Pollen morphology and its taxonomic significance of the genus Crucianella L. (Rubiaceae) in Iran

Abstract

AbstractThe Pollen morphology of nine species of Crucianella L. and ten subspecies of C. gilanica representing two sections: Roseae and Crucianella, was investigated using light microscopy (LM) and scanning electron microscopy (SEM). All the studied species (except for C. angustifolia) are palynologically described here for the first time. The results revealed considerable pollen character variation among the studied species. The pollen grains are monads, isopolar, radial symmetrical and relatively small. The largest pollen grains were observed in C. angustifolia (P = 24.12 µm, E = 26.04 µm), while the smallest pollen was found in C. gilanica subsp. carduchorum (P = 16.32 µm, E = 12.57 µm). The outline pollen grains varied from subcircular to circular in polar view and elliptical to quadrangular and circular in equatorial view. The shape of pollen changed from spheroidal to oblate‐spheroidal, prolate‐spheroidal, suboblate, subprolate and prolate. The pollen grains are zonocolpate and their number of colpi ranges from 6 to 10. The results showed five different types of sexine ornamentation: perforate, reticulate, microreticulate, microfoveolate and psilate. The sexine of all examined specimens is covered with microspines. The current survey shows that the pollen morphological characters of the studies species are taxonomically informative and may provide good help in identification purposes. We used multivariate analysis to determine the potential contribution of palynological data to the species relationships. The result of cluster analysis and principal component analysis showed pollen morphological affinities between the two studied sections.