Pollen micromorphology and ultrastructure of some species of Tulipa and its taxonomical implication

Abstract

Pollen micromorphology of nine species of the genus Tulipa (including three subgenera Tulipa, Clusiana, and Eriostemones) and one species from the genus Amana were examined using light microscopy (LM) and scanning electron microscopy (SEM). Moreover, the pollen wall ultrastructure of five selected taxa from the studied species of Tulipa and one species of Amana were examined by transmission electron microscopy (TEM). Pollen micromorphology (especially exine ornamentation, sulcus margin and sulcus membrane ornamentation, operculum ornamentation) and pollen wall ultrastructure (sporoderm thickness, tectum/foot layer ratio, number of intine layers in sulcus membrane region) varied in the studied taxa. A dendrogram of the pollen micromorphological characteristics (obtained from LM and SEM observations) distinguished three pollen types and six subtypes. Amana edulis (subtype A) and Tulipa biebersteiniana (subtype B) were placed in pollen type 1. Tulipa tetraphylla (subgenus Eriostemones) with Tulipa urumiensis and Tulipa kolpakowskiana (subgenus Tulipa) were placed in pollen type 2. Tulipa clusiana (subgenus Clusiana) and Tulipa suaveolens (subgenus Tulipa) belonged to pollen type 3. Information from pollen wall ultrastructure provided better differentiation of these taxa for better taxonomical resolution. Pollen micromorphology along with ultrastructure can be useful for better understanding the systematic affinities of the species in the genus Tulipa and its relation with the genus Amana and for establishing subgenus rank for T. biebersteiniana and T. clusiana.