Abstract:The aim was to discuss the origin and systematic evolution of Nai plum (Prunus salicina L. var. cordata Y. He). The pollen morphology of 7 cultivars of Nai plum, 2 cultivars of Chinese plum (P. salicina Lindl. var. salicina) and 1 cultivar of Cherry plum (P. cerasifera Ehrhart.) and 3 cultivars of hybrid plum were observed under scanning electron microscopy (SME). The results showed that 13 copies of material of pollen were with striate-foveolate or cerebroid-foveolate decorations, and the shape of pollen grains was prolate or perprolate which were with three split round in polar view. There were three germination trenches equally spacing with a circular distribution of a N3P4C5 type. The P/E value of Nai plum pollen ranged from 1.82 to 2.02 with size from 823.70 to 970.42 μm2, which are among the other 6 cultivars of Prunus. But the perforation densities (0.520-1.141 μm-2) of Nai plum, except of Zaoyuan younai and Zaoshou younai, are bigger than that of other 6 cultivars. The extine wall of pollen had vallate, and the surface distributed perforation with different size and density. There were rich diversity in uplift and ditch deep of vallate, which early-maturing strain and late-maturing strain of younai plum showed two characteristics in pollen morphology, density of perforation, etc. Thus, the pollen morphology of Nai Plum could serve as an important basis for classification and identification. Cluster analysis showed that thirteen plum germplasms could be divided into 3 groups at genetic distance of 6.19, and each group had Nai plum germplasm. It was suggested that there was close genetic relationship between Nai plum and Prunus. So, there was a possibility that Nai plum originated from hybrid plum through pollen morphology and cluster analysis of palynology.