Palynological analysis and taxonomic position of the genusMertensia(Boraginaceae)

Palynological analysis of the genus Mertensia Roth, s. lat. (Boraginaceae) was performed. All pollen grains studied were mostly dumbbell shaped and had 6-heteroaperturate pollen type without exception. The type of pollen of Mertensia does not contradict recent classifications that assign Mertensia to Cynoglosseae. Among six sections of Mertensia, pollen grains of section Oreocharis (the Himalayan Mertensia) were different from those of other sections in having granulate sculpturing on the colpus and pseudocolpus membranes. The results, along with other morphological differences, may support Riedl’s treatment of the Himalayan species of Mertensia in the distinct genus Pseudomertensia Riedl. Of the other sections, four monotypic sections (sections Steenhanmera, Neuranthia, Typomertensia, and Mertensianthe) showed pollen structures similar to each other. Pollen grains in section Eumertensia had some variations in size and ornamentation, especially in the species distributed in western North America.