EI - Published Bioassay Report

Author: Capurso, Ron

Title:

The effect of ethyl alcohol (62%) on lettuce seeds 11705

Research question:

What effect does the presence of ethyl alcohol (62%) have on the germination of lettuce seeds?

Type of bioassay organisms:

Buttercrunch lettuce seeds were used in the experiment. They were attained from a provided packet.

Substance(s) tested:

The substance tested was Purell hand sanitizer. The active ingredient was ethyl alcohol (62%)

Procedure:

The lettuce seeds were prepared for the experiment by being soaked with a 10% bleach solution for five minutes. The seeds were then rinsed with distilled water. First, 30ml of hand sanitizer was combined with 100ml of water. This was used as a 100% solution of ethyl alcohol. Next, a titration was performed to produce decreasing concentrations of alcohol. 10ml of the 100% solution was combined with 90ml of distilled water to form a 10% ethyl alcohol solution. This process was continued until concentrations of 1%, .1%, .01%, and .001% were attained. Three petri dishes were prepared for each concentration (including a control). This resulted in 21 petri dishes, all lined with filter paper. 5 seeds were placed in each dish in a pentagonal fashion. Next, 2ml of each solution(including distilled water for the control) were placed on the petri dishes, covering the seeds. There were three dishes used for each concentration to eliminate any unwanted variables. The result was seven sets of three petri dishes; each set representing a different concentration of ethyl alcohol. The petri dishes were then stacked in two columns and placed in a plastic bag. The bag was wrapped in aluminum foil and allowed to rest for five days.

Data Summary:

Ethyl Alcohol - (100% =130ml of solution)	Average # Germinated	Average Redicle Length (mm)
Control (distilled water)	4	40.9
.001%	1.7	2.1
.01%	2.3	2.6
.1%	3.3	3.8
1%	2	4.5
10%	0	0
100%	0	0
Detailed Explanation: The lettuce seeds had a difficult time germinating when exposed to any concentration of alcohol. It is important to note that our original control did not germinate. Instead, we used the control from our neighboring group. This was logical since they used the seeds from the same packet as we did, and rinsed them with the same bleach solution.

Conclusions:

It is apparent that ethyl alcohol is extremely toxic. Even at small concentrations, it proved to be highly disadvantageous to the seeds. At high concentrations the seeds did not grow at all, suggesting that the lethal concentration for lettuce seeds is around 10% ethyl alcohol. However, the minimal growth of the samples exposed to .001%-1% alcohol, and the lack of growth from the control suggests that there was a problem with the experiment. My conclusion is that vapors (which were highly noticable at the end of the experiment)contaminated all of the petri dishes. Thus, regardless of concentration, all seeds were exposed to toxic levels of ethyl alcohol. This explains why the 100% and 10% samples did not grow at all and the lower concentrated dishes did not follow any sort of trend.

Suggestions for future research:

It is obvious that the solution of 30ml ethyl alcohol and 100ml of water was too toxic for seeds to grow in. In a repeat experiment, I would dilute the alcohol even further, possibly to half that concentration to begin. This would allow the seeds to germinate and grow more, providing a wider range of study.

Suggested experimental design improvements:

The major change I would make to the experimental design is to individually wrap each set of petri dishes. This would ensure vapors from higher concentrations would not contaminate other samples. Also, it would be a good idea to test the effect of temperature on the seeds. Perhaps room temperature is not the optimal condition to grow seeds.