MORPHOLOGICAL AND PHYSIOLOGICAL-RESPONSES OF BEAN-PLANTS TO SUPPLEMENTAL UV-RADIATION IN A MEDITERRANEAN CLIMATE

During the last few decades many experiments have been performed to ev aluate the responses of plants to enhanced solar W-B radiation (280-32 0 nn) that may occur because of stratospheric ozone depletion; most of them were performed in controlled environment conditions where plants were exposed to low photosynthetically active radiation (PAR) levels and high W-B irradiance. Since environmental radiative regimes can pla y a role in the response of plants to W-B enhancement, it appears doub tful whether it is valid to extrapolate the results from these experim ents to plants grown in natural conditions. The objective of this work was to evaluate the effects on physiology and morphology of a bean (P haseolus vulgaris L.) cultivar Nano Bobis, exposed to supplemental UV radiation in the open-air. W-B radiation was supplied by fluorescent l amps to simulate a 20% stratospheric ozone reduction. Three groups of plants were grown: control (no supplemental UV), W-A treatment (supple mentation in the UV-A band) and UV-B treatment (supplemental UV-B and W-A radiation). Each group was replicated three times. After 33 days o f treatment plants grown under UV-B treatment had lower biomass, leaf area and reduced leaf elongation compared to UV-A treatment. No signif icant differences were detected in photosynthetic parameters, photosyn thetic pigments and UV-B absorbing compounds among the three groups of plants. However, plants exposed to UV-A treatment showed a sort of 's timulation' of their growth when compared to the control. The results of this experiment showed that plants may be sensitive to W-A radiatio n, thus it is difficult to evaluate the specific effects of W-B (280-3 20 nm) radiation from fluorescent lamps and it is important to choose the appropriate control. Environmental conditions strongly affect plan t response to UV radiation so further held studies are necessary to as sess the interaction between W-B exposure and meteorological variabili ty.