The aim of this work was to study the polyphenolic composition of Deschampsia antarctica È. Desv. plants grown at natural conditions on different locations on the Galindez Island, Argentine Islands, the maritime Antarctic. The plants were collected during the summer season of the 26th Ukrainian Antarctic Expedition (2020–2022). The extracts of 21 plants were obtained and the composition of the extracts was analyzed by means of high-performance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry. The antioxidant properties of the extracts were characterized using the DPPH (2,2-diphenyl-1-picrylhydrazyl) test. The extracts were found to contain large amount of polyphenolic compounds, with flavonoids and phenolic acids, as well as their derivatives, being the most common classes of the phenols. Using the HPLC data the content of various phenols in the plants was systematic studied. It has been found that in all plants the most abundant phenols are flavonoids/flavonoid derivatives (on average about 75% of total mass of phenols). Among the flavonoids, luteolin derivatives predominate (86–94% of the total mass of flavonoids), and, among luteolin derivatives, the main compounds are orientin, orientin 2"- O-β-arabinopyranoside and isoswertiajaponin 2"- O-β-arabinopyranoside (67–83% of the total mass of luteolin derivatives). It has been also found that all the extracts possess the high activity in inhibition of DPPH radicals and that the antioxidant activity of the extracts correlates with total content of phenols in the samples. Thus, Deschampsia antarctica É. Desv. plants are a valuable source of natural phenolic antioxidants, and the most common antioxidants in the extracts are orientin, orientin 2"- O-β-arabinopyranoside and isoswertiajaponin 2"- O-β-arabinopyranoside.

The embryology of two species, Deschampsia antarctica , a native species, and Poa annua , an alien species in the Antarctic we studied. Flowering buds of plants growing in their natural habitats on King George Island and generative tissues of both plant species grown in a greenhouse were analyzed. Adaptations to autogamy and anemogamy were observed in the flower anatomy of both species. The microsporangia of the evaluated grasses produce a small number of three−celled pollen grains. Numerous pollen grains do not leave the microsporangium and germinate in the thecae. Deschampsia antarctica and P. annua plants harvested in Antarctica developed a particularly small number of microspores in pollen chambers. In D. antarctica , male gametophytes were produced at a faster rate: generative cells in pollen did not become detached from the wall of the pollen grain, they were not embedded in the cytoplasm of vegetative cells, and they divided into two sperm cells situated close to the wall. The monosporous Polygonum type of embryo sac development was observed in the studied species. The egg apparatus had typical polarization, and the filiform apparatus did not develop in synergids. Large antipodals with polyploidal nuclei were formed in the embryo sacs of D. antarctica and P. annua . Poa annua was characterized by numerous antipodal cells which formed antipodal tissue in the chalazal region of the embryo sac. Three distinct antipodals with atypical, lateral position in the vicinity of the egg apparatus were observed in D. antarctica. The diaspores of the investigated grass species were characterized by small size, low weight and species−specific primary and secondary sculpture of the testa and caryopsis coat.