Chromosome behavior during microsporogenesis and variation of pollen size of Populus×xiaozhuanica W.Y.Hsu et Liang cv.‘Baicheng-2’ in greenhouse were studied by aceto-carmine squash technique.The results were as follows:(1)Some meiotic abnormalities,such as univalent in diakinesis,precocious migrated chromosomes in metaphase Ⅰ,lagging chromosomes and bridges in anaphase Ⅰ and Ⅱ,micronuclei in telophase Ⅰ and Ⅱ,abnormal orientation of spindles in metaphase Ⅱ and aberrant cytokinesis,were found with certain frequencies,which could be related with the hybrid origin of the ‘Baicheng-2’.(2)The nucleolus number changed dynamically from one to eight.In daughter nuclei of some telophase Ⅰ and Ⅱ cells,at most 8 small nucleoli were observed,which was probably related with polyploid origin of the genus Populus.The genome of the ‘Baicheng-2’ may have 8 pairs of chromosomes with nucleolus organizer regions.(3) The ‘Baicheng-2’ produced 3.67% empty and shrunken pollen grains.The diameter of plump grains ranged from 21.3 to 52.2 μm,and the frequency of pollen diameter followed a similar Gaussian distribution.However,the diameters of 0.69% pollen grains were more than 37 μm,suggesting a few of unreduced 2n pollen might be produced.