Palynomorphs and floral bloom as taxonomic characters in some species of the genus Amaranthus l. (Aamaranthaceae)

Abstract

Fresh flowers of five species of Amaranthus were studied and documented in detail using light microscope to examine their morphology and pollen characteristics in relation to taxonomy. These species include Amaranthus spinosus, A. viridis, A. hybridus, A. australis and A. tricolor. The species showed close relationship in their pollen surface characteristics with some slight variations in psilate, micropitted or microrugulate ornamentations. The microscopic study of the pollens revealed the presence of 5 types of pollen apertures which include dicolpate, monolete, Inaperaturate, periporate and triporate. The analysis of mean polar and equatorial measurement i.e. the pollen sizes showed that the largest pollen was recorded in A. hybridus (61.95±2.40μm) and the smallest pollen was recorded in A. spinosus (23.70±0.65μm). The mean density of pollens was found to be highest in A. australis (12.55±1.13mm²) and the lowest mean density was recorded in A. hybridus (1.29±0.05mm²). Two diagnostic shapes were noticed in the samples studied, these are – spherical grains in A. spinosus and A. viridis and oval grains in A. hybridus, A. australis and A. tricolor. The study revealed that floral and palynological characters are of taxonomic significance in the genus.

Keywords: Pollen morphology, flower, taxonomy, Amaranthus,