Utility of Modulated Fluorescence in Measuring Photosynthetic Activity of Antarctic Plants: Field and Laboratory Studies

Abstract

Antarctic terrestrial plants face severe physiological stress conditions daily. In winter there is extreme cold and darkness. During summer there is continuous light for some months and plant surface temperatures may fluctuate through more than 50ºC diurnally. Conditions are almost uniformly desiccative, except during spring when snow melt saturates thalli and plants may be completely inundated. The study of photosynthesis in these conditions is fundamental to a proper understanding of plant persistence, productivity and growth in polar regions. Lichens dominate the terrestrial vegetation of Antarctica and are therefore of great interest. Lichen photosynthesis has been shown to be dependent upon thallus water content and temperature as well as the irradiance incident on the thallus. Conventional infrared gas analysis (IRGA) techniques have been used most widely to study lichen photosynthesis in both the field and laboratory. Recent progress in the development of pulse amplitude modulated fluorescence systems has allowed the investigation of chlorophyll fluorescence in the field under naturally illuminated conditions. This paper highlights the utility of modulated fluorescence systems for the study of antarctic lichen photosynthesis, relates fluorescence results to those obtained by IRGA techniques, identifies problems inherent in fluorescence analysis of lichens and discusses possible areas of future research.