Question

what are stomata? Give two function of stomata​

Answer 1

a small pores found in a leaf is called stomata.

it helps in changes of gases

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Answer 2

Answer:

Simply put, they are openings in the surface of plants, found mainly on the leaves, but also on stems and other organs. They are pores surrounded by specialized parenchymatic cells, called guard cells. Stomata have two main functions, namely they allow for gas exchange acting as an entryway for carbon dioxide (CO2) and releasing the Oxygen (O2) that we breath. The other main function is regulating water movement through transpiration. Stomata vary in shape and size, being able to change to adapt to the different environmental factors, thus ensuring optimum conditions for photosynthesis.

Source: Dr. Willem Van Cotthem, University of Ghent (Belgium)

Just as animals breath, plants do so too through the stomata. The gaseous exchange that they are responsible for, facilitate photosynthesis by letting in the essential CO2. Carbon dioxide is used as the fuel to drive photosynthesis, which generates oxygen as a byproduct, which is then released to the atmosphere. Now, how can stomata facilitate photosynthesis? They can do so by playing an important role in transpiration. Transpiration is defined as the absorption of water into the plant, its distribution within it and its final release to the atmosphere from the areal parts. Transpiration through stomata, creates a water potential within the plant, which in turn, favors the passive water absorption in the roots, which will then be transported throughout the plant by the Xylem.

To perform photosynthesis, plants need six molecules of water and six molecules of CO2 to produce sugar and oxygen. Therefore, as mentioned, stomata play an integral part in water and CO2, entry to the plant, thus having facilitating photosynthesis.

Stomata regulate transpiration and CO2 intake by changing its size depending on the environmental signals. In optimum conditions, stomata are wide open, allowing gaseous exchange with the atmosphere. Guard cells are responsible for changing pore size, they do so by expanding or contracting themselves effectively opening and closing stomata. For stomata opening, water is rushed into the guard cells due to osmosis, which is dependent on potassium concentration in the cells. Potassium enters and leaves the cells through active transport, depending on environmental triggers. Such triggers include ion exchange, temperature, light, hormone signaling, CO2 concentration etc.

For stomata to open, potassium is actively transported to the vacuoles, which increases its concentration in the cells, thus driving water entry due to osmosis, increasing cell turgency and size, exposing the pores. The opposite occurs for stomata closure, potassium is transported out the cells, which attracts the water out to the exterior, collapsing the cells on the pore, effectively closing it.