ROOT:RAUWOLFIA - EXPERIMENT

ROOT:RAUWOLFIA

AIM:

To study the histological characters of Rauwolfia Root.

Requirements:

Chemicals:

Chloralhydrate solution, Phloroglucinol solution, conc. HCl, glycerine, Dil. Iodine solution

Glasswares:

Micro slides, cover slips, compound microscope, watch glass.

Crude drugs:

Rauwolfia root

Description:

TS of the root represent a circular outline with typical stratified cork and other secondary features. Following are the tissues seen from the periphery to the center.

ROOT:

PERIDERM:

I)       Cork

II)    Phellogen

III) Phelloderm

·         Starch grain

·         Calcium oxalate crystal

SECONDARY PHLOEM:

SECONDRY XYLEM:

1.      Xylem vessel

2.      Xylem fibre

3.      Xylem parenchyma

4.      Medullary rays

PERIDERM:

Cork:

Stratified cork consists of smaller and unlignified cells up to 8 to 10 rows in radial depth and large lignified cells up to 5 to 7 rows in radial depth. All the stratified cork cells contains suberin ( waxy substance wich is hydrophobic in nature.

Phellogen:

Indistinct but is seen as a narrow layer of thin walled cells.

Phelloderm:

5 to 7 layers, immediately below the phellem, cells are arranged in radial rows whereas away from phellem, cells are oval and have intercellular spaces.

Phelloderm contains abundant starch grains.

Typical twin prism of calcium oxalate are also seen.

Starch grains: They are spherical to subspherical in shape with the star shape hilum. They are simple or compund in appearance.

Calcium oxalate crystals: Are of angular crystal type.

Secondary phloem:

It is made up of unlignified cells and consist of narrow rays of scatered seive tissues and parenchyma cell. Calcium oxalate crystals are also present.

Many of the phloem parenchyma cells contain group of calcium oxalatr crystals and few contains granular secretions, which turns yellow in presence of iodine, starch grains are also present in few cells.

Secondry xylem:

It is made up of lignified cells

It consist of following

Xylem  vessels:

They are very few in number and lignified in nature.

They have simple or bordered pith.

 Xylem fibres:

They are made up of very thick cells whose ends are either pointed or forked.

Xylem parenchyma:

the walls of these cells have many circular piths which make them thick.

These cells contains starch grains.

Medullary rays:

They are made up of large lignified cells

They are  1 to 5 cells wide, contains starch grains and have alternate layers of secondry phloem.

Run radially from the center to the cortex through the phloem.

They extends from center of cortex up to phloem.

Starch and typical oxalate prism are present in medullary ray cells.

RHIZOME:

The rhizome and roots are similar character. The only difference is that other than a cortex, a pericycle with unlignified pericyclic fibres and a small pith are present in rhizome.

In addition to the other characters of the root. Stone cells and phloem fibres are absent in both roots and rhizomes.