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

Abstract

Antarctic bryophyte communities presently tolerate physiological extremes in water availability, surviving both desiccation and submergence events. This study investigated the relative ability of three Antarctic moss species to tolerate physiological extremes in water availability and identified physiological, morphological, and biochemical characteristics that assist species performance under such conditions. Tolerance of desiccation and submergence was investigated using chlorophyll fluorescence during a series of field-and laboratorybased water stress events. Turf water retention and degree of natural habitat submergence were determined from gametophyte shoot size and density and ?13C signatures respectively. Finally, compounds likely to assist membrane structure and function during desiccation events (fatty acids and soluble carbohydrates) were determined. The results of this study show significant differences in the performance of the three study species under contrasting water stress events. The results indicate that the three study species occupy distinctly different ecological niches with respect to water relations and provide a physiological explanation for present species distributions. The poor tolerance of submergence seen in Ceratodon purpureus helps explain its restriction to drier sites and conversely, the low tolerance of desiccation and high tolerance of submergence displayed by the endemic Grimmia antarctici is consistent with its restriction to wet habitats. Finally the flexible response observed for Bryum pseudotriquetrum is consistent with its co-occurrence with the other two species across the bryophyte habitat spectrum. The likely effects of future climate change induced shifts in water availability are discussed with respect to future community dynamics.

Using a Micro-Uav for Ultra-High Resolution Multi-Sensor Observations of Antarctic Moss Beds

“…In a manner similar to trees, old growth mosses also preserve a climate record along their shoots. Our ability to accurately date these mosses and map their extent in sufficient spatial detail means that, for the first time, mosses can be used as sentinels to provide crucial information on how the Antarctic coastal climate has changed over past centuries and how biota has responded to these changes (Lovelock and Robinson, 2002;Robinson et al, 2003;Wasley et al, 2006).…”

Physiological Traits of Organisms in a Changing Environment

“…Species-specific differences in tolerance of desiccation have been detected for three moss species from the Windmill Islands, East Antarctica (Robinson et al 2000, Wasley et al 2006b), with two cosmopolitan species (Bryum pseudotriquetrum, Ceratodon purpureus) able to metabolise at lower turf water content than the endemic Grimmia antarctici Shistidium antarctici. Bryum pseudotriquetrum also shows greater plasticity than the other species, with plants from drier sites showing greater tolerance of desiccation that those from wetter sites, in addition to seasonal changes in desiccation tolerance (Robinson et al 2000, Wasley et al 2006b).…”

“…Species-specific differences in tolerance of desiccation have been detected for three moss species from the Windmill Islands, East Antarctica (Robinson et al 2000, Wasley et al 2006b), with two cosmopolitan species (Bryum pseudotriquetrum, Ceratodon purpureus) able to metabolise at lower turf water content than the endemic Grimmia antarctici Shistidium antarctici. Bryum pseudotriquetrum also shows greater plasticity than the other species, with plants from drier sites showing greater tolerance of desiccation that those from wetter sites, in addition to seasonal changes in desiccation tolerance (Robinson et al 2000, Wasley et al 2006b). The ability to survive repeated desiccation and freezing events is probably related to the high concentrations of soluble carbohydrates found in these species (Melick and Seppelt 1994b) and in particular the presence of compounds such as stachyose and trehalose in B. pseudotriquetrum (Robinson et al 2000, Wasley et al 2006b).…”

“…Bryum pseudotriquetrum also shows greater plasticity than the other species, with plants from drier sites showing greater tolerance of desiccation that those from wetter sites, in addition to seasonal changes in desiccation tolerance (Robinson et al 2000, Wasley et al 2006b). The ability to survive repeated desiccation and freezing events is probably related to the high concentrations of soluble carbohydrates found in these species (Melick and Seppelt 1994b) and in particular the presence of compounds such as stachyose and trehalose in B. pseudotriquetrum (Robinson et al 2000, Wasley et al 2006b). In contrast C. purpureus has a much higher proportion of fatty acids/soluble carbohydrates.…”

“…In contrast C. purpureus has a much higher proportion of fatty acids/soluble carbohydrates. All three species have a high proportion of their fatty acids in polyunsaturated forms (> 67%), a feature characteristic of cold tolerant higher plants (Zuñiga et al 1996, Wasley et al 2006b). Quantifying the relative importance of lipids versus soluble carbohydrates in these freeze tolerant plants stands out as an interesting target for further study, it may be that lipids are a safer storage compound, since soluble carbohydrates are known to leak from bryophytes during desiccation-rehydration and freeze thaw cycles .…”