What is the function of stomata?

What is the function of stomata? this is often asked to understand the main function of the stomata in plants. The major stomata functions in leaves and other organs of the plants would be elaborated.

What is the function of stomata?

Stomata are essential for gas exchange and photosynthesis. They also regulate the rate of transpiration by opening and closing the valves.

Other Stomata Functions

  1. One of the main function of stomata in plants is to allow gases (CO2 and O2) to exchange with the atmosphere. That is they allow carbon dioxide to be taken in and oxygen to be released during the photosynthesis process.
  2. Another major function of stomata in plants is to allow the evaporation of water from the leaf surface, thereby aiding in the process of transpiration. Alongside this major function, the stomata also closes or opens its pores to maintain moisture balance depending on the climatic conditions.
An image of well-labeled stomata. This image helps in the understanding of what is the function of stomata.
A label digaram of a stoma.

Exchange of gases that is used in the photosynthesis process

Stomata which is the plural of stoma are openings in the surface of plants that are mostly found on the leaves but can also be found on stems and other organs. They are pores surrounded by guard cells, which are specialized parenchymatic cells. Stomata come in different shapes and can change to adapt to different environmental parameters, ensuring optimal photosynthesis criteria are met.

Green plants require a source of carbon dioxide and a way to expel oxygen in order to continue photosynthesis. Also, these green plants cells require oxygen and a way to dispose of carbon dioxide in order to continue cellular respiration (just as animal cells do). Thus, the gaseous exchange for which they are responsible facilitates photosynthesis by allowing in the necessary CO2.

Carbon dioxide is used as a fuel to power photosynthesis, which produces oxygen as a byproduct and is then released into the atmosphere. So, how do stomata help with photosynthesis? The main function of stomata in photosynthesis is by contributing significantly to transpiration (which is the intake of water into the plant, its distribution within it, and its final release to the atmosphere from the areal parts). Transpiration through stomata increases the plant’s water potential, which favors passive water absorption in the roots, which is then conveyed all across the plant by the Xylem.

Plants require 6 molecules of water and 6 molecules of CO2 to produce sugar and oxygen through photosynthesis. As previously stated, stomata play an important role in the entry of water and CO2 into the plant, thereby facilitating photosynthesis.

Regulation of transpiration via the opening and closing of the stoma

The main function of stomata is to regulate transpiration and CO2 intake by changing size in response to environmental cues. This is one of the main functions of stomata and guard cells in a leaf because, under an ideal situation or condition, stomata open wide allowing for gaseous exchange within the atmosphere and for the intake and release of water into the environment.

Guard cells are in charge of changing pore size by expanding and contracting, effectively opening and closing stomata. When water rushes into the guard cells due to osmosis, which is dependent on the potassium concentration (which enters the plant cell via active transport) in the cells, it opens the stomata.

To open the stomata, potassium is actively transported to the vacuoles, where it increases its concentration in the cells, allowing water to enter through osmosis, increasing cell turgency and size, and exposing the pores. In the case of stomata closure, potassium is transported out of the cells, attracting water to the outside, thereby, collapsing the cells on the pore, and effectively closing it.

The primary cause of stomatal closure is stress, as the plant produces abscisic acid (ABA), a plant hormone known to regulate numerous key processes involved in plant development and adaptation to biotic and abiotic stresses. In the case of water stress due to drought or salinity, the plant adapts by minimizing unnecessary water loss through stomata.

The plant produces abscisic acid (ABA), which signals stomata closure by binding to intracellular soluble ABA-binding proteins in guard cells, which then initiate second messengers such as ROS, Nitric Oxide, Ca2+ triggering ion channels, causing water to leave the guard cells, shrinking their size and collapsing on the pore, successfully closing it.

Summary of stomata function in plants with respect to their opening and closing

opening of stomata

The uptake of potassium ions (K+) causes an increase in osmotic pressure in the guard cells. The concentration of K+ in open guard cells is far greater than that in surrounding cells. This is how it builds up:

  1. Phototropin absorbs blue light, which activates a proton pump (an H+-ATPase) in the guard cell’s plasma membrane.
  2. The pump is powered by ATP, which is produced by photosynthesis’s light reactions.
  3. The interior of the cell becomes increasingly negative as protons (H+) are pumped out.
  4. This draws more potassium ions into the cell, increasing its osmotic pressure.
Closing of stomata

Even though open stomata are necessary for photosynthesis, they also expose the plant to the risk of water loss via transpiration. 90 percent of the water absorbed by a plant is lost through transpiration. Abscisic acid (ABA) causes stomata to close in angiosperms and gymnosperms (but not in ferns and lycopsids) when soil water is insufficient to keep up with transpiration (which often occurs around mid-day). Below is the mechanism of how it happens.

  • The receptors on the surface of the plasma membrane of the guard cells are bonded by ABA 
  • The receptors activate several interconnected pathways, which converge to cause a rise in cytosol pH and the transfer of Ca2+ from the vacuole to the cytosol.
  • These changes promote the loss of negatively charged ions (anions), particularly NO3 and Cl, as well as the loss of K+ from the cell.
  • The loss of these solutes in the cytosol lowers the cell’s osmotic pressure and thus its turgor thereby shutting the stomata.

FAQ on functions of stomata in plants

What is the function of stomata in plants?

The function of stomata is to regulate the amount of water that goes in and out of a plant a process known as transpiration and to help in the gaseous exchange needed for photosynthesis.

What is the function of stomata in photosynthesis?

The stomata function in photosynthesis via the opening of pores to allow for gaseous exchange (CO2 and O2) and vapor exchange (H2O) that the plant needs to perform photosynthesis

What are the two main functions of stomata?

2 main functions of stomata are the exchange of gases for photosynthesis and the regulation of moisture via transpiration.

What is the function of stomata in aquatic plants?

The function of stomata in aquatic plants is for gaseous exchanges with the atmosphere.

What are stomata?

Stomata are pores found in the leaves and stems of a vascular plant.

What is the function of stomata in transpiration?

The function of stomata in transpiration is that they help in the intake and release of water in the plant. Especially using the opening and closing mechanism.

What is the function of stomata in water gain and loss?

One of the main functions of stomata in water gain and loss is their ability to detect changes within the plant when it comes to releasing hormones such as the ABA hormone that triggers water gain and reduces water loss when the stomata close. Another scenario is when stomata detect environmental changes like humidity which will either trigger water gain or loss.

What is the function of stomata in gas exchange?

Stomata in many plants remain open during the day and close at night. This is because during the day because photosynthesis occurs during this time.
Plants use carbon dioxide, water, and sunlight to produce glucose, water, and oxygen during photosynthesis. During production oxygen and water vapor escape into the surrounding environment through open stomata. As well as more carbon dioxide is obtained for photosynthesis via open plant stomata.

What is the function of stomata in roots?

The root stomata function to facilitate increased gaseous exchange during respiration and/or increased transfer of some nutrients and water in the rapidly growing primary root.

A video showing stomata function in plants

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