Plant Science: What is a Seed?

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?

 

leaf-border

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.

Leave a Reply

Your email address will not be published. Required fields are marked *