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

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.

Keywords:

• Exine ornamentation
• Iris
• pollen micromorphology
• SEM
• systematics

Acknowledgements

We thank Dr. Soonku So (Korea National Park Research Institute) and CNUK (The Herbarium of Chungnam National University) lab members for their help with fieldwork. We appreciate Dr. Jin-Hyub Paik and Mr. Changyoung Lee (Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea) for giving us an access to scanning electron microscopy. We thank two anonymous reviewers for critically reading the manuscript and providing thoughtful suggestions and insights.

Disclosure statement

No potential conflict of interest was reported by authors.

Additional information

Funding

This work was supported by grants from the National Research Foundation of Korea (NRF) funded by the Korea government (grant numbers NRF-2018R1C1B6003170 and NRF-2021R1I1A2045820) to T.-S. Jang.

Notes on contributors

Bokyung Choi

BOKYUNG CHOI is a post-doctoral in the Department of Biological Sciences of Chungnam National University, Daejeon, Korea. She received a BSc and MSc in botany from the Department of Biology in Kung Hee University, Seoul, Korea and PhD in Australian National University, Canberra, Australia. Her research involves micromorphology, morphology, palynology, and population genetics of angiosperms.

Jangseung Ryu

JANGSEUNG RYU graduated with a BSc in the Department of Biological Sciences of Chungnam National University, Daejeon, Korea. He specializes in the palynology of Korean Iris species.

Tae-Soo Jang

TAE-SOO JANG is an associate professor in the Department of Biological Sciences of Chungnam National University, Daejeon, Korea. He received a BSc and MSc in botany from the Department of Biology in Kung Hee University, Seoul, Korea and PhD in the Department of Botany in University of Vienna, Vienna, Austria. He researches the micromorphology, systematics, palynology, and molecular cytogenetics of angiosperms.