Freeze avoidance: a dehydrating moss gathers no ice

Abstract

Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4°C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to~20% of their original volume at a nadir temperature of -20°C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20°C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at~-12°C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20°C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes.

Molecular mechanisms of desiccation tolerance in the resurrection glacial relic Haberlea rhodopensis

“…In addition to drought, H. rhodopensis can also tolerate chilling and the sub-zero temperatures which often occur during harsh winters. This phenomenon is observed in a few other resurrection species such as the mosses Physcomitrella patens and Ceratodon purpureus [20,21].…”

Freezing tolerance of Porphyra yezoensis (Bangiales, Rhodophyta) gametophyte assessed by chlorophyll fluorescence

“…Freezing avoidance through intracellular water loss plays a significant role in freezing acclimated moss (Lenné et al 2010). It is found that external ice induces desiccation of winter acclimated Ceratodon purpureus, which shows no evidence of freezing at −20°C, while internal ice nucleation occurs in hydrated moss at −12°C (Lenné et al 2010 Cellular water content is a critical factor in determining the freezing tolerance of P. haitanensis thalli. Ninety-nine percent of thalli can survive over 30 d freezing at −20°C when their water content is confined to 10-15%.…”

Impacts of the removal of shrubs on the physiological and biochemical characteristics of Syntrichia caninervis Mitt: in a temperate desert

“…Additionally, in their leaves, bryophytes have evolved intensive and transparent papillae in their hair points and coast, which not only reflect strong light but also favor water collection and transportation24. In acutely cold environments, the cells of bryophytes can rapidly dehydrate and successfully prevent damage as result of ice accumulation in cells25.…”