Question

Geeta was asked to prepare a temporary mount of onion peel and list the steps. While writing, she wrote the following steps, which may not be in a proper sequence.
correct sequence would be
(i) Add a few drops of safranin stain and transfer to a slide.
(ii) Cover it with a cover slip
(iii) Add a drop of glycerine
(iv) Take out onion peel
(v) Keep the peel in water in a petri dish

A. i, ii ,iii, iv, v
B. iv, v, iii, ii, i
C. iv, v, i, iii, ii
D. v, iv, i, iii, ii

Answer 1

Hint: To prepare a temporary mount of onion the first step is to peel the onion. To remove the impurities, we need to put the peel into the water. For staining, onion peel has to be transferred to a slide and a few drops of safranin should be added and glycerin prevents the peel from drying out. To see the slide under the microscope we need to cover it with a cover slip.

Complete answer:
Following steps are followed to create a temporary mount of an onion:-
-Take a scale (peel) from an onion bulb.
-Concave side of the onion scale should be broken until a thin translucent membrane is separated.
-Thin onion peel will be transferred into a watch glass containing water to remove impurities (use a brush to transfer the peel on the slide).
-Put a few drops of safranin stain on it. Overstraining should be avoided.
-Put a drop of glycerine on a stained peel and place a cover slip on it (extra glycerine should be removed from the slide and also remove all air bubbles), and then observe it under the microscope.

Hence, the correct answer is option (C).

Note: Safranin is a dye which can be easily taken by the cells and it gives pink color as the background and the cell wall is transparent and the cell is difficult to visualize. Staining by safranin imparts color of the cell and its organelles and enhances its contrast so we can easily see the cell structure.