Abstract: Impacts of turbidity (30±3, 60±3 and 90±3 NTU) of a waterbody on light intensity and hence on growth, photosynthesis and antioxidant activity of Potamogeton cripus growing therein were studied . Changes in plant height, leaf number, and photosynthesis and activities of superoxide dismutase(SOD) and peroxidase (POD) in the shoot of Potamogeton cripus caused by light stress were investigated. Results show that the effects of turbidity on growth rate of the Potamogeton cripus varied with the degree of turbidity, but insignificantly. At the end of the experiment, no significant differences (P>0.05) were observed between CK and groups different in turbidity in effect on plant height; the effect of lower turbidity (<30 NTU) on leaf number was not significant on D20 and D27 and became apparent near the end of the experiment, while the effects of turbidity (60 and 90 NTU) inhibiting leaf number were extremely significant (P<0.01). Before D10, turbidity did not show much influence  (P>0.05) on maximum quantum yield (Ｆ_ｖ／ Ｆ_ｍ) or photochemical quenching (qp), but afterwards Fv/Fm in all the turbidity groups gradually declined with the test going on. The effect of turbidity on electron transport rate(ｒ_ｅ，ｔ) of the plant was always extremely significant (P<0.01) in all the groups. However, the activity of superoxide dismutase (SOD) in the plant increased with rising turbidity in degree, but that of peroxidase (POD) increased first and then decreased.  

Key words: Potamogeton cripus, turbidity, shoot, growth, photosynthetic characteristics, antioxdant activity