Duckweed Lab

Megan Simmons

1B

Duckweed Lab

Question: How does water pollution affect the population rate of duckweed?

Background Information:

Duckweed is the smallest flowering plant. Duckweed floats on the water surface and has no stems and no leaves. It can have small roots. Most species of Duckweed are found in tropical and warm temperate regions, however Duckweed can grow almost anywhere except for in extremely hot and extremely cold regions. Duckweed can grow in the sunlight or in the shade. Duckweed absorbs nutrients in the water and it cannot handle toxic wastes and heavy metals. The most commonly used method of counting duckweed is to count fronds. (The fronds are the green spheres).

Materials:

9 cups

Motor Oil

Dirt

Duckweed

Procedure:

1.      Fill 9 cups of control cups with 200mL of water in each cup.

2.      Put 20 Duckweed fronds in each cup.

3.      Fill 3 cups of water with motor oil with 1 drop in each cup.

4.      Fill 3 cup of dirt with 5 grams of dirt per cup.

5.      Leave 3 cups for control cups with just Duckweed and water in them.

6.      When counting Duckweed, count the fronds.

Data Table:

Class	Motor Oil: 1st cup, 2nd cup, 3rd cup	Motor Avg	Dirt: 1st cup, 2nd cup, 3rd cup	Dirt Avg	Control: 1st cup, 2nd cup, 3rd cup	Control Avg.
1	24, 31, 28	28	27, 21, 28	25	21, 25, 20	22
2	25, 31, 39	32	36, 26, 33	31	26, 28, 24	26
3	25*, 36, 46	36	30, 30, 35	32	24, 26, 23	34
4	26, 35, 44	35	34, 29, 35	33	25, 25, 22	24
5	29, 33, 47	36	35, 28, 31	32	25, 26, 23	25

*1 is on the bottom of motor oil cup.

Range: Class 5- Class 1 (Averages)

Motor Oil	36-28= 8
Dirt	32-25= 7
Control	25-22= 3



Oil and Duckweed Top View of Cup




Oil and Duckweed Bottom View of Cup




Dirt and Duckweed Top View of Cup



Dirt and Duckweed Side View of Cup



Control Cup- Water and Duckweed Top View





Control Cup- Water and Duckweed Side View



In conclusion, our experiment with Duckweed found that the Duckweed reproduced in all of our cups. According to the range numbers in our data, the Duckweed even grew more in the Oil and Dirt Cups than in the Control Cups. On average, the Motor Oil reached a high of 36 Duckweed fronds, the Dirt reached a high of 33 Duckweed fronds, and the Control reached a high of 34 Duckweed fronds. From this data I can conclude that the Duckweed grew about the same amount in total, if not at the same rate in all of the cups. I wanted to know if Motor Oil and Dirt would affect the population rate of Duckweed. According to my data, the Motor Oil and the Dirt did not affect the population of Duckweed as I thought it would. Because it isn’t natural for Duckweed to grow in Motor Oil and Dirt, I figured that these, especially the Motor Oil, would negatively affect the Duckweed. Even though my results and data did not show this in numbers, I still don’t think it is good for Duckweed to grow in Motor Oil. I know that Motor Oil blocks sunlight, and even though Duckweed can grow in shade, it still needs sunlight as all living things do. I think so limitations to this lab were that I don’t think we conducted the experiment for a long enough period of time. I also think that the cup that the Duckweed was grown in was not nutrient rich water, which is where Duckweed thrives. If I were to do this experiment over again, I would conduct it over a period of several months, and I would make sure the Duckweed was grown in nutrient rich water.