Plants

=flat=

=Stomata & Cross Section Labs=

two suggestons: a leaf tissue lab and a stomata lab...

I use a scalpel or razor blade to make thin cross sections of a leaf (sansevieria works well). It helps if you fill a dish with water and do the slicing in water. If you make many cuts then students can fish out the thinnest samples and make a wet mount to look at under the microscope. I have them locate, sketch and describe each of the tissue layers in the leaf (epidermis, palisade, spongy & vein). Another cool lab is to look at leaf's epidermis for stomata. I call it the super glue lab. Using a sharpie, you label two ends of a microscope slide "U" and "L" for upper and lower surface of a leaf. Put one drop of glue next to each label on the slide and ask students to hold the upper surface of a leaf against the glue next to the U and the lower surface next to the L for 60 seconds. They then peel off the leaf which rips off the epidermis and fixes it to the slide (watch their fingers so they don't take a sample of their own epidermis!). Make a wet mount of each sample (two coverslips on the one slide) and examine under high power looking for stomata. They should compare the density of stomata on the two surfaces (hardly find any if at all on the sunny upper surface to prevent excessive transpiration). You can make it quantitative by having them count the number of stomata per high power field, determine the area of a high power field and then calculate density of stomata.

- Bill Schoonover

Different stomata lab with green onions: Try cutting open a ring from the top of a green onion from the grocery store. Roll it out flat on a micro slide and using the edge of a plastic cover-slip or your fingernail scrape away the green colored mesoderm. What is left on the slide will be an epidermis layer containing the guard-cells and the stomata created by them. The cells are still live and if you wish you can get them to open / close the stomata by altering the osmotic potential in the guard cells. The osmosis of the guard cells is regulated by Potassium ions (Cambell 8th ed pgs 776-777).

I also have a stock of wandering Jew (Zabrina) growing in my classroom. Zabrina growing in indirect light seems to have a higher density of purple pigments on its' lower leaf surface, and is a much better microscope prep. Great stomata prep - looks very "Hollywood" special effect like. Brilliant electric green guard cells surrounded by purple field.

- Greg Pittenger

=Stomate Extension= I have the students look at stomates intact from the leaves with scopes. I had them compare C3 and C4 plant stomatal density as well as indoor verses outdoor plants - Leslie Brinson

Clear nail polish over the underside of the leaf and then peel off shows the stomatas. - Deb Retman

The students paint a small patch of clear nail polish on the bottom of a leaf (or top, but there tend to be more stomata on the bottom of the leaf), let it dry, then put a piece of scotch tape over it & lift it up. Then they put it on a clean microscope slide. I think it works best to have the sticky side of the tape up, then tape down over the sticky side (on the sides of the nail polish), but it works with the sticky side down, as well. I try to have them each make one, then look at (and sketch) as many as possible. The patterns of the stomata are cool!

I have done this method, but the best I have ever done is w/Wandering Jew or Tradescanscia. It is a common decorative house plant that is sold everywhere here in CA. Has purple leaves, requires no prep and is very colorful. Just tear off a little piece and put it bottom side up on a slide, drop of water, and a cover slip and you are done. - Mike Mendez

=Leaf Modeling= Clear nail polish over the underside of the leaf and then peel off shows the stomatas. My students make leaf model out of home made dough........I die some of the dough green. Wax paper with holes punched in it represent the lower cuticle, I cut up peices of sponge, I die yellow sponges green if I cannot find enough green........I have the students build the models and make a key with the functions of each part. A straw can be used for the vein...... - Deb Retman