Abstract

The effect of UV-B radiation on growth and photosynthesis of seven Chilean varieties of wheat ( ERP V-8, Lilen, Millaleu, Nobo, Reihue, Talhuen and Huayun) was evaluated during the first six weeks of growth. Plants were irradiated 4 hours daily with 22.5 mu W cm(-2) of UV-B radiation and with a white light intensity (12 h photoperiod) that averaged 400 mu mol m(-2) s(-1). The varieties Talhuen, Lilen and Nobu were the most sensitive to this treatment in terms of their reduction in leaf area and in Fresh and dry matter accumulation. UV-B absorbing compounds increased in all the plants treated with UV-B but this increase was not related with the growth sensitivity shown by the different varieties to this radiation. A decrease in CO2 assimilation was detected in all the varieties as a consequence of the UV-B treatment. However, this decrease was significant only in Talhuen which was one of the most sensitive to UV-B. The PSII quantum yield, measured as Fv/Fm ratio, decreased in all the varieties under high white light intensities. This photoinhibitory effect was reduced when plants were previously irradiated with UV-B, particularly in the more sensitive varieties (Talhuen y Lilen). This kind of photoprotection exerted by the UV-B radiation is discussed. Finally, it is concluded that varieties ERP-V8, Millaleu and Huayun were the most tolerant to the level of UV-B radiation used in this case.