Suberin 1123598 220559127 2008-06-20T13:07:28Z 151.48.99.184 '''Suberin''' is a [[wax|waxy]] substance found in higher [[plant]]s. Suberin is a main constituent of [[cork (material)|cork]], and is named after the [[Cork Oak]], ''Quercus suber''. == Anatomy and physiology == Suberin is highly [[hydrophobic]] and its main function is to prevent [[water]] from penetrating the tissue. In [[root]]s suberin is deposited in the radial and transverse [[cell wall]]s of the endodermal [[cell_(biology)|cells]]. This structure is known as the [[Casparian strip]] or Casparian band. Its function is to prevent water and nutrients taken up by the root from entering the [[Stele (biology)|stele]] via the [[apoplast]]. Instead, water must traverse the [[endodermis]] through the [[symplast]]. This allows the plant to select the [[solute]]s that pass further into the plant. It thus forms an important barrier to harmful solutes. [[Mangrove]]s use suberin to minimize [[salt]] intake from their [[littoral]] habitat, for example. Suberin is found in the [[phellem]] layer of the [[periderm]] (or cork). This is outermost layer of the [[bark]]. The cells in this layer are dead and abundant in suberin, preventing water loss from the tissues below. Suberin can also be found in various other plant structures. For example, the net structure in the rind of a [[netted melon]] is suberin. == Structure and biosynthesis == Suberin consists of two domains, a [[aromatic|polyaromatic]] and a [[aliphatic|polyaliphatic]] domain. The polyaromatics are predominantly located within the primary cell wall, and the polyaliphatics are located between the [[primary cell wall]] and the [[plasmalemma]]. The two domains are supposed to be cross-linked. The exact qualitative and quantitative composition of suberin [[monomer]]s varies in different species. Some common [[aliphatic]] monomers include α-hydroxyacids (mainly 18-hydroxyoctadec-9-enoic acid) and α,ω-diacids (mainly octadec-9-ene-1,18-dioic acid). The monomers of the polyaromatics are [[hydroxycinnamic acid]]s and derivatives, such as feruloyltyramine. In addition to the aromatics and aliphatics components, [[glycerol]] has been reported a major suberin component in some [[species]]. The role of glycerol is proposed to interlink aliphatic monomers, and possibly also to link polyaliphatics to polyaromatics, during suberin [[polymer]] assembly. The [[polymerization]] step of aromatic monomers has been shown to involve a [[peroxidase]] reaction. The [[biosynthesis]] of the aliphatic monomers shares the same upstream reactions with [[cutin]] biosynthesis, and the biosynthesis of aromatics shares the same upstream reactions with [[lignin]] biosynthesis. Lignin and suberin are the only known biological polymers that are irregular. [[Category:Plant anatomy]] [[Category:Plant physiology]] {{Phenylpropanoids}} [[it:suberina]] [[de:Suberin]] [[es:Suberina]] [[fr:Subérine]] [[lt:Suberinas]] [[nl:Suberine]] [[pl:Suberyna]] [[pt:Suberina]] [[sv:Suberin]] [[zh:凯氏带]]