Sporophyte Biomorphology of Athyrium Species in the Various Environmental Conditions of South Siberia

摘要

The aim of this work is to present biomorphological characteristics of ferns of the genusAthyriumRoth in southern Siberia and identify changes in the sporophyte life form during ontogenesis and in individuals of the same biological age in various ecological and coenotic conditions. The most important thing when identifying the life form of fern sporophytes is studying the formation of its perennial part-the rhizome. We define the life form ofAthyriumspecies of southern Siberia as summer green polycyclic densely rosette ferns with monopodial-dichotomously growing underground-aboveground rhizomes and monomorphous homoiohydric fronds. It is represented by two variants: (1) large-rhizome orthotropic weakly branching vegetatively non-growing monocentric ferns (Athyrium filix-femina(L.) Roth. andA. monomachiiKomarov, andA. sinenseRupr.) and (2) large-rhizome ascending weakly branching and weakly vegetatively growing monocentric or implicit-polycentric ferns (A. distentifoliumTausch ex Opiz). Neither variants allow vegetative propagation or vegetative self-maintenance of the population. Our study shows that during sporophyte ontogenesis the sizes of rhizomes and fronds increase and the branching ability of rhizomes is implemented. The branching is dichotomous: the daughter branches are formed inside the terminal bud of the maternal branch and become distinguishable only after several years. It has been determined that rhizome remains uniaxial throughout its entire life in sporophytes with low vitality, whereas the rhizomes of the sporophytes with high vitality usually branch out. Rhizome branching starts in young spore-bearing sporophytes. The largest number of branches of the rhizome and, consequently, rosettes of fronds is typical for middle-aged spore-bearing sporophytes. At the end of the life of the sporophytes with branched rhizomes, non-specialized disintegration (senile partitioning) occurs. It is expressed in the disintegration of the rhizome into the separate branches. According to the results of a study in various phytocoenoses of Kuznetsk Alatau, the intensity of rhizome branching in sporophytes of the same ontogenetic stage depends on environmental conditions: the rhizomes ofA. filix-feminaproduce a larger number of branches in more light mixed forests (fir-aspen and fir-birch); inA. distentifolium, the intensity of the rhizome branching increases from the forest zone to the subalpine one.