Can pollen exine ornamentation contribute to species delimitation in Korean Iris L. taxa (Iridaceae)?

Abstract

ABSTRACT Iridaceae L. is a large and well-known plant family that is widely distributed across the northern hemisphere. According to recent and ongoing taxonomic revision, its largest genus, Iris L., includes 14 species of perennial herbs occurring in Korea. Although pollen morphological data have proved crucial to the resolution of systematic relationships within the Iris genus, detailed palynological studies of Korean irises are scarce. Thus, this study aimed to describe the pollen morphology of 14 species representing two subgenera (Limniris and Pardanthopsis) of Korean Iris and one closely related species (Sisyrinchium rosulatum) using scanning electron microscopy. Pollen grains of all studied taxa were large in size (P = 35.9–86.7 μm, E = 37.3–72.9 μm), oblate (P/E = 0.68) to prolate (P/E = 1.99) in shape, and monosulcate with a granulate-perforate aperture membrane. Three types of exine ornamentation were identified in Korean Iris species: perforate (Type I); microreticulate (Type II); and reticulate (Type III), which was divided into four distinct subtypes based on lumen diameter. The observed pollen micromorphological characters enabled species distinction and taxonomic delimitation to the series level in the genus. The pollen morphological data presented in this study may be of systematic significance to Korean Iris species.