Pollen morphology of seven plant species of the Asteraceae (Compositae) family naturally growing in the Kingdom of Saudi Arabia

The current study included investigated pollen grains morphology (mainlyexine sculpture) of seven species of the A steraceae family from the northern and eastern parts of the Kingdom of Saudi Arabia. These plant species included Artemisia sieberi L, Achillea fragrantissima (Forssk.) Sch. Bip, Calendula officinalis L., Matricaria aurea Loefl, Picris abyssinca L., Rhanterium epapposum Oliv.and Tanacetum santolinoides D.C. The pollen morphology of seven Asteraceae plant species was investigated with light microscopy. Pollen slides were prepared using Wodehouse technique. Measurements were based on 25 -30 pollen grains per specimen. The pollen grains of the studied plant species are radially symmetric and is opolar. The pollen grains are oblate-spheroidal with the polar axes 18.5–23.4 µm and the equatorial axes 19.8–26.7 µm. The pollen grains of the plant species aretricolporate. The pollen grain of all species has echinate ornamentation. The spines have conical shape with a wide base tapering towards an apical section. The spine length ranges between2.1–3.5 µm and its width ranges between 2.6–3.8 µm. The overall exine thickness ranges from 3.7 - 5.1 µm, while intine thickness ranges from 0.37-0.81µm.It is clear that the external surface characteristics of the pollen and the presence of spines are important traits and can be used successfully for species taxonomic classification.