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  • Basis of stomatal opening isOption: 1 ExosmosisOption: 2 Endosmosis<div class

Basis of stomatal opening is

Option: 1

Exosmosis


Option: 2

Endosmosis


Option: 3

Decreases in cell sap concentration


Option: 4

Plasmolysis of guard cells


Answers (1)

best_answer
     
  • Stomata open and close as a result of osmosis.
  • Under hot and dry conditions, when water loss due to evaporation is high, stomata must close to prevent dehydration.
  • Guard cells actively pump potassium ions (K +) out of the guard cells and into surrounding cells. 
  • This causes water in the enlarged guard cells to move osmotically from an area of low solute concentration (guard cells) to an area of high solute concentration (surrounding cells). 
  • The loss of water in the guard cells causes them to shrink. This shrinkage closes the stomatal pore.
  • When conditions change such that stomata need to open, potassium ions are actively pumped back into the guard cells from the surrounding cells. 
  • Water moves osmotically into guard cells causing them to swell and curve.
  • The outer wall of guard cells bend outwards because it is thin and elastic.
  • The inner wall does not bend as it is thick and inelastic.
  • This bending of outer wall causes opening of stomatal pore.

Movement of water in the guard cells increases their turgidity. This causes outward bending of the outer wall of the guard cells and opening of stomata. Hence, the correct answer is option b.

Posted by

Pankaj Sanodiya

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