О. Н. Загричук, Н. М. Дробик
Тернопольский национальный педагогический университет имени Владимира Гнатюка
DESCHAMPSIA ANTARCTICA DESV.: ХАРАКТЕРИСТИКА ВИДА, ЕГО РАСПРОСТРАНЕНИЕ И ОСОБЕННОСТИ АДАПТАЦИИ К СУЩЕСТВОВАНИЮ В УСЛОВИЯХ АНТАРКТИКИ
Проанализированы литературные источники, касающиеся характеристики высшего сосудистого растения Deschampsia antarctica Desv., которое произрастает и успешно вегетирует в суровых климатических условиях Антарктики. Охарактеризованы биологические и анатомо-морфологические признаки вида; рассмотрены факторы его распространения и особенности адаптации к существованию в условиях низких температур, светового стресса, ультрафиолетового излучения, недостатка влаги, cкудных почв и засоления. Для оценки адаптационной способности D. antarctica к неблагоприятным условиям существования исследователи предлагают использовать сводный латентный показатель приспособляемости для каждой популяции.
Ключевые слова: Deschampsia antarctica Desv., характеристика вида, распространение, адаптивные реакции
O. M. Zahrychuk, N. M. Drobyk
Volodymyr Hnatiuk Ternopil National Pedagogical University, Ukraine
DESCHAMPSIA ANTARCTICA DESV.: SPECIES CHARACTERISTICS, ITS DISTRIBUTION AND DETAILS OF ADAPTATION TO EXISTENCE IN THE ANTARCTIC
Literature sources concerning characteristics of the higher vascular plant (Deschampsia antarctica Desv.), that grows in difficult climatic conditions of the Antarctic, have been reviewed. This species was found to have anatomical and morphological adaptations that are typical for most high latitude plants, increasing their resistance to frost and the photosynthetic activity, including: small sizes and a cushion-like shape of clump, height, depending on conditions, from 0,5 to 22 cm, with two or three or numerous leaves that turn yellow sooner or rich green leaves. The anatomical structure of D. antarctica plants is distinctive for arid habitats, stomata and a thick layer of wax are only on the upper side of leaves. D. antarctica forms mainly soddy groups or occurs as single individuals. Species vegetative propagation takes place by outgrowth of dense clumps from one metre to tens of kilometres. Some free icy cover land areas (oases) occupy 1.0-5.0% of the mainland and only 5.0-10% of this area is occupied by soils. Soils or soil substrates, on which D. antarctica grows, differ in their species composition and medium reaction (pH 3,6-7,4). The source for plant growth of D. antarctica is inorganic nitrogen, organics in the form of amino acids as well as nitrogen within the composition of peptide entering through the root system of plants. It has been found that D. antarctica absorbs nitrogen in the form of short peptides three times faster than amino acids, nitrates and ammonium and 160 times faster than the Arctic mosses and lichens. One of the main factors influencing D. antarctica is the placement of penguin colonies that bring the organic matter, guano into terrestrial ecosystems of Maritime Antarctica. The spatial distribution of D. antarctica largely depends on the places of nesting, places of birds’ nurishment and seats of birds’ accidental losses of the viable plant material during its transportation. The details of species adaptation to existence in low temperature conditions, light and UV stress, lack of moisture, depleted soils and salinity were reviewed. D. antarctica demonstrated biochemical attributes that are adaptive in nature to the cold Antarctic climate. Accumulation of the heat shock protein of 70 kDa (Hsp 70) occurs in this species upon cold and heat stress. It is believed that, perhaps, it is the protein in D. antarctica that provides the low temperature optimum of photosynthesis (+13оС). The increased synthesis of dehydryne proteins, which are likely to prevent the formation of ice in cells, is observed during the cold acclimatization of D. antarctica plants. D. antarctica showed a high content of antifreeze proteins that are probably needed to survive during a long period of negative temperatures close to zero. One of the security features of D. antarctica protection from negative temperatures is the accumulation of soluble sugars in tissues: maximum accumulation of sucrose, fructose and glucose in the leaves of plants of this species occurs before the beginning of the Antarctic winter. D. antarctica posesses the genetically determined mechanisms to counteract the harmful effects of ultraviolet radiation. This species is distinguished by higher compared with other plants the superoxide dismutase activity level and ascorbate peroxidase as well as an active xanthophyll cycle. Extracts of D. antarctica show sunscreen properties that may be associated with molecules such as flavonoids and carotenoids that act as UV-absorbing molecules and antioxidants. It is proposed that the photochemical quenching and the high level of antioxidants, in particular, promote D. antarctica to resist photoinhibitory conditions. The relatively high species antioxidant capacity can be considered as one of the key features of its adaptation to survive in critical conditions of Antarctica. The researchers propose to use a latent indicator of adaptability for each population to evaluate the adaptability of D. antarctica to adverse living conditions of existence.
Keywords: Deschampsia antarctica Desv., species characteristics, distribution, adaptive reactions