noun, plural: suberins
(botany) A lipophilic complex polyester biopolymer that occurs in the cell walls
Suberin is lipophilic and hydrophobic. It is comprised of long chain of fatty acids and glycerol. It is a biopolymer that occurs in the cell walls of plant cells, particularly in the cork tissues. It aids in the formation of a protective barrier, preventing excessive water loss and pathogen attack. It also helps in closing tears in plant tissues.
Suberin is found in the epidermal tissues and periderm (particularyly, phellem layer) of the plants. In woody plants, it is a major constituent of cork. In fact, its name is derived from the cork oak plant, Quercus suber.
In roots, suberin is the major constituent of the Casparian strip. The Casparian stip is a band of cell wall material in the radial and transverse cell walls of the endodermal cells. It prevents water and nutrients absorbed by the roots from entering the stele via the apoplastic route. The presence of the suberin prevents solute to pass through the apoplastic route. As a result, solutes are directed to pass via the symplastic route. This is essential as the Casparian strip acts as a barrier to certain solutes that may cause harm to the plant.