EFFECTS OF ULTRAVIOLET-B RADIATION (UV-B) ON GROWTH AND PHYSIOLOGY OFTHE DUNE GRASSLAND SPECIES CALAMOGROSTIS-EPIGEIOS

Seedlings of Calamagrostis epigeios were exposed to four levels of UV- B radiation (280-320 nm), simulating up to 44% reduction of stratosphe ric ozone concentration during summmertime in The Netherlands, to dete rmine the response of this plant species to UV-B irradiation. After si x weeks of UV-B treatment, total biomass of all UV-B treated plants wa s higher, compared to plants that had received no UV-B radiation. The increase of biomass did not appear to be the result of a stimulation o f net photosynthesis. Also, transpiration rate and wafer use efficienc y were not altered by UV-B at any exposure level. Pigment analysis of leaf extracts showed no effect of enhanced UV-B radiation on chlorophy ll content and accumulation of UV absorbing pigments. UV-B irradiance, however, did I educe the transmittance of visible Eight (400-700 nm) of intact attached leaves, suggesting a change in anatomical character istics of the leaves. Additionally, the importance of including an amb ient UV-B treatment in indoor experiments is discussed.