THE EFFECT OF RECIPROCAL TREATMENTS WITH OZONE AND ULTRAVIOLET-B RADIATION ON PHOTOSYNTHESIS AND GROWTH OF PERENNIAL GRASS ELYMUS-ATHERICUS

The impact on plant growth of the simultaneously changing factors of t he global climate, rising tropospheric O-3 concentrations and increasi ng UV-B radiation fluxes, has been tested in a combined glasshouse and growth chamber experiment. The saltmarsh grass species Elymus atheric us was sequentially fumigated for two weeks with O-3 and for another t wo weeks irradiated with UV-B (vv). Exposure to elevated UV-B did not negatively affect photosynthesis or plant growth. Fumigation with O-3 had a depressing effect on net photosynthesis, the number and biomass of flowers, the number of leaves and the number of shoots. O-3-induced damage only was observed in plants which had been fumigated during th e last two weeks of the experiment. Since interactive responses were n ot observed, results suggest different primary target sites for O-3 an d UV-B within the plant. (C) 1997 Elsevier Science Ltd.