Lobelia dortmanna L. is one of the few rare, slowly growing relic plants occupying areas of the littoral zone of water bodies with low nutrient content and subject to wave action. Even in such difficult conditions, this plant successfully passes its entire life cycle, actively blossoms and fruits. That is why the peculiar features of the individual development of this plant in various geographical conditions is a matter of great interest. For the first time, this study considers in detail the ontogeny of the genet of L. dortmanna in oligotrophic lakes of Tver oblast. Detailed characteristics of the following age stages of individuals are given: resting seeds, seedlings, juvenile, young and adult vegetative, latent generative, middle-aged and old generative and quasisenile plants. It is shown that the transition to the juvenile age stage occurs at the end of the first year of life, the virginile age stage lasts two years, and the generative stage of development occurs in the fourth year of life. The change in the growth pattern of the rosette main shoot of Lobelia, from orthotropic to anisotropic, occurs in the second year of life. The establishment and further development of the generative organs of the plant and associated change in the growth of the main shoot from monopodial to simpodial occurs in the fourth year of life. At the same time, the branching of the main shoot begins by formation in the axils of the uppermost assimilating leaves (the last in front of the apical inflorescence) – 1–2 lateral rosette shoots. These are future ramets (vegetative diasporas), which ensure, in the future, the vegetative reproduction of the individual and spread to new territories. Taking into account that in lakes of Tver oblast, Lobelia groupings form dense aggregated clusters on the bottom, the transition of individuals to a quasisenile age state (in the fifth year of life) enables them to rejuvenate and survive after the death of the maternal shoot. The formation and further development of rosette lateral shoots allows the plant to re-occupy the territory via vegetative or seed propagation. Complete morphological disintegration (vegetative reproduction) occurs in the fifth year of life. The genets’ ontogeny is completed by the formation of a compact clone from the detached lateral rosette shoots.
A phytosociological survey of aquatic vegetation in the main freshwater lakes of Greece
