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Practice English Speaking&Listening with: Lignin Staining - Amrita University

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Lignin Staining

Lignin, a complex phenylpropanoid polymer, is primarily deposited in the walls of cells

that have secondary wall thickening, such as tracheary elements and fibers.

Lignin provides mechanical strength to the walls of these sclerenchyma cells. Lignin

is derived from the de-hydrogenative polymerization of the monolignols p-coumaryl alcohol, coniferyl

alcohol, and sinapyl alcohol. These monolignols are synthesized through a phenylpropanoid

biosynthetic pathway.

In the top part of the stem, where the only sclerenchyma cells present are the xylem vessel

elements, lignin staining is only seen in the xylem. In the middle part of the stem,

another type of sclerenchyma cells - the inter-fascicular fibers is present in addition to xylem cells.

Here lignin is seen in both inter-fascicular fibers and xylem cells. In the lower part

of the stem, more xylem cells and inter-fascicular fibers are formed. Consistently, intense lignin

staining is seen in these sclerenchyma cells too. No lignin staining can be detected in

the cortical cells or the pith parenchyma cells throughout the stems.

Materials Required

Potato Stem of the plant

Double edged razor blade Water

Dropper Brush

Glass slide Blotting paper

Phloroglucinol Stain (colorless liquid) Petri dish

PROCEDURE

Using a razor blade cut the potato into a block and make a slit in the middle of the

potato block. Place the stem of the plant in the middle

of the slit made in the potato block. Cut thin sections of the stem along with the

potato block into a Petridish containing water. Using a brush transfer the cut sections of

the stem into a Petridish containing water. Pour few drops of phloroglucinol-HCL stain

into a watch glass using a dropper. Transfer the cut sections of the stem from

the Petridish into the watch glass using a brush.

Take a clean glass slide and pour few drops of water on to the slide. Using a wet brush

transfer the sections from the watch glass onto the slide.

Place a coverslip over the sections on the slide using a forceps.

Remove the excess solution from the edges of the coverslip by touching the side with

a blotting paper and observe the slide under microscope.

RESULT

The red colour seen in the sections indicate Lignin staining. Lignin staining is heavy

in both xylem cells and inter-fascicular fibers.

The Description of Lignin Staining - Amrita University