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For today's lesson, we are going to backtrack a bit to define and investigate the functions of various plant parts. Let's learn more about roots, stems, leaves, flowers, and fruit.

In the book Seed to Seed: The Secret Life of Plants Nicholas Harberd talks about some of the early childhood experiences he had that influenced him to become a plant geneticist. For example, he remembered the teacher "forcing" horse chestnut tree branches in the classroom, causing the leaf buds to swell and unfurl into leaves. He also vividly recalled his father digging parsnips and his own realizations about plants having roots underground. Simple activities with plants like these can have lasting impacts.

Activity:  Edible Plant Parts.

Objective:
Discover what are the parts of a plant and how they relate to vegetables we eat. This can be done informally at home during the preparation of a salad, or more formally in a classroom.

Materials
•    Potted mint plant or other conveniently-sized herb or vegetable, with flowers if possible (optional)
•    Plastic bin or tray to catch soil from potted plant (optional)
•    Spinach and/or lettuce leaves
•    Broccoli and/or cauliflower
•    Celery
•    Radish and/or carrot (preferably with tops intact) - Avoid baby carrots
•    Green beans and/or peas

Have enough pieces so children may explore the vegetables and have enough left over to make a salad.

Procedures
1.  Explain plants have different parts/structures that do different jobs for the plant.
2.  Ask the children to identify the parts of the potted plant. Place the plant in the bin or tray and gently remove the pot to expose the roots.

plant-parts

3. Brainstorm about about what the function of each part might be.
a.     roots- take up water and nutrients, anchor the plant so it can stay upright
b.     stem- move water and nutrients from roots to leaves and flowers, support leaves so they are exposed to sunlight (What would happen if all the leaves were laying on the ground?)
c.    leaves - use the energy from sunlight to make food for the plant
d.    flowers- attract pollinators, make pollen, develop into fruit
e.    fruit - ripened part of flower (ovary) that holds the developing seeds
f.    seeds - contain the stored food and embryo that, given the proper conditions, could become a new plant.
4. Return the potted plant to its pot or plant it in a garden when the lesson is finished. Have the children was their hands.
5. Distribute the vegetables and have the children identify the parts of the plants that are represented.
•    Spinach and/or lettuce - leaves
•    Broccoli and/or cauliflower -stem and flower bud
•    Celery - stem and possibly leaves
•    Radish and/or carrot (preferably with tops intact) - roots, those with tops will have stems and leaves as well
•    Green beans, peppers, and/or peas - technically fruit with seeds inside. Open the pods to see the seeds inside.
6. If appropriate, wash the vegetables and make a salad for everyone to share.

Extension:  Challenge older students with some vegetables that are more difficult to classify.
•    Onion (bulb )- each layer of in an onion bulb is a fleshy leaf base, attached to a short stem. Often the roots are visible on the bottom, too.
•    Potato - because it grows underground, children may guess a potato is a root, but botanically it is a modified stem.
•    Sweet potato - on the other hand, the sweet potato is a tuberous root.
To help explain the difference between the sweet potato and regular potato, ask the children to think about where a new plant would sprout. The sweet potato will only sprout from the top, where the stem was attached. The potato will develop sprouts wherever there are “eyes.” The eyes are buds on a stem.

carrot-top


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Plant-Science-Lessons

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).

Looking for books about plants for children? Be sure to visit our growing list of gardening and plant science books for kids, as well as our list of children’s books about seeds.

For more activities, try our Gardening/Plant Science for Kids Pinterest board.

Plant-Science-Lessons

Today we are going back to visit the book Seed to Seed: The Secret Life of Plants by Nicholas Harberd for more insights.

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The author, Nicholas Harberd, has run into a bit of a roadblock in his research. When he asks his son what he is doing at school, his son tells him he is growing beans in a jam jar, a classic elementary school activity. There's an "Eureka!" moment as Dr. Harberd realizes the importance of these early experiences.

Sprouting bean seeds in preschool or kindergarten is a seemingly universal activity.  Just because it is very common, however, does not mean it has less value. Germinating bean seeds is a significant early introduction to how plants work.

Seed Germination

As you can see from this time lapse video of a mung bean germinating, the process unfolds in a defined sequence.

First, the seed coat begins to wrinkle and the seed swells as water is taken up. If you keep an eye on the center bean, you can see the tiny white radicle begin to emerge first. If you look closely at about 1:00 minute, you will see the end of the radicle, which is still white, starts to produce fine threads. Those are root hairs. At the same time, the part closer to the seed is also elongating and beginning to green up a bit. That is the hypocotyl, which is what supports the cotyledons as they rise about the surface. As the hypocotyl continues to elongate, the cotyledons begin to emerge from the seed coat. By 2:00 minutes, the cotyledons are beginning to open and the first leaves or plumules are beginning to show. The stem-like structure that will eventually arise between the cotyledons and the plumules is called the epicotyl.

