Page 23 - Biology - XII

2. Put a drop of acetocarmine stain over it.
3. Now, gently warm the slide by passing it through a spirit lamp fl ame many times. Do not overheat it.
Repeat the process 2–3 times when the stain dries up.
4. Put a clean coverslip and tap it with the blunt end of the pencil. Now, put a fi lter paper over it, fold it,
and press the coverslip with your thumb. This gives a uniform spread or the squash.

5. Observe the slide fi rst under the low power (10X) and then under high power (45X) microscopes.
6. Study the slide and draw the fi gure of various stages/phases of cell division.
7. Write comments in your practical record fi le.

Cutting the meristematic root apex Addition of acetocarmine stain

Warming the material/ Tapping the material with pencil
staining the material to obtain squash
Fig. 5.1: Making onion root tip squash

Results
1. A mass or strips of purple-blue coloured cells
2. Diff erent stages of mitotic cell division
3. Cells are more or less rectangular in shape

Comments
1. Interphase (Inter—in between): This stage is identifi ed by—
(i) It is a non-dividing phase/stage of the cell.
(ii) Nucleus is large and distinct.
(iii) Nucleus is surrounded by a nuclear membrane.

(iv) Nucleolus is seen.
(v) Chromatin material is not diff erentiated into
chromosome.
2. Prophase (Pro—fi rst): This stage is identifi ed by—
(i) Nucleus is enlarged and occupies most of the cell
volume in early prophase stage. Fig. 5.2: Onion root tip showing
(ii) Long inclined thread-like structures (chromosomes) diff erent stages of cell division
appear inside the cell. (under the microscope)

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