bio allelopathy garlic


We will measure the growth of celery in the presence and absence of garlic volatiles. We expect that growth will be inhibited by garlic volatiles. We will also measure the growth of celery in the presence and absence of broccoli volatiles, but we expect broccoli to have no effect.


Allelopathy (from the Greek, allelon, meaning another and pathos, which means to suffer) is a way some plants deal with competition.

Allelopathic plants release chemical substances which literally make other plants suffer. Some of these allelopathic plants store toxins in their leaves. When the leaves fall to the ground, the toxins are released. These toxins leach through the soil and are taken up by other nearby plants.

Alternately, allelopathic plants can release chemicals through their roots. These toxins travel through the soil where they can be absorbed by the roots of other plants.

Some allelopathic plants use gas warfare by releasing allelochemicals through small pores in their leaves and gassing nearby species.

We will conduct two experiments simultaneously. In one experiment, we will be using garlic volatiles to find out if the gases they emit negatively affect the growth of celery seeds. In the second experiment, we will use broccoli volatiles instead of garlic volatiles.


We took 4 petridishes, put a filter paper at the bottom of each and added about 2 ml of water to each one. In one petridish we placed a portion of crushed garlic in the center, placed in a piece of aluminum foil. This would be compared with a petridish in which the piece of aluminum foil had no crushed garlic on it. Similarly, we had a petridish with and without crushed broccoli. The labeling and contents of each pertridish were as follows:

  • PG1 = petridish with crushed garlic (experimental group 1)
  • PG2 = petridish without crushed garlic (control group 1)
  • PB1 = petridish with crushed broccoli (experimental group 2)
  • PB2 = petridish without crushed broccoli (control group 2)

We carefully placed 20 celery seeds in each petridish, evenly distributed along the filter paper around the center. We covered all four petridishes and taped them along the sides, to minimize loss of moisture.

Over the next 2 weeks, we measured the growth of celery seeds in each petridish. If water had dried up, we added the same amount of water to each and continued to record the growth.


It is very obvious that garlic volatiles adversely affected ability of celery seeds to grow. Even those that sprouted seemed to rot quickly.

As far as broccoli, the results are not so clear. Even though the seeds on the dish with broccoli grew slower than the one without broccoli, they did eventually grow and some grew better in broccoli than without broccoli. This part of the experiment would need to be repeated to come to a decision on whether broccoli inhibited the growth of celery seeds or not. It is even possible that broccoli may help celery to thrive.

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