Gravisensitivity of mosses at different stages of their ontogenesis has an adaptive value and contributes to the functional activity of the gametophyte and its stability under extreme conditions in microhabitats. The aim of our research was to determine the participation of gravimorphoses in the adaptive plasticity of mosses depending on thermal conditions of their habitats and UV radiation effect. The objects of the study were sterile cultures of the following moss protonemata: Weissia tortilis, collected in different thermal conditions of Zaporizhzhya and Lviv regions (Ukraine), Bryum caespiticium from Lviv Region (Ukraine), as well as B. caespiticium and Polytrichum arcticum collected in Antarctica (Galindez Island). In all moss cultures, the gravisensitivity of protonemata, the morphological structure and morphogenesis of stolons were analysed. The protonemata of W. tortilis from two populations in Ukraine and of B. caespiticium from Antarctica and Ukraine, growing under conditions of different UV levels, were compared in terms of their sensitivity to UV radiation. Gravity-dependent morphoses of terrestrial dendrites of W. tortilis under arid conditions, branching of apical cells of gravitropic stolons of Antarctic mosses P. arcticum and B. caespiticium as well as the rapid development of shoots on them demonstrate participation of gravimorphogenesis in adaptation of mosses to stressful environmental conditions. Gravisensitivity and ability to form buds at the apex of a gravitropic stolon are considered an important adaptive morphogenetic process. It has been found that plants of W. tortilis from Zaporizhzhya Region were more resistant to UV irradiation than those from Lviv Region. Antarctic moss after UV irradiation showed significantly higher antioxidants activity and contained larger amount of phenolic compounds and flavonoids.
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