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how do proton pumps help regulate the size of stomata?

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how do proton pumps help regulate the size of stomata?

Postby Mmaiko » Thu Jan 10, 2008 4:57 am

does photosynthesis also pump out protons just like cellular respiration? if it does, how is it related to the size of stomata?
please help..this is killing me.. :oops: :oops:
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Postby mith » Thu Jan 10, 2008 5:24 am

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Postby MrMistery » Thu Jan 10, 2008 1:49 pm

that animation does not answer the question.
ok, so yes, the light phase of photosynthesis does pump protons into the tylakoidal lumen, creating a gradient that is used later in photophosphorilation to make ATP.
There is also some proton pumping involved in stomatal opening, but in this case a plasma membrane proton pump is involved, not one in the tylakoid membrane. When blue light hits zeaxanthin, it triggers an isomerisation reaction similar to that of retinal in the animal eye. This reaction triggers a membrane transduction reaction involving a protein similar with cytochrome P450 that ultimately activates the membrane-bound proton pump, which pumps protons in the cell. This causes a hyperpolarisation of the plasma membrane, which opens a voltage-gated potassium channel, making potassium enter the cell. Then, as it can be seen from Dave's animation, water enters by osmosis and the stomata opens.
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