Abstract. The purpose is to identify infradian rhythms in the seasonal dynamics of apical growth of shoots of Salix ‘Bullata’ plants and to establish the features of morphogenesis associated with the existence of endogenous (genetic and hormonal) mechanisms for the occurrence of nonlinear changes, including fluctuations in the growth characteristics of shoots. Methods. A quantitative approach was used to study the dynamics of morphogenesis processes. There was carried out a comparative research of seasonal dynamics of velocities and accelerations of apical and radial growth of Salix ‘Bullata’ plants shoots, which differ in origin and location on the plant. Results. In the seasonal dynamics of the characteristics of apical growth of branching and plant formation shoots of Salix ‘Bullata’ plants there are observed infradian rhythms, similar to those identified for other willow species. These rhythms are most pronounced for the growth accelerations (about 5 maximums within 3.5 months). Seasonal dynamics of apical growth accelerations of two types of shoots are correlated and almost synchronous. Seasonal dynamics of speeds and accelerations of radial growth of the studied types of shoots are similar and differ from the seasonal dynamics of apical growth. The weak dependence of growth characteristics on weather conditions confirms the concept of the endogenous nature of the growth of plant shoots periodicity. Scientific novelty. The results complement the existing information on biological rhythms and processes of morphogenesis in woody plants. The growth of shoots of willows and, possibly, other species of woody plants has an oscillatory character. Seasonal dynamics of apical and radial growth are different. The occurrence of oscillations in the rate of shoot apical growth is mainly due to the processes of apical meristem development itself. Apparently, the oscillatory nature of shoot growth is the result of the superposition of several processes of different nature in the meristem tissues, including division, extension and differentiation of cells, and also the production and distribution of phytohormones. The results can be applied to the use and modification of methods of woody plants nursing – the grafting, the pruning, the rejuvenation and the vegetative propagation.
