Monorhythmic Systems of Shoots in Conifers

Shoot systems forming within one period of growth outside the bud, have been studied using collections of conifers in Russian botanic gardens. For the 42 genera of contemporary Pinopsida, different structure types with varying position of lateral buds or shoots, the ratio of the length of the lateral shoot and the overlying part of the maternal one, the order of branching of silleptic shoots, the presence or absence of various specialized vegetative shoots is considered. To denote such systems, the term “monorhythmic system of shoots” is proposed. The variety of shoot systems formed from closed or open buds during the post-bud growth phase in Pinopsida representatives is characterized; the degree of branching in such systems, differentiation of shoots within them depending on the order of branching and functional specialization is shown. The structural diversity of lateral sylleptic shoots associated with an increase in photosynthetic surface and growth processes has been established. Polymorphism of systems is described. The number of monorhythmic systems of shoots (MSS) within a genus can vary from 3 to 9. For each genus, there is a limited number of variants that are similar within families. The greatest variety of structural variants of monorhythmic systems of shoots is characteristic to the Cupressaceae family. Sylleptically branched monorhythmic systems of shoots are characteristic to plants living in frost-free climates. Genera from areas with severe winters are characterized by non-branching or limited branching ones.