Plants & Mushrooms

Stomata – Definition and How does it work in Photosynthesis?

What is Stomata?

Stomata is present on the leaves of plants. They are tiny pores that help the plant to take in carbon dioxide and release oxygen. Furthermore, it can also be found on stems of some plants.

Most noteworthy, the opening and closing of the stomata are done by the guard cells. Guard cells surround each stoma. They are large crescent-shaped cells; these cells connect at both ends. Moreover, they contract and enlarge for the opening and closing of the pores.


As a result, the guard also helps in reducing the water loss through transpiration by regulating the opening. Likewise, guard cells, subsidiary cells are also present in support. The subsidiary cells protect the epidermal cells against guard cell expansion.

Moreover, it plays a major role in photosynthesis. Photosynthesis is the process by which various plants make their food. They take in light energy and convert it into chemical energy. Furthermore, light energy converts carbon dioxide, water, and minerals into oxygen.

Thousands of stomata are present on the lower part of the leaf i.e. the underlying part. As a result heat exposure and loss of water due to transpiration get reduced. However, in aquatic plants, it lies on the upper surface. For instance, there are various types.

Various Types of Stomata

  • Anomocytic Stomata
  • Anisocytic Stomata
  • Diacytic Stomata
  • Paracytic Stomata
  • Gramineous Stomata

Anomocytic Stomata – These are irregularly shaped and they look similar to epidermal cells.

Anisocytic Stomata – They have three subsidiary cells surrounding each stoma. However, they are not of the same size. The third is smaller than the other two cells.

Diacytic Stomata – Each stoma is perpendicular to the subsidiary cells.

Paracytic Stomata – Two subsidiary are parallel to the stomatal pore and the guard cells.

Gramineous Stomata – In this the guard cells are wider at the end and narrow in the middle. Further, the guard cells are parallel to the subsidiary cells.

How Does it Work in Photosynthesis?

Stomata help in the gas exchange because of which the photosynthesis in plants takes place. Photosynthesis is the process in which the plants take in carbon dioxide and breathe out oxygen as a waste product. The carbon dioxide intake combines with water in the presence of sunlight to make glucose and energy-rich compounds.

Furthermore, all these reactions take place in the chloroplasts present in the guard cells. Chloroplasts are organelles that produce food, they are similar to mitochondria in an animal cell.

When the air temperature rises the stomata opens the pores to let carbon dioxide in. After entering through the pores the plant starts preparing food through photosynthesis. This process produces oxygen as a by-product which is poisonous to the plant.

Therefore the plants release it out through the stoma. However, at night the vice versa happens. The glucose recombines with oxygen to again produce water and carbon dioxide. In this reaction, the excess water gets released through the stomata again. The water gets evaporated into the atmosphere with the help of a process called transpiration.

In conclusion, it does not play a direct role in photosynthesis but is an important organelle. Furthermore, stomata in plants play an active role in conserving the water. As a result, it maintains the hydration of the plant that is a necessary function.

Solved Question on Stomata

Question. Where are stomata present in a non-aquatic plant?

A. On the upper part of the leaf
B. On the lower part of the leaf
C. On the roots
D. On the tip of the leaf

Answer. Option B is correct. Stomata are present in the lower part of the leaf. To prevent the loss of water through transpiration.

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