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Introduction
Antarctic terrestrial algae are extremophilic organisms capable of surviving in harsh environmental conditions (Hájek et al. 2012, 2016, Gray et al. 2021). One way to withstand extremely low temperatures is via deep dehydration of the algal thallus; however, the molecular mechanisms of cold and drought resistance are not yet fully understood. Low temperature stresses biological systems as it reduces molecular motions and consequently affects the chemical and physical processes that take place in living organism. The effects of low-temperature stresses relate to reduced membrane fluidity, changes in intracellular pH and loss of macromolecular integrity (Clarke et al. 2013). The formation of ice crystals during the freezing of bound water in biological systems causes several additional types of cell damage (Bojic et al. 2021), and the rate of cooling affects the form of ice crystals created. Low cooling rates result in extracellular ice crystals whereas rapid cooling rates result in intracellular crystallites (Chang & Zhao 2021). During ice nucleation, solutes are excluded from the growing ice crystal and the concentration of solutes in the remaining liquid increases.
The analysis of water adsorption in porous materials improves our understanding of the physical and chemical properties of molecules inside the porous polymers of such novel materials as metal-organic frameworks (MOFs) or covalent organic frameworks (COFs; Zhou et al. 2018, Gao et al. 2019, Wang et al. 2019, Zhang et al. 2019). Water adsorbed on the surface of porous materials may reveal different properties than it does in its bulk form. This may be due to the interactions of molecules with the solid material as well as the increased surface-to-volume ratio of materials with smaller pores (Valiullin & Furo 2002).
The aim of our research was to observe the behaviour of water present in the foliose green alga Prasiola crispa (Lightfoot) Menegh. upon cooling of the thallus to -63°C. Prasiola crispa provides a unique opportunity for study, as it is widespread in its free-living as well as lichenized form in the same Antarctic microenvironments. The lichenized form of P. crispa, Turgidosculum complicatulum (= Mastodia tesselata), is created by association with Guingardia prasiolae (Huiskes et al. 1997, Kovačik & Pereira 2001, Kovačik et al. 2003); however, some authors consider Prasiola borealis to be a photobiont of T....