Aim
To study the pattern and distribution of stomata in both the upper and lower leaf surfaces.
Theory
Stomata are tiny openings that are located in the young shoots of plants and epidermis of the leaves. They govern the gas exchange process in plants. The structure of the stomata includes a pair of specialized cells that are found girdling around the opening. These cells are termed as guard cells and are responsible to check and regulate the size of the closing and opening of the stomata.
Through the process of transpiration, water escapes from the stomata into the atmosphere in the form of water vapor. Along with this, carbon dioxide and oxygen too are exchanged in the leaf through these openings.
Stomata are distributed differently between dicots and monocots, between the top side and underside of leaves, between different plant species, etc.
Mostly, stomata are found on surfaces of plants that flourish under greater availability of light, lesser carbon dioxide levels in the atmosphere and also in moist environments.
In a dicot leaf, in comparison with the upper surface, the lower surface has a higher distribution of stomata whereas in a monocot leaf, usually, the upper and the lower surfaces usually see an equal distribution of stomata.
Material Required
- Blade
- Forceps
- Dropper
- Glycerine
- Cover slip
- Watch glass
- Glass Slide
- Distilled water
- Needle and brush
- Safranin solution
- Four O’clock plant
- Compound microscope
Procedure
- One fresh leaf from a four-o’clock plant is used in this experiment
- On two watch glasses, add some distilled water
- Slit the leaf in an oblique manner
- With the help of forceps, peel a section from the upper surface of the leaf
- Set this section into one of the watch glass holding water
- With the help of forceps, peel another section from the lower surface of the leaf
- Set this section on another watch glass which is also holding water
- With the help of a dropper, add few drops of safranin solution into both the watch glasses
- Now place cleared glass slides on each of the peels one at a time with the help of a brush
- From each of the peels, cut a square or a rectangular piece with the help of a blade
- With the help of a dropper, add one drop of glycerine on each of the slides
- With the help of a needle, gently place a cover slip on the peel
- Examine each of the glass slides under the microscope
- Notice and count the occurrence of stomata in each of the peels of both the lower and upper epidermis of the four-o’clock leaf.
Observation And Conclusion
The section of leaf plucked from the four-o’clock plant shows that the number of stomata is much more in the lower epidermis while a few are found in the upper epidermis of the leaf.
Precautions
- Avoid leaf curling
- Gently place the cover slip on the slide to avoid air bubbles
- Transferring peel to the slide from the watch glass should always be done using a brush
Viva Questions
Q.1. What is the scientific name of the four-o’clock plant?
A.1. Mirabilis jalapa
Q.2. What is stomatal apparatus?
A.2. The stomata along with subsidiary cells are referred to as stomatal apparatus.
Q.3. Write about the size of the stomata.
A.3. The average breadth of stomata is 3-10μm and the average length is 20-28μm
Q.4. Write about the types of stomata.
A.4. Based on the orientation of subsidiary cells through the guard cells, stomata can be classified into the following:
| Type of stomata | Number of subsidiary cells surrounding Guard cells | Example |
| Anomocytic | Limited number | Ranunculaceae family |
| Anisocytic | Three – one small and two other large | Cruciferae and Solanaceae family |
| Paracytic | Only two – cells are parallel to guard cells | Magnoliaceae family |
| Diacytic | Only two – it lies right angles to the longitudinal axis of the guard cells | Labiatae and Acanthaceae families |
| Actinocytic | Four or more – Radially elongated to the stomata | – |
Learn more in detail about the Stomata, its structure, functions, their distribution, other related topics and experiments at CoolGyan’S Biology.
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