Pollen morphology of some species of the genus <i>Cephalaria</i> Schrad. (Caprifoliaceae) and its significance for taxonomy

Abstract

Palynology gives the evidence for identification and elimination of taxonomically complex genera. Pollen morphology of nine species (three subg., three sect.) of the genus Cephalaria Schrad. was studied using light microscopy and scanning electron microscopy. Pollen grains of all investigated species are triporate, suboblate to subprolate (P/E = 0.75-1.28), and large-sized (P = 58.52 μm-114.38, E = 63.84-119.70 μm). The outline of pollen grains in equatorial view is circular or elliptic, in polar view circular, circular-triangular, or triangular. Pores are distinct, lolongate, elliptic, or circular, with an annulus, operculum, and distinct or indistinct, wide halo surrounding the aperture. Exine sculpture is echinate-microechinate or echinate-microechinate-nanoechinate. Additional diagnostic characters at the species level in Cephalaria Schrad. that can be used for the purposes of taxonomy are size of pollen grains and pores, the shape of pores, the width of the annulus, structure of the exine, dimension of echini and microechini, location of microechini, and presence/absence of nanoechini. Palynomorphological data are compared with the taxonomical classification system of investigated taxa. It is shown that pollen grains morphology of the genus Cephalaria Schrad. is similar to the pollen morphology of the genus Dipsacus L., which confirms their inclusion in the Dipsaceae tribe.