Pollen morphology of 18 species of the genus Orobanche L. subgenus Orobanche was studied using light and scanning electron microscopy. Pollen grains of the studied species are 2-, 3-rugate (seldom some grains 1-, 4-rugate) and inaperturate; prolate, spheroidal and oblate-spheroidal in shape; medium-sized, rarely small-sized. Five types of sculpture are identified: retirugulate, scabrate-verrucate, verrucate, verrucate-gemmate, and gemmate. Palynomorphological data confirm the placement of the studied taxa in subgen. Orobanche and provide evidence for recognition of sect. Inflatae as separate from sect. Orobanche. Pollen morphology is consistent with the phylogenetic split of the genus Orobanche s. l. into two clades, Phelipanche and Orobanche, which, depending on taxonomic decisions, can be treated as subgenera or segregate genera.
More advanced pollen characters are peculiar to the Orobanche clade as compared to those in the Phelipanche clade. Evolution of aperture types in the genus Orobanche s. l. proceded in a correlated and parallel manner with sculpture evolution: from the colporate type with retipilate sculpture to the colpate type with the same sculpture, and then to the rugate type with scabrate-verrucate and verrucate sculpture, and finally to the inaperturate type with gemmate sculpture.
Full text: PDF (Ukr) 663K