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photosynthesis lab

N. Harrison vulpia at sonic.net
Tue Mar 14 17:09:02 EST 2000

On 13 Mar 2000 16:48:48 -0000, monroejd at jmu.edu (Jon Monroe) wrote:

>For my daughter's 4th grade class a few weeks ago we did this but 
>instead of using negatives they cut out shapes from black paper and 
>paper-clipped them to the leaves.  After staining the contrast 
>between shaded and lighted parts of the leaf was wonderful :-) but 
>after pressing the leaves in paper towels over night all of the 
>iodine stain disappeared. :-(  Does anyone know why this happened and 
>how to prevent it?

Jon: We do this experiment with geranium leaves - using foil
with crosses cut out (same idea). The leaves with and without
masks are boiled in alcohol to remove pigment, then placed
in petri dishes with Iodine solution. After everyone has observed
and sketched the leaves, we pour off the I2KI soln, cover
the dishes, and place in our specimen frig. They keep fine,
with stain intact, for several months! -
  Maybe it's the boiling in alcohol that helps them keep - you
might not have wanted to do this in a 4th grade class! - NH

Nancy Harrison
T.A.Botany at Santa Rosa Jr.College
Milo Baker Chapter, California Native Plant Society

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