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Science Project  
The Effect of Detergents on Brassica rapa.

Researched by Michael M.



The purpose of this experiment was to determine the effect of different concentrations of detergents of plant growth.

I became interested in this idea when I had a to wash clothes for a week as a homework assignment and I was looking at the ingredients and noticed some of them were volatile substances. 

The information gained from this experiment will alert consumers to the dangerous effect of detergents on plants.




My hypothesis is that higher concentrations of detergents will kill Wisconsin Fast Plants.

I base my hypothesis on the fact that most detergents contain volatile chemicals dangerous to plants.


Experiment Design


The constants in this study were:
      1. Size of plant
2. Kind of plant
3. Amount of water.
4. The source of the water.
5. The soil type.
6. The size of the pot.
7. The amount of light shining on the plants.
8. The location of the experiment.
9. The amount of fertilizer the plants get.

The manipulated variable was the amount of detergent in the water.

The responding variable was the size and health of the plants.

To measure the responding variable I used a ruler for size and my eyes for color and number of leaves. 



2 planter 36 packs (Wal-mart)
180 Brassica Rapa seeds
bag of fertilizer
5ml Water per plant per day
1 bottle of Tide
1 25ml graduated cylinder
3 gallon jug
9 quarts of water
1  ruler
1 recording paper




1. Get all materials. 
2. Dig small holes in the center of each pot.
3. Drop WFP seeds into the hole.
4. Cover the seeds with the soil you dug to make
5. Label 64 pots (16 per group) A (control), B (25%), C (6.25%), D(1.56%).
6. Mix 1 tablespoon of fertilizer with 1 gallon of water.
7. Mix 1 quart detergent with 3 quarts water.
8. Mix 1 quart of the 25% mix with 3 quarts water.
9. Mix 1 quart of the 6.25% mix with 3 quarts water.
10. Shake the gallon jugs
11. Put 5ml of fertilizer into each pot.
12. Water the control group with one tablespoon of pure water.
13. Water the B group with 5ml water mixed with 25% liquid Tide‰ dissolved in the water.
14. Water the C group with 5ml water mixed with 6.25% liquid Tide‰ dissolved in the water.
15. Water the D group with 5ml water mixed with 1.56% liquid Tide‰ dissolved in the water.
16. Continue steps 9-10 for 21 days
17. After 7 days, put half a teaspoon of the same fertilizer onto the plants. 
18. Repeat after 14 days.
19. Everyday, record the status of the plants in all of the group.



The original purpose of this experiment was to determine the effect of different concentrations of detergents of plant growth.  I became interested in this idea when I had a to wash clothes for a week as a homework assignment and I was looking at the ingredients and noticed some of them were volatile substances. The information gained from this experiment will alert consumers to the dangerous effect of detergents on plants.

The results of the experiment were any plant not in the control died.

See the table and graph below.


My hypothesis was higher concentrations of detergents will kill Wisconsin Fast Plants. 

The results indicate that this hypothesis should be correct in a way.  I hypothesized that high concentrations of detergents would kill the plants, but any detergent killed the plants.

Because of the results of this experiment, I wonder how detergents would affect other kinds of plants 

If I were to conduct this project again I would use more kinds of detergents.


Introduction to Detergents and Plants

 Detergents have only been around for about 85 years, even 
though soaps have been around for about 3,000 years.  Detergents were first produces in Germany about the beginning of World War I.  Plants are one of four families in scientific classification.  They differ from animals in that they have chlorophyll and cell walls in their cells.


 Detergent is defined as "a cleansing substance that acts similarly to soap but is made from chemical compounds rather than fats and lye." by the American Heritage Dictionary of the English Language.  Modern detergents contain a chemical called a surfactant, which, defined by WordNet 1.6 is "A substance capable of reducing the surface tension of a liquid in which it is dissolved."  This allows the detergent to spread further, penetrate better and clean much more efficiently.  With the addition of "builders," which make the surfactants work much better.  Detergents are used mainly for four different things: personal cleansing, laundry, dish washing and house cleaning.