Brittannica Kids has a good graphic showing the bean germination process.

Activity 1. Sprouting Bean Seeds (Observing and Experimenting)

This activity can be done any number of ways. I will give instructions for one way and links to other sites with good instructions.

Gather:

  • Dry bean seeds, especially big types like lima beans, available in the grocery store in the dried food area. Dry bean soup mix is another fun source of different types of beans, and some contain barley or other grains.
  • Paper towels
  • Water
  • Plastic sandwich bag or paper plate covered with plastic wrap
Bean Soup Mix
Bean soup mix is fun to sprout.

Procedure:

Wash hands before starting to cut down the chances of mold.
1. Wet two or three paper towels until damp, not dripping wet. Lay the towels flat.

2. Place enough beans for all the children on half of the towel. Fold the top over, creating a sandwich with the beans inside.

3. Slip the paper towels into a plastic bag and close, or onto a paper plate and cover with plastic wrap. The plastic will help prevent the towels from drying out too quickly.

4. Check the beans every day to see how the beans germinate. Depending on the temperature, the beans should start to swell and a root start to form as early as 24 to 48 hours later.

Add enough water to keep them damp if the towels begin to dry out.

bean-soup-mix-sprouting5. Have the children draw the beans each day and measure how much each part has grown, if possible. Record the results.

6. Allow the children to experiment with the seeds. They might want to remove portions of the plant or seed or change the growing conditions (moisture, light, add soil) to see what happens.

Extension: Compare seeds with two cotyledons with seeds from plants like barley, corn or wheat, which have only one. See What is a Seed for dissection instructions.

Related links (some sites have ads):

Activity 2: Germination Test for Older Kids

Ever have a pile of leftover seed packets tucked away in a cupboard somewhere? You know, the ones with the “Packed for 2009” stamped on them?

seed-packets

 

If you are not sure whether the seed is still viable or whether planting it would be a waste of time, there’s an easy test to find out. It is called a germination test.

Pull out your old seed packets. Note: check the packages carefully to see if the seeds are treated with pesticides, such as fungicides or insecticides. Avoid handling pesticide-treated seeds.

For each packet you and/or your children want to test, gather the following:

  • Paper towels
  • Either paper plates and plastic wrap /or zip-loc style plastic bags
  • Water

Wash your hands prior to starting and try to keep everything as clean as possible.

1. Prepare a separate damp paper towel for each different seed packet.

2. Select 10 seeds from each packet you want to test. For example, you might have 10 marigold seeds and 10 corn seeds.

3. Lay the 10 marigold seeds on a damp paper towel and fold it over. Then either lay the towel on a paper plate and cover with plastic wrap, or slip the damp paper towel into a zip-loc bag. Repeat for the 10 corn seeds or whatever kinds of seeds are in the rest of the packets.

germination test

3. Come back in 24 hours and 48 hours and look for the tiny root (radicle) poking out of the seed, a sign that it is germinating.  Count how many seeds germinate and how many do not. Certain seeds, like carrots, take a long time to germinate (up to 2 weeks), so keep them moist and don't give up on them right away. If no seeds germinate after two weeks, then perhaps it is time to invest in a new batch of seeds.

You can calculate the percent germination by dividing the number that germinated by the number you set up. For example if 9 seeds germinated out of 10, then your percent germination = 90%. If only 5 germinated out of 10, then the percent germination is 50%.

 

Do you have any questions or seed germination activities to suggest? Feel free to leave us a comment.
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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 activities, try our Gardening/Plant Science for Kids Pinterest board.

Our mystery seeds from last week are from a cucumber, Cucumis sativus.

Cucumbers grow on a vine.

They have separate male and female flowers on the same plant. In order to produce fruit, either an insect pollinator or a human must move the pollen from the male flower to the female flower.

You may not have recognized the seeds from what you have observed when you cut open a fruit to eat. That is because we eat the fruit before it is fully ripe and the seeds are not yet mature.

Here the seeds are soft and not fully filled.

cucumber-seeds

The mature seed has a hard seed coat.

If you are interested in saving seeds, you should leave the last of the season cucumbers on the vine to ripen fully. Often the fruit will yellow as it becomes fully ripe. Apparently cucumber seeds also benefit from a period of fermentation, like tomato seeds do. It has to do with the gel covering inhibiting germination.

Although not the best quality, this video explains how to do it (there is a pop-up ad):

Cucumbers are interesting plants. Scientists have found that cucumber plants produce chemicals from their roots (while they are fruiting) that inhibit the growth of other nearby plants. This has implications for people trying to grow plants hydroponically, as the chemicals enter the water.

References:

Jing Quan Yu and Yoshihisa Matsui. (1994.) Phytotoxic substances in root exudates of cucumber (Cucumis sativus L.) Journal of Chemical Ecology. Volume 20, Number 1 (1994), pages 21-31.