A micromorphological study of some Prunella L. (Lamiaceae) taxa and its taxonomic implications

Pollen morphology and nutlet structures of some Prunella L. taxa were examined in detail by light microscopy (LM) and scanning electron (SEM) microscopy. Pollen grains of Prunella vary in size from small to large (Polar axis (P) = 22.25-66.04 µm, Equatorial diameter (E) = 17.56-75.64 µm). The shape of pollen grains are suboblate to prolate (P/E = 0.78-1.75) and the aperture structure is hexacolpate with granular membranes in apocolpium. Examinations of exine ornamentation show that pollen grains were recognized as bireticulate ornamentation with varying characteristics of the primary muri and secondary reticulum and four subtypes were identified. Nutlet measurements of four taxa were taken and their surfaces were examined by using SEM. While pollen ornamentations are represented by different characters among taxa, it has been concluded that nutlet surfaces do not have distinctive characters among investigated taxa. Pollen morphology of 7 taxa of Prunella has been investigated in detail for the first time.