The purpose of the study was to identify the features of the shoot system of Betula pendula from the standpoint of the concepts of architectural models and two plans of constructive organization. In this species, which has closed buds, no bud ring is formed at the base of annual shoots developing from apical buds, which is not typical for species with endogenous rhythm of development. Due to sylleptic branching, unstable monopodial growth, and the ability of the apical meristem to abort not only at the end, but also in the middle of summer, in B. pendula not only monopodial, but also sympodial systems are formed during one growing season, in which sylleptic shoots perform the function of replacement shoots. Due to the above features of growth and branching, in this species, sylleptic shoots take part in the formation of the trunk and powerful branches along with shoots from regular renewal buds. In B. pendula, one-biennial polyarchic or implicitly hierarchical systems regularly arise, consisting of two or three, rarely more, practically equivalent substitution axes. However, as a result of competitive relations, the differentiation of these axes into the leading one, which is part of the trunk, and the subordinate ones, which give rise to branches, usually occurs already in the second or third year. Early differentiation of the axes contributes to the preservation of the overall hierarchical organization of the crown. However, in plantations, and especially often in open space, one can also observe signs of a polyarchic organization, manifested in a bifurcation of the trunk and the formation of powerful branches, making the crown wider. This indicates the influence of environmental conditions on the completeness of the implementation of one or another constructive plan. The complex architectural model of Betula pendula is based on the Rauh model, which has a hierarchical organization plan and equivalent orthotropically oriented axes. It can also implement elements of the Leeuwenberg models (bifurcation of the trunk), which has a polyarchic organization; Koriba (appearance of powerful branches), which is formed as a result of the alternation of hierarchical and polyarchic constructive plans for the organization of the crown, and Prèvost (participation of sylleptic shoots in the formation of branches). The concept of two plans for the constructive organization of the crown successfully complements the concept of architectural models.Keywords: adaptation, architectural model, Betula pendula, branching, growth, hierarchical and polyarchic plans for the constructive organization of trees, shoots, skeletal axes
All articles can be accessed under Creative Commons Attribution 4.0 International Public License (CC BY 4.0).