Q:

How do guard cells regulate the opening and closing of the stomata?

A:

Quick Answer

A plant's guard cells regulate the opening and closing of the epidermal stomata by expanding or contracting in response to environmental signals. When a pair of guard cells surrounding a stoma receives the signal that the stomatal pore needs to open, the guard cell pair fill with water, changing the cell's shape and opening the pore. An inverse process occurs when the guard cells receive a signal to close the stoma, initiating a loss of water and causing them to shrink and close the pore.

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Full Answer

The change in turgor, or hydrostatic pressure, within a guard cell pair is the result of the osmotic water flow across the cell walls. The water potential inside the cell pair changes as a result of the related movements of ions and sugar solutes, and when that potential decreases, it lets the cells absorb water, expand and open the stoma.

Although sugar solutes within the guard cells play a role in the expansion and contraction processes, the primary mediators are chlorine and potassium ions. The accumulation of potassium ions within a guard cell, triggered by an environmental signal such as sunlight, causes the osmotic pressure to decrease and attracts water into the cell. The triggered increase of chlorine ions and an additional anion called malate within the cell contribute to the opposite effect, causing water to exit and the guard cell pair to contract and close the stomatal pore.

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Related Questions

  • Q:

    What causes the stomata to open and close?

    A:

    There are guard cells surrounding each stoma that cause them to open or close throughout the life cycle of the plant. This occurs in response to water and ion concentration in the plant cell, according to Pearson Education.

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  • Q:

    Where are stomata found?

    A:

    The stomata in plant cells can be found in the epidermis of leaves, stems and other parts of the plant involved in gas exchange. The pores inside the spongy layer of the plant leaf help aid in the exchange of gases between the leaf and its environment, and these pores eventually open up to the outside through the stomata.

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  • Q:

    When are the stomata usually open?

    A:

    Stomata open when there is sunlight. Therefore, stomata are usually open during the day and closed at night. However, according to Darwinian principles, plants that reside in arid environments have developed characteristics that affect the opening and closing of stomata to help withstand water shortage.

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  • Q:

    What is the function of stomata?

    A:

    Stomata are microscopic openings on the surfaces of plant leaves that allow for the easy passage of water vapor, carbon dioxide and oxygen. They are crucial to the function of leaves as photosynthesis requires plenty of carbon dioxide as well as the release of waste oxygen and excess water. "Stomata" means "mouth" in the Greek language.

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