Peculiarities of the ontogenesis of Alisma plantago-aquatica L. (Alismataceae)

Long-term data on the ontogeny ofA. plantago-aquatica L. are summarized. Eleven age stages are identified and described: the 1st year of life - seedlings and juvenile; the 2nd year - adult vegetative, latent generative and young-generative; the 3rd year -young and middle-generative plants; the 4th year - middle-generative, old generative and senile plants. Patterns of individual development are identified. Special attention is paid to the formation of vegetative and generative sphere of plants and their changes during the transition from one ontogenetic state to another. This study of ontogenesis of A. plantago-aquatica was conducted during the vegetation seasons of 1996-1999, 2001-2003, 2005, 2008-2011 in shallows of the Rybinsk reservoir and inflowing small rivers Ild, Sytka and Korozechna; a moist depression near the excavated pond in the village of Grigorovo and a section of disturbed meadows, among willow shrubs near the town of Borok; in roadside depressions along the roads. Alisma plantago-aquatica L. is a representative of the family Alismataceae Vent. It belongs to the ecological group of short grass helophytes. This plant has the Eurasian-North African range, wide ecological amplitude and is found along the shores of lakes, river banks, in shallows of reservoirs, in ponds, trenches, canals, ditches, and areas with surface and groundwater flooding. A. plantago-aquatica is a pioneer plant which appears in mass in water bodies during the first years of their existence. However, the competitive ability of this species is low. This plant is an indicator of eutrophic freshwater areas with alluvial sediments, habitats disturbed due to grazing, low water areas and the presence of thick deposits of silt. Our research has shown that: - The structure of the first leaves, which develop from seedling, depends on the water content in soil and varies from linear, when developed in water, to differentiated into the petiole and leaf blade, when developed on land. - Before flowering (seedlings, juvenile and adult vegetative plants) the primary shoot of A. plantago-aquatica grows monopodially, then - sympodially. Side shoots, which are formed in plants of different age groups, develop in the same way. "Metacoryphismus" occurs through acrosimpodial growth. - From the moment of the generative organs development, clearly expressed quantitative growth is observed. Apparently, the value of quanta depends on the age of the plant. In most cases, it is equal to 4-6 phytomers. - Morphological fragmentation of the plant, both partial non-specialized and complete, occurs in the 4-th year of life of the individual, which leads to the formation of a clone from isolated uneven lateral shoots that passed to an independent existence.

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