Pollen Morphology in the Taxonomic Delimitation of Melliferous Flora: Insights into Plant–Pollinator Interaction

Plant taxa provide natural products for the survival of almost every species. Plant parts, including fruit, seeds, and flowers, are directly consumed by humans, while pollen and nectar are specifically used by honeybees to produce honey. Among plant species, the melliferous and nectariferous species are of great importance for honey production. This study aimed to elucidate the taxonomic significance of pollen morphology, which may be beneficial for taxonomists in identifying melliferous taxa from the Bannu division, Khyber Pakhtunkhwa. The morpho-palynological characteristics of 22 melliferous plants belonging to 14 different families (Poaceae; Sorghum halepense Solanaceae; Datura innoxia, Physalis angulata, Solanum virginianum Amaranthaceae; Dysphania ambrosioides Asteraceae; Erigeron bonariensis, Parthenium hysterophorus, Sonchus asper, Symphyotrichum subulatum Boraginaceae; Arnebia linearifolia Plantagineceae; Plantago lanceolata Apiaceae; Anethum graveolens Mimosaceae; Leucaena leucocephala Fabaceae; Melilotus indicus, Vachellia nilotica, Cicer arietinum Convolvulaceae; Convolvulus arvensis Lamiaceae; Mentha longifolia, Salvia moorcroftiana Asphodelaceae; Asphodelus tenuifolius Brassicaceae; Eruca vesicaria and Euphorbiaceae; Euphorbia helioscopia) were studied using light and scanning electron microscopy (SEM). Significant variations were recorded among melliferous taxa. The pollen shape of all the taxa investigated was spheroidal and circular in the equatorial polar view respectively. The maximum exine thickness was noted in C. arvensis (4.8 μm) and psilate, echinate, reticulate, verrucate, perforate, scabrate, striate and micro-reticulate exine ornamentation was observed in examined species. The maximum polar and equatorial diameter (43.77 and 59.58 μm) was measured in C. arvensis. The highest P/E ratio was recorded for Sonchus asper (3.2 μm). In most species, inaperturate pollen grains were common, and high pollen fertility indicated the strong adaptability of melliferous plants in the region. These findings support their taxonomic value and highlight their potential in tracing the origin of honey and ensuring its purity for both local and global markets.