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

Culture of Papaver somniferum ira vitro was used for a characterisation of cell surface structures and mode of cell adhesion and cell separation durin g cell differentiation and plant regeneration in somatic embryogenesis and shoot organogenesis. In early stages of somatic embryogenesis, cell type-sp ecific and developmentally regulated change of cell morphogenesis was demon strated. Cell wall of separated embryonic cells were self-covered with exte rnal tubular network, whereas morphogenetic co-ordination of adhered cells of somatic proembryos was supported by fine and fibrillar external cell wal l continuum of peripheral cells, interconnecting also local sites of cell s eparation. Such type of cell contacts disappeared during histogenesis, when the protodermis formation took place. Tight cell adhesion of activated cel ls with polar cell wall thickening, and production of extent mucilage on th e periphery were the crucial aspects of meristemoids. Fine amorphous layer covered developing shoot primordia, but we have not observed such comparabl e external fibrillar network. On the contrary intercellular separation of d ifferentiated cells in regenerated organs, and accepting distinct developme ntal system of somatic embryogenesis and shoot organogenesis, cell adhesion in early stages and ultrastructural changes associated with tissue disorga nisation, and the subsequent reorganisation into either embryos or shoots a ppear to be regulatory morphogenetical events of plant regeneration in vitr o.