Lesson 56: Seeds and Germination
This lesson opens a bean seed to find the embryo, stored food, and seed coat, and introduces dormancy. Germination begins when conditions allow a seed to resume growth. Sprouting beans show water uptake, the emergence of roots and shoots, and the roles of water, oxygen, and temperature.
Key Ideas
- A seed holds an embryo, which is a tiny plant, along with stored food and a protective coat. In beans, the food is mainly in two seed leaves called cotyledons.
- A dormant seed is alive but not ready to sprout. Dormancy helps some seeds wait until the right conditions arrive.
- Most seeds need water, oxygen, and a suitable temperature to sprout. Some also need conditions that end dormancy.
- A dry seed absorbs water and swells. Swelling alone does not mean the seed will begin to grow.
- In a sprouting bean, the first root usually comes out before the shoot and becomes the main root. Stored food in the seed leaves supports early growth.
Vocabulary
- Germination: When a seed’s tiny plant begins growing again and starts to sprout.
- Radicle: The first young root inside a seed.
- Cotyledon: A seed leaf. It can store food or take in food stored elsewhere in the seed.
- Imbibition: A dry seed taking in water and swelling.
- Embryo: A tiny plant already formed inside a seed.
- Dormancy: A waiting stage in which a living seed does not start growing yet.
Discussion Questions
- A farmer plants seeds too deep in the soil. What might go wrong, using what you know about the shoot pushing toward light?
- Overwatered seeds often rot instead of germinating. Using the oxygen requirement, explain why.
- Some seeds need a cold winter before they will germinate, even with plenty of water. Why might a plant evolve that requirement?
Supplies
- Large dry beans, a bowl of water, and a few beans left dry for comparison
- A few large beans soaked overnight, a paper towel, water, a clear sandwich bag, and tape