The Effect of Detergent
Concentration on Plant
Growth
Erin Annunziato
Ms. Pietrangelo
PJAS December 2010
Reason- Environment

laundry detergent in run-off

fatal to plants

human obstinacy

more eco-friendly run-off
Hypothesis
If there is more than 5% laundry
detergent in the water given to the
plants, then the plants will not
grow.

Types of Peas


Field Peas:

“split peas”

used in farming

Pisum arvense
Gardening Peas:

popular for home gardeners

sweeter and softer
Growing Pea Plants

Environment:

about 12-24º C (55-75º F)

moist soil

sunny or partially-sunny
Key Terms

photosynthesis: energy from the sunlight





water and carbon dioxide -> food and oxygen
detergent: cleans soiled surface (usually refers only to synthetic detergents)
soap- a kind of detergent (different chemical-makeup than synthetic
detergents)
surfactants/surface active agents- consists of molecules that pull away dirt
particles from surface
ANOVA- an analysis of variance
Lab Details

Independent Variable: concentration of detergent in the
waterLevels: 1% detergent, 2% detergent, 3% detergent,
4%detergent, 5% detergent, 6% detergent, and 7%
detergentTrials: 3Control: 0% detergentDependent Variable:
Growth of plants (cm)Constants: type of plant, total amount of
detergent/water added,, watering times and frequency, growing
environment and time
Design Diagram
Levels
(Control)
detergent
0%
Results of
Trials
1-3
Average
1%
2%
3%
4%
5%
6%
7%
Materials

Pisum sativum seeds

Tide Laundry Detergent

water

potting soil

8 pots- 11 centimeter circumference; 9.5 centimeter height

graduated cylinder

ruler

7 plastic bottles
Procedure
1. Plant 5 pea seeds 2 centimeters deep per 8 pots, each pot filled 6.3 centimeters with potting soil
2. Water the pots with pure water (0% detergent) every day until stems are at adequate heights to begin experiment
3. Measure test levels 1-7% detergent by mixing water and detergent in 500 mL water plastic bottles:

1%: 5 mL of laundry detergent and 495 mL of water

2%: 10 mL of laundry detergent and 490 mL of water

3%: 15 mL of detergent and 485 mL of water

4%: 20 mL of detergent and 480 mL of water

5%: 25 mL of detergent and 475 mL of water

6%: 30 mL of detergent and 475 mL of water

7%: 35 mL of detergent and 470 mL of water
4. Water plants each pot with the same amount (100 mL) of corresponding concentration level every day.
5. Record the plant height in centimeters every third day.
Results
Average Plant Heights (cm)
Nov. 16
0%
12.3
15
1%
12.6
14
2%
5.5
5.5
3%
12.8
13
4%
10.6
11.8
5%
10.5
10.75
6%
13
13.6
7%
9.3
9.2
Nov. 19
16.6
Nov. 22
16.9
12.25
* These values have been gathered with only two trials, rather than three
Heights (cm)
Nov. 13
Measurement Day
Results
Average Growth (cm)
13-16
0%
0
2.7
1%
0
1.4
2%
0
0
3%
0
0.2
4%
0
1.2
5%
0
0.7
6%
0
0.6
7%
0
-0.1
16-19
1.6
-1.35
19-22
0.3
Difference in
Heights (cm)
start-13
Measurement Day
Addressing 6%
13th

16th
19th
1
17
16.5
2
14
14
3
8
10.5
22nd
15
height of plant 1 decreased

cells may have shrunk

unlikely measurement error because there is a trend

plant 1 was the tallest

plant 3 increased, then decreased

plant 2 did not change then died
9.5
Null hypothesis: There are no differences in the
observed heights between the treatment groups
ANOVA: Results
Source of
Variation
Sum of
Squares
between
error
total
202.8
266.2
469.0
d.f.
7
16
23
Mean
Squares
28.97
16.64
F
1.742
The probability of this result, assuming the null
hypothesis, is
0.169
The null hypothesis is not rejected:
There was no significant difference of the heights between the different
groups that were treated with different concentrations of detergent
Conclusions




Hypothesis:
If there is more than 5% laundry detergent in the water given to the
plants, then the plants will not grow.
I cannot support nor refute my hypothesis

1-5% died, while 6% survived

not enough data
control survived
Sources of Error

inadequate sunlight

different starting maturity

small pots

human error

graduated cylinder
Improvements

more mature plants

growing lamps

same plant height

lower laundry detergent concentrations

larger growing space

regulate root depth
Extensions

root depth

soap

different plants
Thank you :)

Ms. Pietrangelo

My mother and my au pair