Parts of a seed
After fertilization inside the ovary of a flower, the fertilized egg cell divides many times to form the embryo. The plant embryo forms a hard wall around itself and is then known as a seed.
Although seeds may differ in size, shape, and color, they have common parts. These are the seed coat, the embryo, and the food supply. The seed coat is tough and waterproof. It covers and protects the embryo and the food supply. The embryo is the baby plant. A part of the embryo, the radicle, grows into the primary root. As mentioned above, the seed has its food supply, the endosperm. The cotyledon, or seed leaf, absorbs the food in the endosperm and transports it to the embryo.
A bean seed has two cotyledons. Each half of the seed is a cotyledon. These cotyledons absorb all the food supply. A corn seed has only one cotyledon. Seeds with two cotyledons are called dicotyledons or dicots, while those with one cotyledon are called monocotyledons or monocots.
Simple seed facts and germination process
Did you know that some fruits are mistaken for seeds because they are dry? Dry fruits have a seed enclosed in a thin, hard layer formed from the ovary. Examples of dry fruits are rice and corn.
When you plant a seed and the conditions are favorable, it will begin to grow or germinate. But how does a seed germinate? To germinate, a seed needs three things, water, oxygen, and the right temperature. When a seed gets wet, it absorbs the water. Then it starts to germinate. Germination is the sprouting of a seed. When a seed sprouts the embryo grows into a new plant.
Soak any kind of bean seeds in water. Observe the changes that happen to the seeds as they begin to sprout. First, the seeds swell or become large as water enters them. The seed coat softens and then breaks. Soon a tiny root (the radicle) appears from the seed and grows downward. A shoot, which will become the stem, also appears and grows upward. Later, the first leaves appear on the stem and the seed coat drops off. As the stem grows upward, more and more leaves appear, while the cotyledons become smaller. The germinating seed needs food. It uses the food stored in the cotyledons as it grows. Later, the cotyledons (which, by then, have shrunk to a much smaller size) will drop off. By this time, the leaves of the growing plant can already make food. The plant will use this food as it continues to grow.
Did you know that scientists found lotus seeds stored for ten thousand years could still germinate under favorable conditions?