The periderm is a protective tissue that develops in plants as a
response to the growth of secondary tissues (secondary
meristiem).
• It replaces the epidermis, which is the outermost layer of the
primary plant body.
• The periderm consists of three main layers:
0. Cork Cells (Phellem): The outermost layer of the periderm is
composed of cork cells (dead) suberin, a waxy substance that
makes them impermeable to water and gases.
0. Phellogen (Cork Cambium): meristematic cells that divide to
produce new cork cells.
0. Phelloderm: The innermost layer, its cells are usually alive and
function in storage and wound healing. They are typically
parenchyma cells that store starch and other substances.