Introduction. Due to the global pharmaceutical pollution of water bodies in many countries, there is currently an increasing interest of researchers in finding effective, including microbiological, ways of processing pharmaceutical waste to obtain new useful products based on them. The results of previous studies have shown that the product of bacterial destruction of paracetamol exhibits pronounced stimulating properties in relation to medicinal plants of the aster, linseed, clear-flowered, plantain, etc. families. There is no information about the effect of this product on plants of the liliaceae family.Aim. To investigate the effect of the paracetamol biodegradation product on the quantitative indicators of the anatomical structure of the lily of the valley leaf – Convallaria majalis L., fam. Liliaceae.Materials and methods. The experiments were laid in the Kirov region (2021, 2022) in accordance with the Guidelines for Conducting Registration Tests of Growth Regulators (2016). The scheme of the experiment: the control area – natural watering with water; the test area – watering with the product of biodegradation of paracetamol obtained on the basis of the laboratory of alkanotrophic microorganisms of the PFRC UB RAS (Perm); the reference area – watering with the growth stimulator "Zircon" (NRPP "NEST M", Russia). Quantitative parameters of the anatomical structure of the lily of the valley leaf were evaluated by the linear dimensions of the epidermis, elements of the conducting system and mesophyll. Viewing, photographing and processing of photographs was carried out using a microscope Motic (Motic Deutschland GmbH, Germany) in the program Motic Image 2000. Mathematical processing of experimental data was carried out by the method of variance analysis using Excel 2019, STATISTICA 12.6, STATGRAPHICS Plus 5.1 programs.Results and discussion. Anatomical examination showed an increase in the size of the cells of the upper and lower epidermis of the lily of the valley leaf in the designated growing seasons on the accounting sites treated with a product of the biodegradation of paracetamol and a standard ("Zircon") in comparison with the control (water). When using the biodegradation product of paracetamol, an increase in the thickness of the mesophyll by 10–16 % and the number of layers by 14–30 % was recorded. When using the growth stimulator "Zircon", the thickness of the mesophyll and the number of its layers increased by 3–6 % and 8–15 %, respectively. The increase in the thickness of the phloem and xylem of the conductive beam when treated with the paracetamol biodegradation product was 20–30 % greater than in the control, and 2 times greater than when treated with the growth stimulator "Zircon".Conclusion. The product of the biodegradation of paracetamol in different years of use, regardless of environmental factors, shows a pronounced stimulating effect on the lily of the valley of the May, significantly increasing the quantitative indicators of the anatomical structure of the leaf compared with the growth stimulator "Zircon" and control (water). The obtained data can be used in medicinal plant growing in the development of agrotechnical methods for growing raw materials of the lily of the valley of the May, as well as in the formation of a dossier when registering this product as a new plant growth stimulator.
