Stomata closure

[Zebra]

this is triggered by abscisic acid? yeah?

or... is it caused by the movement of potassium ions out of the guard cells?

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is this even in the current course?

[a/b]

Yepp, it's thought the hormone ABA is involved in the closing of stomatal pores in periods of stress as it stimulates the potassium ions to move out of the guard cells. This changes the osmotic concentration, and water leaves the guard cells casing them to become flaccid and closes stomata.

The guy at the Pathways Lecture at Caulfield said we should definitely know about it :/

[Charmz]

It's due to turgor pressure. If too much water is in the cell, the stomata close.

[simpak]

Too much water!?  Nope, when there is more water in the cell, as a/b implies, the stomata are open because they are swollen like big lips!  It's when the water leaves the guard cells that they will close.

And yes, ABA is known to be responsible for stomatal closure in times of stress.

[vexx]

H+ is pumped out of the cell and K+ pumped in. the increased K+ ion causes H2O to flow in via osmosis making the cells turgid. the cells inability to expand the stomatal pore causes causes them to open..

[simpak]

Was that meant to be different to what I just tried to say?  (I don't mean to offend you, it might be different, I am just too tired to realise what I wrote).

[WhoTookMyUsername]

H+ is pumped out of the cell and K+ pumped in. the increased K+ ion causes H2O to flow in via osmosis making the cells turgid. the cells inability to expand the stomatal pore causes causes them to open..

why would H+ be pumped out? wouldn't it be more efficient to solely pump in K+_ ?

[Russ]

You'd get an electrical gradient if you only pumped in positive charges.