Home – Home – Jornals – Contemporary Problems of Ecology 2021 number 5

During the study, the structural adaptations of the desiccation-resistant homosporous fern Ceterach officinarum Willd were revealed at the organ and cellular-tissue levels. Among them, the main role is played by features that contribute to the maintenance of cell hydration. Xero-heliomorphic signs at the organ level: nanism, area reduction and leatheriness of fronds; dense cover of trichomes and scales. At the cellular-tissue level, water is retained due to the relatively thick blade of fronds, their small cells, a large number of cells per unit area and pycnomorphy, high values of the specific surface area of the fronds (UPW), dorsiventrality of the mesophyll, a relatively dense network of veins per unit area of the frond. Biochemical and functional - by increasing the concentration of osmotically active substances, lowering osmotic pressure, accumulation of water-retaining chemical compounds (catechins and tannins); on the phytocenotic - due to facultative bryophily. Sciomorphic features: at the cellular-tissue level - hypostomaticity, a relatively small number of stomata per unit area of frond, tortuous seams of epidermal cells, minimal values of the ratio of cell surface to volume. Mesomorphic features: differentiation of the mesophyll into columnar and spongy tissue, a thin cuticle layer on the surface of the epidermis, the presence of stomata in the lower epidermis. Another adaptation mechanism that determines the rhythm of fern development is the ability to inactivate life processes and fall into cryptobiosis under conditions of water stress and high temperatures. Unlike poikilohydric ectohydric bryophytes, the sporophytes of this fern, resistant to dehydration, can withstand drying out (and are, to this extent, poikilohydric), but are endohydric. In a word, the poikilohydricity of fern sporophytes is realized on a different structural basis, which is more evolutionarily advanced in comparison with thalloid plants. However, the frequent state of cryptobiosis, especially under conditions of alternating wet and long dry seasons, leads to an imbalance in carbon metabolism. Apparently, poikilohydricity is not the most perfect and productive way to combat drought.