Seed Bearing Plants & Trees

Classification

• Plants and trees are classified by the number of cotyledons, or seed leaves, that are within the seed. Plants with single leaves, such as grasses, are called monocots. Monocots contain only one seed leaf. Plants with two seed leaves are referred to as dicots.

Seed Structure

• Seeds from seed-bearing plants and trees have an outer layer known as a seed coat. The seed coat protects the embryo within the seed from drying out and from damage. Seed coats vary depending on the species of plant. For instance, coconut seeds have extremely hard and durable seed coats. Most beans have soft seed coats. Beneath the seed coat is a store of food for the embryo called endosperm. This food supply surrounds the embryo in the form of the cotyledons, or seed leaves.

Seed Germination

• Germination is the process in which the plant embryo begins to emerge from the seed and grow into an adult plant or tree. Seeds are dormant until conditions are right to begin growing. All seeds need water, oxygen, sunlight and the right temperature to begin germination. During germination, a radicle, or embryo root, is the first part of the plant to emerge from the seed. The shoot, or plumule, emerges next and contains the stem and leaves of the plant.

Fruit

• Some types of trees and plants produce fruits that are ripened plant ovaries containing seeds. Fruits develop on flowering plants and trees after a flower is pollinated. The flower is fertilized, then its petals fall off and its ovule swells. This is the fruit.