Еколого-анатомічна характеристика деяких видів роду Tragopogon (Asteraceae) флори України
Ecological-anatomical characteristics of some Tragopogon (Asteraceae) species of the flora of Ukraine

Summary/Abstract: The results of the study of the anatomical structure of assimilating organs of the three species of the genus Tragopogon are described. Nowadays the anatomical structure of vegetative organs of representatives of many taxa have already been researched. The in-depth study of the anatomical structure of species of the genus Tragopogon which was conducted revealed the presence of different ways of structural adaptation of plants to growing on sands, on the one hand, and, on the other hand, revealed that the investigated taxa have structurally different leaves and stems, whose main features do not depend on the influence of conditions of existence. Almost all species of the genus Tragopogon are mesoxerophytes, the purpose of this work was to investigate the species of the Tragopogon genus which inhabit sandy soil. Such researches will be useful for solving problems of genus taxonomy and for detection of adaptive features of plants. The specimens for investigation were collected from a natural habitat. The plants were in the generative phase of development. Leaves and stems in the middle of their length were conserved for investigation. As a result, we detected features which distinguish species but they can not be used for taxonomy, as they depend on ecology. Thus, the studied species differ in the length of leaf lamina. T. ucrainicus has the thinnest lamina and T. orientalis has the thickest one. In addition, T. orientalis has the most laminaled mesophyll (it is distinctly multilayered). The type of mesophyll varied from isolateral (T. borysthenicus and T. ucrainicus) to pseudo-isolateral (T. orientalis). The numbers of layers of palisade parenchyma (both adaxial as well as abaxial) hardly varied at all between species, except that a third layer of cells was rarely represented in T. orientalis. The species differ in the degree of development of spongy parenchyma. It is most developed in T. orientalis (five or six layers of cells) and it is less developed in T. borysthenicus (two layers of cells). There are differences between the species in the anatomical structure of the stem. Thus, T. borysthenicus has the most developed chlorenchyma (four or five layers) and in T. orientalis it is less developed (two or three layers of cells). Cholophylless parenchyma is represented by the greatest number of layers in T. borysthenicus and by a smaller number of layers in T. ucrainicus, it is less developed in T. orientalis. The conduction system of the three investigated species is developed approximately equally. As the result of the analysis, it is possible to conclude that in the anatomical structure of all investigated species of the genus Tragopogon there is a combination of xeromorphic and mesomorphic features . T. borysthenicus from the Black Sea Biosphere Reserve exhibits the most xeromorphic features. The least xeromorphic characteristics are shown by T. orientalis from the sandy terraces of the Desna river (Chernihiv Region). We singled out a complex of anatomical features which can be additional diagnostic ones for the investigated species. T. borysthenicus is characterised by the presence of cortical conducting vascular bundles and by the placement of laticifers in the perimedullar region of the pith; in T. ucrainicus laticifers are also in the perimedullar region but cortical vascular bundles are absent; cortical vascular bundles are observed in T. orientalis but laticifers are placed all over the pith.

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