(Image from Bioschool, which has a number of micrographs free for teachers to use in PowerPoint presentations - this is a good representation of what we were able to see.)
In order to do this well, however you really need a microscope for every child, because it's really nice to observe the whole process without fighting for "eye time." It could conceivably also be done in stations, but that would be difficult given the way the lab is formatted. Of course I don't have a microscope for each child, and there are other problems to solve. I do, however have a FlexCam that I can hook up to a microscope and a Monitor for showing the whole class.
As with other aspects of the diffusion lab, there are some issues with complicated procedures and manual dexterity. The lab calls for cutting an onion into little pieces, then taking a little slice and peeling off the top layer of skin from the onion (not the thin and easily separated layer on the underside). The top layer is where all the purple pigment is concentrated, but it isn't easy for students to peel off the thin skin without taking a thick chunk. Now this piece of skin curls up on itself quite readily, but it needs to be placed flatly against the slide. I think it might help to have pre-moistened fingers, but I didn't try that yet. I tried to flatten the skin with a foreceps, but managed to rupture most of the cells in the process and lose most of the purple pigment - I could see the color leaving the skin. I was nonetheless able to find a few pockets of intact cells and focused on them. On the monitor we were able to see the cytoplasm/cell membrane shrinking away from the cell wall quite nicely when exposed to 10% saltwater solution, then plumping up again in distilled water.
Still a cookbook lab, but under the right circumstances interesting and useful.
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