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How the Environment Impacts Root Growth

How the Environment Impacts Root Growth. By Amy Elkin. Big Question. Which effects root growth more gravity or soil nutrients? Reasoning: To determine if the roots of plants grow down because of gravity, because that is where the soil is, or because of some other reason.

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How the Environment Impacts Root Growth

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  1. How the Environment Impacts Root Growth By Amy Elkin

  2. Big Question • Which effects root growth more gravity or soil nutrients? • Reasoning: To determine if the roots of plants grow down because of gravity, because that is where the soil is, or because of some other reason.

  3. Hypothesis and Reasoning • Hypothesis: Root growth is effected by gravity more than nutrients found in soil. • Reasoning: I believe this hypothesis to be true since gravity makes the roots of plants grow down and the stem of the plants grow up. In the past I have seen roots growing downward in plastic bags containing wet paper towels.

  4. Interesting Facts • Many seeds will grow even if there is little light • Geotropism is the growth of a living organism in response to gravity • Roots bend in response to gravity because of the hormone auxin • Roots do not need soil to grow, some can grow in plastic bags containing wet paper towels • Radishes are one of the fastest growing types of seeds

  5. Experiment: Materials • 1 package of radish seeds • 1 roll of paper towels • 1 package of small white labels • 18 CD cases • Modeling clay • Potting soil • Shallow cooking tray • Lab notebook • Ruler • Black marker and brown marker • Computer paper • Pen • Pencil • Computer • Eye dropper filled with water • Camera • CD rack • Plastic cup • Printer • Computer paper

  6. Experiment: Instructions • Fold 6 paper towels to the size of the CD cases. • Place the paper towels inside each CD case. • Write “up”, “down”, “left”, and “right” each on 6 different white labels. • Label each CD case with one of each of the labels, on the correct side. • Fill 3 of the CD cases halfway with potting soil. • Wet the paper towel in each CD case with 3 drops of water. • Place six seeds in each CD case. In the three cases with the potting soil, place the seeds directly against the edge of the soil. • Close the CD cases tightly. • Use 6 additional labels to label the horizontal cases #1 to #6. • Using the modeling clay, and CD rack, place CD’s #1, #2, #3, #4 in a vertical position with the “up” label at the top inside the cooking tray. • Using the modeling clay, and CD rack, place six CD's labeled horizontal #1 to #6 in the cooking tray • Take measurements and photographs of the root growth every 2 days. • Take pictures of changes in CD's. • Every other day, rotate cases labeled "rotation" 90 degrees clockwise. • Note whether the root growth is affected by the direction of gravity or the presence of soil. • Record root growth and direction by day for each of the CD cases. • Repeat the entire procedure (Steps 1-16) two more times to make sure the results don’t change.

  7. Control Group/Variables • Control Group: paper towels in horizontal position • Variables: soil group in different positions

  8. Observations • Vertical group grew mainly down • Some grew diagonally down after growing up • Most grew towards gravity • The ones with soil in the vertical group grew in random directions or did not grow

  9. Observations • Only a few of the roots in the rotation group grew down and a lot of them either did not grow or grew in random directions • The roots in the horizontal group mostly grew in random directions or did not grow at all

  10. Data

  11. Analysis of Data • Almost half the seeds did not grow • 30 of the seeds that did grow, grew in random directions • Only one seed grew towards the soil

  12. Analysis of Data • The cases with soil had the least seed growth • The cases with paper towels positioned vertical had the most growth toward gravity • Seeds in horizontal cases with paper towels mostly grew in random directions

  13. Conclusion • My hypothesis was correct. Gravity had a greater impact on root growth direction than soil • The only consistent direction of root growth was toward gravity when the CD case stayed in a vertical position • The random growth in horizontal CD cases shows the roots didn’t know which way to grow • Soil is important for normal root growth because it holds water

  14. References www.ag.arizona.edu/pubs/garden/mg/botany.environmental.html (September, 2009) Environmental Factors That Affect Plant Growth www.en.wikipedia.org/wiki/Geotropic (September, 2009) Gravitropism www.ksnn.larc.nasa.gov/webtext.cfm?unit=plants(September, 2009) Exploration Systems www.library.thinkquest.org/C003763/index.php?page=human03 (September, 2009) Gravitational Biology Parker, S. (1995) Isaac Newton and Gravity Spilsbury, L. (2008) Plant Habitats Tagliaferro, L. (2007) The Life Cycle of a Bean www.uoregon.edu/~melliot2/plants/gravity.htm (September, 2009) Gravity www.esmdeo.arc.nasa.gov (September, 2009) Gravity and Plants

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