MORPHOLOGY OF THE EXCRETORY TISSUE AND SECONDARY METABOLITES IN CAMPSIS RADICANS (L.) SEEM. AND LONICERA CAPRIFOLIUM L. LEAVES DUE TO DROUGHT RESISTANCE

In order to assess the drought resistance of shrub vines Campsis radicans (L.) Seem. and Lonicera caprifolium L. in the conditions of Nalchik, an investigation of the morphology of excretory tissue, secondary metabolites, and a morphometric analysis of the structural elements of the leaf epidermis under optimal moisture and soil moisture deficiency conditions were carried out. Excretory tissues are represented by capitate hairs (L. caprifolium and C. radicans), peltate glands (C. radicans) and secretory sinks of lysigenic (L. caprifolium) and schizogenic types. Glandular trichomes synthesize phenolic compounds, alkaloids and essential oil. Schizogenous sinks produce and secrete polyphenols, while lysigenic ones produce essential oil. The secretory activity of epidermal cells at the base of individual covering hairs (polyphenols and alkaloids) of L. caprifolium leaves was revealed. Co-localization of polyphenols and guaiacol peroxidase in glandular trichomes and epidermal cells of the bases of the covering hairs was established. Under optimal moisture conditions, the leaves of L. caprifolium and C. radicans exhibit mesophytic features (large-celled adaxial epidermis, arrangement of stomata on the abaxial epidermis, anomocytic unoriented stomata, weak pubescence). Under moisture deficiency conditions, an increase in xeromorphism is observed (a decrease in the size of epidermal cells and stomata, an increase in the density of stomata, covering hairs and glandular trichomes). The results obtained complement the available information on the resistance mechanisms of shrub vines to soil-air moisture deficiency (physical protection - covering trichomes; biochemical protection – synthesis of polyphenols and terpenoids by structural elements of the excretory tissue, oxidation and polymerization of polyphenols), pathogens, pests (synthesis of terpenoids, anthracene derivatives, tannins, alkaloids). The drought resistance of L. caprifolium and C. radicans makes it possible for them to be widely used in places of mass recreation in the climatic conditions of Nalchik.