The glutathione status of mature Scots pines during the third season of UV-B radiation exposure

Impacts of UV-B radiation on the glutathione level were studied in mature S cots pine needles (Pinus' sylvestris L.) during the third season of a UV-B field experiment. Studies were made on 4-week-old (July) to 14-week-old (Se ptember) current-year needles and 3-year-old needles which had their third UV-B-exposure season in progress. Depending on the season and the year (199 6-98), the supplemental UV-B dose varied from 0.92 to 5.09 kJ m(-2) day(-1) UV-B-BE compared to 0.47-2.44 kJ m(-2) day(-1) UV-B-BE under the ambient t reatment. Fully grown UV-B-treated current-year needles showed lower total glutathione concentrations after the vegetation period in September, wherea s in UV-B-treated 3-year-old needles the total glutathione content was sign ificantly lower and the proportion of oxidized glutathione (GSSG%) 56% high er in July. The significant differences in total glutathione in current-yea r needles in September and in active 3-year-old needles in July seem to ind icate that the effect of enhanced UV-B radiation on glutathione status coul d be cumulative. (C) 2000 Elsevier Science Ltd. All rights reserved.