Transcript 1)A title page – include your name and the name of your school 2

Does alfalfa- leaf extract,
an allelochemical, affect
the formation of root
nodules of leguminous
plants?
• Allelopathic plants are plants that • Leguminous plants are plants
hinder the growth of the plants
such as peas, beans, lentils, and
around them by releasing
peanuts that have a symbiotic
chemicals into their surroundings
relationship with nitrogen fixing
which inhibits their growth and
bacteria in the soil, rhizobia.
development.
• These rhizobia attach onto these
• Allelopaths possess chemicals,
plants’ roots and form nodules
called “allelochemicals,” which
to fix nitrogen for the plant.
are released from their roots,
• Nitrogen Fixation is a process by
passed through the soil and
which nitrogen (N₂) in the
absorbed by other plants. These
atmosphere is converted to
allelochemicals are harmful to
inorganic nitrogen compounds
other plants because it can
such as ammonium (NH₄⁺). This
restrain their nutrient intake or
can then be turned into amino
impede root growth.
acids and used by the plant.
The alfalfa-leaf extract
will restrict the
formation of root
nodules by nitrogenfixing bacteria.
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10 cm. diameter plastic pots
2 lbs. sterile sandy soil (4 parts sand to 1 part soil)
Autoclave
2 lbs. topsoil
50 g. alfalfa seeds
Plastic wrap
40 white clover seeds
Microscope
Beaker
Water
Growth Light
1) 1) Prepare alfalfa-leaf extract: Grow alfalfa seeds for 2 weeks and
soak sprouts in 50 ml for two days in cool place.
2) 2) Fill pots with sterilized, sandy soil (4 parts sand to 1 part topsoil)
1 cm. from the top.
3) Label pots with either “distilled water” or “alfalfa-leaf extract
4) Plant 10 clover seeds in each pot. Water each pot with either
distilled water or alfalfa-leaf extract depending on the pot’s label.
5) Grow clover for about 6 weeks.
6) Gently remove plants from pots with the roots and rinse them to
remove extra soil.
7) Using a microscope, count the number of nodules on each plant’s
roots.
8) Record results and find the mean number of root nodules per
plant.
three weeks after planting seeds
six weeks after planting seeds
Plant roots (water on left, alfalfa-leaf extract on right)
• The independent variable is the substance that the
plant is watered with (either distilled water or
alfalfa-leaf extract)
• The dependent variable is the amount of root
nodules that form on the plant roots as a result of
what it was watered with
• The control are the plants watered with distilled
water
• The type of soil, amount of light, amount of water,
and growing time for each pot was kept constant.
Number of Root Nodules
Substance Used to Water Plant
Water
Alfalfa-Leaf Extract
17
9
14
7
18
10
14
8
16
11
13
9
13
7
Average
Standard Deviation
T Test
15.33
9.25
1.97
2.05
0.00011917
Average Number of Root Nodules
Average Number of Root Nodules Formed
20
18
16
14
12
10
8
15.33
6
9.25
4
2
0
Water
Alfalfa-Leaf Extract
Substance Used to Water Plant
This graph shows the average number of root nodules for the plants watered with alfalfaleaf extract and the plants watered with distilled water. Notice that the clover plants watered
with the alfalfa- leaf extract formed fewer root nodules than the plants watered with water.
This suggests that alfalfa- leaf extract impedes the formation of root nodules.
• The purpose of this experiment was to test how alfalfa- leaf
extract affects the formation of root nodules of leguminous
plants. Alfalfa-leaf extract restricts the growth of root nodules.
• This supports the hypothesis: The alfalfa-leaf extract will restrict
the formation of root nodules by nitrogen-fixing bacteria.
• This experiment contributes to the agricultural society by
showing not to plant leguminous plants such as peas, beans,
lentils, and peanuts near allelopathic plants. This ensures that
the leguminous plant is able to healthily grow root nodules and
fix nitrogen from the atmosphere.
• This can lead to other useful studies, such as determining
whether allelopathic plants can be used as natural pesticides
instead of artificial fertilizers which are harmful to the
environment.
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kzcUWBvoUT9EuTznPGv3KSlyIr2JAnePal_zOEDftBqY7C6nrk7kGHcUEa5_KAqjH3oRqGEYAFketH3GbvbE0vUqtJ3ZebWp8jTexUkls4fYf3tbbvFNQQ1oni&sig=AHIEtbQBXmWsqgBDLp_6PvP1kKy87jGYAg
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