Crown shoots in the ontogenesis of Salix viminalis L. species “aeroxyl shrub” life-form

Background. Boreal willow species have not yet been sufficiently investigated from the standpoints of ontogenesis and the structural and functional organization of adult crowns. We analyzed the formation of the structural and functional organization of S. viminalis in ontogenesis. Materials and methods. The ontogenesis of S. viminalis species was studied on model specimens growing in high areas of river floodplains, valleys, as well as in ditches with apical and lateral shading in Nizhny Novgorod region. Generally accepted classification is used for distinguishing ontogenetic states. Three features are used in the classification of shoots and shooting systems of the crown: 1) the length of the internodes that makes up a shoot; 2) the age of the shoot; 3) the presence of branching. The architectural module is allocated in accordance with the previously developed methodology (Nedoseko, 2014, 2015b). Results and conclusions. Complete ontogenesis is described with S. viminalis species of seed origin of life form, the aeroxyl shrub. It includes 4 age periods: latent, pregenerative, generative-and-senile and 7 ontogenetic states. Eight main variants of vegetative shoots and shoot systems as well as 2 variants of generative shoots are formed in the crown during ontogenesis in this species. As part of the annual vegetative shoot, 8 variants of metamers are identified, which differ structurally and functionally. As the main structural unit of the shoot system, a three-year shoot system (ThSS) is allocated, and on its basis, an architectural module is allocated with reference to 3 features