Skin

• The cell layer directly below the epidermis changes into a cork cambium (phellogen).


• On the outside, the phellogen produces cells that suberize phellem.


• The periderm of a mature tuber consists of 5-15 cell layers.


• The phellem and the phellogen together are called the periderm.


• In immature tubers, where the phellogen is still active and the cambium cells are thin-walled, the skin can easily be removed and is easily damaged.


• At maturity ( or after haulm destruction) the cork cambium stops its activity, its cell walls as well as the tuber skin becomes stronger (setting of the skin).


• The skin of a mature tuber is almost impermeable to chemicals, gases and liquids and also provides good protection against micro-organisms and water loss.


• Tubers without a sufficiently well-developed skin are easily damaged and will lose much moisture during storage. Furthermore, micro-organisms can easily enter such tubers.


• When a tuber is injured or deliberately cut, the formation of a new cork layer is needed to protect the tuber against infection as well as against excessive loss of moisture.