Seed Travels  

Adapted from "Scholastic News," February 1993.

Scattering Seeds

Imagine you're a plant and you're about to drop your seeds. Wherever one hits the ground, a new plant will grow.

Think: do you want your seeds to fall close to you — or far away? (Hint: all plants need soil, water, sunlight, and space to grow. Will your sprouting seeds get more of these if they're bunched together or far apart?) If you're like most plants, you want to scatter your seeds around. But how? (After all, as a plant, you're rooted to the spot.) Test your seed-sending skills with these experiments.

Seed Sources

Look for seeds in these places:

  • Supermarket shelves: Dried beans and popcorn are seeds. So are nuts like pecans.

  • Gardening sections: Look for packets of planting seeds.

  • Inside fruits: Collect ripe apples, oranges, cantaloupes, pumpkins, bell peppers, etc. Cut the fruits open and carefully remove the seeds. Wash the seeds and spread them on a paper towel. Let them dry on a sunny windowsill for two days.

  • Schoolyard: Just look around! If you don't see any try this: Pull on an old sock over your shoe. Walk in a grassy or wooded area for five minutes. Remove the sock carefully and check it for tiny seeds.

Motion Detectors

Think: How do seeds travel?

    1. Gather five seeds of different sizes and shapes.

    2. Describe your seeds on a chart.

    3. Next to each seed description, predict whether that seed could travel by wind, water, or hitchhiking.

    4. Try out your predictions using the tests below. Record your answers on the chart.

  • Wind Test: With an adult's help, stand a fan on a chair so that the top half sticks over your desk. Use tape to make a starting line 25 cm (10 in.) away from the fan. Place seeds on the starting line. Turn the fan on at medium speed for 20 seconds. Measure how far your seeds traveled. A seed passes the Wind Test if it blows more than 1 m (40 in.) away from the line.

  • Water Test: Fill a small container half full of water. Drop the seeds into the water and stir. A seed passes the Water Test if it floats.

  • Hitchhiker Test: Place a seed on a table and cover it with one test material. Gently press down on the material with your palm. Lift and check -- does the seed stick to the material? Repeat with two other test materials. A seed passes the Hitchhiker Test if it sticks to any test material.

    Wrap-up: Were you surprised by any of the ways your seeds could travel? Look at the seeds that passed the Wind Test. How are they similar? (Hint: Are they all small? Big? Do they have the same shape?) How are these seeds different? What do the floating seeds have in common? How about the hitchhiking seeds?

    Wind Rider

    Think: What helps a seed travel in the wind?

    1. Choose a seed that did not pass the Wind Test. Find a second seed of the same kind and size to be your control seed.

    2. How can you change your seed so that it could travel in the wind? Brainstorm a list of ideas. (Hint: What do the best wind-traveling seeds have in common?) Think about the seed's:

  • shape

  • density (how heavy something is compared to its size)

  • what else?

    3. Choose one idea from your list. Make that change to your seed.

    4. Give both your changed seed and your control seed the Wind Test. Which moves farther?

  • If the control seed moves farther: Undo the change on your other seed. (That will make both seeds the same.) Pick a different idea from your list to test.

  • If the changed seed moves farther: Your change is a success! Add it to your control seed too. Then make a new change to your winning seed.

    5. Repeat step 4 until your changed seed passes the Wind Test.

    Wrap-up: Compare your seed design to others in the class. What do they have in common? What change seemed to help our seed the most? Which helped it the least?

    Bonus: Combine the best ideas in your class to design a seed that's a champion wind traveler.

Adapt-a-seed

Think: Will a seed travel just as well in any environment? Why or why not?

    1. Choose a seed to adapt. Find a control seed that matches it.

    2. Read your Environment Card. What are some ways a seed might travel in your environment? How couldn't a seed travel there?

    3. Brainstorm changes that might help your seed travel in its environment. (Remember: Your seed has to pass both tests on your Environment Card.)

    4. Choose one idea from your list. Make that change to your seed.

    5. Put your seed (and the control seed) through both of the tests listed on your card. How well do they do?

  • If the control seed is better at both: Undo the change on your other seed. (That will make both seeds the same.) Pick a different idea from your list to test.

  • If the changed seed is better at both: Your change is a success! Add it to your control seed too. Then make a new change to your winning seed.

  • If there's no clear winner: Did each seed win in one test? Then the next step is up to you. Decide which seed design you think holds the most promise. (Keep a sketch of the other design. Scientists sometimes hit a dead end, and have to go back to an earlier design.) Give both seeds the design you like. Then make a new change to one seed.

    6. Repeat step 5 until you have a seed you know will succeed in your environment.

    7. Draw a diagram of your seed, label the materials you used to adapt your seed, and explain how your seed can disperse (scatter) in your environment.

    Wrap-up: Compare your seed with others from your class. Can you guess which seeds share the same environment as yours? Switch Environment Cards with another group. How would your seed do in this new environment?

    Bonus: Describe the environmental conditions of your schoolyard. (Is there much wind? Do many animals visit?) Design a seed that could travel easily in your schoolyard.



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