ANATOMICAL STRUCTURE OF THE LEAFS OF ORNAMENTAL STONECROPS OF THE GENERA SEDUM L. AND HYLOTELEPHIUM H. OHBA UNDER CONDITIONS OF DIFFERENT LIGHT LEVELS

Abstract

The paper presents the results of determining the quantitative and qualitative characteristics of the anatomical structure of the leaf of the ornamental stonecrops of the genera Sedum L. and Hylotelephium H. Ohba during the seasonal development at different levels of illumination in the conditions of the Kryvyi Rih Botanical Garden of the NAS of Ukraine, which is located in the steppe zone of Ukraine (arid agroclimatic zone).The objects of the study were the plants Hylotelephium ewersii, Hylotelephium spectabile, Sedum album, Sedum reflexum and Sedum spurium. Research was carried out on sites with different levels of illumination: a well-lit place of growth (control site) - the level of illumination at lunchtime reached 39,000–56,500 lux in clear weather and 14,500–23,500 lux on an overcast day; shadow area - the light level at lunch time in clear weather reached 2,500-3,500 lux, and on an overcast day 1,200-2,000 lux. The research was conducted in three stages: the end of May, the end of July, and the end of September. We used 5 individuals of each species, which were grown in open ground (ordinary black soil) at a natural level of moisture supply. Anatomical studies were performed on live specimens using standard methods. The material for the studies was preparations of morphologically mature leaves taken from the middle tier of individuals. It was found that during the seasonal development of plants, changes occur in the anatomical structure of leaves. In plants of H. ewersii, H. spectabile, S. reflexum and S. spurium, leaf thickness was greater in conditions of sufficient light and there was a decrease in leaf blade thickness during seasonal development (from May to September), both in the sun and in the shade. Under conditions of shade at the end of the season, leaf thickness decreased most significantly in H. spectabile and S. spurium - almost twice. On the other hand, in S. spurium, under insufficient lighting, the thickness of the lower and upper epidermis increased more than twice, and in H. spectabile, the thickness of the cuticle increased in both variants of the experiment - in the sun by 2.1 times, in the shade by 1.4 times. In stonecrops with flat leaves, the diameter of the central conducting bundle during the season in sunny conditions was 26 % (S. spurium) – 52 % (H. spectabile) larger than in the shade. Only in S. album, from May to September, leaf thickness and the diameter of the central conductive bundle, in absolute terms, were larger in the shade than in the sun. The obtained results indicate high plasticity of the studied species and peculiarities of phenotypic changes in the anatomical structure of leaves. Key words: family Crassulaceae, leaf anatomy, light level, steppe zone, Krуvorіzhzhуа, seasonal development