Volume 26, Issue 78, July - December, 2025

Root anatomical diversity in epiphytic Orchids: Taxonomic implications and adaptive significance

Preshina Rai, Kesang Bhutia, Saurav Moktan^♦

Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata-700019, West Bengal, India

^♦Corresponding Author
Saurav Moktan, Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata-700019, West Bengal, India

ABSTRACT

Root anatomy is fundamental to both ecological adaptations and taxonomic understanding in Orchids, yet it has received far less attention than floral morphology. To address this gap, the present study investigates the root anatomical features of 20 epiphytic Orchid species representing 12 genera. Transverse sections were analysed both qualitatively and quantitatively, focusing on velamen, cortex, exodermis, endodermis, vascular tissue, pith composition, root hairs, mycorrhizal associations and crystalline idioblasts. Our results showed a significant variation among the studied species. The velamen ranges from a single layer to as many as nine layers, while the cortex ranges between three and thirty-one layers. Similarly, the vascular cylinders differed considerably, with the xylem pole varying from five to thirty-six. Furthermore, distinct differences in exodermal and endodermal thickening types, the presence of passage cells and the structure of pith highlight the underlying taxonomic diversity. Mycorrhizal pelotons and calcium oxalate crystals (raphides and druses) were recorded in several species, highlighting their functional roles in nutrient acquisition and defence. The multivariate analysis which includes Cluster Analysis and Principal Component Analysis showed strong associations between root anatomical traits. Species like Aerides multiflora and Vanilla planifolia are distinct due to their unique root anatomy. Overall, this study demonstrates that root anatomical traits not only underpin adaptive strategies to the epiphytic niche but also provide valuable diagnostic features for taxonomy and conservation of Orchids.

Keywords: Epiphytic orchids, Root anatomy, Systematics, Multivariate analysis

Species, 2025, 26(78), e46s3207

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DOI: https://doi.org/10.54905/disssi.v26i78.e46s3207

Published: 25 October 2025