FAQ for "How Do Roots Grow..."

Questions related to the "How Do Roots Grow When the Direction of Gravity Changes?" Project Idea and/or kit. (http://www.sciencebuddies.org/science-f ... l?from=AAE)

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FAQ for "How Do Roots Grow..."

Post by amyc »

The following FAQ contains frequently asked questions and answers about the "How Do Roots Grow When the Direction of Gravity Changes?" Project Idea. If you are having trouble with the procedure, you may find assistance in the answers below.

Q: I am having trouble telling the root from the shoot. Can you help me?
A: The root and shoot can look very similar, especially when the seedling is just sprouting. For this project it is important to distinguish between the root and the shoot, so it is a good idea to learn to tell them apart. The seed itself should not be used to determine what is "up" and "down" because the seed sandwiches will rotate throughout the experiment and the seed itself will move as it sprouts.

Here are some tips to help you tell the root from the shoot when a seed begins to germinate:
  • The root is the first part of the seedling to come out of the seed. The root will be whitish in color and thread-like. See Figure 1.

    Figure 1. The root is the first part of the seedling to come out of the seed.
  • The root will grow down, towards the ground, if nothing gets in its way. However, if roots are not allowed to grow downwards (like in the sandwiches that are horizontal, lying flat), then this tip is not applicable.
Here are some tips to tell the difference between the root and the shoot once the seedling is a little older.
  • The shoot is the second part of the seedling to come out of the seed, and it will grow upwards (when not obstructed). (If the lightproof box is not completely lightproof, the shoot will also grow towards the light.) The seed coat will remain on the end of the shoot as it grows for a while, until leaves emerge.
  • As the seedling grows, the shoot (which includes the stem) will be thicker than the root. There may be a point on the seedling where this change in thickness is very clear; this should be where the root and shoot meet. See Figure 2.

    Figure 2. The differences between the root and the shoot
  • The shoot, but not the root, will develop tiny leaves. See Figure 2.
Q: I think I see the shoot but not the root. Why is this?
A: If you see the shoot of the seedling but not the root, it is possible that the root is hiding. Carefully examine the seedling, looking to see if the root is hiding under the shoot. You should also look closely to see if the root burrowed into the blotting paper (this happens more often in folded paper towels). If you cannot see the root, note this in your lab notebook and continue with the experiment; it may show up in a day or so.

Q: I am trying to measure the angle of the root but I cannot figure out how to use the protractor. How should I use a protractor?
A: The project asks you to measure the angles ranging from 0 to 360 degrees (°). See Figure 3. A protractor that only has 180 degrees can also be used. Here are some tips to make measuring easier.

Figure 3.
  • If you are measuring an angle that goes left, and your protractor only has 180 degrees, turn the protractor so that 0 degrees pointing "down" and 90 degrees at the "left."
  • If you are measuring an angle that goes right, and your protractor only has 180 degrees, turn the protractor so that 0 degrees is pointing "up" and 90 degrees is at the "right," measure your angle, and add 180 degrees.
  • If the root is too short to reach the markings on the protractor, use your ruler to follow the root line until it hits the protractor, and then read off the angle measurement.
Q: My root keeps changing directions, and I am having trouble figuring out what angle I should measure. Can you help me decide what angle I should measure?
A: The purpose of measuring the root's angle is to determine the direction the root is currently growing. Since the root grows outwards from its tip, this means that we would like to find what direction the tip of the root is pointing. It is very difficult to get this exact measurement so our goal is to find a suitable approximation for this measurement. We do this by avoiding measuring major turns in the root. The next points have more detailed instructions (and images) to show what to measure.
  • If you have a short, straight root, then measure the angle from the top of the root to the tip of the root. See Figure 4.

    Figure 4. Simple root measurement
  • If you have one turn in the root (and it may only be a minor turn), then measure from after that turn to the tip of the root. See Figure 5.

    Figure 5. Angle measurement with one turn
  • If your root winds back and forth, start at the tip and follow the root until it begins to turn and is no longer straight. Measure the angle from the beginning of the turn to the tip of the root. See Figure 6.

