Germination
Understanding how seeds germinate

  Materials: dry lima beans or garden bean seeds, egg carton (one per group), potting soil, rulers, and copies of Germination Record

Activity One

 Having soaked your dry lima bean overnight or at least two hours in warm water - Take a close look at your bean seed. It is wearing a coat. When it is soaked in water, the coat comes off. Gently rub the coat off between our fingers. the seed coat is protection for the embryo seed or baby plant. The seed coat may be thin like this bean seed or very thick like a coconut. Draw the seed coat on the bean seed picture. Draw a line to the seed coat and label it.

Feel the seed between your thumb and pointer finger. Find the line that divides the seed into two parts. Use your fingernail and gently break the seed into two parts. What do you see?

The two large parts are called the cotyledons (pronounced cot-i-LEE-dunz). they are sometimes called the "seed leaves" because they are the first "leaves" to emerge from the soil. Some plants such as corn only have one cotyledon, while plants such as beans have two. The cotyledons are the stored food for the young plant until it starts making its own food. Draw a line to the cotyledon on your drawing and label it.

On the inside curve of the bean seed you will see a tiny plant called the embryo. The embryo has a root, stem, and leaves. Draw the embryo on your seed picture and label the root, stem, and leaves.

When water is present, the seed coat will soften and water will soak into the cotyledons. The embryo soaks up some of the water and starts to grow. The root is the first part of the embryo to grow. It stretches out and pushes its way through the seed coat. The stem and leaves of the embryo then push out of the seed coat and grow up. The cotyledons on some plants such as beans grow above the soil. They stay in the soil on other plants such as corn. .

We are learning about germination or how a seed begins to grow. The seed is a time capsule that opens as soon as the conditions are right. For some seeds, this can be as soon as there is moisture present. Some tree seeds and tulip  and daffodil bulbs need a few months of cold temperatures before they will sprout and grow. This prevents a seed from sprouting in the fall and the new, young plant from being killed by freezing temperatures.

Seeds of some plants need to pass through the body (digestive system) of a bird or animal before they will germinate. The acid in the stomach of the animals softens the seed coat, protecting the embryo. Once the seed passes through the animal, it is able to take up the moisture and sprout.

Some seeds live a very long time, waiting for the right conditions before they start to grow. Seeds might be considered the "resting stage" of a plant. Seeds for a lily-like flower called a lotus have been known to germinate or sprout more than 200 years after they fell from the plant. Seeds of beans and squash have been found in ancient ruins that are more then 500 years old. They were kept cool and dry in the ruins all that time. When planted and watered, they grew!

1. What would happen to the seed if it were given enough water to start growing, then it dried out?
2. Would a seed germinate if it were soaking in a glass full of water? Why or why not?
3. If a seed has a very hard seed coat, how can you make that seed germinate faster?
4. Why do you think the root is the first thing to grow when the seed germinates?
5. Why is it helpful to know how long it takes for a seed to germinate?
6. How do scientists conduct germination tests?

Activity Two

In your groups, using the egg carton and 12 bean seeds, fill the cells of the egg carton with potting soil and plant one bean seed 1cm deep in each cell. with a pencil, marker, or pen number the cells on the lid beside the cell from 1 to 12, or A1 to A6 and B1 to B6. Water the soil well and set the egg carton in a location that receives bright light (GrowLab or window sill). Pictures

Document the growth of your bean seeds on the Bean Seed Growth Chart.

Two days after planting, dig up the seeds in two cells. Record what you see on the Bean Seed Growth Chart. Keep the soil moist, but not soggy, at all times.

Four days after planting, dig up the seeds in two more cells. Record what you see on the Bean Seed Growth Chart. Repeat every two or three days until all of the seeds have been dug up.

1. What was the first part of the young plant to break out of the seed coat?
2. How many days did it take before you saw the seedlings above the ground?
3. What grew faster and longer on the young seedling, the stem or the roots?
4. Were the cotyledons above or below the soil after the young plant came out of the soil?

Extension Activity

Using 3 different untreated seeds, put 10 seeds from one variety on a damp, sturdy paper towel. Roll up the towel and place it in a clear plastic bag. Tape the name of the variety and the number of seeds on the top of the bag. Repeat for the other varieties. Set the bags in a location that receives indirect light. After 5 days, check the seeds.

Which variety germinated the best? That is one of the criteria farmers look at when they select which variety to plant.