SPECTRAL SHAPING OF ARTIFICIAL UV-B IRRADIATION FOR VEGETATION STRESSRESEARCH

Ecological plant experiments using artificial light sources require ca reful shaping of the spectral irradiance. This includes the steep UV-a bsorption characteristics resulting from the filtering of solar radiat ion by atmospheric ozone. Borosilicate and soda-lime glass filters scr een radiation very similarly to ozone. They have a high mechanical sta bility and are available in large filter sheets and are, therefore, su ited for the simulation of future scenarios of enhanced solar UV-B rad iation in large scale vegetation stress experiments. Although such fil ters meet many requirements of light engineering, there are limitation s due to the slope of the UV-edge and due to solarisation effects. Thu s, the interpretation of the artifical radiation spectra and their com parison to UV scenarios of decreasing stratospheric ozone need careful discussion. Different methods to classify spectra of artificial UV-ra diation are presented, and a new classification by a cut-off wavelengt h of the UV-edge and its slope is introduced.