do the experiment to prepare stained temporary mount of an onion peel and record it's observation and draw labelled diagram
Answers
AIM
To prepare stained temporary mount of onion peel cells and to record observations and draw labelled diagrams.
MATERIALS REQUIRED
Onion, plain slides, coverslip, watch glass, needles, forceps, brush, blade, safranin, blotting paper, glycerine and compound microscope.
THEORY
Onion is a multicellular plant. Like other plant cells, the cell of onion peel consists of a cell wall, cell membrane, cytoplasm, a large vacuole and a nucleus. The nucleus lies at the periphery of cytoplasm and vacuole is located in the centre. Presence of large vacuoles and cell wall confirms that cells of onion peel are plant cells.
PROCEDURE
Take a piece of onion and bend it to remove the transparent membranous structure called onion epidermal peel. With help of forcep remove the peel from its inner side.
Place the peel in water in a watch glass.
Add a few drops of stain safranin, to the watch glass containing the peel for staining.
Now, wash the leaf peel with water and transfer it on to a clean slide with the help of brush.
Remove extra water from the slide surrounding the peel with the help of blotting paper.
To this slide, add a drop of glycerine over the peel and place the coverslip in a manner to avoid entry of air bubbles.
Soak away the extra glycerine with blotting paper.
Examine slide under the microscope.
CBSE Class 9 Science Practical Skills – Slide of Onion Peel and Cheek Cells 1
OBSERVATIONS
A large number of rectangular cells with distinct cell wall can be observed.
Cytoplasm is seen as thin layer of deep coloured substance on inner surface of cell wall.
A big central vacuole is present in the cell.
A deeply stained round body called nucleus is seen in each cell.
CBSE Class 9 Science Practical Skills – Slide of Onion Peel and Cheek Cells 2
RESULT
The epidermal peel of onion comprises of rectangular shaped cells. Each cell comprises of a nucleus, a central vacuole, thin layer of cytoplasm and cell wall.
As cell walls and large prominent vacuole are present in each cell, the cells placed under observation are plant cells.
PRECAUTIONS
Always take a clean slide and hold it by its edges to avoid making the slide dirty.
Peel should be properly stain. Avoid under-staining or excessive staining of the peel.
Always transfer the peel with the help of brush.
Mounting of the peel should be done in centre of slide.
Avoid folding of the leaf peel.
Remove extra glycerine with the help of blotting paper.
Avoid entry of air bubbles while placing the cover slip.
Answer:
Onion peel: For the preparation of stained temporary mount of onion peel.
Requirements: Onion, brush, distilled water, saffranine, watch glass, forceps, dropper, glass slide, cover slip, glycerin and microscope.
Procedure:
1) Take a watch glass and pour small quantity of distilled water into it.
2) Take an onion and cut the fine piece of peel of onion with the help of forceps.
3) After cutting the fine piece of onion peel, separate transparent onion peel in order to observe it under the microscope.
4) Place the transparent onion peel into watch glass containing distilled water, to remove any dust from the epidermis.
5) Take a small quantity of safranine with the help of dropper and pour in into watch glass.
6) Transfer the epidermis of onion peel into the watch glass containing safranine.
7) Keep the peel in safranine for approximately 30 sec and allow it to react with safranine.
8) After 30 seconds, transfer the onion peel from safranine containing watch glass to distilled water containing watch glass with the help of brush.
9) Now take a clean, grease free slide and pour 2-3 drops of glycerin on the slide. Along with that take onion peel and place it on the slide containing glycerin.
10) On this glass slide place a dry cover slip on the area containing glycerin and onion peel.
11) Remove the excess glycerin with the help of bloating paper.
12) Observe the slide under the microscope.
Observations:
1) By observing under the microscope, the separate cells can be visualized.
2) The cells contain protective covering called cell wall also observed among the cells.
3) The separate nucleus was seen in the center of the cell and the cytoplasm is surrounded in entire cell.
Cell structure of onion peel under microscope
Result: In the slide, cell wall, nucleus and cytoplasm visualized easily.
Conclusion: The onion peel was successfully isolated and observed various structures under the microscope
