Studie On Water Ecological Criteria Of Paraquat Aquatic Higher Plants In The Yangtze Deita

Water ecological criteria is the basic theory of water quality standard. It is of significance to study water ecological criteria to make water quality standard, to control the categories and quantities of the pollutants, and to protect the water biological diversity and the structure and function of ecosystem. We shall emphatically study the higher plants in the Yangtze Delta. Seven aquatic higher plants is selected as the experiment materials, which had different life forms in order to have a good representativeness. Based on some physiological indexes, the sensitivity of seven aquatic plants response to paraquat was analysised. Using the chronic value and half inhibited concentration (IC50) to study the water ecological criteria on the three plants which belongs to Lemnaceae. The main results are as follows:There are416wild species belonging to185genera and65families in the Yangtze Delta,11ferns belonging to7genera and7families. There are404angiosperms, belonging to177genera and57families. Most of aquatic plants are dicotyledonous plants (205species). The most family with the numbers of species in flora is Cyperaceae (58species), the next is Gramineae (55species), and then Polygonceae (26species) and Scrophulariaceae (58species). There are416wild species belonging to four life forms, and the main type was hygrophyte plants in terms of life form. There are119wild species belonging to hygrophyte plants, accounting for55.53%in all aquatic plants in this area, then emergent plants (119species), accounting for28.61%, the next is submersed plants (41species), accounting for9.86%and the last is floating plants (12species). Most of aquatic plants in the Yangtze Delta are herbaceous plants. In terms of growing environment, most of aquatic are freshwater plants in this area. The ecological types of aquatic plants can be divided into8types. The number of species from ditch was the256. Then there are203species growing in Rice-field, then wet places (187species), and fewer aquatic plants are growing in streams and lakes. We choosed Lemna minor, Landoltia punctata, Spirodela polyrrhiza, Ceratophyllum demersum, Hydrocharis dubia, Elodea Canadensis and Potamogeton crispus to test the Paraquat sensitivity of seven plants. The results showed that (1) Under the stress of paraquat, the activity of POD, SOD, CAT were enhanced, and meanwhile, MDA content increased drastically (2) Soluble protein content dropped (3) Potamogeton crispus had stronger sensitivity ability than other quatic plant. The result is consistent with that of fuzzy subordinate function methed method conclusion. The values of U(X) in order are Potamogeton crispus(0.8949), Ceratophyllum demersum(0.7439), Hydrocharis dubia(0.5738), Lemna minor(0.5577), Landoltia punctata(0.4121), and Elodea Canadensis (0.3860) respectively. Among them, Spirodela polyrrhiza is the most insensitive, whose U(X) of index average value is0.3059.We choosed Lemna minor, Landoltia punctata, Spirodela polyrrhiza to study on the toxicity of paraquat. The results indicated that Lemna minor and Spirodela polyrrhiza had the same value of chlorophyll contend index(9.57μg/L as the Chronic Value). IC50values of Lemna minor fronds of paraquat was14.48μg/L, while Landoltia punctata, Spirodela polyrrhiza were6.11μg/L and3.81μg/L respectively. Lemna minor, Landoltia punctata, Spirodela polyrrhiza all belong to Lemnaceae, but their IC50values of fronds are different. These results illustrated that it is necessary to take different genera within a family into account when we choose the proper tested plants to study water ecological criteria.