Question

what controls the opening and closing of stomatal pores and how

Answer 1

Answer:

Stomata are small pores or opening present in the epidermal cells of leaves. They open during the day and close during night. They take carbon dioxide required during photosynthesis during the day. Also, they release excess water released in the process of respiration during the night along with carbon dioxide. This opening and closing of stomata is controlled by concentration of solutes in the guard cell.

During daytime, the pH of the guard cells is alkaline. This results in the hydrolysis of water. The solutes from neighbouring epidermal and mesophyll cells enter the guard cells and lowers the osmotic potential and water potential of guard cells. This lowered water potential and osmotic potential allow the movement of water into guard cells from neighbouring cells. Due to this, guard cells become turgid. This results in the opening of the guard cells. During night time, carbon dioxide accumulates in the guard cells. Hence, it becomes acidic. The acidic pH favors the formation of starch in the guard cells. Hence, the solute concentration decreases. This makes the water from the guard cells to move away into neighbouring cells. The guard cells then become flaccid with no water. They collapse against each other and result in the closing of stomata.

Answer 2

Answer:

Guard cells

• Specifically designed cells called guard cells regulate the opening and shutting of stomata.
• Guard cells can open and close depending on the turgor pressure inside of them.
• As a result of water absorption, guard cells expand, and when they contract, stomatal pores open.
• Additional variables like light, temperature, carbon dioxide and humidity will affect how quickly stomata open and close.

Explanation:

• During stomatal opening and closing, the guard cells' plasma membrane-resident ion channels, pumps, and transporters are regulated. H+-ATPase activates K+ inward rectifying channels during stomatal opening (A) by pumping H+ out of the guard cells and hyperpolarizing the membrane (KAT1, KAT2, AKT1).
• The development of intracellular solutes that can facilitate the import of sugars or be utilized for sugar production includes anionic species such malate2 from the breakdown of starch and transported NO3 and Cl ions.
• The turgor required to keep stomata open is produced by ions delivered into the guard cells and water carried by aquaporins. H+-ATPase is blocked during stomatal closure (B), and S- and R-type anion channels are turned on.
• The outflow of malate2, Cl, and NO3 is facilitated via S-type and R-type channels as the plasma membrane depolarizes. The membrane is depolarized at the same time, which causes K+ to leak out and activate K+ outwardly rectifying channels like GORK.
• The conversion of malate into starch by gluconeogenesis also contributes to the drop in malate2 levels. Another phenomenon that occurs in conjunction with stomatal closure is an increase in Ca2+ concentration as a result of Ca2+- being released through channels found in both the plasma membrane and the tonoplast.

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