Allelopathy Between Cucumber Seeds and Eucalyptus Oil

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Allelopathy Between Cucumber Seeds and Eucalyptus Oil

Allelopathy is an interaction between plants. It produces toxins which

attack target plants, thereby inhibiting their growth and germination.

The example of this which I am investigating is that between cucumber

seeds and eucalyptus oil.

A suitable method for investigating the above is described in the

literature. I am going to prepare a Petri dish with a cotton wool pad

soaked in water. I will thoroughly wet the cotton wool pad and then

turn the Petri dish upside down so that any excess water drips off. I

will drip the eucalyptus oil into a small beaker which I will stand on

the lid of the Petri dish, beside the Petri dish in a polythene bag. I

will partially inflate the bag. It will be in a polythene bag so that

the vapour cannot escape and to stop the cotton wool from drying out.

The variable which I will change will be the concentration of

eucalyptus oil. I am going to do a preliminary experiment. I will,

from this, decide on appropriate concentrations for the main

experiment. I will control all the other variables: the cotton wool

pads will have approximately the same amount of water, the bags will

all be kept close together in the same place for the same time: the

temperature will therefore be the same for all of them. I will get all

the seeds from the same source and use the same number for all the

tests

I predict, from the information in the literature, that the eucalyptus

oil will inhibit the growth of the cucumber seeds. I also predict that

the larger the concentration is, the shorter the hypocotyl will be.

For my preliminary test, I did the following concentrations of

eucalyptus oil: 0, 8 and 15 drops. I put 10 seeds in each Petri dish.

I used I got the following results:

The results from my preliminary experiment go against the literature

and my predictions, because they suggest that eucalyptus oil increases

growth and germination. I predict that this will not be the case when

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