Pinus Stem after two years of growth All Conifers produce Periderm . Periderm usually arises in the subepidermal Parenchyma. Several cells divide Periclinally and continue to divide this way. This results in radial files of cells which emanate from these Meristematic Cells which are called the Cork Cambium or Phellogen. The Phellogen tends to produce cells towards the outside of the Stem or Root.
Meristematic activity spreads laterally until the entire circumference of the organ is encompassed.
Suberin is waxy and prevents excess evaporation. It is almost indigestible by microbes and thus provides a barrier against pathogens. The absence of protoplasm in the dead cork cells deprives pathogens of any nutrients. It also insures that there are no Symplastic connections through which viruses might spread. It has insulating properties because air is trapped within the individual cork cells.