Encyclopedia:
Suberin,
Talk:Suberin
Suberin is a
waxy substance found in higher
plants. Suberin is a main constituent of
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
roots suberin is deposited in the radial and transverse
cell walls of the
endodermal 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 via the
apoplast. Instead, water must traverse the
endodermis through the
symplast. This allows the
plant to select the
solutes that pass further into the plant.
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
polyaromatic and a
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
monomers 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 acids 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 monomer
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