AUTHOR=Sierra-Almeida Angela , Cavieres Lohengrin A. , Bravo León A. 

TITLE=Warmer Temperatures Affect the in situ Freezing Resistance of the Antarctic Vascular Plants

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01456

DOI=10.3389/fpls.2018.01456

ISSN=1664-462X

ABSTRACT=<p>Although positive effects on growth and reproduction of Antarctic vascular plants have been reported under warmer temperatures, it could also increase the vulnerability of these plants to freezing. Thus, we assessed <italic>in situ</italic> whether warming decreases the freezing resistance of <italic>Colobanthus quitensis</italic> and <italic>Deschampsia antarctica</italic>, and we compared the level and mechanism of freezing resistance of these species in the field with previous reports conducted in lab conditions. We assessed the freezing resistance of <italic>C. quitensis</italic> and <italic>D. antarctica</italic> by determining their low temperature damage (LT<sub>50</sub>), ice nucleation temperature (NT) and freezing point (FP) in three sites of the King George Island. Plants were exposed during two growing seasons to a passive increase in the air temperature (+W). +W increased by 1K the mean air temperatures, but had smaller effects on freezing temperatures. Leaf temperature of both species was on average 1.7K warmer inside +W. Overall, warming decreased the freezing resistance of Antarctic species. The LT<sub>50</sub> increased on average 2K for <italic>C. quitensis</italic> and 2.8K for <italic>D. antarctica.</italic> In contrast, NT and FP decreased on average <italic>c.</italic> 1K in leaves of warmed plants of both species. Our results showed an averaged LT<sub>50</sub> of -15.3°C for <italic>C. quitensis</italic>, and of -22.8°C for <italic>D. antarctica</italic>, with freezing tolerance being the freezing resistance mechanism for both species. These results were partially consistent with previous reports, and likely explanations for such discrepancies were related with methodological differences among studies. Our work is the first study reporting the level and mechanisms of freezing resistance of Antarctic vascular plants measured <italic>in situ</italic>, and we demonstrated that although both plant species exhibited a great ability to cope with freezing temperatures during the growing season, their vulnerability to suffer freezing damage under a warming scenario increase although the magnitude of this response varied across sites and species. Hence, freezing damage should be considered when predicting changes in plant responses of <italic>C. quitensis</italic> and <italic>D. antarctica</italic> under future climate conditions of the Antarctic Peninsula.</p>