Seeds are made inside a plant’s fruit. Within a seed, you will find everything necessary to grow a new plant of the same type that the seed came from. A seed remains in a plant’s fruit until it is mature, at which point it will be released from the fruit. Some seeds simply are released to the ground, while others are dispersed to new areas by way of wind, animals, or bugs. Because a seed is self-contained and protected by a covering called a seed coat, it can wait until conditions are ideal before it begins to grow. In order to grow, or germinate, a seed needs water, soil, and of course, sunlight.
You can see from the picture below that seeds have many parts. On most seeds, you can see a scar known as the hilum that shows where the seed was attached to the fruit of the plant it came from. The place where the pollen entered the seed is known as the micropyle. When a seed first starts to grow, things take place within the seed itself. The radicle forms a small root and the hypocotyl begins to grow into a stem. As the stem grows upward, the seed comes along with it, shedding the protective coat as it grows. The cotyledon provides food for the new plant as it grows. When the stem grows beyond the cotyledon, new leaves sprout and grow, eventually causing the cotyledon to drop from the plant. Eventually, the plant develops its own seeds, and the process begins again.
Experiment
Materials needed:
- Several pinto beans
- Jar with lid, ziplock bag, or tupperware container
- Paper towel or cloth
- Water
- First, examine your pinto beans and try to identify the hilum, micropyle, and seed coat.
- Next, put your beans in the jar, bag, or container and add the water. Soak the beans overnight in the refrigerator.
- Remove the beans from the jar and dry them. Carefully peel the seed coat off the outside of the bean. Then use your fingernails to split the beans open.
- See if you can identify the inside parts of the bean – the cotyledon, radicle, and hypocotyl.