Main conclusion A cell death signal is perceived and responded to by epidermal cells frst before being conveyed inwards across the anther wall in male sterile Plantago lanceolata fowers. In gynodioecious plants, foral phenotype is determined by an interplay between cytoplasmic male sterility (CMS)-promoting factors and fertility-restoring genes segregating in the nuclear background. Plantago lanceolata exhibits at least four diferent sterilizing cytoplasms. MS1, a “brown-anther” male sterile phenotype, segregates with a CMSI cytoplasm and a non-restoring nuclear background in P. lanceolata populations. The aim of this study was to investigate the cytology of early anther development in segregating hermaphrodite and male sterile fowers sharing the same CMSI cytoplasm, and to determine if the sterility phenotype correlates with any changes to the normal pattern of programmed cell death (PCD) that occurs during anther development. Cytology shows cellular abnormalities in all four anther wall layers (epidermis, endothecium, middle layer and tapetum), the persistence and enlargement of middle layer and tapetal cells, and the failure of microspore mother cells to complete meiosis in male sterile anthers. In these anthers, apoptotic-PCD occurs earlier than in fertile anthers and is detected in all four cell layers of the anther wall before the middle layer and tapetal cells become enlarged. PCD is separated spatially and temporally within the anther wall, occurring frst in epidermal cells before extending radially to cells in the inner anther wall layers. This is the frst evidence of a cell death signal being perceived and responded to by epidermal cells frst before being conveyed inwards across the anther wall in male sterile plants.