noun, plural: corks
(botany) A part of the periderm that protects the inner plant tissues from mechanical injuries, water loss, and pathogens, and comprised of cells that are dead at maturity and filled with air, tannins or resins
In woody plants, the outermost covering (epidermis) is replaced by a tougher layer called bark. The bark is composed of the periderm, the cortex, and the phloem. The periderm is the outermost layer and in turn is made up of the cork (also called phellem), the cork cambium (also called phellogen), and the phelloderm. The cork cambium is a meristematic layer that provides new cells through mitosis. New cells that it produces form the phelloderm (inner layer) and the cork (outer layer). The cork cells replace the epidermis in roots and stems of woody plants. These cells eventually become dead at maturity and become filled with air or with materials, e.g. resins or tannins. The cork is relatively tougher than the epidermis and acts as a better protective barrier against water loss, pathogens, and mechanical injuries.
The cork of certain plants, particularly the oak (Quercus suber) is harvested for commercial use. One of its uses is for making stoppers for bottles, for fishing floats and buoys floats, and as handles for fishing rods.