Consequences of depletion of stratospheric ozone for terrestrial Antarcticecosystems: the response of Deschampsia antarctica to enhanced UV-B radiation in a controlled environment

Mini UV lamps were installed over antarctic plants at Leonie Island, Antarc tic peninsula, and shoot length measurements of Deschampsia antarctica were performed during the austral summer January-February 1999. We studied the response of the antarctic hairgrass, Deschampsia antarctica to enhanced UV-B. In a climate room experiment we exposed tillers of Descha mpsia antarctica, collected at Leonie Island, Antarctic peninsula, to ambie nt and enhanced levels of UV-B radiation. In this climate room experiment w ith 0, 2.5 and 5 kJ m(-2) day(-1) UV-B-BE treatments we observed that lengt h growth of shoots at 2.5 and 5 kJ m(-2) day(-1) UV-B-BE was markedly reduc ed compared to 0 kJ m(-2) day(-1) UV-B-BE. In addition, there was an increa sed number of shoots and increased leaf thickness with enhanced UV-B. The R elative Growth Rate (RGR) was not affected by UV-B, possibly because reduce d shoot length growth by enhanced UV-B was compensated by increased tilleri ng. Light response curves of net leaf photosynthesis of plants exposed to 5 kJ m(-2) day(-)1 UV-BBE did not differ from those exposed to 0 kJ m(-)2 da y(-1) UV-B-BE. The content of UV-B absorbing compounds of plants exposed to increasing UV-B did not significantly change. Mini UV-B lamp systems were installed in the field, to expose the terrestri al antarctic vegetation at Leonie Island to enhanced solar UV-B. In that st udy, the increment of shoot length of tagged plants of Deschampsia antarcti ca during the January-February 1999 at Leonie Island, was recorded and comp ared to shoot length growth under controlled conditions. The consequences of enhanced UV-B radiation as a result of ozone depletion for the terrestrial antarctic ecosytems are discussed.