Symplastic isolation and symplastic continuity are related to a process of cell-to-cell commu- nication via plasmodesmata. Functional states of plasmodesmata are dynamically changing. Opened plasmodesmata facilitate symplastic transport between cells. Closed plasmodesmata isolate a cell or a group of cells and assure their functional integrity. Cell-to-cell communication may also be regulated due to formation of new plasmodesmata and elimination of existing ones.