A synopsis of the genus Rheum (Polygonaceae) in Iran with description of three new species

According to previous studies, the genus Rheum in Iran includes four species: R. turkestanicum Janisch., R. persicum Losinsk., R. ribes L. and R. khorasanicum Baradaran & Jafari. During the long-term study, based on field and many herbaria specimens, three new species including R. iranshahrii Taheri & Assadi sp. nov., R. kordestanicum Taheri & Assadi sp. nov. and R. austro-iranicum Taheri & Assadi sp. nov. were discovered in Iran. In this paper, all new species are compared with their putative relatives. Botanical characters are elaborated and a brief taxonomic synopsis for all accepted species is also provided.