Question

How do the guard cells regulate opening and closing of stomatal pores?
NCERT Class X
Science - Exemplar Problems
Chapter_Life Processes

Answer 1

Opening of stomata: Solutes from neighbouring epidermal and mesophyll cells enter the guard cells lowering its osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water into guard cells from neighbouring cells. Guard cells become turgid due to water accumulation in them which results in the opening of the guard cells. 
Closing of stomata: As the somata open the solute concentration is reduced. This makes the water from the guard cells to move away into neighbouring cells. Now, guard cells becom flaccid with no water. They collapse against each other and result in the closing of stomata. 

Answer 2

Hello There !
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Guard cells regulate opening and closing of Stomatal pores 
We can understand it BY Potassium ion (k+) Hypothesis
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IN this hypothesis in mitochondria absorb H+ ion ....Then pH increases
then STarch ----> PEP -----> CO2 -----> OAA(oxaloacetic acid )  ---> Malaic acid ----> malate ion + H+ 
This increase solute potential 
K+ ion enters in the guard cells 
includes Cl- ions 
then stomata will open 
same with closing stomata 
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