Comparative study of the development of anther and pollen grain in some <I>Dioscorea</I> species, section Stenophora (Dioscoreaceae)

A comparative analysis of the development of anther and pollen grain in 6 species of the genus Dioscorea L. from the section Stenophora Uline (D. villosa, D. tokoro, D. nipponica, D. deltoidea, D. caucasica, D. balcanica) revealed common and individual characteristics in the species. It is shown that the species are characterized by the simultaneous microsporogenesis, and the tetrahedral tetrads. In D. villosa, D. nipponica and D. deltoidea the isobilateral type of tetrads was also found. The structure of the formed and mature anther walls is similar among the species. Based on the aggregate of individual structural features and duration of the tapetum functioning, the time of appearance of reserve substances in the pollen grain, the studied species are subdivided into 2 groups: 1) D. caucasica, and D. balcanica with an earlier (before meiosis of microsporocytes) start of the development of large 3–4-nucleated tapetum cells and a shorter period of their functioning (up to the stage of a highly vacuolated microspore), as well as with an earlier time of accumulation of reserve substances in the pollen grain, namely at the time of completion of mitotic division of the nucleus; 2) D. villosa, D. tokoro, D. nipponica, and D. deltoidea with 2-nucleated tapetum cells, short (D. villosa, D. tokoro) and long (D. nipponica, D. deltoidea) periods of its functioning, and with a later onset of accumulation of reserve substances in the pollen grain – at the time of movement of the generative cell inside the vegetative one. Pollen grains in all the species are monosulcate, 2-celled, with a well-developed exine and 2-layer intine in the area of the open aperture.