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    How to guard cells work?
    How to they control the size of the stoma?

    If possible could you attach a decent, detailed animation
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    could you explain the role of K+ ions and how they are caused to control guard cell
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    Final point, why and how are guard cells thicker in some area than in others (have more cell wall in some places than in others)
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    Guard cells are specialised cells with spiral thickenings of cellulose. When water is moved into the cells they become turgid, and because of these spirals of cellulose in the walls of the inner edges, only the outer walls stretch.This causes the pair of guard cells to bulge at both ends so that the pore opens between them.

    Therefore it is the movement of water within the guard cells that determines whether the stoma is open or closed. As you mentioned though, the movement of water is actually determined by the movement of K+ ions in/out the vacuole of the guard cells beforehand. Water molecules basically follow the movement of K+ ions in/out of the guard cells (in short).

    Searching the web quickly I have found a useful link which explains this clearly with an animated diagram

    http://www.phschool.com/science/biol.../stomamov.html

    Hope this has helped you!
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    Thanks for that.

    Can I just ask why is the amount of cellulose in the wall NOT spread evenly??
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    The presence of unevenly thickened walls (uneven distribution of cellulose) is related to the changes in shape and volume the guard cell undergoes due to changes in turgor.

    They have a curved shape due to the angled arrangement and uneven thickness of cellulose fibers in their cell wall. This therefore allows the guard cells to perform their function (their shape allows them to open and close with turgidity).
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    thanks
 
 
 
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