Abstract: Based on the in situ UV-B doses observed in the late spring and early summer, the photosynthesis fluorescent parameters of the adult plants of Potamogeton cripus under the ultraviolet radiation stress (50, 100, 150, and 200 μW·cm^-2) were determined. The results revealed that F_o and  F_m increased in the initial period and then decreased with the increasing the dose of UV-B radiation. F_v/F_m, Φ_PSII and NPQ consistently increased with increasing the radiation dose. The findings suggest that when the adult plants of P. cripus were irradiated under UV-B radiation, PSII reaction center was injured to reversible inactivity or irreversible damage, the light energy conversion efficiency and the electron transport rate were reduced, and the actual photochemical efficiency declined. In conclusion, UV-B radiation accelerates the decline of P. crispus, indicating that ultraviolet radiation might be an important factor leading to mass mortality of P. crispus in late spring and early summer. However, further research is necessary to discover whether UV-B radiation combines with other environmental factors to cause the decline of P. crispus.

Key words: white gene, curly wing, oxidation., Drosophila melanogaster, H₂O₂