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The majority of plants can't move from where they are planted once they start growing, yet we see plants almost everywhere. How do they get there?

Plant-Science-Lessons

Many plants travel as seeds, which have many different ways to spread and scatter. Some seeds are carried by animals, some float on the wind, others float on water, some simply roll down hill due to gravity, and still others have ways to shoot out of their seed pods. The ways that seeds move from place to place is called "seed dispersal."

See for example, these spectacular examples of seed dispersal in this video from the Smithsonian Channel.

 

Activity 1. Investigate seed structure and movement through observation.

Take a look at some of seeds and guess how they might be transported from place to place.

mystery-seed-221How about these tickseed sunflower seeds? How do you think they are dispersed?

chinese-elm-seeds

How do the Chinese elm seeds (samara) look? How do you think they move around?

acacia-salicina-seedWillow acacia seeds have red or orange structures attached to  them. Any idea how those might help the seeds move around?

mystery-seed18-2Do you have any idea how these filaree seeds move about?

shagbark hickory nutsHow about these hickory nuts?

For the answers, see the bottom of this post.

Go outside and look for seeds, particularly in the fall. Observe them and try to figure out how their structure helps them get from place to place. Look at them through a hand lens. Toss them in the air. Blow on them. Put the seeds in a puddle. See if they will stick to your sleeve. Think about where you see seeds and how they got there.

Once you have made your observations, research what others have found out about how those particular seeds disperse. If little is known, design and conduct your own experiments.

Activity 2. Floating Seeds

Seeds - like the sea bean - can float from place to place. They don't have to be in a big body of water like the ocean, either. A small trickle created by a downpour of rain may be enough to float seeds away.

Gather:

  • Large bowl, sink, tub or aquarium to fill with water
  • Seeds or fruits to test for ability to float:   coconuts, cranberries, a pinto bean or other dried bean, etc.

Predict what will happen to each item and then test each item. Let the seeds or fruit float as long as possible to show that they might reach land without sinking. You might want to cut open a cranberry to show the seeds inside.  (Remember that cranberries are harvested by floating them in ponds). Is a cranberry that has been cut open still able to float?

cranberries-2

More advanced activity:

Scientists in Hawaii needed to know how plants arrived on the islands in order to protect native species and prevent introductions of invasive species. A scientist named Henry Guppy placed different seeds in jars of seawater for several months to see how long they could float.

Design your own experiment to test which seeds float in your area and investigate how they do it.

Have you ever gone to the beach or the shore of a lake? Look for seeds on the shore that were carried there by water.

Wayne's World has an extensive discussion of the botany of drift seeds and drift fruit (those that float).

Activity 3. Flying Seeds

Most of us have seen seeds flying in the air at one time or another. Dandelions, milkweeds, maple keys and cottonwoods are just a few examples of trees with seeds that ride the wind.

Dandelion and oleander seeds fly with structures that are like tiny parachutes. If you are interested, try investigating parachutes.

Design an experiment to test how far a dandelion seed can fly. How would you measure it?

Science Buddies has suggestions for how to carry out a seed dispersal experiment called Gone with The Wind (based on a similar experiment at Scientific American).

red-maple-keys-461

Advanced:

Maple keys are so interesting that scientists take high speed movies of them to discover the secrets of their movements. According to this study, the keys produce swirling air like mini-tornadoes while they spin. Here the seed has been dropped in oil to make the whirls easier to see.

Do you see the tiny swirls that form over the end of the "tail" part of the key? Cool!

For more about maple key science, try these links:

If you want to learn more details about the botany behind wind dispersal, try Wayne's World.

Do you have a question about seed dispersal? Feel free to free to leave your questions or further activity suggestions in the comments.
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To see our complete plant science lessons, either visit the plant science category (newest posts to oldest posts) or the plant science section of our experiment archive page (links to posts in order).

For more information about plants and seeds, try our Seed of the Week archive or the mystery seed tag and Seed of the Week category.

Seed dispersal answers:

  1. Tickseed sunflower seeds have barbs that stick to clothing and fur. They are carried by animals.
  2. The wings on the Chinese elm seeds help them float on the wind.
  3. The red and orange structures on the willow acacia seeds are eaten by birds and other animals. The animals carry away the seeds, eat the red part and discard the hard, slippery seeds.
  4. Filaree seeds have an interesting ability to twist themselves into the soil. They are like tiny drills.
  5. Nuts, like hickory nuts, are often carried away and buried by animals.

 

Plant-Science-Lessons

Today let's learn about seeds.

Seeds are the way certain plants reproduce. Only gymnosperms (conifers, ginkgoes, etc.) and angiosperms (flowering plants) produce seeds.

A seed consists of a plant embryo surrounded by a protective seed coat. Many seeds also contain a source of food for the developing embryo.

Seeds come in a remarkable variety of sizes, shapes, and colors.

