Study On The Functions And Its Mechanism Of The Inhibition Of Eichhornia Crassipes To Microcystis Aeruginosa

Water hyacinth [Eichhornia crassipes (Mart.) Solms] considered one of the water weeds. But in recent years, more and more researches had indicated that Eichhornia crassipes has great allelopathic effects on many kinds of green algae growth in eutrophication freshwater. Until now, there are few literatures about the inhibitory effect of water hyacinth on Microcystis aeruginosa, which is the major algae type of water bloom. In our study, the inhibitory effects of water hyacinth against Microcystis aeruginosa (PCC7806) was examined with the methods of M. aeruginosa co-cultivated with water hyacinth, M. aeruginosa cultured with water hyacinth co-cultivated water and cultured with root powder of water hyacinth. The major results were summarized as below:(1) Co-cultivate experiments shown that:Water hyacinth had different effects accordance with different cell densities of algae (M. aeruginosa). When the cell density of algae is lower (OD650=0.10or OD650=0.05), the growth of algae were inhibited,whereas the growth of algae were stimulated by water hyacinth co-cultivated with higher started density of algae(OD650=0.20), after seven days co-cultivate, the inhibition ratio were up to95.6%and97.3%respectively. Our results also shown that water hyacinth roots made the mostly contribute to the inhibitory effects on algae growth.(2) While cultured M. aeruginosa with water hyacinth cultivated-water, collected from lab cultured water hyacinth/from natured growth water hyacinth, the algae growth rate were all inhibited. While the water hyacinth co-cultivated water collected from natured grown environment, its inhibitory effects to algae growth was lower than that collected from lab cultured cultivated-water. The growth inhibition was increased in line with the increased concentration of cultivated water. But, no obvious inhibitory effects were observed when treated cultivated water in high temperature (105℃), that indicated that high temperature may depressed allelopathic activity of water hyacinth against algae growth. Moreover, whether filtrated cultivated water by common filter papers or by millipore filters, both have the inhibitory effects on algae growth, which indicated that the algae inhibitory effects reflected by water hyacinth cultivated-water was not influenced by microorganism.(3)0.8g/L and4g/L fresh root powder of water hyacinth promoted algae growth, while20g/L fresh root powder inhibited algae growth. Compared with the CK, all groups treated with dry root powder samples (the sample groups have three concentration) shown inhibitory effects on algae growth, and its inhibition enhanced along with the increased concentration of dry root powder.(4) Under water hyacinth cultivated water treatment, chlorophyll a content and soluble protein of M. aeruginosa declined significantly from the beginning of the treatment, while SOD activity and POD activity increased during early experimental period and then decreased; MDA content also shown "first increased and then decreased" trend.