Ontogenesis of the genets and ramets of some European species of the genus Sparganium subgenus Xanthosparganium

Abstract

Representatives of the Sparganium L. genus belong to an ecological group of short grass helophytes which live in the shoreline area of different water bodies. Despite the fact that most representatives of the genus exhibit notable polymorphism (depending on the level regime of a water body, they can form various ecological forms), characteristic of all of them is presence of only one living form – vegetative mobile clear polycentric long-rhizomatous pseudoannual polycarpic plant with racemose root system. The objective of the article was to study the ontogenesis of genets and ramets on the example of representatives of the Xanthosparganium subgenus (S. emersum Rehm., S. glomeratum (Laest. ex Beurl.) Neum., S. gramineum Georgi and S. natans L.). The research was conducted using the ontogenetic approach. In the study, we analyzed ontogenesis of genet (from generative diaspore) and ontogenesis of ramets (from vegetative diaspores – tuber-like structures and axillary buds of vegetative-generative monocarpic and vegetative rosette shoots). We demonstrated that ontogenesis of genets and ramets (on the basis of tuber-like structures) in laboratory conditions is abrupt. It was found that the model species of Sparganium are characteristic in combining of incomplete and special ontogenesis, which is related to the omission of phases of the post-generative period. Such peculiarity is conditioned by increase in tempi of ontogenetic development. On the basis of specific ontogenesis, a variant of shortened ontogenesis is possible, during which the virginile ontogenetic condition is omitted. This feature could be characterized as dynamic polyvariance of ontogenesis, whereas bud initiation and development of shoots throughout the vegetative season, characterized as heterochrony, has been formed over the process of natural selection. Heterochrony (on the basis of iterative branching without periods of rest) includes a property of formation of vegetative-generative shoots which develop on the basis of sylleptic shoots of subsequent orders of branching. The main course of ontogenesis in natural conditions corresponds to D-type which occurs in order of generations of individuals of vegetative origin.

Keywords

• bur-reed; vegetative and generative reproduction; polyvariance of ontogenesis; age state; ramet; adaptation.