Influence of solar ultraviolet-B radiation on Antarctic terrestrial plants: results from a 4-year field study

We examined the influence of solar ultraviolet-B radiation (UV-B; 280-315 n m) on the performance of Antarctic vascular plants (Colobanthus quitensis a nd Deschampsia antarctica) by placing filters that either absorbed or trans mitted most solar UV-B over tundra along the Antarctic Peninsula for four c onsecutive growing seasons. The difference in biologically effective UV-B l evels between our treatments was 65%, which was similar to the enhancement in ambient UV-B levels that appeared attributable to ozone depletion during the first 2 months of the growing season (November and December) at our si te (62%). In both species, exposure to UV-B reduced vegetative growth, prim arily through slower leaf elongation rates that led to shorter fully expand ed leaves. In C. quitensis, exposure to UV-B also led to reductions in leaf longevity, branch production, cushion diameter growth, aboveground biomass , and thickness of the non-green cushion base and litter layer. Exposure to UV-B accelerated the development of reproductive structures and increased the number of panicles (D. antarctica) and capsules (C. quitensis) that rea ched maturity per unit of ground surface area covered by mother plants. How ever, this effect was offset by a tendency for these panicles and capsules to produce fewer spikelets and seeds. Ultimately, U-V-B exposure did not ef fect the numbers of spikelets or seeds produced per unit of ground surface area. While seeds from plants exposed to UV-B tended to be lighter, germina tion rates were similar between UV-B treatments. The relative reductions in leaf elongation rates in D. antarctica attributable to UV-B exposure incre ased from the first (23%) through the fourth (43%) growing season, and rela tive reductions in leaf longevity in C. quitensis tended to increase from t he first (9%) through the fourth (19%) growing season, suggesting that UV-B growth responses tended to be cumulative over successive years. (C) 2001 E lsevier Science B.V. All rights reserved.