THE EFFECT OF SOLAR UV-RADIATION ON 4 PLANT-SPECIES OCCURRING IN A COASTAL GRASSLAND VEGETATION IN THE NETHERLANDS

During the summer of 1992, growth and some physiological parameters of four native plant species occurring in a coastal grassland in The Net herlands, were studied after reduction of solar UV irradiance using di fferent cut-off filters. Biomass production, morphology and photosynth esis of all species tested were unaffected by the different treatments . Litter production of Plantago lanceolata was increased in the absenc e of the total UV waveband, indicating a possible role for this waveba nd in plant senescence. Depletion of the total UV waveband from sunlig ht resulted in alterations in biomass allocation in Calamagrostis epig eios and Urtica dioica while no changes were observed in P. lanceolata and Verbascum thapsus. In C. epigeios an increase in the specific lea f area was observed, whereas in U. dioica root weight per total plane weight was decreased resulting in an increase in the shoot/root ratio. Both photosynthetic and W-absorbing pigment concentrations were alter ed by the different filter applications. When compared to control plan ts receiving full sunlight, depletion of W-B resulted in a significant increase in chlorophyll concentration in U. dioica leaves, this howev er did not affect photosynthetic rate. The presence of UV-B radiation enhanced the UV-absorbance of leaf extracts of all species except P. l anceolata. Optical characteristics of the leaves were also changed. Bo th the quantity (P. lanceolata and U. dioica) and the quality (all spe cies) of radiation transmitted by the leaves was affected by the diffe rent treatments.