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?

[estación seca]

Well, stomata were discovered before electron microscopy. Somebody managed to see them with a visible light microscope.

(By the way, singular stoma; plural stomata; from Greek, "mouth")

It's very hard to focus on something more than a few microns thick with a 100x microscope lens. Thicker objects are usually too close to the lens.

I think stomata respond primarily to light and darkness, not relative humidity. I don't know what VPD means. I'm not familiar with experimental literature on keeping them open by manipulating environmental conditions, but I suspect it's been well studied.

[naoki]

Yes, you can see them easily with 10x or 40x objective lens and 10x ocular lens (that's probably what you have). I'm guessing that you are talking about a compound microscope.

You need nail polish and scotch tape. Paint the bottom side of leaf with nail polish (about the size of dime is good enough). After a minute or so (when the polish is dry), you paint the area again to make the coating a thicker. Then you can peel it off by attaching the scotch tape at the edge of the paint. Put it on slide and you can see the imprint.

You can see some of them are open and others closed.

Regulation of stomata is elaborate and controlled by many factors, time of the day (photoperiodism), green and blue light, water stress sugar concentration from photosynthesis etc. One of the best known regulation is abscisic acid (plant hormone) related mechanism. When roots sense that there isn't any water available, they signal it to the leaf by the hormone, and stomata changed ion concentration and close the stomata in response. So vapor pressure deficit is only one of the factors.

I'm not sure if you can keep them open for 48 hours. They usually open and close, and the ratio could be changed in the day time and night time. Why do you want to do it?

Also quite a few species of orchids are CAM. But many of the CAM orchids are facultative. For example, Phalaenopsis behaves like C3 when there is plenty of water around the root, but behaves like CAM when it is drier.

[Orchid Whisperer]

When Naoki says nail polish, remember that it is clear nail polish.

You can do roughly the same thing if you have clear acetate film and acetone. Wet a small area on the leaf with acetone, apply the acetate film to the wet spot, let it dry then peel off.

Remember that any efforts to look at stomata will destroy some leaf tissue. Probably don't want to so this too many times.