Pollen Morphological Characteristics of Some <i>Crataegus L.</i> Species from West of Iran

Abstract

The genus Crataegus L. (hawthorn) belongs to Rosaceae family (subfamily Amygdaloideae). In this study, pollen morphological characteristics were evaluated in ten Iranian Crataegus species by Light Microscope (LM), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). Data were standardized and analyzed using MVSP software. Our results showed that all the pollen grains were oblate-spheroidal in shape and medium in size. Different types of pollen exine surface ornamentations were observed among the studied species. According to UPGMA tree and PCO plot, three clusters were identified as following: C. assadi and C. psedoheterophylla (cluster A); C. meyeri, C. kurdistanica and C. zarrei (cluster B); and the other species were grouped as cluster C. PCA-biplot revealed that pollen equatorial and polar axes length were the distinguishing features for separation of C. assadi and C. psedoheterophylla from the rest, either exine ornamentations for placement of C. rhipidophylla in cluster C. In addition, TEM obtained data showed C. assadi was well-distinguished from C. pontica according to intine and exine thickness, shape and diameter of the caput, height and width of the columella. The caput shape was diplococcic or peroblate in C. pontica and prolate or oblate in C. assadi . Also, we detected the thin and discontinuous endexine and a high T/F ratio in Crataegus species. Our finding revealed that several pollen grains features were useful in infrageneric classification and identification of Crataegus species.