Pollen morphology and systematic implications of Impatiens species native to the Garhwal Himalaya, Northwest India

Abstract

This study examines the pollen morphology of nine species belonging to the genus Impatiens (Balsaminaceae) in the Garhwal Himalaya of Northwest India, employing light microscopy (LM) and scanning electron microscopy (SEM) to discern their characteristics and evaluate their systematic importance. Additionally, this study employs both simple cluster analysis (CA) and a numerical taxonomic approach, including UPGMA cluster analysis, principal component analysis (PCA), and principal coordinates analysis (PCoA), to investigate groupings by similarity and to represent visually the hierarchical relationships. The pollen grains of the studied species were monad, isopolar, radially symmetrical, medium-sized, peroblate or oblate in shape, featuring homobrochate reticulate ornamentation and typically having 4-colpate apertures, with the exception of Impatiens chungtienensis (which showed pollen heteromorphism). The findings of multivariate analyses using quantitative and qualitative characters of pollen grains highlight the significance of pollen characteristics, including grain size (polar axis length and equatorial diameter), shape, reticulated stratification variations, and other pertinent factors, for distinguishing Impatiens species. Additionally, the analysis showed that I. laxiflora, I. brachycentra, and I. racemosa formed one closely related group, while I. sulcata, I. bicornuta, and I. devendrae comprised another closely related group. In contrast, I. chungtienensis, I. scabrida, and I. balsamina exhibited an affinity with the second group but formed distinct clusters on their own. In conclusion, this study has bridged an existing knowledge gap and enriched the available database for easy reference and accessibility.