Morphological and anatomical structure of cypselas of species of the genus Olgaea (Asteraceae: Cardueae)

Abstract

This paper is a continuation of a series of our investigation of the morphological and anatomical structure of the cypselas of the family Asteraceae. The article presents the results of an investigation of the morphological and anatomical structure of the cypselas of 6 species of the genus Olgaea Iljin of the tribe Cardueae Cass. (O. baldschuanica (C. Winkl.) Iljin, O. leucophylla (Turcz.) Iljin, O. lomonossowii (Trautv.) Iljin, O. nidulans (Rupr.) Iljin, O. pectinata Iljin, O. tangutica Iljin) by light and scanning electron microscopy (SEM). The carpological examination of the cypselas revealed specific features of the species of the genus Olgaea: the shape of the cypsela, the sculpture of the surface of the pericarp, the absence (or presence) crowns and carpopodium, the ratio of the thickness of the pericarp and exotesta, the number of rows and the nature of thickening of the walls of mesocarp cells, the presence or absence of endocarp, the shape and size of exotesta cells, the coefficient of their palisade (the ratio of the length of the radial walls to the length of the tangent). Cypsela of Olgaea species have significant differences, which indicates the heterogeneity of the genus and the need for its revision. Based on the data obtained and the previously published results of the study (Novozhilova, Boyko, 2019), a comparative analysis of the morphological and anatomical features of the cypsela of representatives of the genera Olgaea and Alfredia Cass. was carried out, which revealed the main differences in the structure of the cypsela of these two genera. It was found that the cypsela Olgaea and Alfredia have different structures, and therefore it is inappropriate to combine them into one genus.