MORPHOLOGICAL, PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF CURLY PONDWEED (POTAMOGETON CRISPUS L.) TO UV-B RADIATION STRESS.

Causes of Potamogeton crispus population decline in the late spring and early summer are not fully understood. Given that strong UV-B radiation can penetrate the water column and damage aquatic organisms, it may be a key factor in the P. crispus decline. In this study, adult P. crispus plants were exposed to different intensities of UV-B radiation for 6 hours every day, the control group was only exposed to UV-A and photosynthetically active radiation. All groups were exposed to UV-A and photosynthetically active radiation at the same intensity. We monitored the morphological changes, and physiological and biochemical indexes. The results showed that plant height, internode length, and leaf area decreased with corresponding increases in radiation intensity. Additionally, photosynthetic pigment content could be improved with low-intensity UV-B radiation (<10.8 kJ/m²), inhibited with continuous radiation, and decreased by high-intensity of UV-B radiation (>10.8 kJ/m²). Catalase activity improved by short-term radiation, but inhibited by long-term radiation. Superoxide dismutase activity increased gradually with longer irradiation time. The malonaldehyde content increased at the beginning but then decreased with continuing radiation. These results suggest that UV-B radiation may contribute to the mass mortality of P. crispus in late spring and early summer. [ABSTRACT FROM AUTHOR]