Pollen morphological diversity in the genus Xanthium L. (Asteraceae) in Iran

Pollen grains of 19 geographical populations (representing 4 species) of the genus Xanthium L. distributed in Iran were investigated by light and scanning electron microscopy. pollen grains type of all studied species belongs to X.strumarium type except X. spinosum. There were mainly 3-zonocolporate and rarely 4-zonocolporate pollen grains with very short, narrow and ends acute colpus. Apocolpium index was large. Cavea is distinct. Based on exine sculpturing pattern, two types are distinguished: in three species that belongs to X. strumarium complex was scabrate (echinate with spines <1 μm), acute at the top and very broad in base, and in X.spinosum was conical echinate with obtuse tip of echinate. Outlines of pollen in equatorial view were oblate- spheroidal, spheroidal, subprolate and prolatespheroidal. Twelve quantitative and seven qualitative palynological features were examined by multivariate analysis. The result of multivariate analysis and exine sculpturing pattern indicated high diversity among different specimens even in specimens of a single species. Only X. spinosum was separated from other overlapping species (X. strumarium, X. sibricum, and X. brasilicum). Pollen morphology confirms separation of species and subspecies in the genus Xanthium

کلیدواژه ها:

Xanthium ، Plant systematic ، Pollen diversity ، Asteraceae