OBJECTIVETo study the karyotype of four Ephedra plants in order to provide the cytologic evidence for the genetic diversity and identification genetic resources of Ephedra.

METHODThe roots of germinating seeds were used to study the karyotype of four Ephedra plants by staining and slide-preparing technique of mitotic chromosomes.

RESULTthe optimal root-sampling time was about 10: 20 - 10:40 am. Using 0.002 mol x L(-1) 8-Hydroxyquinoline to pretreating the intravital root tips, the optimal pretreatment time for E. Sinica, E. intermedina, E. equisetina and E. przewalskii was 4, 5, 4.5 and 3.5 h, respectively. E. przewalskii and E. equisetina were diploid, E. Sinica and E. intermedina were belonged quadruple. The karyotype formulae of the four species were 2n = 2x = 14 = 2M + 8m + 4sm, 2n = 2x = 14 = 10m + 4st, 2n = 4x = 28 = 20m (2SAT) +8st, and 2n = 4x = 28 = 20m (SAT) + 6st + 2sm, respectively.

CONCLUSIONAll the karyotypes of four Ephedra species were 2A type, which was the symmetric karyotype.