Parts of the stoma

We begin by explaining what the stomata are and in what part of the leaf are located, as well as what their functions are. Stomata are defined as the pores or adjustable openings that are located in the epidermal tissue of plants (here you can learn more about plant tissues ) and that are structured by occlusive cells . These cells are responsible for opening and closing the stomata.

The ostiolus is an opening that communicates with the interior of the substomatic chamber, which is where the gas exchange takes place. In addition, next to each occlusive cell, there are one or two modified epidermal cells that have the role of carrying out the opening and closing of the stomata .

Therefore, we can say that the main function of stomata is to help in the process of gas exchange , essential to optimally carry out photosynthesis and respiration. Remember that photosynthesis is the process by which plants transform sunlight into energy that they can use for their development and should not be confused with plant respiration. For this reason, plant respiration is understood as the process in which the stomata take carbon dioxide from the atmosphere and release the oxygen created as a resulting disposable product. In these other articles we talk about What is photosynthesis, its process and importance and the Difference between photosynthesis and respiration .

Another function of the stoma is to carry out the perspiration process. Thanks to this, the plant can eliminate excess water, making the specimen capable of regulating the water inside it and thus adapting to the climate. All this mechanism performed by the occlusive cells is known as stomatal movement .

The stomatal system is made up of two types of specialized cells:

• Occlusive or protective cells: they are larger than the attached cells and are found bordering the pore, also called ostiole. These cells are able to increase in size and contract to cause the pore to open or close. In addition, these cells have chloroplasts, organelles essential for the photosynthetic process.
• Subsidiary or accessory cells: this other type of stomatal cell has the function of creating a protective barrier.

Finally, we also find the substomatic chamber , which is the space created between cells and which is communicated with the outside.

There are two large groups to classify the stomata of a plant : according to their attached cells and according to their origin and development.

Types of stoma according to their attached cells

• Anisocytic or Cruciferous: those that have three attached cells. Two of them are of equal size and one smaller. This type of stomata is mainly found in the Solanaceae family .
• Anomocytic or Ranunculáceo: these are have attached cells and are characteristic of dicotyledonous plants. However, they can also be found in other families such as the Amaryllidaceae and Dioscoreaceae.
• Cyclocytic: they are characterized by having numerous subsidiary cells.
• Diacytic or Caryophilic: formed by two attached cells perpendicular to the stops. This type of stomata is typical of the Acantáceas and Carioofilaceas families.
• Helicocytic: they have several subsidiary cells that are around the occlusive cells.
• Paracytic or Rubiaceous: in the case of this type of stomata, we find two attached cells arranged in parallel to the occlusive cells that make it up.
• Tetracytic: those that are made up of four subsidiary cells. They are characteristic of many of the monocot families.

Types of stoma according to their origin and development

• Mesogen: this type of stomata has the peculiarity that both the occlusive cells and the attached cells are formed from the same cell after completing a cell division three times.
• Mesoperigenic: these stomata originate from a stem cell that gives rise to several occlusive cells and a single attached cell. The remaining cells are created from other protodermal cells.
• Perigen: in this case the stem cell only creates the occlusive cells. Attached cells are created from other cells found in the protodermis.

Why do we make this classification? Well, because the leaves are where there is a greater number of stomata. However, it is also important to know that stomata are present throughout the epidermis of the plant , so we can also find them in stems, flowers and fruits. In fact, in some plants they can also be found at the root.

We can talk about three types of leaves according to the location of their stomata :

• Epiestomatic: they are present in those plants with stomata in the bundle.
• Hypostomatic: unlike the epiestomatic, here the stomata are located only on the underside of the leaf. They are leaves of the arboreal species .
• Amphiestomatic: in this case, the stomata are present on both sides of the leaf and it is a very characteristic feature of most herbaceous plants .

A curious fact is that the frequency or density of stomata can vary both due to the influence of environmental factors, as well as the morphology of the leaves and even their genetic makeup.

We also recommend learning about the types of leaves according to other classifications.

If you want to read more articles similar to Parts of the stoma , we recommend that you enter our Biology category .