Jackie Timmins
Ms. Hunteman
AP Bio Per D
October 6, 2013, 2013
I. Introduction
a. Back ground information:
For past projects, I have studied invasive species in the area, and I wanted to learn more
about the Periwinkle vine (Vinca minor). Many people put these vines underneath
evergreen trees because they look nice, but they do not realize that they are introducing a
non-native plant to that habitat. This invasive species will choke out other small plants
and flowers growing in the area. Weed-B-Gone is used for eliminating invasive grasses
and weeds and should be sprayed on the leaves of the plant.
The water cycle consists of liquid water being evaporated into clouds, then raining back
down to water the plant. For this experiment, I chose not to water the plant, but rather see
the effects of water wicking up a cotton string from a body of water. Also, because of
rain water washing though soil in farmlands, for example, any kind of fertilizer or
pesticide applied there would wash into the water supply and possibly have negative
effects on the surrounding ecosystem.
b. Purpose:
If I spray a healthy Periwinkle plant with Weed-B-Gone weed killer, will it stunt the
plant’s growth?
c. Hypothesis: If I spray a healthy Periwinkle vine with Weed-B-Gone, then the number
of healthy leaves will decrease.
II. Procedure:
a. Equipment Used
2L soda bottles
½ cup small pebbles (from a local hiking trail)
½ cup large-grit sand (from a craft store)
Cotton Shoestring
2 large safety pins
1 cup Miracle-Gro potting mix soil
Healthy periwinkle vine (from Lowe’s)
2 cups tap water
Pocket Knife/ scissors
Cutting board
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Pink Academic ruler with metric measurements
Camera
Notebook and pen
*Note: These are the supplies needed to make one aqua-terra setup. Two were used in the
experiment.
b. Collection of Data
1. Begin by following the directions on how to make a Terra Aqua Ecosystem. Cut
the soda bottles at the neck using the pocket knife on cutting board. Invert top of
bottle into the bottom. Cut hole in cap of bottle with scissors and thread
shoestring through hole. Tie knots in the end of laces and fray remaining lace to
increase absorbency. Insert 2 safety pins per bottle around the top lip to keep top
of bottle from slipping down.
2. Create filtration system in top by placing small pebbles in, then sand.
3. Insert plant into top and fill in gaps with potting soil. Prune plants to remove
dead, crispy leaves and sprouts.
4. Add tap water to the base of the bottle.
5. Label bottles “A” (control) and “B.” Take initial measurements and observations:
 Sprout number
 Water level at base
 Moisture level of soil
 Number of new leaves
 Total number of healthy leaves (recorded every other day)
 Lengths of sprouts (recorded once a week)
6. Observe daily for 2 weeks until stabilized.
7. After plants are stabilized, spray plant B with one dosage of Weed-B-Gone weed
killer. Spray leaves of plant for about 30 seconds. Observe.
8. Repeat treatment twice on following two days (total of three treatments).
III. Results:
a. Tables or Graphs:
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Periwinkle Growth
# of Healthy Leaves
140
120
100
80
60
40
Plant A (control)
20
Plant B
0
Day 0
Day 1
Day 2
Day 3
Day 4
Days After Weed-B-Gone Was Added
Water Level (cm)
Water Level during Stabilization
Period
8
7
6
5
4
3
2
1
0
Plant A (control)
Plant B
Day during Stabilization Period
b. Description of Data
Plant A was bigger that plant B. Both plants grew steadily in the stabilization period.
Continuous growth took place for plant A and plant B until the Weed-B-Gone was added
to plant B. After pesticide was added, plant B continued to grow a little, then the
chemicals took effect and plant B began to decay. Most of the larger leaves were okay,
but the newer, smaller leaves were most affected by the Weed-B-Gone and began to wilt
and turn yellow.
Sometimes the plants were kept outside in full sun if nice weather or inside with partial
sun if inclement weather. This time outdoors could have exposed plants to harmful
insects or unwanted chemicals. In the future, I should keep them either inside (more
controlled) or outside (more like nature) throughout the duration of the experiment.
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I knew that the shoestrings were wicking water up into the top of the bottle because of the
steady decrease in water level. The soil on top remained dry throughout the project, but
the soil underneath where the laces came out was normally slightly damper. The bottom
end of shoestring remained submerged in water the whole time.
Condensation was consistently noted on the inside of the top of the bottle where the soil
was, as well as in the bottom of the bottle by the tap water. This is proof of the water
cycle at work.
When originally creating the Aqua Terra ecosystem, I had to remove larger rocks and
some sand due to space limitations. Next time, I should use greater precaution when
cutting the soda bottle in two because the bottles were cut too small on top and refused to
remain upright in the bottom of the bottle. Two safety pins per bottle were used to secure
the top part of the bottle at the top of the bottom bottle.
About 25 drops of concentrated Weed-B-Gone were originally added to the water supply.
This pesticide, however, acts when sprayed onto the surface of the leaves, not absorbed
into the soil with the water supply. I sprayed the chemical on the leaves instead. In the
future, I should not change my experiment to match my hypothesis. This is investigator
bias, and should not be included in a scientific experiment because it invalidates the data.
Bias was also used when determining the health of a leaf on the periwinkle plants. In the
future, I should be very specific when stating what I am measuring and how much. I
should also not stray from the original independent variable or measurements. I could
have measured the height of the plants instead of judging the health.
As another experiment, I could change the amount of Weed-B-Gone I used, or even try
different pesticides such as Round-Up. I could also try an herbicide on flowers or grasses
to observe the side effects of toxins on the plants that share soil or water with an invasive
plant. I could also add worms or other insects to see how herbicides affect them. The
main ingredient in the Weed-B-gone is quinclorac, an herbicide for rice crops and
domestic lawn control. The secondary chemical in Weed-B-Gone is 2,4Dichlorophenoxyacetic acid (2,4-D) which is used for weed control and is valued for its
low cost. This is an acid, so it must have a low pH. I could also test the effects of adding
a basic substance to the vine.
I did not water the periwinkle plants during this experiment. This could have stunted
growth or lead to the browning and wilting of leaves on plant B. I did this to observe the
wicking effect of the cotton shoestring, but I didn’t realize I was supposed to water the
plant, too. In my research, I found that one could kill vinca vines by overwatering them.
In another experiment, I could compare overwatering with under-watering, or with use of
an herbicide.
In the future, I should also grow the vines from seeds so that I can better control the
environmental factors like sunlight, water, soil conditions, and pest exposure. By buying
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the vines at a store, I didn’t know the age of the vines, or whether or not they would
survive the transition to an aqua-terra ecosystem.
IV. Discussion
a. Support of the Hypothesis
I hypothesized that if a healthy Periwinkle plant is sprayed with Weed-b-Gone, then the
number of healthy leaves will decrease. My data supports my hypothesis because after a
few days, the Weed-B-Gone took effect, and, as plant B died, the healthy number of
leaves began to decrease. The leaves shriveled, yellowed, and wilted in response to the
Weed-B-Gone
b. Explanation
I used a qualitative system of determining the health of the plant, but I should have used a
quantitative system. I decided whether or not a leaf was healthy by the vibrancy of green,
wilting of the leaf, damage by insect to surface, and growth over the duration of my
experiment. In the future, I should create a scale to determine health. I could have a color
palate with assigned numbers or measure daily growth of a select population of leaves.
c. Conclusion.
In conclusion, the data supported my hypothesis. In the future, I would more thoroughly
research the topic before beginning. Also if a person considers planting an invasive
species in their yard, they should first know how to properly contain it so that it doesn’t
choke out other plants. This experiment shows one possible way to control vinca vines.
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