Abstract. The features of the biology of the rare relict petrophytic-steppe species Helianthemum nummularium (L.) Mill., growing on steppe limestone slopes along the southeastern border of the South Ural Reserve, are discussed. Morphometric parameters of medium-aged plants have been established: mature bushes form from 8 to 48 shoots, depending on the habitat; the height of the generative shoot is on average 18.29 cm; inflorescences are loose, from 2 to 7.5 cm long, with an average of 5-6 flowers in diameter from 0.7 to 2.2 cm. The dependence of linear parameters on the influence of weather conditions during the period of active growth and flowering of plants has been determined: shoot height and the number of pairs of leaves per generative shoot depend on climatic conditions by 65-71 %. Based on the correlation analysis, the average dependence of linear parameters on the amount of atmospheric precipitation has been revealed. The metric parameters of the seeds have been established: the pods are on average 0.71 cm long, the seeds – 2.13 mm long. The number of matured seeds that have started is on average 8.71 pcs. per box per, the number of unfulfilled ones is 10.60 pcs. The actual seed productivity per shoot is 43.51 seeds, while the potential seed productivity per shoot is 96.52 pcs. Dry storage of seeds at room temperature for 6 months showed a positive result in their germination. When determining ground germination of seeds, the most optimal methods to obtaine seedlings were identified. The influence of growth stimulants and indoor soil in greenhouse conditions proved to be the most promising and favorable for obtaining friendly shoots. Over a three-year period, it was possible to grow young generative plants from seeds and introduce them at the experimental site of the reserve. A preliminary assessment of the success of the species' introduction on the experimental plot has been obtained.

Key words: rare species, morphometric parameters of plants, seed productivity, seed germination, introduction.