RHIZOME:GINGER - EXPERIMENT

RHIZOME:GINGER

AIM:                                                  

To identify Ginger rhizome by studying its histological characters.

Requirements:

Chemicals:

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

Glasswares:

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

Crude drugs:

Ginger rhizome

Description:

A cross section of unpeeled mature rhizome broadly consist of following tissues from the periphery to the center.

·         Cork

·         Cortex

·         Endodermis

·         Ground tissue

CORK:

Cork is devided into outer cork and inner cork

Outer cork

It consists of paremchymatous cells which are irregylarly arranged few layer ( 3 to 4 layers )of outer cork is dark brown in colour , made up of irregular parenchymatous cells.

Inner cork

It consists of parenchymatous cells which are radially arranged in 2 to 4 layers, usually colourless.

CORTEX:

It is differenciated into outer zone and inner zone of the cortical cells.

Outer zone of cortical cells

It consists of parenchymattous cells which are flat in structures.

Inner zone of cortical cells

It consists of parenchymatous cells.

1.      Vascular bundles:

Three rings of vascular bundles are present in the inner zone of cortex.

The vascular bundles are collateral( xylem and phloem are present in the same vascular bundles on the same radius) and closed (cambium is absent in the vascular bundles) type.

Sheath of non lignified fibres are present.

Vascular bundles contains xylem and phloem

Xylem: Xylem vessels range from 1 to 14 in number. Their walls are thick with spiral and reticulate or annular thickenings.

2.      Secretion cells:

Secretion cells are  rarely present. The cells contains dark coloured substance.

In both the zone of cortex, starch cells are present in abundance

Starch grains are simple or ovoid in shape, they shows the presence of hillum.

Distinct striations are very prominent on the grain.

3.      Oil  cells:

A large number of oil cells are scattered in the cortex

The walls of oil cells are thickened with suberin

The cells contains oleo resin which is yellowish brown in colour.

Number of oleo resin and vascular bundles are seen.

The oleo resin cells have suberized walls and contain yellowish mater.

ENDODERMIS:

Single layered with radial wall thickened and with no starch grains.

GROUND TISSUE:

Large, parenchymatous( similar to that of cortex) and with abundant starch, oleo resin cells and vascular bundles.

A group of sclerenchymatous fibre partially covers the vascular bundles of cortex and also of central ground tissue and these bundles are therefore called fibrovascular bundles.

Just below the endodermal layer, that is to the periphery of the ground tissue, a ring of narrow zone of vascular bundles appears which however are not covered by sclerenchymatous fibers.

While the phloem represents the usual well developed sieve element, xylem element are somewhat characteristic.

Xylem consists of mainly vessels, some tracheids which have annular, spiral or reticulate thickenings but without any reaction to lignin. The fibers are also unusually unlignified, pitted and septate.