Transcript Final Platform Presentation

Effects of Intraspecific Competition
on Varying Groups of Marigolds
Tiffany Landis
Microbiology Major
Tennessee Technological University
Cookeville, TN 38505
Introduction
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“The purpose of making plant competition studies is
ultimately to be able to predict the dynamics of natural
plant communities.” (Damgaard, 1998 )
“For many plants, an increase in density results in a
decrease in reproduction, total biomass, height and/or
survival.” (Antonovics and Levin, 1980)
The more crowded a population the more competition
there is for resources.” (Tansley, 1917)
“Spatial arrangement of plants in a community can be
an important determinant of species coexistence and
biodiversity” (Stoll et al, 2001).
Introduction Continued…..
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“Plants biomass and seed production were always
higher in plants growing with reduced competition”
(Aquiar et al., 2001).
In my experiment with marigolds I looked to
Intraspecific competition to determine if plants with
more competitors will end up smaller than plants
grown with fewer competitors.
The idea being that competitors will take up light and
nutrients and leave a lot less of those nutrients for the
other plants.
Methods and Materials
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I obtained six pots and labeled them according to the number of seeds in
each pot.
The plants were kept in a sunroom and watered regularly. Each of the six
pots was filled with soil until it came to about one centimeter from the top
of the pot.
I obtained marigold seeds and planted the following densities of seeds in
each pot: 3, 5, 10, 18, 34, or 68 seeds. After germination, the plant
populations were thinned to 2, 4, 8, 16, 32, or 64 plants per pot. I then
placed more soil on top of the seeds and watered them. Starting with
higher initial densities will increase the likely hood of getting more
germinated seedlings. (Damgaard, 1998 )
Each week I measured the number of leaves on each plant in each pot,
heights of the plant stems, and number of flowers on each plant.
I then gathered detailed information from each pot number of plants,
weights of plant stems, number of leaves and length of stems.
I obtained stem weights of the plants by clipping out the plants at soil
level, clipping off the leaves and placing them on a scale.
Results
Density vs Percent Survival
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
120
Density vs Total
Plant Weight
Percent Survival
Total Plant Weight
Density vs Total Plant Weight
100
80
Density vs Percent
Survival
60
40
20
0
0
0
20
40
60
100
Density
80
Density
50
Fig. 2
Fig. 1
As density goes up plant
weight goes up, which would
not be expected if nutrients
were being depleted due to
competition.
Despite density survival
rates for the pots with 16
and 64 marigolds was the
same. The survival rate
was higher in the pot
with 32 marigolds.
Results
60
50
40
Density vs Average
Leaf Weight
30
20
10
Density vs Average Stem Length
Average Stem Length
Average Leaf Weight
Density vs Average Leaf Weight
6
5
4
Density vs Average Stem
Length
3
2
1
0
0
0
0
20
40
60
Density
20
40
60
80
Density
80
Fig. 4
Fig. 3
Leaf weight began accurate to
plant competition standards, but
then the pot with 64 marigolds
was weighed the average leaf
weight increased instead of
decreased.
Stem length began accurate
to plant competition
standards but as seen with
the leaf weight the pot with
64 marigolds increased
instead of decreased.
Results Explained
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As can be seen by the various
graphs density had little or no effect
on the growth of the marigolds.
My results proved my null
hypothesis.
My results went against the norms
of many other experiments done in
this field.
Discussion
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My null hypotheses was found to be correct. According to the
graphs the density had, no effect on the growth of the plants. Thus,
concluding that there is no significant difference in all aspects of
growth of the plants. The results were not conclusive enough to
say that competition affected their growth. Studies done by
scientists as mentioned in the introduction were conducted over a
longer period and proved that competition intra- had an effect on
plant growth. The experiments that I conducted was over a shorter
period and thus we could not prove that competition intra- had a
significant effect on plant growth. However, through my various
researches on this topic I found that competition can be avoided
and that the plants through natural selection would be allowed to
converge. Avoidance of competition may imply that the species
have gotten used to each other’s presence.
Conclusion
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Density did not affect the amount of
intraspecific competition among the
marigolds.
My results showed that there was little plant
competition among the marigolds. This could
be because the plants grew for a short amount
of time and never reached full maturity.