Palynological study of Allium L. (Amaryllidaceae) in the flora of Egypt

Abstract

Allium (Amaryllidaceae) is diverse and taxonomically problematic, with controversial subdivisions and polymorphic species. In Egypt, the genus has not been investigated satisfactorily in terms of palynology. The present study aims to provide palynological information on the endemic and near-endemic species of Allium for the first time in Egypt and to characterise the pollen diversity of the investigated taxa. The pollen morphology of 21 Allium taxa was studied comprehensively via Scanning Electron Microscopy. Twenty-five traits were surveyed, then subjected to hierarchical cluster analysis (HCA) and principal coordinate analysis (PCoA). Pollen grains are monads, heteropolar, monosulcate, or trisulcate, small to medium-sized (polar axis (P) = 10.44–29.76 μm, equatorial diameter (E) = 18.97–59.24 μm), and peroblate or oblate in shape. The sulcus may be anasulcate, meridionosulcate, or subzonasulcate. Sulcus ends are blunt, pointed, rounded, or undulated. The exine ornamentation is variable and diversified between the distal pole and the equator. The current study highlights the importance of pollen characteristics such as pollen size parameters, pollen shape, aperture type, polar outline, sulcus size parameters, sulcus type and end shape, distance between sulcus ends, exine ornamentation, presence or absence of perforations on the exine, and perforation size and density for the discrimination of Allium taxa in Egypt. The HCA confirms that pollen morphology has limited taxonomic usefulness at the sectional level for the studied taxa. The PCoA results, on the other hand, were more informative to visualise the infrageneric classification based on the studied palynological traits. A dichotomous identification key for 21 Allium taxa in Egypt based on palynological data is presented.

Keywords:

• Allium
• Amaryllidaceae
• hierarchical cluster analysis
• PCoA
• pollen morphology
• sulcus
• taxonomy

Acknowledgements

The authors wish to express our deep gratitude to Dr Trevor C. Wilson of the Royal Botanic Garden, Sydney, Australia, for his diligent proofreading and comments, which improved the manuscript. Sincere thanks to Mr Moatamad M. Tawfik, the technical operator of the Scanning Electron Microscope Unit, Faculty of Science, Alexandria University, Alexandria, Egypt, for his skillful technical help in taking SEM micrographs. We also thank the two anonymous reviewers who took the time to read and give constructive comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Iman H. Nour

IMAN HASSAN NOUR graduated in botany from the Faculty of Science, Alexandria University, Alexandria, Egypt (2009). She has a master’s degree (2014) and PhD (2019) in plant taxonomy and palynology from the Faculty of Science, Alexandria University, Alexandria, Egypt. Her research focuses on the taxonomy and systematics of angiosperms, and the palynology of the current flora.

Rim S. Hamdy

RIM SAMIR HAMDY is a professor in the Department of Botany and Microbiology, Faculty of Science, Cairo University. She received a BSc in botany and MSc and PhD degrees in plant taxonomy and flora from the same university. She has experience in botany with emphasis on plant taxonomy, working mainly on archaeobotany, systematic botany, plant anatomy, and seed and pollen morphology.

Ahmed K. Osman

AHMED K. OSMAN is a professor of plant taxonomy and flora in the Department of Botany and Microbiology, Faculty of Science, South Valley University, Egypt. His research focuses on plant systematics and evolution, and the origin and maintenance of plant diversity in all photosynthetic lineages, including flowering plants, gymnosperms, bryophytes, ferns and lycophytes.

Mohamed O. Badry

MOHAMED OWIS BADRY is a lecturer in the Department of Botany and Microbiology, Faculty of Science, at South Valley University, Egypt. He received his BSc degree from South Valley University, Egypt (2008), a master’s degree in science – botany (2012) from the same institution and a PhD in plant systematics (2018) from the PhD joint supervision programme between his home university and Massey University, New Zealand. He has experience in the areas of palynology, plant anatomy and morphology, phylogenetics, and flora. He specializes in the current systematics of many plant families, such as Asteraceae, Fabaceae, and Malvaceae.