Cytology and pollen morphology of Bougainvillea glabra ‘Elizabeth Angus’, a cultivar with low pollen fertility

•Many abnormal phenomena were observed in pollen mother cells (PMCs) during meiosis, which might be the cause of the large and small pollen grains.•Dlayed callose degradation in the early mononuclear stage during meiosis may account for the low pollen fertility of ‘Elizabeth Angus’.•The fertility of the pollen grains was associated with a certain number of columellae in the pollen wall.