Are the stomas open?

[dethswatch]

I've got a microscope (10x, 40, 100), would it be possible to take a sample (with a paper hole punch possibly?) to find out if the stomas are open at any random point throughout the day?

Or are we talking electron microscopy? Or would they quickly close?
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Also, what would happen if the stomas were kept open (is this possible?) as a consequence of the VPD in the environment- say, 48 hours?