoxeroides invaded more severely, other plant species was lower, and the plant community diversity was smaller. The research indicated alien invasion plant could cause huge impact on native plant community, and the supervision should be strengthened and managed through target-oriented.2. The main breeding methods of the host plant are vegetative propagation. The characteristics of its underground stems were studied, which reflects the ability of vegetative propagation of the plant. First, the characters of underground stems of the plant, including the numbers of nods on stem, diameter of the stem, may significantly influence on the ability of vegetative propagation.3. Indoor Petri dish bioassay was adopted to study allelopathy function of the different organizations of A. philoxeroides. The results showed that the water extracts of the host plant inhibited the germination and final rate germination of seed of Lolium perenne. The extract inhibited the growth of the latter roots and stem. Some physiological and biochemical indexes of treated L. perenne indicated that the extract of the host plant by water increased the relative conductivity, and remarkably reduced the content of chlorophyll. Moreover, the inhibition of allelopathy from belowground organizations was stronger than of allelopathy from aboveground parts at the same concentration.4. For studying the tolerant ability to heavy metals of this host plant, the morphological traits including the plant height, root length, number of nods and number of tillering of the host plant was investigated and studied with different concentration of heavy metals. According to the results, we found all morphological traits of the host plant decreased significantly as the heavy metals concentrations raised compared with the other heavy metals, the tolerance of the host plant showed stronger. The results indicated that A. philoxeroides was a tolerant species in polluted heavy metals soil.