Seed Activities for Kids

Caution:  Commercially-available seeds may be treated with pesticides, particularly fungicides. Whenever possible use organic seeds, seeds for food use, or seeds you saved yourself for these activities.

bean-soup-mix-for-sorting

Activity 1. Sorting Seeds (for the youngest set)

This activity is for children old enough not to place small objects in their mouths and with adequate fine motor skills to pick up a seed.

Sorting is an important skill for science, but one we tend to overlook. Repeat this activity as often as the child(ren) desire(s), using different mixtures each time. Simply look through your cupboards and spice jars for seeds.

Materials for Sorting Activity:

  • Large seeds, such as different kinds of dried beans, dried watermelon, corn, pumpkin, squash and sunflower seeds. Sorting the beans in dried bean soup mix is fun too.
  • Paper plates, egg cartons, or small bowls (optional)
    For optional seed collage:
  • Construction paper, paper plates, or tag board
  • White glue

Procedures
1. Examine the seeds closely. Ask questions. Which is the biggest? Which is the smallest? What colors do you see? What do the seeds feel like? Smell the seeds. Is there an odor?
2. Ask the children to sort the seeds into piles (sorting into small paper plates, egg cartons, or dishes helps make clean up easier). Add forceps or tweezers for fine-motor skill practice.
3. Option 1: add some similar-sized beads, and ask the children to sort the seeds from the beads. You can introduce the concepts of living versus non-living if your children are ready.
4. Option 2: Use the seeds to make a simple picture or pattern by gluing them with white glue onto a paper plate or card stock.
5. You may want to save some of the seeds for sprouting activities.

Activity 2. What is in a seed?

Older children can (a.) dissect seeds and (b.) do an experiment with them.

a. For the dissection

Gather:

  • Bean seeds and corn seeds (larger varieties like lima beans work best)
  • Age-appropriate dissecting equipment, such as plastic knives, pins, or small kitchen knives
  • Hand lens or dissecting microscope, if available
  • Diagrams of the parts of seeds
  1. Count out a few seeds of each kind for each participant and soak them at least 24 hours in moist paper towels.
  2. Distribute the seeds to the participants. Have the children pull off the seed coat of the bean seed. Ask them to look for the seam and gently pry the two halves apart. Look for the "baby plant," which is the embryo.
  3. Allow the children to cut the corn seeds open and look for the embryo, cotyledon, etc. Corn is more difficult, so have extra seeds on hand.

Bean-seed-partscorn-seed-parts copy

Explain the difference between the bean seed and the corn seed is the number of cotyledons. Beans have two cotyledons and are called dicots. Corn and other grass seeds have one cotyledon and are called monocots.

Have the children draw their seeds and discuss what they find out.

b. Experiment with bean embryos

Gather:

  • Plastic zip-loc style bags
  • Paper towels
  • Pre-soaked bean seeds
  • Age-appropriate dissecting equipment, such as plastic knives, pins, or small kitchen knives
  1. Explain that the cotyledon supplies food to the growing embryo. Ask whether the students think an embryo can grow without the cotyledon. How would they test this?
  2. One way would be to seal an intact bean and an embryo that has been separated from the rest of a bean in a plastic bag with a wet paper towel. See if the bean embryo begins to grow without the cotyledon. The intact bean would be the control. If the intact bean doesn't germinate, then the conditions of the experiment were not suitable for growth.
  3. Another variable is whether dissection, or removal of the embryo from the bean, has harmed it. How would you test that idea? (Perhaps the children could add a third bean that has had its embryo removed and then put back on the cotyledon. Would the embryo grow in this case?)

Activity 3. Arabidopsis thaliana experiment - Introduction

At the beginning of this project, we learned about the thale-cress plant, Arabidopsis thaliana, which is the "lab rat" of the plant science world.

Recently we obtained some thale-cress seeds for a genetics experiment we will be carrying out over the next few months (more details later). If you would like to try this yourself, we obtained our seeds from the Arabidopsis Biological Resource Center at Ohio State University. Seeds are also available from Carolina Biological Supply (I am not affiliated with either of these businesses).

arbidopsis-seeds-in-vial-0335

The Arabidopsis thaliana seeds came in a tiny vial.

arbidopsis-seeds-with-rice-grainIt turns out that Arabidopsis thaliana seeds are incredibly small. Here are the seeds placed next to and on a rice grain. Because of their small size, I suspect they are going to be a challenge to grow.

Next week we are going to look at how seeds move around or seed dispersal. How do you think these teeny thale-cress seeds get from place to place?

 

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To see our complete plant science lessons, either visit the plant science category (newest posts to oldest posts) or the plant science section of our experiment archive page (links to posts in order).

For more information about plants and seeds, try our Seed of the Week archive or the mystery seed tag and Seed of the Week category.

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Nonie correctly identified last week's mystery seed pod as being from a mesquite.

We commonly call them screwbean mesquites because of the spiraling seed pod. The scientific name is Prosopis pubescens. These mesquites are small trees. They have lovely yellow flowers.

For more information and photographs, see The University of Arizona's Master Gardener page on Screwbean Mesquite