Pollen studies in the genus Viola (Violaceae) from Iran

Pollen morphology of 17 species of Viola representing five sections, Melanium, Plagiostigma, 'Spathulidium' ined., Sclerosium, and Viola, was studied using light and scanning electron microscope. Pollen grains were usually symmetrical, tetrazonocolporate to pentazonocolporate in section Melanium and trizonocolporate to tetrazonocolporate in the other four sections. Pollen shape was circular to subtriangular, tetragonal or pentagonal in polar view and prolate to oblate, spheroidal or pyramidal in equatorial view. Exine ornamentation was granulate, psilate and mostly perforate. The psilate type was only observed in V.modesta. We found heteromorphy in aperture number in V.caspia of section Viola, V.occulta of section Melanium and V.behboudiana of section Sclerosium, which corroborates their higher ploidy than in related species (octoploid versus tetraploid).