FORMATION OF THE VEGETATIVE SPHERE OF SPECIES OF THE GENERA HYLOTELEPHIUM H. OHBA AND SEDUM L. AT DIFFERENT LEVELS OF ILLUMINATION

Introduction. To optimize and ensure the stability of plantations in park territories, which represent a significant part of recreational plantations in city Kryvyi Rih, it is necessary to implement herbaceous ornamental plants that are able to function in conditions of partial and complete shading. To determine hardy species, it is necessary to study the features of the formation of the vegetative sphere of perennial plants. Aim. The aim of the work was to study the peculiarities of the formation of the vegetative sphere of species of the genera Hylotelephium H. Ohba and Sedum L. which are not common in culture at different levels of illumination during seasonal development in conditions of the Kryvyi Rih Botanical Garden of the National Academy of Sciences of Ukraine. Methods. The objects of the study were plants Hylotelephium ewersii (Ledeb.) H. Ohba, Hylotelephium spectabile (Boreau) H. Ohba, Sedum album L., Sedum reflexum L. and Sedum spurium M. Bieb.. Plots with different levels of illumination were organized outdoors: a well-lit area (control plot) – the level of illumination at lunchtime reached 39 000–56 500 lux; a shady area – the level of illumination at lunchtime was 2 500–3 500 lux. The study was conducted in three stages: the third decade of May, July and September. The elongation coefficient of the leaf was determined as the ratio of the length to the width, the area of the leaf using the method of impressions and morphology monocarpic shoots. The main results. It was determined that with sufficient lighting, active shoot formation took place – at the end of September in S. album plants were formed 16 shoots of the II order and 2-4 pcs. ІІІ order shoots were formed; in S. reflexum – 12 pcs. and 1–2 pcs. In S. spurium and H. ewersii, the shoots branched only up to the II order – in September there were 2–6 pcs. Under the conditions of growing in the shade, S. reflexum and S. spurium occasionally formed 1–2 shoots of the II order in the basal part of generative shoots and S. album – 3–7 pcs. Plants of H. ewersii under shade conditions did not form monocarpic shoots. The length of the shoots under the conditions of growing stonecrops with sufficient lighting until September increased by 1.5 (S. spurium, H. ewersii) – 2.2 times (S. album, H. spectabile). On the other hand, in the shade, the length of monocarpic vegetative shoots exceeded the control indicators by 1.6–2 times only in species of the genus Sedum (in S. reflexum it reached 17.8 cm). Under these conditions, the smallest growth rates were characteristic of H. ewersii – 8.9 cm in September. The study of morphometric parameters of leaf development proves that both in light and in shade conditions, S. reflexum, H. ewersii and H. spectabile formed fewer leaves on an annual shoot, both in May – 1.2–1.4 times and in September – 1.3–3 times. In contrast, S. spurium had 1.4 times more leaves. Growing plants in shade conditions leads to a significant decrease in leaf surface area, compared to the sunny areas in H. spectabile by 35% in May, while in H. ewersii it almost halved. In S. reflexum and S. album, the coefficient of leaf elongation increased by 1.2–1.6 times in May and by 2.4–2.6 times in September. Conclusions. Thus, the data obtained indicate that there are changes in the growth and development of the vegetative sphere of the studied species during the seasonal development of plants in the conditions of the Kryvyi Rih Botanical Garden of the National Academy of Sciences of Ukraine. Under conditions of insufficient illumination, the smallest quantitative changes in the development of the vegetative sphere were characteristic of S. album plants, in which, relative to the indicators from well-lit areas, the length of monocarpic shoots decreased by only 9%, and the length of internodes did not change significantly. In contrast, in S. spurium, the length of vegetative shoots in the shade was 11% longer than in the light, but this was due to the lengthening of internodes by 33%, which led to “stretching” of shoots. With full shading, the decorativeness of S. reflexum plants decreased, in which not only the length of the internodes increased by 1.7 times, but also the number of leaves per shoot decreased by 40%. In conditions of complete shading, H. ewersii plants “felt” the worst, because the growth processes of assimilation organs were inhibited almost twice and there was no additional branching of shoots. The results of the research will allow not only to expand the range of ornamental plants in urban landscapes, but also to determine the practical principles of their rational use. The prospects of their application in landscaping will be determined to optimize costs when performing work on the reconstruction of flower and ornamental plantations in the urban landscapes of the steppe zone of Ukraine.