The Respond Of High Light And UV-B Radiation Treatment With Wolfia Arrhiza And Its Applications

Wolfia arrhiza, one species of the duckweeds in the family Lemnaceae, is the smallest flowering plant in the plant kingdom. It generally floats on the surface of the water, as small circular floating weed about1-1.5mm in length it lives in tropical and subtropical lakes and marshes. In summer, the vegetative frond grows quickly and absorbs large amounts of nutrient salts. Wolfia arrhiza, adapts to various stresses, such as high light, high temperature and UV-B radiation. The speed of growth of Wolfia arrhiza is fast and easy to harvest,and the growth process needs to absorb a lot of the eutrophication elements, for example, nitrogen, phosphorus and so on. Therefore can be used to purify water. High light and UV-B radiation has been the two stresses of growth of plant, but the two stress conditions on the physical effect of Wolfia arrhiza is still not clear. In this dissertation,we study the influences of high light and UV-B radiation to the Wolfia arrhiza impact of photosynthesis and the capability of Wolfia arrhiza in water purification have very important significance.The main results were as follows:(一) Effects of high light treatment the Wolfia arrhiza, antioxidant enzyme activity of Wolfia arrhiza we found to change with the different light. When the light intensity was low, the activity of SOD and POD in Wolfia arrhiza had been rising with radiation time; when the light intensity was high, the trends of the activity of SOD, POD, APX and Fv/Fm values were consistent, and, with the treatment of time presents the trends to decline after rising; It suggested that in a short time, Wolfia arrhiza have antioxidant repair ability, and resistance of the damage of the strong light stress; But if the long stress, may be caused by the system destroyed, the antioxidant capacity of Wolfia arrhiza were reduced.(二) It was found that UV-B radiation promoted the activity of antioxidant system to protect photosystem II (PSII) and exogenous nitric oxide had an obvious protection on PSII activity response to UV-B radiation. The activity of SOD, CAT, POD were improved by0.05mmol/L and0.10mmol/L nitric oxide, but0.1mmol/L SNP(sodium nitroprusside, nitric oxide donor) decreased the activity of antioxidant system. Low concentration NO promoted the enzymes'activity but high concentration NO decreased enzymes'activity which happened in Wolfia arrhiza only under oxidant stress. Therefore, our data indicated that low concentration NO can affect as an effective antioxidant and high concentration may exert as a source of oxidant stress. It suggested that exogenous nitric oxide may be play double roles as sources of reactive free radicals or ROS scavengers in protection of PSII under UV-B radiation.(三) It was studied water purification by Wolfia arrhiza in sewage pond in a rural. The sewage pond with the biomass of Wolfia arrhiza is4x106M-2(dry weigh:8.9g-M-2) before treated. After160days treated, Wolfia arrhiza kepping in good condition. PH,TP, TN, BOD and COD values were shown in a downward trend. The biomass of Wolfia arrhiza increase as7.3xlO7M-2(dry weigh:163g-M-2). The results showed that the water quality can be improved by Wolffia arrhiza.