CHANGES IN EPICUTICULAR FLAVONOIDS AND PHOTOSYNTHETIC PIGMENTS AS A PLANT-RESPONSE TO UV-B RADIATION

Treatment of Gnaphalium vira-vira plants with UV-B radiation caused ch anges in plant growth and in plant chemistry The leaf surface containe d two O-methylated flavones, araneol and 7-O-methylaraneol. HPLC analy sis showed that 20 days of UV-B radiation increased the synthesis of 7 -O-methylaraneol at the expense of araneol. Spectrophotometric analysi s of the photosynthetic pigments showed that UV-B radiation also incre ases the pigment content in treated plants. Another UV alteration is e pidermal hair damage, as observed in SEM pictures of treated leaves. T his combination of physiological and phytochemical effects may be inte rpreted as a plant response to UV-B stress.