Detergent Popularity

 Detergents are far from being as old as soap, but today they
 are the best selling method of washing clothes and dishes.  Detergent popularity has grown exponentially since around 1950.  In between 1940 and 1972 the sales of detergents went from about 4,500 tons per year to around 4,448,000 tons per year.  At the same time, soap sales went from 1,410,000 tons a year to 587,000 tons per years, decreasing almost 30%, although sales in soap rose 4,000 tons per year from 1960 to 1972.  Detergent sales surpassed the sales of soaps in 1953. 

Detergent history

 Detergents, as was stated, were first seen around the beginning of W.W.I.  The exact year is 1916.  They were first used Because of the war related shortage of fats.  It were sold under the general name Nekal.  The discovery of detergents was in part because the people where looking for a cleaning substance, that, unlike soaps, would not mix with the minerals in water to make a wax like residue called "soap curd."  They were not as high quality detergents as we have now, and were used mostly as wetting agents in textile work.  The quality didn't change much in the 20's and 30's, with only minor enhancements.  The sales for detergents really skyrocketed around the beginning  of W.W.II, with a shortage of fats and oils needed to produce soap.  The military badly needed a cleaning agent that wouldn't mix with the mineral rich waters to make soap curd.  The breakthrough came at the end of the war in 1946.  Up to then detergents were used for hand dish washing and washing sensitive clothing.  The first all-purpose laundry detergent had surfactants and builders.  The builders greatly improved the efficiency of the surfactants.  By the end of 1950, soaps had almost been forgotten as a way to wash clothes and dishes, but were still used at the same time as detergents.  Through the years, detergents have changed a lot.  In the 50’s detergents were used in dishwashers and for the laundry.  They were adapted to be bleaches.  Fabric softeners were also developed.  In the 70’s they manufactured liquid hand soap.  In the 80’s they made liquid dishwasher detergent, detergents for colder water washing and concentrated detergents.  In the 90’s they manufactured super-concentrated detergents and dishwasher gels.

Wisconsin Fast Plants

 Wisconsin Fast Plant's scientific name is Brassica rapa, and is commonly referred to as a Rapid Cycling Brassica rapa, or RCBr for short.  There are six other plants in the Brassicaea family, and are in the same family as cabbage, mustard and turnips.  All plants go from seed to seed and RCBr go from seed to seed in less than 40 days and are in premium growing conditions in twenty-four hour cool fluorescent light.  This is why they are often called the perfect classroom plant.  Seeds can be planted in a 2 cm pot and can grow to a height of 15 cm.  The seed is supposed to break the surface after 3 days.  They are very easy to manage and do not require much water per day.  The current RCBr grow about five times faster than its ancestors, but thanks to efforts by Dr. Paul H. Williams they now grow much faster.   Dr. Williams teaches as a professor of plant pathology at the University of Wisconsin, hence the name Wisconsin Fast Plants.  Wisconsin Fast plants started when Dr. Williams was trying to improve disease resistance in the Brassicaea family.  He spent almost 20 years breeding Brassica rapa until it had developed into a small, fast growing plant.  His result greatly improve methods of cellular reasearch.  He had many goals for the plants.  They had to grow quickly and start growing immidiatly.  They had to be small and have a high seed crop in high denstity.  They also had to grow well in potting soil.

Detergent are a relatively recent innovation that greatly improved almost all kinds of cleaning.  Wisconsin Fast Plants are a fast growing plant that are very useful in classroom experiments.


DeMichele, William D.   "Plants"  World Book Encyclopedia,  1991.

Carter, Joseph L.   Life Science: A Problem Solving Approach,  1971
Webster's Revised Unabridged Dictionary,  1996

Hershey, David R.    Plant Biology Science Projects,  1995

Reed, Catherine.    Environment,  1992

The American Heritage® Dictionary of the English Language, Third Edition,  1996

WordNet ® 1.6, © 1997

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