Pollen morphology of 33 species belonging to 12 genera of Orobanchaceae tribe Rhinantheae was studied using light and scanning electron microscopy. Pollen grains of the studied species are 3(4)-colpate, prolate, oval, spheroidal and oblate-spheroidal. Outline in equatorial view is elliptical or circular, outline in polar view is slightly-3-lobed, 3(4)-lobed, rounded, rounded-triangular or triangular; pollen grains are mainly medium- and sometimes small-sized. Colpi are long, sometimes medium or short. Pollen grains in Rhinantheae have different patterns of their exine sculpture: retipilate, retipilate-rugulate, rugulate, rugulate-foveolate, implecto-microreticulate, implecto-microreticulate-tuberculate, rugulate-tuberculate, unequally-tuberculate, tuberculate, granulate-tuberculate-perforate, and perforate-tuberculate. Pollen grains in the studied taxa can be subdivided into 10 basic types, based on their exine sculpture. Within some types, 6 additional subtypes are distinguished, mainly according to their exine sculpture peculiarities, size, shape, outline, colpi, colpus membrane and exine thickness. Pollen grains in members of the tribe are distinguishable at generic and species levels. At the generic level, pollen grains of Pterygiella, Melampyrum, Rhynchocorys and Tozzia are well distinguished. Pollen grains of Odontites and Rhinanthus are similar in their implecto-microreticulate and rugulate-foveolate exine and differ in other characteristics (shape, outline, size, peculiarities of colpi structure) at the species level. Pollen grains of Bellardia and Lathraea are similar in their retipilate and retipilate-rugulate exine sculpture and differ in shape, outline, structure of colpi, and sculpture membranes. Pollen grains of Bartsia, Parentucellia and Macrosyringion are similar in having retipilate exine sculpture and differ in size, outline, of colpi structure and characters of exine sculpture. Palynomorphological data correspond well to the plylogenetic pattern of genera of Rhinantheae according to molecular phylogenetic data, and partly correspond to traditional systems. Possible trends of evolution of exine sculpture in pollen grains of Rhinantheae are revealed.
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