Choose several of your favorite trees and collect about 10 leaves from each of them. Look around the trees and try to determine if they are allelopathic. (Is there little or no vegetation surrounding the tree?)
Then place the leaves in a plastic bag and label the bag with any known fact about the tree, such as its location and distinguishing features. Try to identify the plant but if you are having trouble go to your local library and ask the librarian for a field guide about trees. If you do not use the leaves immediately, place the bag in the refrigerator and identify and analyze them later.
Collect two or three leaves from a few different trees (you could use the same leaves collected in Experiment 1) and tear them into small pieces. Put the pieces from each tree into separate glass jars with some water. Each of the mixtures should have more plant matter than water. When you make up the jars, make sure you repeat the same procedures for all of them.
Label the jars with the name of the tree from which the tree leaves came and any other information you think is important. Swirl the jars several times a day for two to three days with your spoon.
Now you are ready to start the main part of the experiment. Place a radish seed inside a piece of folded paper towel with a mixture of leaf bits and water from each of your glass jars. Enclose each of the paper towels inside separate plastic bags and place them in a dark room. Wait seven to ten days and analyze the growth of the plants. Whick of the radish plants grew? Which did not? Does the growth of the radish help you see which of the leaves had allelopathic chemicals in them? What traits did those seeds demonstrate? As a side note, one paper towel should be dampened with plain water to serve as the control. You can use the control to compare with your experimental seeds. Using one paper towel with plain water is also important in case something goes wrong with the experiment. One possible problem might occur if the chemicals in your water are killing the seed instead of the leaf chemicals killing the seed.
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3/25/96.
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