Thursday, November 29, 2012

Internal structure of dicot root

Dicot root consist of following internal structures:

1.epiblema : epiblema is outermost covering of the root.it is also called piliferous.it consist of thin walled,compactly arranged living parenchymatous cells.epiblema lacks of cuticle and possess unicellular root hairs.it helps in absorption of water and protection.

2.cortex: epidermis or epiblema is followed by well developed cortex.it consist of thin walled parenchymatous cells with large intercellular space.cells are larger and rich in leucoplast.they store starch.

3.endodermis : cortex is followed by endodermis.it is covering region of stele.it is composed of single layer of barrel shaped parenchymatous cell without intercellular space.they are covered externally by suberin and lignin.these thickenings are called casparian strips.unthickened cells are called passage cell.they allow radial diffusion of water.

4.pericycle :

it lies internal to endodermis.it usually contain single layer of parenchymatous cells.hydrophytes have no pericycle.lateral roots araise from pericycle.they actively take part in secondary growth.

5. vascular bundles: vascular bundle are radial.the number number of vascular bundles vary from 2-6.xylem shows exarch condition.centripetal development of xylem occurs.metaxylem consist of larger pitted or reticulate thickenings .proto xylem consists of smaller vessels with spiral thickenings.
phloem consis of phloem parenchyma,companion cells and sieve tubes,bast fibre is absent.xylem help in conduction of water and phloem help in conduction of food material.

6.conjunctive tissue :

they separate xylem and phloem strands.they are thin walled parenchymatous tissue.

7.pith : pith is the central mass of tissue made up of loosely arranged parenchymatous cells.they are absent or reduced in dicot root.



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