Studies On Biological Mechanisms Of Lanthanum In Eutrophia Water

Abstract:Ducekweed(Spirodela polyphiza) is a kind of aquatic plant. It grows rapidly and is easy to get. It has high capability to absorb nitrogen and phosphorus in water. Duckweed is a good target to control water eutrophication.The studies tried to understand the mechanism of La3+ in medium for cultivating duckweed on affacting absorb N, P from the medium. The experimental system contained (1)differnt N, P and La3+ concentration respectively, (2) complex of differnt N, P and La3+ concentration, (3) orthogonal design of three factors and four levels for differnt N, P and La3+ concentration. The main results were as follows:1. Eutrophia water can be cleaned through duckweed's growth. Duckweed's capability to absorbing N and P increased within 10-50mg/L for N concentration and 0.5-8mg/L for P concentration. Deckweed grew best when concentration of N and P were 50g/L and 15mg/L respectively, N and P concentration in medium declined fast at the same condition.2. Duckweed's capability to absorbing N and P associated with duckweed's growth. Duckweed grew best for 6 days cultivation.3. Chl b concents in duckweed can be highly influented by La3+ which translated into duckweed as well. La3+ contents in duckweed reached to 181μg/g FW when La3+ concentration was lmg/L in medium. Chl b contents in duekweed (0.2mg/g FW) significantly increased for 42.9% comparing to CK (0.14mg/g FW). It suggested that photosynthesis can be up-regulated by La3+ in duckweed. Chl a and Car contents.had little changes as following La3+contents in duckweed.SOD specific activities [18.16U/(min-mg Pr.)] in duckweed significantly declined for 30.9% comparing to CK [26.29U/(min-mg Pr.)] and O2- production rate [16.03μg/(min-g FW)] significantly increased for 26.4% comparing to CK [12.68μg /(min-g FW)] and NR activities [39.23μg/(h-g FW)] in duckweed significantly declined for 6.8% comparing to CK[42.1μg/(h-g FW)] when La3+ contents in duckweed reached to 181μg/g FW. It had negative influence to ROS (reactive oxygen system) and nitrogen metabolism when La3+ contents increased in duckweed. Duckweed's growth may be harmed by peroxidation.It is suggested that adequate La3+ concentration is good for duckweed's growth and metabolism and also has benefit for water eutrophication controlling. But it may promote water eutrophication when La3+ concentration over 1.0mg/L.