Mounting Of Leaf Peel Class 10th Science Lab Manual CBSE Solution

Class 10th Science Lab Manual CBSE Solution

Lab Experiment 6
Question 1.

AIM

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


Answer:

MATERIALS REQUIRED


Leaf of tradescantia or periwinkle or balsam, slides, coverslips, forceps, needles, cotton cloth, brush, blotting paper, watch glass, blade, dropper, glycerine, safranin


THEORY


1. Stomata (singular: stoma) are tiny pores found in the epidermis of leaves of the green plant through which exchange takes place.


2. Each stoma is bounded by two guard cells which unlike the other epidermal cells, possess chloroplast.


3. The walls of guard cells are thicker and more elastic, i.e., they are thickened on the inner side and thinner and more elastic on the outer side.


4. The guard cells control the opening and closing of stomata.


5. When water flows into the guard cell, they swell expand and cause the stomatal pore to open. On the contrary, when they lose water, they shrink and close the stomatal pore.


PROCEDURE


1. Take a leaf of the green plant and remove the peel from its lower surface by tearing the leaf.


2. Place the leaf peel in the watch glass containing water, so that the peel does not dry during the experiment.


3. Add 1-2 drops of safranin to the watch glass containing the peel of leaf to stain.


4. Select a thin leaf peel and place it in the centre of a clean slide with the help of the brush


5. Put few drops of glycerine on the slide over the peel with help of a dropper.


6. Now, using a needle gently place a coverslip over the strained peel slide.


7. Remove the excess stain and glycerine with a blotting paper.


8. first, observe the slide under the lower magnification (i.e., 10 X) of a compound microscope and then, under the higher magnification (i.e., 45 X).


OBSERVATIONS


1. Epidermis or leaf peel consists of many cells which are irregular in outline and are arranged in a single layer with no intercellular spaces.


2. These tiny pores are called as stomata and are seen in the epidermal cells.


3. Each stoma consists of two kidney-shaped guard cells.


4. Each guard cell has a nucleus and chloroplasts.


5. The diagram of the leaf peel shown below:




RESULT



Minute apertures called stomata are well observed in the temporary mount of leaf peel.


PRECAUTIONS


1. The peel should be freshly plucked from the leaf.


2. The peel should not be allowed to dry.


3. Leaf peel should not be over stained.


4. The slide to be used must be clean.


5. The peel should be placed in the centre of the slide for best view.



Viva Questions
Question 1.

What are stomata?


Answer:

Stomata are tiny pores present on both upper and lower surfaces of leaves.



Question 2.

What is a Compound Microscope?


Answer:

A Compound microscope is an instrument which is used to observe the enlarged and magnified image of the small objects.

A labelled diagram of compound microscope is attached here:




Question 3.

Why does compound microscope has higher magnification?


Answer:

The microscope consists of two systems of lens called as an objective lens and ocular lens which is used to obtain a higher magnification value.



Question 4.

What are the optical parts of a compound microscope?


Answer:

1. Mirror: It is used for reflecting light into the microscope, and it is located at the lower end of the arm, it is concave on side and plane on the other.


2. Eyepiece: It is lens fitted at the top of the body tube, it has 10X or 15X magnification.


3. Objective lens: These are attached to nosepiece and is responsible for the magnification action of the microscope.



Question 5.

Why is safranin is used as a stain for staining section of plants?


Answer:

Safranin stains the lignin and suberin and other plant material easily. It can easily stain all cell nuclei in red colour.



Question 6.

Why should leaf peel be mounted in glycerine?


Answer:

Glycerin is applied as it avoids drying up the specimen. The leaf peel should be mounted in glycerine so that the peel does not dry up.



Question 7.

What is guard cell?


Answer:

Guard cells are the cells surrounding the stomatal pore. Each guard cell consists of a nucleus and chloroplast.

The diagram is given below:




Question 8.

Give an Example of a plant in which stomata is absent?


Answer:

In hydrilla, no stomata is present. The exchange of the gases is through the epidermal surface.



Question 9.

What is the important function of stomata?


Answer:

The most important function include gaseous exchange and transpiration.



Question 10.

What is transpiration?


Answer:

The loss of water in the form of vapor from leaves of the plant is called transpiration.



Question 11.

Name the plant hormone which helps in stomata opening?


Answer:

Cytokinin.

Cytokinins (CK) are a class of plant growth substances (phytohormones) that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation.



Question 12.

Name the plant hormone which causes stomatal closure?


Answer:

Abscisic acid(ABA)



Question 13.

Name the inorganic ion which helps in opening and closing of stomata?


Answer:

Potassium Ion.



Question 14.

Why do guard cell bend when they swell up?


Answer:

The guard cell bend because of differential thickenings of its inner and outer walls.

The inner wall is thicker and less stretchable as compared to the outer walls.



Question 15.

Why are stomata are absent in roots?


Answer:

The stomata are present in the aerial plant for transpiration to occur. While the function of the root is to absorb minerals from soil not to exchange gas.



Question 16.

What is the difference between an eye-piece and objective lens?


Answer:

The eyepiece is fitted at the top of the body tube. It is the lens through which we view the cells.

The objective is attached at the nose piece and is closed to the object.




Question 17.

Why is mirror an important part of the microscope?


Answer:

Mirror is an important part of the microscope as it reflects light into the microscope. Without light, the object cannot be seen.



Question 18.

Give two major differences between epidermal and guard cells.


Answer:

1. Epidermal cells lack chloroplast whereas guard cells have chloroplast.


2. Epidermal cells are irregular in shapes whereas guard cells are in kidney shape.



Question 19.

How can you remove the extra stain from the glass slide?


Answer:

The extra stain can be removed by soaking with the filter paper.



Question 20.

Where do we put the objects to observe in a microscope?


Answer:

The objects are put on the “stage”. Stage is a rectangular plate & has a hole in center through which light can pass so that object can be viewed.


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