Pollen morphology of Asteraceae from Garhwal Himalaya (Uttarakhand, India): part I

Abstract

Palynotaxonomy is crucial for understanding plant evolution, biodiversity, and ecological history by systematically classifying and identifying species based on pollen morphology. In addition, a regional pollen flora is crucial for precise pollen identification in various applied fields of palynology, including melissopalynology, aeropalynology, forensic palynology, paleopalynology, and copropalynology. In this communication, we explore the pollen morphology of 28 species of Asteraceae, employing both light (LM) and scanning electron microscopy (SEM). The results revealed that the grains were monad, isopolar, radially symmetric, tricolporate, and exhibited oblate-spheroidal to prolate-spheroidal shapes. The infratectum was found to be columellate, caveate, or noncaveate. The supratectum exhibited echinate or microechinate characteristics, with the exine surface showing perforate, microreticulate, or perforate regulate features. Among some species, a lophate pattern was observed, revealing two distinct variations: one characterized by a ‘15 lacunae type,’ while the other exhibited a ‘21 lacunae type’. Some unusual variations were observed in the aperture character among certain species, like the occurrence of tricolpate grains and pollen dimorphism due to variation in aperture number. Light microscopic examination was preliminary for resolving columellar structure but it clearly showed a double level of columella in some species. A cluster analysis, incorporating qualitative and quantitative features of pollen grains and an artificial pollen key have been set forth to distinguish studied species, supplemented by LM and SEM micrographs. The current findings have enriched the existing pollen database of Asteraceae and could play an important role not only in palynotaxonomy but also in allied fields.

Keywords:

• Regional pollen flora
• Compositae
• pollen dimorphism
• lophate pattern
• cluster analysis
• morphology

Acknowledgements

We would like to express our deep gratitude to the Department of Instrumentation at USIC, HNB Garhwal University, Srinagar (Garhwal) for their support to carry out the SEM procedure. Shivani Negi is grateful to the University Grants Commission (UGC), New Delhi for granting a fellowship (Ph.D. fellowship) during the study period. We are grateful to the anonymous reviewers for their critical evaluation, constructive comments, and suggestions on the earlier version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by University Grants Commission (UGC), New Delhi, India.