Changes in the formation of an extracellular matrix surface network during early stages of indirect somatic embryogenesis inDrosera spathulata

Our attention was focused on the changes occurring in the cell surface network linked to the induction of embryogenic competence of pre- and pro-embryogenic stages of indirect somatic embryogenesis in the callus tissue of Drosera spathulata Labill., which originated from isolated leaves. This surface network forms as a distinct and compact layer on globular somatic embryos before formation of protoderm. Young protodermal cells had a typical furrowed surface, whilst mature protodermal cells were practically smooth. Embryogenic cells show changes in structural organisation and chemical composition of cell surface network, during different stage formation of somatic embryogenesis. Using SEM, TEM analysis and enzymatic digestion of proteins and pectins, we have shown that granular components, which represent pectic polysaccharides, were linked to induction and acquisition of embryogenic competence and pre-embryogenic stage. Fibrillar network was linked to proembryogenic stage of somatic embryogenesis. Our study has revealed that combined effect of protease and pectinase after 5 hours caused a complete disappearance and removal of the cell surface network.