Preparing a temporary mount of a leaf peel to show stomata

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Aim

To prepare a temporary mount of a leaf peel to show stomata.

Materials Required

Leaf of Tradsscantia or periwinkle or balsam, slide, coverslip, forceps, needles, cotton cloth, brush, blotting paper, watch glass, blade, dropper, glycerine, safranin and compound microscope.

Theory

Stomata (singular: stoma) are tiny pores present on the surface of the leaves. Through they are found on both upper and lower epidermis of leaf but they are more in number on the lower epidermis. Each stoma is bounded by two kidney-shaped guard cells. These guard cells possess a nucleus and a number of chloroplasts. The walls of guard cells are differentially thickened and elastic, i.e. they are thickened on inner side and thinner and more elastic on outer side.

The opening and closing of stomata is operated by the change in the turgidity of guard cells. The stomata help in exchange of oxygen, carbon diodide and water vapour between atmosphere and plant.

Procedure

• Take a freshly plucked leaf, and remove the peel from its lower surface by tearing it.
• Put the leaf peel in a watch glass containing water so that the peel does not dry.
• To the watch glass containing leaf peel, add 1-2 drops of safranin to stain the peel.
• With the help of brush, place the leaf peel in the centre of a clean slide.
• Put a drop of glycerine on the slide over the peel.
• Now, with the help of a needle, gently place a coverslip over the peel.
• Remove the excess glycerine with a blotting paper.
• Observe the slide, first, under the lower magnification (i.e., 10 X) of a compound microscope and then, under the higher magnification (i.e., 45 X).

Observations

• Epidermis or leaf peel consists of a number of cells which are irregular in outline and are arranged in single layer with no intercellular spaces.
• Tiny pores called stomata are seen in the epidermal cells.
• Each stoma consists of two kidney-shaped guard cells.
• Each guard cell has a nucleus and many chloroplasts.

Result

Minute apertures called stomata are seen in the temporary mount of leaf peel. Each stoma is enclosed by two kidney-shaped guard cells. These guard cells differ from other epidermal cells in having chloroplast.

Precautions

• Peel should be taken from freshly plucked leaf.
• Peel should not be allowed to dry.
• Leaf peel should not be over stained.
• The slide should not be dirty.
• Use a brush to transfer the leaf peel from watch glass to slide.
• Peel should be placed in centre of slide.
• Curling of peel should be avoided while placing it on slide.
• The epidermal peel should be small in size.
• Place the coverslip gently to avoid entry of air bubbles.
• Excess stain and glycerine should be removed with blotting paper.

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