<i>Helleborus caucasicus</i> А. Br.: biological characteristic and methods of its preservation (literature review)
Based on modern literature, this paper substantiates the relevance and necessity of preserving a rare, endemic species Helleborus caucasicus A. Br. growing in the natural flora of the Northwestern Caucasus. Information on the taxonomy and geographical distribution of H. caucasicus is briefly presented. The description of its biological and morphological features is given. Also, due to the fact that the species has a category and status: 3, "Vulnerable", rare, "in a state close to endangered", and taking into account that the problem of its preservation is acute, the paper has analyzed and provided information on the introduction of Caucasian hellebore into sterile conditions, as well as other species of the genus Helleborus L. Techniques of their micropropagation and preservation in vitro are presented. An effective method of sterilizing explants is described, which significantly simplifies the process of obtaining a sterile culture. It is shown that shoots and seeds of plants are the best explants for introduction into culture. The review also considers the optimization of nutrient media and growth regulators for accelerating micropropagation of H. caucasicus and other hellebore species. Optimal substrates at the stage of adaptation of micro-propagated hellebore plants to non-sterile conditions are given. The resulting specimens are used to replenish collections that are the basis for creating in vitro genetic banks of rare and endangered plant species. The protocols described in the literature allow us to develop optimal conditions for in vitro introduction, preservation and reproduction of Caucasian hellebore which is a rare species of natural flora.