St.-Petersburg State University, Universitetskaya nab. 7/9, St.-Petersburg 199034, Russia

Abstract

Module is a structural unit of organism or its subsystem that has a high degree of integrity and repeats in onthogenesis. Modules of low levels unite into a module of higher level that has some new specific characters. Modules of different levels are subordinated. A plant can be represented as a hierarchical system with modules at any level. Minimal growth unit of short rhizome ferns is a part of rhizome with close and rarefied turns of spiral arranged phylloides with fronds. The next level - linear system of rhizome, branched system of rhizomes is a module of the third level. Different species of Pinus have four levels of subordination: shoot (auxiblast), axis, lateral branches and crown. The analysis of 13 genera of arboreal angiosperms revealed five subordination levels: shoot, small branched ramule, porrect branch, crown, the system of crowns for clonal plants. Multilevel hierarchy of angiosperms helps to adopt to asymmetric environment on the level of one genet. The number of hierarchical levels increases in parallel to decrease in size of structural units. In evolution of gymnosperms as in that of angiosperms one can see how large modules are replacing by smaller ones.