Photosynthetic activity and protective reactions of mosses in forest ecosystems of the Ukrainian Roztochia under changing ecological conditions

Background. The photosynthetic activity of mosses has not been studied sufficiently, in contrast to vascular plants. Taking into account the specifics of the moss gametophyte organization (poikilohydricity, absence of epidermis, stomata, cuticle), it is relevant to perform a comparative analysis of photosynthetic activity and flavonoid-based antioxidant systems in endohydric and ectohydric moss species in relation to microecological gradients of moisture and temperature in forest ecosystems of the Ukrainian Roztochia. Materials and Methods. The objects of the research were forest endohydric mosses Polytrichum formosum Hedw., Atrichum undulatum (Hedw.) P. Beauv. and ruderal ectohydric moss Ceratodon purpureus (Hedw.) Вrid. from experimental plots of forest coenoses that differed in environmental conditions. The content of photosynthetic pigments, Rubisco activity, photosynthesis intensity, antioxidant activity and flavonoids content were determined using standard methods. Results. Significant plasticity of the mosses’ photosynthetic apparatus (chlorophylls and carotenoids content, Chl a/b ratio) was noted, which indicates an adaptation of bryophytes to changes in water and temperature regimes as well as light intensity. It was shown that the carboxylase activity of Rubisco is an indicator of the photosynthesis intensity of mosses and differs in endohydric and ectohydric species. Increasing antioxidant activity in moss cells relative to the environmental conditions was studied. The content of flavonoids and their absorption spectra in the moss shoots were studied. Conclusions. Under unfavorable environmental conditions, an increase in the content of carotenoids in moss shoots, a decrease in the proportion of chlorophyll a in the total pool of chlorophylls to 52–56 %, as well as an increase in the proportion of chloro­phyll b, was established. The higher intensity of photosynthesis in endohydric mosses Atrichum undulatum and Polytrichum formosum was ensured by a 25–53 % higher and more stable Rubisco activity, compared to the ectohydric moss Ceratodon purpureus. Under conditions of moisture deficiency, an increase in antioxidant activity by 27–30 % and in the flavonoid content by 22–48 % in moss shoots was noted. In Atrichum undulatum gametophores, a 3.5–4.0 times higher antiradical activity was observed, indicating prospects for its further research. Analysis of absorption spectra of flavonoids extracts from P. formosum and C. purpureus showed the presence of flavonols and anthocyanins.