Stoma or stomata are tiny openings like pores that facilitate gas exchange and are found mostly under the surface of plant leaves on almost all land plants. The term is generally used to refer to the stomatal complex as a whole collectively, which consists of paired guard cells and the pore, also referred to as stomatal aperture.

Stomata Definition

When examined under a microscope, we observe multiple tiny pores located in proximity on a leaf. These pores are collectively called stomata; a single pore is called Stoma. This is the stomata meaning that you must know. These minute openings are generally located in the epidermis layer of leaves; however, they can be found on other parts of a plant like a stem. Stomata facilitate the movement of gasses like oxygen and carbon dioxide, which are essential for photosynthesis.

Types of Stomata 

Stomata are classified based on the strength of their cluster and the subsidiary cells that surround them:

Anomocytic Stomata 

Commonly known as the irregular-celled type or ranunculaceous cells, Anomocytic stomata are surrounded by cells that are not much different from other epidermal layers as far as their size and shape are concerned. A Stoma is not surrounded by a definite number or arrangement of cells; it appears to be embedded in the epidermal cells.

Anisocytic Stomata 

An Anisocytic Stomata is surrounded by three lopsided subsidiary cells, where one is distinctly smaller than the other two; Anisocytic stomata is also known as cruciferous or unequal celled type stomata.

Paracytic Stomata 

Also called parallel-celled type or rubiaceous cells, Paracytic Stomata are accompanied on each side by one or more subsidiary cells; the longitudinal axes of these subsidiary cells lie parallel to the aperture of the guard cells.

Diacytic Stomata 

A pair of subsidiary cells surround Diacytic stomata; the walls of these subsidiary cells lie at right angles to the guard cells; They are also called caryophyllaceous or cross-walled stomata.

Gramineous Stomata 

Gramineous stomata possess two guard cells shaped like dumbbells; each guard cell consists of a narrow middle portion and two bulbous ends. The narrow central part is sturdy and thickened; the subsidiary cells are parallel to the long axis of the pore.

Structure of Stomata 

The stomata are made up of minute pores called Stomata, which are surrounded by guard’s cells. A Stoma exhibits turgor pressure; they swell and become rigid upon absorption of fluids; with this characteristic's help, the cells operate by opening and closing according to the turgidity of the guard cells. However, the cell wall surrounding the Stoma tends to be robust, flexible, and thinner; how the guard cells are shaped differs in both dicots and monocots, but the mechanism remains the same. These minute openings can be found in the epidermis layer of leaves and other plant organs like stems. Stomata help in the movement of essential gases like carbon dioxide and oxygen, diffusing water vapour between the outer and interior surface of the plant tissues; 

A Stoma's Structure is Made of the Following:

Epidermal Cell 

It's the outermost layer of a plant made up of specialized cells that originate from the dermal tissues; Epidermal cells tend to be irregular in shape, and their function is to provide mechanical support to the plant.

Subsidiary Cell 

Located adjacent to guard cells in the Stroma of a leaf, subsidiary cells provide support, which helps in the movement of guard cells; subsidiary cells are generally formed in proximity to mother cells. However, they can be seen growing independently too.

Stomatal Pore 

They refer to the minute pores or the openings found under the surface of a leaf; these pores play a significant role in the exchange of gases like oxygen and carbon dioxide.

Guard cells 

These cells resemble the shape of a kidney or dumbbell-shaped, and its primary function is to properly carry out the opening and closing mechanism of the Stoma.

What is the Function of Stomata?

The primary stomata function is to take in carbon dioxide and release oxygen, this is done with the assistance of guard cells which voluntarily open and close the pore for the exchange of gases; the process involving gas and water exchange is called transpiration. Plants intake carbon dioxide and then go on to separate them into oxygen and carbon dioxide atoms.; the plants end up using carbon, which is essential for its growth and oxygen atoms bond with hydrogen atoms to create water, which is then released into the atmosphere with the help of stomata.

The intake and release of water are facilitated by osmotic pressure created when water moves across permeable membranes such as a plant leaf. Water naturally flows towards the highest concentration of atoms, molecules, and ions in a liquid. This pressure causes the guard cells to open and close. Stomata also play a critical role in photosynthesis.

FAQ (Frequently Asked Questions)

1. Where Can You Find Stomata in the Cells?

Ans: Stomata, across all the plants, is placed in the epidermis of stems and other organs.

2. Why Do Plants Need Stomata?

Ans: Stomata are the pores that are specialized and placed in the epidermis of the cells of plants, which plays a crucial role in exchanging gases during photosynthesis.

3. What Do You Mean By Guard Cells?

Ans: The cells that are shaped in beans, surrounding the Stoma is known as Guard Cells.

4. What is the Structure of Stoma?

Ans: The structure of Stoma is considered to be tiny and is in the shape of beans.

5. How Many Types of Stoma are there?

Ans: There are many types of Stoma. Some of them are listed below:

· Paracytic

· Actinocytic

· Cyclocyctic

· Graminaceous

· Diacytic

· Anomocytic

· Anisocytic

· Perigynous

· Mesogynous

· Meso Perigynous