BIOLOGY PRACTICAL
Experiment:1
Objective:
To prepare a temporary mount of a leaf peel to show stomata.
Apparatus and Materials Required:
A potted Tradescantia or Bryophyllum plant, forceps, needles, watch glasses, glass slides, a
dropper, coverslips, a brush, blotting paper, safranin, glycerine and a compound microscope.
Theory:
Stomata are small openings found widely scattered on the epidermis of leaves and young stems.
They are mostly found on the lower surface of a dicot leaf and on both the surfaces of a monocot
leaf. Stomata regulate the exchange of gases and water vapour between the atmosphere and
leaves.
Procedure:
1. Remove a healthy leaf from the potted plant.
2. Remove a part of the peel from the lower surface of the leaf. You can do this by folding the
leaf over and gently pulling the peel apart using forceps. Keeps the peel in a watch glass
containing water.
3. Put a few drops of safranin stain in a watch glass.
4. After 2-3 minutes take out the peel and place it on a clean glass slide.
5. Put a drop of glycerin over the peel and place a clean coverslip gently over it with the help of a
needle.
6. Remove the excess stain and glycerin with the help of blotting paper.
7. Observe the slide under the low-power and high-power magnifications of the compound
microscope.
Observations:
1. The epidermal cells are visible. These are irregular in outline and have no intercellular spaces.
2. Many small pores (stomata) are seen scattered among the epidermal cells.
3. Each pore is guarded by two bean-shaped guard cells, each containing chloroplasts and a
nucleus.
Conclusion:
Epidermal layer of leaf peel has many stomata pores. Each stomatal pore has two kidney shaped
guard cells, in dicots plants. Each guard cell has one nucleus and many chloroplasts.
Precautions:
While removing the epidermal peel, ensure that you pluck the thinner scrap of leaf.
Do not overstain the peel.
Avoid air-bubbles formation while placing the coverslip.
The peel should not be folded.
The slide should be clean and dry before placing it under microscope.
Experiment: 2
Aim:
To show experimentally that carbon dioxide is given out during respiration.
Materials Required:
A conical flask, small test tube, cork, thread, germinating seeds, a bent tube, a beaker, water and
freshly prepared lime water.
Procedure
1. Take two conical flasks, add germinating seeds with little water sprinkled over it.
2. Fix the mouth of conical flasks with cork in which a bent tube is fixed.
3. Suspend a small test tube containing KOH solution in it with the help of a thread in conical
flask A.
4. Allow the mouth of the bent tube to be immersed in water in set-up A and in lime water in
set-up B as shown below.
5. Record your observations after few hours.
Observations
1. In set-up A, the water level in the bent tube dipped in beaker increases after few hours.
This is because the oxygen present in the conical flask is taken up by germinating seeds
and CO2 released due to respiration is absorbed by KOH present in small tube. Hence, the
air pressure in the flask reduces and water level rises.
2. In set-up B, the freshly prepared lime water turns milky. This is due to excess
CO2 released into the test tube during respiration of germinating seeds.
Conclusion:
This shows that CO2 is given out during respiration.
Precautions
1. Lime water should be freshly prepared.
2. KOH solution should be freshly prepared.
3. Germinating seeds should have lot of moisture in them.
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