2. Does alfalfa- leaf extract, an allelochemical, affect the formation of root nodules of leguminous plants?

3. Allelopathic plants are plants that hinder the growth of the plants around them by releasing chemicals into their surroundings which inhibits their growth and development. Allelopaths possess chemicals, called “allelochemicals,” which are released from their roots, passed through the soil and absorbed by other plants. These allelochemicals are harmful to other plants because it can restrain their nutrient intake or impede 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.

4. The alfalfa-leaf extract will restrict the formation of root nodules by nitrogen- fixing bacteria.

5. 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

6. 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.

7. three weeks after planting seedssix weeks after planting seeds Plant roots (water on left, alfalfa-leaf extract on right)

8. 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.

9. Number of Root Nodules Substance Used to Water PlantWaterAlfalfa-Leaf Extract 179 147 1810 148 1611 139 7 Average15.339.25 Standard Deviation1.972.05 T Test0.00011917

10. This graph shows the average number of root nodules for the plants watered with alfalfa- leaf 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.

11. 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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