Structural and functional characteristics of the assimilation apparatus of Alisma plantago-aquatica at different stages of development

This paper deals with the features of the structural and functional organization of the assimilation apparatus of individuals of the plantain fly, which are in five ontogenetic states (juvenile, immature, virginal, young and middle-aged generative). The changes in the morphometric parameters of the assimilation apparatus in j, im, v, g₁ and g₂ individuals of Alisma plantago-aquatica are analyzed. During the ontogenesis of Alisma plantago-aquatica, the length, width, area and mass of the sheet plastic, as well as the growth coefficient, changed along an S-shaped curve. In the middle-aged generative plants of Alisma plantago-aquatica, all morphometric parameters had maximum values. During the pregenerative (three ontogenetic states) and generative (two ontogenetic states) periods of ontogenesis, the number of chlorophylls a and b, carotenoids in the leaves of the helophyte increased. Regardless of the ontogenetic state of plants, the concentration of yellow pigments was 3,0–6,0 times lower than of the green ones. The degree of functionality of the photosynthetic apparatus in individuals of different ontogenetic states can be judged both by the ratio of chlorophyll a to chlorophyll b, and the ratio of the sum of chlorophylls to carotenoids. With an increase in the total assimilating surface of the leaves, the intensity of photosynthesis and, as a consequence, the amount of organic carbon in the leaves of Alisma plantago-aquatica individuals increased. The structural and functional changes of the photosynthetic apparatus observed in the ontogenesis of Alisma plantago-aquatica can be explained by the peculiarities of adaptation mechanisms to long-acting external environmental factors. Medium-aged generative plants of Alisma plantago-aquatica are promising for assessing carbon accumulation and overall productivity of coastal-aquatic phytocoenoses.