Comparison of percent germination, size, and CO2 production in arugula plants
affected and unaffected by fire, as well as with and without mycorrhizae assisted
growth
Michael French Alex Visconti and Michelle Mendez
Department of Biological Science
Saddleback College
Mission Viejo, CA 92692
Introduction
Around the world, and especially
increase their availability, since
in southern California, forest fires are a
mycorrhizae facilitate the absorption of
near constant concern for any species
nitrogen and phosphate ions, and the
growing in the wild. The rate of
burnt soil has a tendency to not be able
secondary succession for a plant species
to retain as much water as its unburnt
is an important factor for the species’
counterpart (Alghren 1974) (Ortas
overall survival chances in areas with a
2003). There has not been much research
high fire risk because if the plants are
done on the effect mycorrhizae may
unable to grow back effectively, they
have on the growth of plants in firewill be swiftly replaced by a species that
damaged soil compared to plant growth
can. One of the most prevalent methods
in regular soil. This experiment is meant
of gaining a proverbial leg up in terms of
to find out whether mycorrhizal
growth rate, is the formation of
relationships in burnt soil will facilitate
mutualistic relationships with
the growth of arugula plants more
mycorrhizae, a type of fungus that
effectively compared with burnt soil
ineracts with plant roots, present in the
without mycorrhizae. This experiment
surrounding soil (Callaway 1995). These
will also determine if there is a
relationships between plants and
significant difference in the effect
mycorrhizal fungi form commonly in
mycorrhizae has on plants grown in
plant roots as a way of more effectively
regular soil compared to those grown in
providing both with a greater amount of
burnt soil. It is expected that there will
nutrients. The mycorrhizae are supplied
be a significant difference in the growth
with a constant supply of carbohydrates
of plants with mycorrhizae in burnt soil
to be ingested, while the plant roots use
compared to those without mycorrhizae.
the comparatively greater surface area of
the fungi’s mycelia to increase their
Materials and Methods
water and mineral absorption from the
A pack of wild arugula seeds
soil (Harrison 2005).
(Eruca sativa) weighing one gram and
Fire has been shown to increase
containing about 150 seeds was
the amount of certain raw nutrient
purchased at Green Thumb Nursery in
factors present in soil such as nitrogen
Lake Forest, California. Also purchased
and phosphorous (Ahlgren 1974). If the
were a bag of Miracle Gro potting mix
soil was sterilized by a fire and the
(28.3l) and a pack of Mykos arbuscular
microorganisms living within it were
mycorrhizae. The experiment consisted
eliminated, simply having a greater
of four different groups: unburned soil
amount of the nutrient factors may not
with no mycorrizae, unburned soil with
mycorrizae, burned soil with no
mycorrizae, and burned soil with
mycorrizae. In order to simulate a fire,
roughly 14.15 liters of potting soil was
placed in the oven at 550 ̊F for one hour
and fifteen minutes. For the groups
containing mycorrhizae, one half of a
teaspoon of arbuscular mycorrizae was
added and mixed into the soil.
Three days prior to preparing the
variables for each group, 105 arugula
seeds were placed in between a moist
paper towel and put aside to germinate.
Out of the 105 germinating seeds, the
healthiest looking 60 seeds were
transferred to containers containing
about 355mL of soil. All 60 plants were
grown and maintained outside. Each
plant was given 150mL of water twice a
day, once in the morning and once at
night.
After twenty five days of
growing, various tests were conducted
on the arugula plants. The total number
of plants that grew in each group was
counted and documented. Individually,
each plant was placed into an 8L airtight
plastic container. Using a PASPORT
carbon dioxide gas sensor, carbon
dioxide production was measured for
each plant for four minutes.
Results among the four groups
were compared using a Chi2 analysis
followed by a one way analysis of
variance (ANOVA).
Differences were considered significant
at P<0.05.
