New Light on Dark Stars

Abstract

Mini UV lamps were installed over antarctic plants at Leonie Island, Antarctic 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 Deschampsia antarctica, collected at Leonie Island, Antarctic peninsula, to ambient and enhanced levels of UV-B radiation. In this climate room experiment with 0, 2.5 and 5 kJ m(-2) day(-1) UV-B-BE treatments we observed that length growth of shoots at 2.5 and 5 kJ m(-2) day(-1) UV-B-BE was markedly reduced compared to 0 kJ m(-2) day(-1) UV-B-BE. In addition, there was an increased number of shoots and increased leaf thickness with enhanced UV-B. The Relative Growth Rate (RGR) was not affected by UV-B, possibly because reduced shoot length growth by enhanced UV-B was compensated by increased tillering. 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 day(-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 terrestrial antarctic vegetation at Leonie Island to enhanced solar UV-B. In that study, the increment of shoot length of tagged plants of Deschampsia antarctica during the January-February 1999 at Leonie Island, was recorded and compared 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.