MONOCOTYLEDONOUS
ROOT
This can be inferred from the following structures given below
1. Epidermis
It is the outermost, thin-walled, compactly arranged layer of
cells. Some of the cells give rise to root hair. The root hairs
are unicellular and lie in contact with soil water. Both
epidermis and root hair are devoid of cuticle. These help in
absorption of water and minerals. In older parts, the
epidermis is shed or impervious.
2. Cortex
It is a broad zone of parenchyma cells. The cells are
thin-walled and enclose intercellular spaces. They normally
store food. The cortex provides for radial movement of
water and minerals from epiblema to the root interior.
3. Endodermis
It is single-layered and made up of barrel-shaped cells which
do not enclose intercellular spaces. The young endodermal
cells possess an internal strip of suberin and lignin, which is
known as casparian strip. Endodermal cells lying opposite
the protoxylem groups however, remain in the primary
stage with usual casparian strip.
These unthickened cells are called passage or transfusion
cells. These cells help in conduction of fluids and minerals
from cortex into the xylem.
4. Stele
All tissues inside the endodermis, i.e., pericycle, vascular
bundles and pith form the stele.
i. Pericycle
It forms the outer boundary of stele. Pericycle may be
uniseriate (single-layered) or multiseriate (multilayered).
The pericycle does not form cambium. It only produces
lateral roots. The pericycle is composed of thin-wand
parenchymatous cells in a young root. Later, it becom5
thick-walled in many monocot roots.
ii. Vascular Strand
Vascular strand is in the form of several alternate and radial
xylem and phloem bundles. The vascular bundles are
arranged in the form of a ring around a central pith.
The xylem bundles are exarch, i.e., protoxylem lies towards
the outside while, the metaxylem faces inwards. Due to the
pressure of numerous xylem bundles and exarch condition,
the xylem of monocot root is polyarch.
Protoxylem vessels are narrow while, the metaxylem vessels
are the broad. Xylem provides mechanical strength and
helps in conduction of water and mineral salts.
Phloem and xylem are separated from each other by means
of a narrow strip of conjuctive tissue. The phloem cells store
food, if parenchymatous. They provide mechanical strength
on becoming sclerified. They are involved in the formation
of cambium.
iii. Pith
It is large and well-developed. It is large and made up Of
parenchymatous cells with intercellular spaces. These cells
contain starch.
Features for Identification of
Monocotyledonous Root
Monocotyledonous root can be easily identified with the
following features
(i) Presence of root hairs.
(ii) Endodermis with passage cells.
(iii) Presence of pith.
(iv) Radial bundles are more than eight.
(v) Xylem exarch.
(vi) Presence of an exodermis.