Seeds and Seedlings

INTRODUCTION

Reproduction is part of the life cycle of all living things. Many plants produce offspring by making seeds that can grow into adult plants. Seeds come in all different shapes, colors and sizes, but they all have a few common characteristics. Let’s investigate seeds, their parts, and how they grow into plants.

MATERIALS

• Variety of seeds (to show diversity)
• Raw peanuts
• Beans (soaked in water overnight)
• Popcorn kernels (soaked in water overnight)
• Several glass jars with corn plants at different stages of development
• Seedlings for all students to plant
• Potting soil
• Containers for seedlings

WHAT TO DO

1. First look at a variety of seeds. Ask students what these seeds all have in common.
2. Pass out one peanut, one bean, and one popcorn kernel to each student.
3. Ask all students to look at their peanut and find the line that divides it into two halves. Gently push the two halves apart so the inside of the peanut can be examined. Help the students all find the embryo and explain the function of the two cotyledons.
4. Examine the bean in the same way as the peanut.
5. Carefully peel the outer covering from the popcorn kernel. The tiny embryo of the plant is visible near the base of the seed.
6. Point out that the popcorn kernel is a monocot seed and the peanut and beans are dicot seeds. Explain the difference between a monocot and a dicot.
7. Ask students to compare and contrast the seeds they have examined. What do all seeds need?
8. To grow seeds need: water, light and warmth. Examine lima beans or corn seedlings in various stages of growth to help explain how seeds grow into plants.
9. Let each student plant a seed or a seedling. Ask students what care the seed(ling)s need in order to become plants. Help define exactly what they need, then leave the young plants with them for the students to care for and observe.
10. Possible extension: As a class decide upon a variable to test, such as effect of light on plant growth, effect of fertilizer on plant growth, etc. and devise an experiment using the seedlings.

QUESTIONS

1. What is the difference between a monocot and a dicot?
2. What do all seeds have inside? What are the parts of a seed?
3. What do seeds need to grow?
4. What are some experiments you could do with your seedlings?

SUMMARY

Monocot and dicot are shortened terms for monocotyledon and dicotyledon. The cotyledon is the embryo leaf or "seed leaf" that stores food to feed the baby plant before it can photosynthesize. Flowering plants have either one seed leaf, monocot, or two seed leaves, dicot. Corn is a monocot and inspection of the seed reveals that it does not naturally split in half (although you can cut it in half). The peanut and the bean will split in half, especially if soaked in water first so they are not hard and dried.
Looking at the outside of the seed, especially the bean, you will observe a small scar. Similar to a belly button, this is where the seed was attached to the fruit. The seed coat will often easily come off of soaked sees, especially beans and peas. Inside the seed is the embryo, the baby plant.
Plants need water, soil, air and light to grow. Some seeds can be covered under the soil a little bit and some need to have light to germinate (lettuce of example). All seeds need water to grow. Most plants need soil, but some will sprout in a puddle or on a piece of filter paper, but these will eventually need soil and the nutrients it provides to keep growing. Carbon dioxide in the air is very important in plant growth because it is an ingredient plants use to make their food.

SOURCE

Leonard, Joan. Greenhouse Director. Department of Plant Biology, The Ohio State University.

© S. Olesik, WOW Project, Ohio State University, 2003.