Friday, October 17, 2014

Epidermal Leaf Slides

Leaves are incredible. They are the primary site of photosynthesis, as evident by their nice bright green color due to being full of chlorophyll. In general the structure of a leaf includes a cuticle (waxy protective covering), upper epidermis, mesophyll (home of the chlorophyll), lower epidermis and another cuticle.

When we were at the science outreach day the other week, my Post-Doc showed me how to make leaf epidermal slides. And it is so easy we let the kids make their own slides! Which they loved. All you need are: a leaf, clear nail polish, clear tape, a slide, and a microscope.

The first step is to paint a small area of the underside of the leaf with the clear nail polish. The reason you use the underside is 2 fold: typically cuticles (that waxy layer) are thinner on the bottom side and this is where the stomata are which are really cool to see. They kind of resemble cats eyes,more on those later. Note that the polish has to dry completely before you can move onto the next step.

Step 2 involves carefully putting the tape onto the nail polish. Be sure it seals along the nail polish but you keep a hold of the edge of the tape so you can do step 3 easier.

In step 3, you rip the tape back off, like you're waxing someones eyebrows. You should see the nail polish and a layer of leaf cells came off on the tape. Simply put this piece of tape on the slide, smooth it out so there are no air bubbles, and fini!

Then you simply pop it onto your microscope and you see this beautiful epidermal layer, complete with stomata and cell walls. Stomata are the cells that open and close to regulate water and gas exchange between the leaf and the environment.
40x objective lens (400x total magnification)
For more information on the role of stomata, I refer you to the wonderfully written Frozen Parody Stomata Open the Door by my favorite plant blogger @JLRoose.

The rules above are simply the start point. To make this more than a simple observation with your kids, have them examine leaves from different species of plants. How do the epidermal layers differ? How are they the same? To do some quantification have them count the number of stomata in one microscope field and compare it among the different leaves. Those are just a few examples, I'm sure there are dozens of other ones!

If you give this technique a try, I'd love to hear about your experiences! Leave me a comment :)

1 comment:

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