Study On The Biology, Ecology Of Alligator Weed [Alternanthera Philoxeroides(Mart.)Griseb.] And Synergism And Mechanism Of Herbicides

, Alternanthera philoxeroides Griseb (Amaranthacea), is a perennial herbaceous plant. Alligator weed, originated from South America, has been distributed in more than 30 countries and regions of Oceania, Southeast Asia, South of North America, South of Europe and East and West of Africa. Alligator weed was introduced to China in 1930s. After 1950s, it widely spread in the Yangtze valley and South China. It has become one of the most serious exotic noxious weeds in Jiangsu Province. It has been badly threatened to ecological environments, agriculture, fishery, health of citizen and waterway transportation. The research is to discuss morphological and anatomical structures, character of community distribution and occurrence law of alligator weeds under different habitats, and to screen new herbicide combinations adapting to different habitats.Comparisons of morphologic features of hydrophytes and xerophytes of alligator weeds were conducted by direct observation, and the structures of their vegetative organs were also observed by light microscopy and electron microscopy. The results showed that the plant of xerophytes of alligator weed is dwarf, and with well developed rhizome and storage root. The stem of hydrophytes of alligator weed is thick, long and without or with few rhizome and storage root. The primary xylem of the root of alligator weed is diarch, triarch and tetrarchy. Adventitious buds mainly originate from the supernumerary cambium of the anomalous roots. The pith cavity of stem in hydrophytes accounts for 3/4 of stem wideness, the clearance among parenchyma is large, aerenchyma is developed, the mechanical tissue is underdeveloped, and suitable to aquatic environment. The pith cavity of stem in xerophytes is small, the parenchyma is small and regular, the clearance among parenchyma is small, the amount of cambium cell layers is much more, sclerehchyma tissue is up to 5-7 layers, the mechanical tissue and transporting tissue are fully developed. The hypogeal stem is wider than aerial shoot, the amount of cambium cell layers is less, parenchyma is large, tertiary structure is formed during the growth of hypogeal stem. The anomalous structure results from supernumerary cambium derived from the outmost elements of secondary phloem. And the supernumerary cambium derives from parenchyma.