POLLEN MORPHOLOGY OF THE GENUS RHEUM L. (POLYGONACEAE) IN IRAN

Pollen morphology of the genus rheum (polygonaceae) from iran was studied by light microscope (lm) and scanning electron microscope (sem). pollen grains are usually auxiliary symmetrical, isopolar and tricolpate in equatorial view, while circular in polar outline. exine sculpturing is variable and are sparsely faveolate to perforate, less microechinate (rh. turkestanicum), perforate-favusus, microechinate (rh. ribes) and perforate to foveolatus, densly microechinate (rh. persicum). on the basis of qualitative and quantitative characters identification keys for species were prepared.