Polyol and sugar content of terrestrial plants from continental Antarctica

Abstract

Ethanol extractable polyols and sugars from the dominant cryptogams of the Windmill Islands, Wilkes Land, East Antarctica, were characterized and quantified by gas liquid chromatography. Arabitol, ribitol and mannitol were the major low molecular weight carbohydrates extracted from all eight species of lichen analysed. Total extractable carbohydrate levels (20–60 mg g−1 dry weight) were comparable to those for temperate lichens. Extracts of four common bryophyte species were dominated by sucrose, glucose and fructose; little polyhydric alcohol was detected except in the liverwort Cephaloziella exiliflora which contained a substantial proportion of mannitol. Total carbohydrate levels in the bryophytes (9–60 mg g−1 dry weight) were comparable to those in lichens. The compositions of eight species of algae varied considerably. Prasiola crispa, Desmococcus vulgaris and Schizogonium murale possessed sorbitol as their main constituent and had extractable carbohydrate contents comparable to those found in bryophytes on a dry weight or chlorophyll a content basis. The one snow alga with comparable carbohydrate levels, Mesotaenium berggrenii, contained sucrose, glucose, glycerol and a number of unidentified compounds. The remaining four species (Oscillatoria sp., Chloromonas sp.1 and Chlorosarcina sp. 2 and Chlamydomonas pseudopulsatilla) did not accumulate comparable levels of sugars and polyols. Though the levels of these compounds were much lower in the Windmill Islands lichens than in maritime Antarctic species, their content with respect to water content (0.7–7 molal) was well above that at which cold acclimated plants accumulate these compounds (c. 100–500 millimolal), and which provide cryoprotection in vitro. In the case of the bryophytes and algae, however, the in vivo content was generally < 100 millimolal.

Some like it wet — biological characteristics underpinning tolerance of extreme water stress events in Antarctic bryophytes

“…5), but concentrations for this species were still within the range found for the three study species in a previous study (Roser et al 1992) and in arctic Polytrichum (Sveinbjornsson andOechel 1991, Barsig et al 1998). Conversely, C. purpureus had the highest concentration of fatty acids and the ratio of total fatty acids: identified soluble carbohydrates was approximately 5-fold higher in C. purpureus (0.756) than the other two species: B. pseudotriquetrum (0.158) and G. antarctici (0.145).…”

“…This compound is common in many organisms capable of withstanding near-complete desiccation, including cyanobacteria, fungi, yeast, arthropods and plant seeds, as it is very effective at stabilizing proteins and other macromolecules during dehydration (Crowe et al 1992). It has been suggested that caution should be exercised, however, regarding the detection of trehalose in fieldcollected, continental Antarctic bryophytes; as it usually occurs only in low levels, and is absent from laboratory grown C. purpureus and temperate moss species (Roser et al 1992). Roser et al 1992 suggest trehalose maybe derived from epiphytic fungi rather than bryophyte tissue, however if this is the case it would indicate high fungal contamination.…”

“…It has been suggested that caution should be exercised, however, regarding the detection of trehalose in fieldcollected, continental Antarctic bryophytes; as it usually occurs only in low levels, and is absent from laboratory grown C. purpureus and temperate moss species (Roser et al 1992). Roser et al 1992 suggest trehalose maybe derived from epiphytic fungi rather than bryophyte tissue, however if this is the case it would indicate high fungal contamination.…”

“…In addition to providing energy rich storage, fatty acids are important for cell membrane structure and function (Hulbert 2003), and fatty acid composition is important in development of chilling and freezing tolerance. Various soluble carbohydrates can provide protection during desiccation and freezing (Roser et al 1992, Montiel 2000, Robinson et al 2000 and bryophytes are known to contain soluble carbohydrate contents that parallel those in the embryos of maturing seeds (Proctor 2000). Since the quantity and type of soluble carbohydrate and lipid compounds can be important factors for protection during desiccation in plants ( Koster andLeopold 1988, Ghasempour et al 1998), concentrations of these biochemical factors were determined for the study species.…”

Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

“…We suggest these pools to have different functions within the lichendominated BSC. The short-chained sugars and sugar alcohols with low-molecular weight in the alcohol fraction have been assigned to many different roles in terms of stress resistance and survival, desiccation protection (Kranner et al, 2008), freezing protection (Tearle, 1987;Roser et al, 1992) or being antioxidants (Kranner et al, 2005;Green et al, 2011;Figure 4). No such roles have been described for the hot water soluble long-chain carbohydrates and we suggest this pool to be an intermediate storage mainly to support growth but also to sustain the short-chained sugar pool if necessary (absolute transfer rate from one compartment to another is 2.5 Â 10-4/h, Farrar, 1978).…”