histology

1. Internal structure of
root
Presenter -Dr. Manoj Kumar Das

2. Plant anatomy
• Primary internal structure of root
• Diagnostic features of root-
• The epiblema or piliferous layer is present. Here the stomata
and cuticle layer are absent.
• The root hairs are unicellular.
• The endodermis has casparian layer.
• The vascular bundles are radial type.
• The xylem is exarch
• Anatomy of dicot root

3. Diagnostic features of dicot root
• Number of VB varies from 2-6.
• The pericycle produces lateral roots and cambium during the
secondary growth
• The pith is poorly developed or absent.
• The secondary growth is present

4. • Internal structure of a typical dicot root shows the following
structure –
• 1. Epiblema or piliferous layer- It is the outermost protective
supporting and uniseriate layer. It is made up of compactly
arranged parenchymatous cells. Some cells produces unicellular
root hairs Both epiblema and root hairs absorb sap from the soil.
• 2. Cortex- It lies below the epiblema. It occupies the massive part
of the root. It is made of loosely arranged parenchymatous cells
with a large number of intercellular spaces that allow gaseous
exchange. The cortical cells help in the storage of food materials.

5. • 3. Endodermis- I It is the innermost layer of the cortex. It iis composed
of uniseriate and barrel shaped parenchymatous cells. Most of the
cell are characterized by the presence of band like thickenings of
suberin and lignin on their radial wall and tangential walls. These
thickenings are called as casperian strips. But some cells laying
opposite to the proto xylem remain un thickened and are called as
passage cells that allow diffusion of sap.

6. • 4. Pericycle- It lies just below the endodermis. It consists of a
uniseriate parenchymatous cells. The lateral roots, vascular
cambium and cork cambium are originated from this layer.
• 5. Conjunctive tissue- The xylem and phloem are separated from
each other by thin walled parenchymatous conjunctive tissue.
• 6.Vascular bundles- VBs are radial type. Number of xylem and
phloem varies from 2-6 i.e diarch to hexarch. Both xylem and
phloem are equal in number. The xylem is exarch.
• Xylem- The protoxylem vessels bear annular and spiral Thickening
while metaxylem vessels have reticulate and pitted thickenings,
xylem parenchyma and fibres are absent .

7. • Phloem- It lies alternate to xylem . The patches are smaller
and consist of sieve tube , companion cells and phloem
parenchyma. The phloem fibers are absent.
• Pith – The central mass of parenchymatous tissue is called
pith. In dicot roots , the pith is absent on highly reduced .

9. Diagnostic features of monocot root
•Number of VB varies from 8-20.
•The pericycle produces only lateral roots
•The pith is developed.
•The secondary growth is absent.

10. • Internal structure of atypical monocot root shows the following
structure –
• 1. Epiblema or piliferous layer- It is the outermost protective
supporting and uniseriate layer. It is made up of compactly arranged
parenchymatous cells. Some cells produces unicellular root hairs Both
epiblema and root hairs absorb sap from the soil.
• 2. Cortex- It lies below the epiblema. It occupies the massive part of
the root. It is made of loosely arranged parenchymatous cells with a
large number of intercellular spaces that allow gaseous exchange. The
cortical cells help in the storage of food materials.

11. • 3. Endodermis- I It is the innermost layer of the cortex. It iis composed
of uniseriate and barrel shaped parenchymatous cells. Most of the
cell are characterized by the presence of band like thickenings of
suberin and lignin on their radial wall and tangential walls. These
thickenings are called as casperian strips. But some cells laying
opposite to the proto xylem remain un thickened and are called as
passage cells that allow diffusion of sap.

12. • 4. Pericycle- It lies just below the endodermis. It consists of a
uniseriate parenchymatous cells. The lateral roots are originated
from this layer.
• 5. Conjunctive tissue- The xylem and phloem are separated from
each other by thin walled parenchymatous conjunctive tissue.
• 6.Vascular bundles- VBs are radial type. Number of xylem and
phloem varies from 8-20 i.e polyarch. Both xylem and phloem are
equal in number. The xylem is exarch.
• Xylem- The protoxylem vessels bear annular and spiral Thickening
while metaxylem vessels have reticulate and pitted thickenings,
xylem parenchyma and fibers are absent .

13. • Phloem- It lies alternate to xylem . The patches are smaller
and consist of sieve tube , companion cells and phloem
parenchyma. The phloem fibers are absent.
• Pith – The central mass of parenchymatous tissue is called
pith. In monocot roots , the pith is highly developed.