Structural diversity of Papaver somniferum L. cell surfaces in vitro depending on particular steps of plant regeneration and morphogenetic program

Culture of Papaver somniferum in vitro was used for a characterisation of cell surface structures and mode of cell adhesion and cell separation during cell differentiation and plant regeneration in somatic embryogenesis and shoot organogenesis. In early stages of somatic embryogenesis, cell type-specific and developmentally regulated change of cell morphogenesis was demonstrated. Cell wall of separated embryonic cells were self-covered with external tubular network, whereas morphogenetic co-ordination of adhered cells of somatic proembryos was supported by fine and fibrillar external cell wall continuum of peripheral cells, interconnecting also local sites of cell separation. Such type of cell contacts disappeared during histogenesis, when the protodermis formation took place. Tight cell adhesion of activated cells with polar cell wall thickening, and production of extent mucilage on the periphery were the crucial aspects of meristemoids. Fine amorphous layer covered developing shoot primordia, but we have not observed such comparable external fibrillar network. On the contrary intercellular separation of differentiated cells in regenerated organs, and accepting distinct developmental system of somatic embryogenesis and shoot organogenesis, cell adhesion in early stages and ultrastructural changes associated with tissue disorganisation, and the subsequent reorganisation into either embryos or shoots appear to be regulatory morphogenetical events of plant regeneration in vitro.