Comparative Floral and Pollen Micromorphology of Leonurus japonicus and L. macranthus (Lamiaceae)

Floral micromorphology and pollen morphology of two Leonurus (Lamiaceae) species were examined and compared using scanning electron microscopy to evaluate the diagnostic value of these features to facilitate future studies on floral biology and taxonomy. Floral epidermal patterns were similar in both species, with the conical to central-conical epidermal cells on the adaxial side of the lower lip (corolla). Capitate, peltate, scale-like glandular, and non-glandular trichomes were distributed on the surface of the floral organs. Notably, scale-like anther glands and floral stomata were found on the anthers and abaxial side of the calyx, respectively. Pollen grains had bi-reticulate exine with angular primary lumina and rounded secondary lumina. These characteristics provide indirect evidence of a close association between plant-pollinator interactions and effective pollination. In addition, quantitative traits of pollen grains and trichome types on the adaxial side of the lip differed between the two species. These characteristics may have diagnostic and taxonomic value for the genus Leonurus and family Lamiaceae.