Anatomical and morphological features of leaves of Rhodiola rosea L. in natural conditions of the mountains in Southern Siberia (Altai Mountains)

The study of natural coenopopulations of the rare medicinal species Rhodiola rosea is of highest relevance for conservation of this valuable plant species. Analysis of the adaptive response of the species growing under different environmental conditions is basically used to elaborate recommendations for its protection and rational use. The aim of this work was to study the anatomical and morphological features of the leaf blades of Rh. rosea growing under different environmental and coenotic conditions of the Altai Mountains. We studied the anatomical features of leaves of Rh. rosea from 7 coenopopulations (in one coenopopulation, both female and male plants were studied) and assessed the adaptive response of plants to different growing conditions by conventional methods. The values of indicators from different coenopopulations were compared by one-way analysis of variance (ANOVA), and the correlation coefficient was calculated to estimate the correlation between different indicators. The study revealed a reserve of adaptive plasticity for Rh. rosea, which allows the species to grow under different light and water conditions. For specimens from one geographic location studied, statistically significant differences in the indicator values were fewer compared with specimens from different areas. Heliophytic and xerophytic adaptations of the studied plants varied depending on coenopopulation. The analysis of male and female Rh. rosea species from the Kurai ridge (CP 3) revealed that the most photosynthetically active layer and vascular tissue are better developed in leaves of females compared to males. It was found that Rh. rosea growing in the mountains bear shorter and thicker leaves; the thickness of integumentary tissue with cuticle increases at higher altitudes, the number of stomata and cells on integumentary tissue per epidermis unit area decreases, and the thickness of photoassimilating tissue grows. Changes in anatomical and morphological characteristics are adaptive responses to increased insolation at higher altitudes and, probably, to decreased partial pressure of carbon dioxide.