THE EFFECT OF ENHANCED ULTRAVIOLET-B RADIATION ON GERMINATION AND SEEDLING DEVELOPMENT OF PLANT-SPECIES OCCURRING IN A DUNE GRASSLAND ECOSYSTEM

The germination of seeds of seven plant species occurring in a dune gr assland vegetation of the Netherlands, was studied at four levels of U V-B radiation simulating unto 45% stratospheric ozone reduction during April. With the exception of seeds of Senecio jacobaea, germination o f the dune grassland species was not affected by enhanced W-B irradian ce. Although a clear W-B fluence-response relationship was not observe d, the germination rate of S. jacobaea seeds and maximal germination p ercentage were reduced at enhanced UV-B. Germination rate in the dark was higher than germination in the light for Oenothera biennis, Planta go lanceolata, Rumex obtusifolius and S. jacobaea. Total dry biomass a ccumulation of seedlings was not affected by increased UV-B radiation in any of the species tested. Clear-cut differences in W-absorbance of methanolic extracts were observed between species. Enhanced UV-B irra diance stimulated W-absorbance of seedling extracts of Holcus lanatus and Verbascum thapsus. A clear UV-B fluence-response relationship was observed for both species. The results indicate that germination of th e studied plant species probably will not be adversely affected by the expected stratospheric ozone reduction in The Netherlands.