Euryale Ferox Salisb. (Nymphaeaceae) micromorphology study from the Middle Amur region basin

The article presents the results of a micromorphological study of the vegetative organs of Euryale ferox Salisb., Nymphaeaceae. The relevance of the study is related to the fact that the species belongs to rare taxa in the region that are threatened with extinction due to its relict nature, borderline range and belonging to the subtropical floral complex of the Russian Far East. The analysis of the literature data showed that the issues of morphology, anatomy, biology and taxonomy of the species remain poorly studied. The purpose of our work is to generalize the results of the micromorphological study of E. ferox on the material from the Amur region. The studies were carried out according to the generally accepted method of microstructural analysis. Detailed descriptions of the leaf blade and petiole are given. The main histological and topographical complexes and their proportions, histochemical features are determined. The assessment of the constitutional, adaptive, and taxon-specific features of the species is given. The study of E. ferox revealed the following microstructural constitutional features: dorsoventrality of floating leaves; epistomatous leaf blade; anomocytic stomatal apparatus; the presence of astrosclereids; epidermal outgrowths (coverts and head trichomes, and hydropotes) and epidermal-subepidermal emergences (spines); general aerenchymatization of leaf and petiole tissues; compact (rather than diffuse) localization atypical for macrohydrophytes collenchyma in the petiole; atactostelia; presence of collateral and concentric conducting bundles; reduction of xylem; absence of cambium. It is shown that general aerenchymatization, reduction of conductive elements, and weak sclerification of tissues are effective adaptations of the species to the conditions of the aquatic environment. Secretory formations of epidermal origin provide waterproofing protection to plant organs. The absence of cambial activity is probably due to the shortening of the life cycle inherent in the extreme northern populations of the species. The presence of atactostela and astrosclereids in the species gives grounds to consider the species as part of the family Nymphaeaceae. However, in terms of paired concentric conducting bundles, E. ferox is close to Brasenia schreberi J. F. Gmel. from the monotypic family Cabombaceae. Further research will involve microstructural analysis of the root system and reproductive organs of the species.

Euryale ferox, Nymphaeaceae, Brasenia schreberi, Cabombaceae

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