Preparing A Temporary Mount of a Leaf Peel To Show Stomata

Biology experiment - Experiment preparing a Temporary Mount of a Leaf Peel to Show Stomata

Plants are considered as living organisms because they can perform the functions of growth, development and reproduction. One such quality that the plants have which is similar to animals is the ability to perform gaseous exchange. This gaseous exchange in plants is done by tiny pores known as stomata. Stomata are present on the leaves where photosynthesis takes place. This is an advanced feature which is found in higher plants such as gymnosperms and angiosperms. 

Table of Contents

The following article contains: -

• Aim 

• Requirements 

• Theory 

• Methodology 

• Observations

• Conclusion 

Aim 

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

Requirements

Leaf, forceps, blade, glycerin, slides, coverslips, compound microscope, water, safranin, blotting paper, etc.

Theory

Stomata are small pores which are guarded by kidney shaped or dumb bell-shaped guard cells. These guard cells absorb water and swell as a result the stomata opens up; when water is lost from the guard cells they turn flaccid and  the pores close. These guard cells contain chloroplast and nucleus. Stomata is present in large numbers on the lower epidermis in dicot leaf and are uniformly distributed between both surfaces in monocots.

Procedure

1. For this leaf activity, take fresh leaves from any plant and clean and dry it.

2. Flip the leaf on the lower side and tear the leaf tangentially i.e., at an angle. Due to this process a transparent tissue is seen which contains the stomata.

3. Take the leaf peel with forceps in a petri dish and add a few drops of safranin to it.

4. Keep the peel in the stain for 2-5 mins so the stain can be absorbed by the peel.

5. Place this stained leaf peel on a glass slide. 

6. We generally mount the material in the slide after adding a drop of glycerin over it and then gently placing a coverslip.

7. Clean excess glycerin using a blotting paper.

8. Place the slide under a compound microscope and visualize the leaf peel first at low power and then at high power.

9. Record the observations.

Observations

• At low power of the microscope epidermal cells were visible which were a single layer and do not contain any intercellular spaces.

• Scattered throughout the epidermal cells were small tiny pore-like structures.

• At high power these tiny pores appear with proper stomatal openings.

• These pores were surrounded by two kidney-shaped guard cells which control the opening and closing of the stomatal pore.

• Each guard cell contained one nucleus with multiple chloroplasts.

Result

In this leaf activity the stomata were observed on the lower epidermis of the leaf. These pores contain kidney shaped guard cells, hence it can be concluded that this leaf was a dicot leaf. The guard cells contain a nucleus and chloroplasts.

This diagram shows the microscopic view of a dicot stomata.

Precautions

• Do not over stain the specimen.

• Use an adequate amount of glycerin.

• Clean the slide properly before putting it under the microscope.

Lab Manual Questions

1. Why is the temporary mount slide mounted in glycerine? 

Ans: In general mounting of material in the slide is done using glycerin. Glycerin   has the capacity to remain moist for a long time and hence prevents the dehydration of the sample.

2. How to differentiate between guard cells and epidermal cells?

Ans: Epidermal cells are irregular in shape, have no intercellular spaces and lack chloroplast. Guard cells are specialized cells and they are either kidney or dumb belled shaped, They are green as they contain many chloroplasts.

3. How is the distribution of stomata in monocot leaves?

Ans: In monocot leaves, the stomata is equally distributed on lower and upper epidermis as they contain equal amounts of chloroplast and both surfaces perform equal amounts of photosynthesis.

4. What is the shape and function of guard cells?

Ans: In dicot leaves the guard cells are kidney shaped, whereas in monocot leaves the guard cells are dumb-belled shaped. The function of guard cells is to protect the tiny pores and control the opening and closure of the stomata.

Viva Questions

1. Why is safranin used for staining plant cells?

Ans: Safranin is a red colored stain and stains lignin, suberin and other plant parts very easily.

2. What is the shape of guard cells when seen under a microscope?

Ans: In monocot plant guard cells are dumb belled shaped; in dicot plant guard cells are kidney shaped.

3. Which instrument can be used to know the size of stomata?

Ans: A porometer is used to know the size of the stomata.

4. Which plant does not contain stomata?

Ans: Hydrilla does not contain stomata.

5. What is the modification of stomata in gymnosperms and xerophytic plants?

Ans: In gymnosperms and xerophytic plants the stomata are sunken.

6. What are the functions of a leaf?

Ans: Leaf performs the functions of Photosynthesis, Respiration and Transpiration.

7. Why is transpiration required by plants?

Ans: Transpiration helps in building a transpiration pull in plants, this helps in the movement of water from roots to the top leaves ( movement against gravity).

8. Give examples of plants having kidney shaped stomata.

Ans: Banyan, Betel leaf plant, Peepal, Mango, False Ashoka etc.

9. Give examples of plants having dumb- belled shaped stomata. 

Ans: Banana, Grasses, Rice, Jowar, Bajra, etc.

10. Which part of the stomata contains chloroplast?

Ans: The guard cells of the stomata contain chloroplast.

Practical Based Questions

1. For the above leaf activity, we generally mount the material in the slide using _____

1. Water

2. Glycerin

3. Alcohol

4. Wax

Ans: Glycerin

2. Find the odd man out

1. Guard cells

2. Epidermal cells

3. Stomata

4. Trichomes

Ans: Trichomes

3. Which of the following is not a function of stomata?

1. Transpiration

2. Respiration 

3. Photosynthesis

4. Gaseous exchange

Ans: Photosynthesis

4. Hormone responsible for closing of stomatal pore

1. Abscisic acid

2. Auxins

3. Gibberellins

4. Cytokinin

Ans: Abscisic acid

5. Inorganic ion assisting in opening and closing of the stomata are

1. Ca+ ions

2. Na+ ions

3. K+ ions

4. Cl- ions

Ans: K+ ions

6. A temporary mount of a tissue is made in which of the following has to be used?  

1. Safranin and glycerin

2. Acetocarmine and alcohol

3. Iodine and water 

4. Safranin and water

Ans: Safranin and glycerin

7. Hormone responsible for opening of stomatal pore

1. Abscisic acid

2. Cytokinin

3. Gibberellins

4. Auxins

Ans: Cytokinin

8. In an experiment a temporary mount of a leaf peel is prepared from betel leaf to show stomata, from where the peel should be taken?

1. Petiole of the leaf

2. Vein of the leaf

3. Lower surface of the leaf

4. Upper surface of leaf

Ans: Lower surface of the leaf

9. Regarding the distribution of stomata in monocot leaves which of the following is true?

1. In monocots, leaves are amphistomatic

2. Monocot leaves stomata are situated only on the dorsal surface

3. Grasses have stomata only on upper surface

4. Monocot stomata are large and kidney shaped

Ans: In monocots, leaves are amphistomatic

10. Which part of the leaf peel is pink colored after staining with safranin?

1. Stomata only

2. Epidermal cells

3. All parts of the peel

4. Only the nucleus

Ans: All parts of the peel

11.  Which of the following is used to see the stomata

1. Electron microscope

2. Compound microscope

3. X-ray microscope

4. Simple microscope

Ans: Compound microscope.

Summary

Stomata is the most important part of the plant, as it helps in exchange of gases and facilitates most vital processes of the plants i.e., photosynthesis, respiration and transpiration. A stoma contains a stomatal pore, guard cells, subsidiary cells and epidermal cells.