Ecophysiological traits of Antarctic vascular plants: their importance in the responses to climate change

Only two vascular plants have been able to colonize some of the ice and snow-free lands of the Antarctic Peninsula: the hair grass Deschampsia antarctica (Poaceae) and the pearlwort Colobanthus quitensis (Caryophyllaceae). This low species diversity may be due to the permanent low temperature even during summer time. Beside low temperature, Antarctic plants must be able to cope with other severe physiological stressors such as desiccation, low soil water availability, and high irradiance. However, these factors are found in other cold areas of the globe. Thus, what is so special about these two species that has enabled them to be the only successful flowering plants in the Antarctica? Although this question has been addressed in other articles, we still lack of an integrative ecophysiological framework that helps to disentangle what it is unique of these species in terms of adaptations to the Antarctic environments, and how these adaptations will help or preclude their responses to future climate change. Several adaptations seem to help to withstand the Antarctic climate: xerophytic anatomical characteristics, sufficient freezing tolerance, ability to maintain positive net photosynthesis at near 0 degrees C, adequate management of excess photosynthetic active radiation, resistance to photoinhibitory conditions, tolerance to water stress, and ability to form associations with endophytes that help in their mineral nutrition. Besides the very effective stress tolerance strategies, several ecophysiological traits show considerable response flexibility. The evidence reviewed here indicates that small increases in air temperature may be beneficial in terms of photosynthetic performance. However, increased frequency of leaf temperatures over 20 degrees C could be harmful affecting photosynthesis and reducing the ability of these plants to tolerate freezing temperatures and photoprotection at low temperatures, attributes by which they are able to colonize these very harsh environment.