Understanding Flowering Plant Seed Composition

Flowering plants, also known as angiosperms, reproduce through seeds. A seed is essentially a package containing everything needed to grow a new plant under suitable conditions. Let's break down the key components that make up a seed.

Main Parts of a Seed

A typical seed of a flowering plant consists of three primary parts:

• The embryo
• Food reserves
• The seed coat

The Embryo

The embryo is the miniature, undeveloped plant housed within the seed. It is formed from the zygote after fertilization. The embryo has basic structures like:

• The radicle (which develops into the root)
• The plumule (which develops into the shoot - stem and leaves)
• One or two cotyledons (embryonic leaves)

Food Reserves

Seeds contain stored food that the embryo uses for growth during germination before it can photosynthesize. These food reserves are often stored in the cotyledons or in a specialized tissue called the endosperm. The type of food stored can include carbohydrates (like starch), proteins, and lipids (oils).

The Seed Coat

The seed coat is the protective outer layer of the seed. It develops from the integuments of the ovule. The seed coat protects the embryo and food reserves from mechanical damage, drying out (desiccation), and pathogens until conditions are right for germination.

Analyzing the Options

Let's look at why the other options are not the complete or correct answer regarding the composition of a seed:

• Ovary and ovary wall: The ovary develops into the fruit, and the ovary wall becomes the pericarp (fruit wall). The seeds are contained within the fruit, but the fruit itself is not the seed.
• Cotyledons: Cotyledons are indeed part of the embryo within the seed, often storing food. However, they are only one component of the embryo and not the entire composition of the seed. The seed also includes the rest of the embryo (radicle, plumule) and the seed coat.
• Zygotes: A zygote is a single diploid cell formed by the fusion of male and female gametes. The zygote develops into the embryo. While the embryo is a crucial part of the seed, the seed itself is a more complex structure containing the developed embryo, food reserves, and a protective coat.

Therefore, the most accurate description of what makes up the seeds of flowering plants is the embryo, food reserves, and the protective coat.

Revision Table: Seed Structure

Additional Information: Types of Seeds and Food Storage

Flowering plant seeds can differ based on how they store food:

• Endospermic Seeds: In these seeds (e.g., corn, wheat, rice), the endosperm remains prominent and stores the food. The cotyledons are usually thin and absorb food from the endosperm.
• Non-endospermic Seeds: In these seeds (e.g., beans, peas, peanuts), the endosperm is absorbed by the embryo during development. The food reserves are primarily stored in the fleshy cotyledons.

Seeds are vital structures for the dispersal and survival of flowering plants, ensuring the next generation can grow when conditions are favourable.