Question

Explain the internal structure of Dicot root with the help of well-labelled diagram and also differentiate between vascular bundle od Monocot and dicot root?

Answer 1

1. Epiblema:

• ( = piliferous layer = rhizodermis)
•  It is the outermost layer.
• Consists of thin walled, living parenchymatous cells.
• The outer walls of the cells of epiblema form unicellular tubular prolongations called root hairs.
• These hairs help in absorption of water from the soil.

2. Cortex:

• It is situated below the epiblema upto endodermis.
• It is made up of thin walled circular or polygonal living parenchymatous cells with numerous intercellular spaces.
• Cortical cells store starch.

3. Endodermis:

• The innermost layer of cortex that surrounds the stele is called endodermis.
• Cells of endodermis have special thickenings called casparian strips in their radial and tangential walls.
• Endodermal cells outside the protoxylem, do not have casparian strips.
• Such cells are called passage cells.

4. Pericycle :

• This unilayered structure is found inside the endodermis.
• Consists of thin waded cells.

5. Vascular bundles:

• These are always arranged in a ring and are radial i. e., Xylem and phloem are situated at different radii.
• The protoxylem is always away from the centre and metaxylem towards the centre.
• This condition of xylem is called exarch.
• The vascular bundles in gram root are tetraeh.

6. Conjuctive tissue:

• In between the xylem and phloem patches of paren-chymatous cells are found called as conjunctive tissue.

7. Pith:

• It is found in the centre and is feebly developed.
• It is made up of parenchymatous cells with intercellular spaces.