# Effect of Growth Regulators on the Quality of Apple Tree Whorls
## 1 Introduction  
A prerequisite for the dynamic cultivation of orchard plants is high-quality nursery material. Its quality determines the earliness of entering the fruiting period, the yield and intensity of growth, and from the economic point of view, the profitability of the entire crop [1, 2]. The basic parameter affecting the quality of a given nursery stock is the structure of the tree crown, i.e., the number of lateral shoots [1, 2]. In addition, according to [PERSON] (2000) [3], it should be free of viruses and have a strongly expanded root system, so as to adequately supply the plant with water and nutrients it needs. The nursery stock most desired by orchardists is a tree with a strongly expanded crown, which makes it possible to shorten the investing period of newly planted orchards. Therefore, nursery men try to meet the expectations of orchardists by producing very good quality trees affecting the productive efficiency of the orchard in the following crop years [4, 5, 6, 7]. However, the production of such a tree at the nursery stage still causes a lot of trouble for growers, since many popular apple tree varieties struggle to form crowns consisting of 5-8 lateral pedicels, and it is almost impossible to obtain it naturally. As a result, it is relatively difficult to obtain a very good quality oculant in a single season, so nursery men produce trees on a 3-year cycle (i.e., knip-boom) or on a 2-year cycle from grafting in hand [8, 9, 10, 11, 12, 13]. The quality of a tree and the degree of its branching depend on internal factors, which include: the strength of the rootstock [5, 9, 10], the ability of a given variety to form lateral shoots [6] and external factors, i.e., the type and effectiveness of treatments used to stimulate branching, soil and climatic conditions associated with the location of the nursery and the course of the weather during the initiation and growth of young shoots [10, 11, 12]. The main reason for the lack of branching in the perianth is the strong apical dominance of the main shoot, which, depending on the variety, can greatly limit the growth of syleptic shoots, leading to the growth of trees with only the main shoot. Therefore, in order to prevent this phenomenon, treatments are used to improve the quality of nursery stock, the main purpose of which is to stimulate branching and obtain trees with a properly formed crown with a large number of lateral shoots. These include mecha-technique treatments, which involve pinching off the apical shoot and youngest leaves, twisting the top of the growth by 180\({}^{\circ}\), and removing side shoots from the lower parts of the tree and rootstock [4; 13]. These types of treatments are labor-intensive and require a large investment by the orcharist. Chemical treatments are also used using growth regulators, i.e., phytohormones, the effectiveness of which largely depends on the type of replacement and weather conditions during the application of the above-mentioned compounds [14]. The group of plant protection products called growth regulators includes a separate pool of products which, as the name suggests, are designed to correct and regulate plant growth. Phytohormones are a large group of organic compounds of natural or synthetic origin that modify the physiology of plants. This action involves stimulating or inhibiting specific physiological processes occurring in the plant, including development and growth processes, such as branching of maden plants. The correct response of the plant does not depend on the concentration of a single phytohormone. It occurs as a result of quantitative changes between individual phytohormones [12]. In fruit nurseries, they are used for early defoliation of perianths in order to accelerate their digging and placing in cold stores and to stimulate the branching of shoots.