Ультраструктурні особливості пилкових зерен видів роду Arctium L. (Asteraceae Bercht. & J.Presl.)

Abstract

The plants of the Arctium genus are generally characterized by the similarity of morphological characteristics and the absence of clear diagnostic criteria, which complicates the visual recognition of taxa. In order to determine the plants under our investigation, it is important to attract additional features; therefore, we have studied the exines of pollen grains of species of the genus Arctium of the flora of Ukraine. Pollen grains for the research were collected from the plants of the collection fund of medicinal plants of the laboratory of medical botany of the M.M. Hryshko National Botanical Garden. As a result of palynomorphological studies of four species of the genus Arctium using a scanning electron microscope (SEM), it was found out that the shape of the pollen grains varies from ellipsoidal ( A. lappa, A. minus, A. tomentosum ) to rounded-ellipsoidal ( A. nemorosum ). The maximum sizes of pollen grains are characteristic of A. tomentosum and A minus . The outline of the studied pollen species are three-lobed from the pole, broadly elliptical from the equator, meanwhile in A. lappa , A. nemorosum , A. minus species, the plicae are long, with clear edges, and in of A. tomentosum , their edges are poorly defined; the ori are sharp, equatorially stretched. It was revealed that the surface sculpture of pollen grains in A. lappa is tuberculate (covered with perforations at its base), in A. nemorosum and A. tomentosum it is spinose (thorns without perforation), in A. minus it is spinose (thorns at the base are covered with perforations). The texture of the exine of pollen grains is predominantly intrareticulate in A. lappa , A. nemorosum , A. minus species; while in A. tomentosum it is maculate. The size of the bases of the thorns of pollen grains in A. tomentosum is the smallest, in A. lappa it is the greatest, the height of the thorns is the smallest in A. nemorosum and the largest in A. tomentosum . It was discovered that the widest base in the thorns of pollen grains are found in A. lappa , the narrowest ones are in A. tomentosum . The detected palynomorphological features of pollen grains of the studied species may have diagnostic value and may be used as additional criteria for identifying the species of the genus Arctium .