PJAS December 2010

The Effect of Detergent

Concentration on Plant Growth

Erin AnnunziatoMs. Pietrangelo

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

Pisum sativum

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

Levelsdetergent

(Control)0%

1% 2% 3% 4% 5% 6% 7%

Results of Trials1-3

Average

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.

Nov. 13 Nov. 16 Nov. 19 Nov. 22

0% 12.3 15 16.6 16.9

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 12.25

7% 9.3 9.2

Average Plant Heights (cm)

Results

Measurement Day

Heig

hts

(cm

)

* These values have been gathered with only two trials, rather than three

Average Growth (cm)

Results

Measurement Day

Diff

ere

nce

in

H

eig

hts

(cm

)

start-13 13-16 16-19 19-22

0% 0 2.7 1.6 0.3

1% 0 1.4

2% 0 0

3% 0 0.2

4% 0 1.2

5% 0 0.7

6% 0 0.6 -1.35

7% 0 -0.1

Addressing 6%

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

13th 16th 19th 22nd

1 17 16.5 15

2 14 14

3 8 10.5 9.5

ANOVA: Results

 Source of     Sum of       d.f.    Mean         F Variation     Squares              Squares

 between      202.8          7      28.97      1.742      error        266.2        16     16.64      total         469.0         23

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

Null hypothesis: There are no differences in the observed heights between the

treatment groups

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