The response of Ceratophyllum demersum L. and Myriophyllum spicatum L. to reduced, ambient, and enhanced ultraviolet-B radiation

The response of Ceratophyllum demersum and Myriophyllum spicatum to three levels of UV-B radiation - reduced (ca. 50% reduction), ambient and enhanced UV-B radiation, simulating 17% ozone depletion - is discussed. The research revealed that UV-B stimulated the production of UV-B absorbing compounds in C. demersum, but not in M. spicatum. The relative amount of UV-B absorbing compounds was about four times lower in C. demersum. Enhanced UV-B also affected respiratory potential in C. demersum (on average 3.7 mg O-2/gDM/h), but no effect on M. spicatum (on average 5.5 mg O-2/gDM/h) was detected. Increased need for energy revealed that UV-B radiation exerted stress in C. demersum. No changes in chlorophyll a and no disturbance to photochemical efficiency due to UV-B were observed in either species.