    Figure 6. Angle measurement for turning root
  • The main root may have small, thread-like growths, called secondary roots, coming off of it. When measuring the root, make sure to measure the main root, not one of the secondary roots.
The most important thing is that you are consistent in how you measure root angles. Measure similar roots the same way, and make notes in your lab notebook about how you measure the angles.

Q: My root is curving and I do not know how to measure the length. Can you give me ideas for how to measure the length of my curving root?
A: Measuring the length of the root can certainly be tricky when the direction the root is growing changes! Here are some tips for measuring roots.
  • If the root is straight you can simply use your ruler to measure the root from the beginning to the tip. See Figure 7.

    Figure 7. Simple length measurement
  • If your root turns, you have a few options for measuring the length of the root.
    • Use a string to follow the root from beginning to end, making sure to follow all the turns in the root. Cut the string at the tip of the root and measure the length of the string. See Figure 8.

      Figure 8. Length measurement using string

      Alternatively, you could use a ruler to measure the length of the root until it starts turning. Then measure from the point you left off, continuing down the root until it turns again. Continue this pattern until you reach the tip of the root, and then add the measurements to get a total root length. See Figure 9.

      Figure 9. Length measurement using segments
    Again, it is important to be consistent in how you measure root length. In your lab notebook, write down your procedure for measuring root length.
Q: My seeds keep falling down when I stand the CD case up. What should I do?
A: There are a few ways you can fix this problem. First, be very gentle when you are standing the cases up, making sure to not jostle them. Next, make sure that the blotting paper is sufficiently damp so that the seeds having something to adhere to. If you have done both of these and your seeds are still falling, you can try putting your seeds between two sheets of blotting paper.

Q: What should I do if the CD case keeps falling over?
A: If your CD cases (or other sandwich materials) are falling over, make sure that you are not accidentally hitting the lightproof box while setting up the experiment. If you are still having problems, you can try taping CD cases to the side of the box.

Q: What do I do if my seeds are not sprouting?
A: Radish seeds generally germinate (sprout) within 3-7 days, with some varieties having longer or shorter germination times (the packaging may give a time estimate for the specific variety). If it is still within the expected germination time, the radish seeds may simply need more time. If you are using seeds other than radish seeds, your seeds may take longer to sprout.

If just one or two of your seeds are not sprouting, then there is no need to worry. It is actually quite common for a few seeds to not germinate. Use your lab notebook to record which seeds do not germinate.

If it has been long enough that the seeds should have germinated, but most of the seeds have not sprouted yet, wait a couple of days more. If they still have not sprouted, it may be that the seeds cannot grow under the conditions you have them in or that some of the seeds have not been handled well. Whatever the case is, make sure you make notes about it in your lab notebook so you can look back and determine what may have caused the problem. If none of the seeds have sprouted after a week, you may need to buy new seeds.

Q: I have multiple roots coming out of one plant. Which should I measure?
A: If you have one main root with a lot of smaller roots (secondary roots) coming out of it, you should measure the main root.

If you have two roots but it does not look like either of them are secondary roots; that is, they both look like main roots, you may actually have two seeds instead of one. Check the seeds closely to see if you have two seeds that may have stuck together when you put them in the case. If you do have two seeds, randomly remove one of the seeds by flipping a coin to pick which seed you remove.

Q: What should I do if the roots run into the bottom of the CD case?
A: Unfortunately, there is not much you can do about this for the test you are currently running. You should continue running the test, tracking in your lab notebook which roots have hit the bottom of the case and how they grow after having hit the bottom of the case. You can talk about how you think that this could have affected your data when you are analyzing your project.

For your next test, try this: make sure your seeds are far away from the edges of the case (try to place them all near the center), do not make the blotting paper too damp, and use a single layer of paper towel if you are using multiple layers of paper towels now. If the roots still run into the bottom of the CD case, you can start over with slower growing plants or run the project for fewer days.

If you have other questions about the procedure or need assistance troubleshooting your "How Do Roots Grow When the Direction of Gravity Changes?" project, please post your question in the forum for this kit at Ask an Expert: https://www.sciencebuddies.org/science- ... m.php?f=75. Our team of volunteer Experts is available to assist. We attempt to reply to questions within 24 hours. Please note that you will need a free Ask an Expert account in order to post questions.

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