Results
A Chi analysis was run on each
of the distinctions in the groups. In the
comparison of plants grown in burnt and
unburned soils, regardless of
mycorrhizae content there was a
significant difference in plant growth
(p=.0042 Chi2). In the comparison of
mycorrhizae presence’s effect on plant
growth, regardless of soil condition, no
2
significant difference was found (Chi2
P=.0698). In The comparison of
mycorrhizal presence in unburned soil
only, a significant difference was found
(P=.0142 Chi2). In the comparison of
mycorrhizal presence in burnt soil only,
no significant difference in the growth of
plants was found. (Chi2 p=.1.000)
The rate of cell respiration based
on CO2 production was also measured.
No significant difference (ANOVA) was
present between any of the groups.
25
20
15
Plants That
Grew
10
No Growth
5
0
Unburned Burnt Soil
Soil
Figure 1: Number of plants grown in
burnt and unburned soils. There is a
significant difference in plants grown in
burnt vs. unburned soil (P=.0042 Chi2
two-tailed)
20
12
10
15
10
Plants That
Grew
5
No Growth
8
Plants That
Grew
6
4
No Growth
2
0
0
Myco.
Present
Burnt
Burnt
with Myco without
Myco.
Myco.
Absent
Figure 2: Number of plants grown in
any soil with mycorrhizae present or
absent. There is no significant difference
in cumulative plant growth with or
without mycorrhizae present (P=.0698
Chi2 two tailed)
Figure 4: Number of plants grown in
burnt soil with and without mycorrhizae.
There is no significant difference in
plants grown in burnt soil with or
without mycorrhizae present (P=1.000
Chi2 two-tailed)
2.00E-01
16
14
1.50E-01
12
10
1.00E-01
Plants That
Grew
8
6
5.00E-02
No Growth
4
0.00E+00
2
Unburned burnt Unburned burtn w/
w/o myco w/o myco w/ myco myco
0
Unburned Unburned
with Myco. without
Myco.
. Figure 3: Number of plants grown in
unburned soil with and with
mycorrhizae. There is a significant
difference in plants grown in unburned
soil with or without mycorrhizae
(P=.0142 Chi2 two-tailed)
Figure 5: Comparison of rate of CO2
production in all groups. No significant
difference rate of CO2 production was
found (ANOVA)
Discussion
In the observation of how many
plants grew in each group, there was a
significant difference between unburned
soil and burnt soil. There was also a
significant difference between the
groups unburned with mycorrhizae and
burnt with mycorrhizae. The data
indicates that both plants and
mycorrhizae had a difficult time growing
in sterilized soil. The burnt soil was a
much more difficult environment, and
therefore the mycorrhizae may have
been unable to survive effectively
enough to form effective symbioses with
the arugula roots. This may be a reason
why there was a significant difference in
the unburned soil in terms of
mycorrhizal acitivity but not the burnt
soil. On the contrary there was no
significant difference between the
presence of mycorrhizae compared to no
mycorrhizae present. Lastly there was no
significant difference between the burnt
soil containing mycorrhizae and burnt
soil without mycorrhizae present. The
rate of CO2 production was not
significant between all four groups. The
experiment indicates that cellular
metabolism is unaffected by the
presence of mycorrhizae.
References Cited
Ahlgren, I. F. (1974). The Effect of Fire
on Soil Organisms. Fire and
Ecosystems.
Amaranthus, M. P., & Trappe, J. M.
(1993). Effects of erosion on ecto- and
VA-mycorrhizal inoculum potential of
soil following forest fire in southwest
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Callaway, R. M. (1995). Positive
interactions among plants. The Botanical
Review, 61(4), 306-349.
Ortas, I. (2003). Effect of selected
mycorrihzal inoculation on Phosphorus
sustainability in sterile and non-sterile
soils in the harran plain in south anatolia.
Journal of Plant Nutrition, 26(01), 1-17.
Retrieved March 3, 2014
Harrison MJ (2005). "Signaling in the
arbuscular mycorrhizal symbiosis".
Annu Rev Microbiol. 59: 19–42.