Cold resistance in Antarctic angiosperms

Abstract

Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Cariophyllaceae) are the only two vascular plants that have colonized the Maritime Antarctic. The primary purpose of the present work was to determine cold resistance mechanisms in these two Antarctic plants. This was achieved by comparing thermal properties of leaves and the lethal freezing temperature to 50% of the tissue (LT50). The grass D. antarctica was able to tolerate freezing to a lower temperature than C. quitensis. The main freezing resistance mechanism for C. quitensis is supercooling. Thus, the grass is mainly a freezing‐tolerant species, while C. quitensis avoids freezing. D. antarctica cold acclimated; thus, reducing its LT50. C. quitensis showed little cold‐acclimation capacity. Because day length is highly variable in the Antarctic, the effect of day length on freezing tolerance, growth, various soluble carbohydrates, starch, and proline contents in leaves of D. antarctica growing in the laboratory under cold‐acclimation conditions was studied. During the cold‐acclimation treatment, the LT50 was lowered more effectively under long day (21/3 h light/dark) and medium day (16/8) light periods than under a short day period (8/16). The longer the day length treatment, the faster the growth rate for both acclimated and non‐acclimated plants. Similarly, the longer the day treatment during cold acclimation, the higher the sucrose content (up to 7‐fold with respect to non‐acclimated control values). Oligo and polyfructans accumulated significantly during cold acclimation only with the medium day length treatment. Oligofructans accounted for more than 80% of total fructans. The degrees of polymerization were mostly between 3 and 10. C. quitensis under cold acclimation accumulated a similar amount of sucrose than D. antarctica, but no fructans were detected. The suggestion that survival of Antarctic plants in the Antarctic could be at least partially explained by accumulation of these substances is discussed.

Carbohydrates in Colobanthus quitensis and Deschampsia antarctica

“…Starch content in tissues of C. quitensis was relatively low, still it was twice as high as reported by Bravo et al (2001) and comparable to the level found in A. reptans (Bachman et al 1994). Microscopic analyses have shown that it was localized in chloroplasts only.…”

“…It is possibly another way of setting up a carbon (assimilate) reserve, which will be used in autumn for cellular structures reconstruction, and synthesis of cryoprotectants. The level of starch in tissues of Deschampsia antarctica is very high, several fold higher than might be inferred from studies by Bravo et al (2001), carried out under unnatural conditions. These data are corroborated by microphotographs, in which many chloroplasts can be seen, containing globular, typically shaped and coloured starch grains.…”

“…Bravo et al (2001) have shown that Deschampsia antarctica is highly freeze-tolerant even during the austral summer. To function at low temperatures plants must have membranes with sufficient fluidity, without which normal metabolism would not be possible.…”

Changes in soluble carbohydrates in polar Caryophyllaceae and Poaceae plants in response to chilling

“…The accumulation of the above SCs could be a mechanism which conditions plant resistance to cold stress (Bravo et al 2001;Krasensky and Jonak 2012). In our study, all of the analyzed plant species responded to chilling by accumulating sucrose (Figs.…”

Genetic variability of Colobanthus quitensis from King George Island (Antarctica)

“…Although C. quitensis and D. antarctica were intensively analyzed to− wards their morphological, anatomical and physiological adaptations to local cli− matic conditions (e.g. Bravo et al 2001;Bravo and Griffith 2005;Giełwanowska et al 2008;Ruhland and Krna 2010), we still have limited knowledge about the genetic variability of these species. Our knowledge concerning the genetic diver− sity of these plants is based mainly on a small number of publications devoted to D. antarctica (e.g.…”