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The opening of the stoma is controlled by the

Biology
JAMB 2004

The opening of the stoma is controlled by the

  • A. presence of a pore
  • B. increase in solute concentration in the guard cells
  • C. presence of guard cells
  • D. decrease in solute concentration in the guard cells
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Correct Answer: Option B
Explanation

The opening of stomata is indeed driven by an increase in solute concentration within the guard cells, leading to water entry and cell swelling, which then causes the stoma to open. In the process of stomatal opening, guard cells actively accumulate solutes, particularly potassium ions (K+) and sometimes chloride (Cl-) and malate (Mal). This increase in solute concentration lowers the water potential inside the guard cells. 

The lower water potential inside the guard cells causes water to move into them from the surrounding cells via osmosis. As water enters the guard cells, they swell, leading to an increase in turgor pressure (the pressure of the cell contents against the cell wall). 

There is an explanation video available below.


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Explanation Video

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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts