Pollen Morphology of Crataegus L. (Rosaceae) in Armenia: Taxonomic Implications

Abstract

Pollen morphology is an important source of taxonomic evidence for species delimitation. The aim of this study was to identify diagnostically informative pollen morphological characters of Armenian Crataegus L. species (Rosaceae) and to evaluate their taxonomic significance at both interspecific and sectional levels. Pollen grains of 13 species representing three sections of the genus (Crataegus, Pentagynae C.K. Schneid., and Azaroli Loud.) were examined using light microscopy (LM) and scanning electron microscopy (SEM). Our analysis indicates that representatives of Crataegus in the flora of Armenia are predominantly characterized by medium-sized (occasionally small) pollen grains with a uniform 3-zonocolp-poroidate(porate) aperture, very elongate colpi that may occasionally fuse at the poles, and weakly developed poroid endoapertures. In addition, some 4-zonocolp-poroidate(porate) pollen grains of C. pontica K. Koch (sect. Azaroli) exhibited supplementary slit-like or colpus-like apertural areas at one or both poles, resulting in heteroaperturate pollen grains with five to six apertures. Exine ornamentation is predominantly striate, often combined with perforations in sect. Crataegus, finely striate or finely perforate and sinuously rugulate in sect. Pentagynae, and striate to rugulate-striate with a wavy exine surface in sect. Azaroli. From a taxonomic perspective, the observed variation in pollen morphology among Armenian Crataegus species appears to be informative primarily at the interspecific level. In contrast, the principal pollen characters examined did not reveal clear diagnostic features supporting sectional differentiation within the genus.