Saturday 21 January 2012
SCLERENCHYMA
Mature sclerenchyma
cells are dead and have secondary cell walls
thickened with
cellulose and usually impregnated with
lignin. In contrast to collenchyma, which is
pliable, sclerenchyma is elastic. The cell cavity or lumen is very small or it may disappear completely.
There are two types of sclerenchyma cells, namely sclereids and fibres . 1. Sclereids : The cells are irregular in shape. The cell
walls are thick, hard and
lignified which makes the
lumen very small. Simple
pits (canals) are found in
the thickened cell walls and link adjacent cells. Sclereids
are commonly found in
fruit and seeds. 2. Fibres : The cells are needle-shaped with
pointed tips, thick walls
and rather small lumen.
Secondary cell walls,
impregnated with, are
formed. Simple pits are also present. Fibres are
abundant in the vascular
tissue of angiosperms, i.e.
flowering plants. Functions: sclerenchyma is an
important supporting
tissue in plants, sclereids are responsible
for the hardness of date
seeds and the shell of
walnut, fibres probably play a role
in the transport of water in
the plant, starch granules are stored
in the young, living fibres.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment