Transcript Amrita`s PJAS ppt revised

Does alfalfa- leaf extract,
an allelochemical, affect
the formation of root
nodules of leguminous
plants?
• Allelopaths are plants that release chemicals into their surroundings
that inhibit the growth/development of the plants around them
• Allelochemicals are chemicals that are released from allelopaths’
roots, passed through the soil, and absorbed by other plants. They
harmful because they can restrain other plants’ nutrient intake or
impede their root growth.
• Leguminous plants are plants such as peas, beans, lentils, and peanuts
that have a symbiotic relationship with nitrogen fixing bacteria in the
soil, rhizobia.
• These rhizobia attach onto these plants’ roots and form nodules to fix
nitrogen for the plant.
• Nitrogen Fixation is a process by which nitrogen (N₂) in the
atmosphere is converted to inorganic nitrogen compounds such as
ammonium (NH₄⁺). This can then be turned into amino 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) Prepare alfalfa-leaf extract: Grow alfalfa seeds for 2 weeks and
soak sprouts in 50 ml of water for two days in a cool place.
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
Root Nodules
• Independent Variable: the substance that the plant
is watered with (either distilled water or alfalfaleaf extract)
• Dependent Variable: the amount of root nodules
that form on the plant roots as a result of what it
was watered with
• Control: the plants watered with distilled water
• Constants: The type of soil, amount of light,
amount of water, and growing time for each pot
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
6
15.33
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 plant’s roots could have choked each other out
since they were planted so close to each other in
the pots
• Different percentages of plants grew in both
groups (60% of the seeds planted in the control
group grew and 80% in the experimental group
grew)
• Some nodules may not have fully formed yet and
thus may not have been accounted for in the data
• Hypothesis supported: 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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Achenbach, J., & . (n.d.). Plants on the Warpath. National Geographic Magazine,
http://ngm.nationalgeographic.com/ngm/0402/resources_who.html.
Ferguson, J. J., & Rathinasabapathi, B. (n.d.). Allelopathy: How Plants Suppress Other Plants
[Data file]. Retrieved from edis.ifas.ufl.edu/pdffiles/HS/HS18600.pdf
A Study of Allelopathy in Plants. (2000) (M. DeLacy & L. Selger, Eds.). In Encouraging Student
Biological Research (pp. 21-31, 46-51). National Association of Biology Teachers.
Tebo, M. (2010). Chemical Warfare in the Plant Kingdom. In Killer Plants. Retrieved from
http://www.hgtv.com/landscaping/killer-plants/index.html
Westra, E. P. (n.d.). Can Allelopathy be Incorporated into Agriculture for Weed Suppression?
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kzcUWBvoUT9EuTznPGv3KSlyIr2JAnePal_zOEDftBqY7C6nrk7kGHcUEa5_KAqjH3oRqGEYAFketH3GbvbE0vUqtJ3ZebWp8jTexUkls4fYf3tbbvFNQQ1oni&sig=AHIEtbQBXmWsqgBDLp_6PvP1kKy87jGYAg
Wojciechowski, M. F., & Mahn, J. (2006). Nitrogen Fixation and the Nitrogen Cycle. Retrieved
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