Pollen morphology of the genus Justicia (Acanthaceae) in Peninsular India: Taxonomic and Phylogenetic implications

Pollen morphology of the genus Justicia (Acanthaceae) from Peninsular India is documented in detail for the first time using scanning electron microscopy (SEM) to evaluate their taxonomic significance within the genus. Pollen grains are 2-porate or 2–3-colporate, small to medium-sized, with a polar axis (P) of 17.5–45 μm and an equatorial diameter (E) of 10.4–33.7 μm. They are predominantly prolate (P/E = 1.32–1.93) or perprolate (P/E= 2.29–2.35), circular or triangular in polar view, and elliptic in equatorial view. Exine sculpturing is predominantly a well-defined reticulum. Diagnostic features identified include pollen size and shape, number of apertures, exine ornamentation, number of insulae, and dimensions of the trema and mesocolpium regions. The results indicate that pollen characters alone are insufficient for delimiting species or sections within Justicia due to high levels of homoplasy; however, they provide valuable diagnostic information when combined with other morphological and micromorphological characters and interpreted within a phylogenetic framework.