Pollen and floral micromorphological Studies of the genus Cotoneaster Medik. (Rosaceae) and its systematic importance

Abstract

The micromorphology of petal and pollen grain of 16 species of the genus Cotoneaster Medik., belonging to two subgenera (Cotoneaster and Chaenopetalum) has been studied by light and scanning electron microscopy. We used different multivariate statistical methods to reveal the species relationships. Results showed that in comparison to most genera of the family Rosaceae, both tri- and tetracolporate pollen grains are observed in one specimen. Palynological observation revealed that shape of tricolporate pollen in most species is prolate-spheroidal, but also subprolate and prolate pollen grains can be recognized. In the other hand, tetracolporate pollen is quadrangular. The main ornamentation type was mainly striate which in turn can be subdivided to several categories; however, psilate one is also recognized also (C. persicus). The results revealed that pollen traits are probably effective in separating the sections and using these traits for placing a species in a particular section is probably helpful. Apomixis is one of the reasons for not changing the ornamentation of the both surface of the petals and their similarity to each other in different species. Totally, the studied micromorphological characters of petal cannot be used as diagnostic tools for Cotoneaster in Iran.