Question

Draw a labelled diagram of TS of dicot root and give description in brief

Answer 1

Dicot roots of gram shows following distinct region in its Transverse section with following features:

Epiblema

Cortex

Endodermis

Pericycle

Vascular bundles

Pith

1. Epiblema or Epidermis - It is the outermost unilayered with several unicellular root hairs. It consists of thin walled, compactly arranged living parenchymatous cells. Usually epiblema is characterised by absence of stomata and cuticle. Sometimes the epiblema may be less cuticularised. It provides protection to the roots due to presence of unicellular root hairs it also helps in absorption of water and minerals from soil.

2. Cortex - It is thin walled, multilayered region made from circular or polygonal parenchymatous cells. they usually have intercellular spaces. The cortical cells have no chloroplast but may contain leucoplast for storage of starch grains. The cortex is responsible for transportation of water and salts from the root hairs to the center of the root.
3. Endodermis - It is the innermost layer of cortex and covers the stele. It consists of compactly arranged barrel shaped parenchyma without intercellular spaces. Most of the cells are characterised by the presence of special thickening of suberin and lignin on their radial and tangential walls called casparian strips. Some endodermal cell near protoxylem has no casparian strips and called passage cells or transfusion cells. These cells allow radial diffusion of water and minerals through the endodermis.
4. Pericycle - It is the outermost layer of stele and composed of uniseriate layer of parenchymatous cells without intercellular spaces. Some dicots and hydrophytes do not bear pericycle. Several lateral roots and lateral meristem arise from pericycle region (hence lateral roots are endogenous in origin). At the time of secondary growth, it produces secondary cambium or phellogens.
5. Vascular bundles - They are 2-8 in number, radial and arranged in ring. Xylem and phloem bundles are separated from each other by parenchymatous cells called conjuctive or complementary tissue.

Xylem is exarch (i.e. protoxylem towards the periphery and metaxylem towards the centre) and consists of tracheids, vessels, xylem parenchyma and xylem fibres.

The pholem forms oval masses beneath the pericycle, alternating with xylem bundles. Pholem consists of sieve tubes, companion cells and pholem parenchyma. Usually pholem fibres are absent or reduced.

6. Pith - it is feebly developed and centrally located. It consists of thin walled, polygonal parenchyma cells with intercellular spaces. In dicots roots, it may be reduced or absent. It helps in storage of food materials.


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Answer 2

Dicot Root

Explanation:

There are six part of the dicot root which is follows:

Epidermis: It is made out of flimsy walled cells and It is single-layered.The Outer side  epidermal cells are not cutinised. Many  epidermal cells show out shape is long bristly bodies.

Cortex: It is very enormous and broad in roots. it  is made of Thin  walled living leucoplasts and Perenchymatous cells , which converted  sugar into starch grains.  

Endodermis: It is made out  of barrel-molded cells which are firmly organized without having intercellular spaces.  

Stele or Central Cylinder: Pericycle is the seat of the starting point of parallel roots. Vascular packs are regularly spiral in roots. It is  interceded by non-conduct­ing cells and Phloem and xylem  structure are different.  

Conjunctive Tissue: It is made of Thin-walled parenchymatous cells which present  in the middle of  phloem and xylem  bunches establish the conjunctive tissue.  

Pith: At the middle there is a little parenchymatous essence. It absent in the   dicotyledonous roots.