Suberins form gas- and water-impermeable layers between cells Suberin is the polymeric compound formed from phenyl propanoids, long chain fatty acids and fatty alcohols (C18–C30), as well as the hydroxyl fatty acids and dicarboxylic acids (C14–C20). In suberin, the phenyl propanoids are to some extent related with each other as in lignin. However, most of the 9′-OH groups are not involved in the specific linkages and instead form esters with fatty acids. Often two phenyl propanoids are connected by a dicarboxylic acid via ester linkages, and fatty acids and hydroxyl fatty acids also can form esters with each other (Fraser et al., 1978). Although the mechanism of suberin synthesis is to a large extent still not known or yet to be explored, it appears that the peroxidases are also involved in this process (Foster et al., 1983). Suberin is a cell wall comprises that forms gas- and watertight layers. It is portion of the Casparian strip of the root endodermis

1. BY Dr. S.SREEREMYA
FACULTY OF BIOLOGY
*

2. *
*INTRODUCTION Suberins form gas- and water-
impermeable layers between cells Suberin is the
polymeric compound formed from phenyl
propanoids, long chain fatty acids and fatty alcohols
(C18–C30), as well as the hydroxyl fatty acids and
dicarboxylic acids (C14–C20). In suberin, the phenyl
propanoids are to some extent related with each
other as in lignin. However, most of the 9′-OH
groups are not involved in the specific linkages and
instead form esters with fatty acids.

3. *Often two phenyl propanoids are connected by a
dicarboxylic acid via ester linkages, and fatty acids
and hydroxyl fatty acids also can form esters with
each other (Fraser et al., 1978). Although the
mechanism of suberin synthesis is to a large extent
still not known or yet to be explored, it appears
that the peroxidases are also involved in this
process (Foster et al., 1983).
*Suberin is a cell wall comprises that forms gas- and
watertight layers. It is portion of the Casparian strip
of the root endodermis

4. *Suberin is present in many of the C4 plants as an
impermeable layer between the bundle sheath and
mesophyll cells. Cork tissue, comprising of dead
cells surrounded by alternating layers of suberin and
wax, has particularly high suberin content (Fraser et
al., 1979). Cork cells are found in the secondary
protective layer called the periderm and in the bark
of trees. Cork layers comprising suberin protect
plants against loss of water, infection by
microorganisms, and heat exposure (Franich et al.,
1982). Due to this, some plants even survive short
fires and are mstlyable to continue growing
afterwards (Freudenberg, 1978).

5. *Biochemistry and functions of suberin in
rhizospheres
*Suberin is the complex biopolymer found on the inner
face of primary cell walls in aerial and root parts of
the plant(Fig:1).
*Polyaliphatics and polyaromatics are the major
molecular components (Fussel et al., 1980). The
aliphatic domain is an insoluble polyester hugely
comprised of fatty acids and glycerol, such as ω-
hydroxy fatty acids, α,ω-dicarboxylic acids, mid-chain
oxygenated fatty acids, unsubstituted fatty acids, and
primary fatty alcohols(Godkin et al.,1978).

7. *The phenylpropanoid-derived aromatic domain
mostly encompasses of ferulate, which is a p-
hydroxycinnamic acid (Geiger et al., 1986). Suberin
is also copious in monomers ranging in size from C20
to C24 (Glazener, 1982). The relative abundance of
suberin monomer constituents differs considerably
between species (Godkin et al., 1977). Another
much major component of the suberin aliphatic
domain is glycerol, which in partial
depolymerization experiments is found esterified to
ω-hydroxy fatty acids and α,ω-dicarboxylic
acids(Gibson,1981). SUBERIN BIOSYNTHESIS

8. * Deposition of the suberin requires biosynthesis of aliphatic,
phenolic and glycerol monomers, and then the transportation
to the cell wall to form an insoluble macromolecular
assembly (Godkin et al., 1983). Although the monomeric
composition of the suberin bio-polymer is known for a broad
variety of plants, numerous processes underlying suberin
biosynthesis, such as the sequence of biosynthetic reactions,
transport mechanism of the monomers, and controlled
polymerization, remain elusive(Goldberg et al.,1985).The
development of quantitative analytical equipments to
measure suberin composition following depolymerisation and
the characterization of Arabidopsis mutants with altered
suberin composition have been pivotal to identifying most of
the genes encoding enzymes involved in suberin biosynthesis
(Gômez-Vazquez,1984).