Lab:  Allelopathy--Chamical Warefare Amonth the Plants


(Chemical Warfare Among The Plants)


Plants can be complex chemical factories. They may produce chemical scents and nutrients to
attract pollinators. They may produce and store poisons in their tissues to discourage potential browsers and parasites. Plants also compete with other plants for sunlight, soil nutrients, and water. Since they do not have the option of avoiding competition by running away (like animals) they resort to chemical warefare. To reduce competition they may produce chemicals that inhibit the germination and growth of neighboring plants. This last phenomenon is termed allelopathy. This chemical warfare can be against other plants of the same species (intraspecific competition) of "plants of a different species (interspecific competition).

Plants may release allelopathic substances in a variety of ways:

1. Directly into the soil from their roots.

2. Allelopathic substances may be leached from living or dead shoots into the surrounding soil, or

3. Volatile compounds pass into the air and then are deposited on the soil or the surface of other plants when dew forms.

Allelopathy appears to be 
best developed in perennial and woody species of more humid regions.

Testing of Allelopathic Effects:

We will be using radish seeds and lettuce seeds to find out if one, the other, or both are allelopathic.  As a result, talk amongst your group members and decide how many petri dishes you will need in order to complete this lab (between 3-5).  Remember…you will need a control group(s).   You want to use a test group of 10 radish or 10 lettuce seeds.  Create a data table for your experiment for a 1-week growth period.  For each group of seeds in a petri dish, you will want to show:  Number of seeds tested, number of seeds successfully germinated, percentage of successful germination and the length of each seedling in mm.  You will also find the average seedling length.


            +  The results will be gathered after a 1-week growth period.

            +  Examine your cultures and record them on a data sheet.

           +  Create a formal laboratory write-up that discusses the allelopathic nature of each type of seed, using your data to support your results.




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