Palynological investigation of some genera of Cichorieae (Asteraceae) in Iran

The pollen morphology of 33 species belonging to the genera Lactuca, Launaea, Cicerbita, Sonchus, Condrilla (tribe Cichorieae: Asteraceae) from Iran were studied with light and electron microscopies. The pollen grains of the investigated taxa are almost oblate-spherical to prolate-spherical, the shapes are circular in equatorial view, hexagonal in polar view, only Sonchus species are triangular or quadrangular in polar view, isopolar, symmetrical and trizonocolporate, except Sonchus and Chondrilla species, which have tri- to tetrazonocolporate pollen grains, and echinolophate. The size and number of spines in the polar area and the number of spines in the paraporal ridges and equatorial ridges proved to be the most taxonomically authentic characteristics in this study. Three pollen types were distinguished, as in alignment with previous studies. Cluster analysis by Ward method based on 10 quantitative morphological characteristics of pollen grains revealed that the species could be grouped based on the pollen characteristics. Moreover, three species of Cicerbita including Cicerbita scoparia (Rech. f. & Köie) Kitam, C. rechingeriana (Tuisl) Coșkunç., M. Güzel & N. Kilian and C. microcephala (DC.) M. Güzel, Coșkunç. & N. Kilian were recorded for the first time in Iran. Although the characteristics of the pollen grains were useful for distinguishing the species in sub-tribes, in some cases, this did not confirm recent phylogenetic results. The pollen characteristics described in this study provide data that may be useful for future systematic studies aiming to complete the knowledge on Cichorieae species. RESEARCH HIGHLIGHTS: In the present study, the pollen morphology of 33 species belonging to five genera of the Cichorieae are investigated with scanning electron microscopy and 12 species are analyzed for the first time. The cluster analysis based on the quantitative morphological characteristics of pollen grains revealed that the species could be grouped based on the pollen characteristics. In addition, three species of Cicerbita are reported for the first time in Iran.