Saturday, June 22, 2024

Seed structure and functions of seed: knowledge hub

The structure in plants that contains the embryo, stored food, and protective coverings. It develops from the ovary of a flower after fertilization and is capable of giving rise to a new plant. Seeds are an essential part of the life cycle of plants and are used by many species as a means of reproduction and dispersal.


Here's a simple diagram showing the main parts of a seed:

```

  +---------------+

  | Seed Coat | 

  +---------------+

  | Embryo |

  | (Baby Plant) |

  +---------------+

  | Endosperm | 

  | (Food Storage)|

  +---------------+

Knowledge of the seed
Knowledge of seed

Anatomy of a Seed

Seeds are the basic units of reproduction in flowering plants. Each seed contains all the essential structures needed to grow into a new plant. The anatomy of a seed can be divided into three main parts: seed coat, embryo, and endosperm.


1. Seed Coat

The seed coat is the outer protective covering of the seed. It develops from the integuments of the ovule and usually consists of two layers:

  • Testa (outer layer): Thick, hard, and protective.
  • Tegmen (inner layer): Thin, delicate, and lies just below the testa.

Functions:

  • Protects the seed from mechanical damage, infections, and drying.
  • Helps maintain dormancy until favorable conditions for germination.

2. Embryo

The embryo is the young plant inside the seed. It is the most important part since it develops into a new plant after germination. The embryo has three main parts:

  • Radicle: The first part of the embryo to emerge; it grows downward to form the primary root.
  • Plumule: The shoot part of the embryo; it grows upward to form the stem and leaves.
  • Cotyledons (seed leaves): These are food-storing structures that nourish the growing embryo. In dicot seeds (like beans), there are two cotyledons; in monocot seeds (like maize), there is one.

Functions:

  • Radicle → root formation.
  • Plumule → shoot and leaves.
  • Cotyledons → food storage and supply to embryo.

3. Endosperm

The endosperm is a tissue that stores food for the developing embryo. It is rich in starch, proteins, and oils. Some seeds (e.g., maize, wheat) have a large endosperm, while others (e.g., beans) consume the endosperm during development and store food in cotyledons instead.

Functions:

  • Provides nutrients during germination.
  • Ensures the embryo has enough energy to grow before photosynthesis begins.

Special Features of a Seed

  • Micropyle: A small pore in the seed coat that allows water and gases to enter during germination.
  • Hilum: A scar on the seed coat showing where it was attached to the fruit wall.

Conclusion

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Seed as the Result of Fertilization

Seeds are the outcome of fertilization in flowering plants. Fertilization is the process where the male and female gametes unite to form a new life. In plants, the male gamete is carried by pollen grains, while the female gamete is present inside the ovule.

When pollen reaches the stigma of a flower, it grows a pollen tube that carries the male gamete to the ovule. Here, the male gamete fuses with the female gamete (egg cell). This union is called fertilization, and it produces a zygote. The zygote is the first cell of the new plant.

                      

Seed structure
Seed structure

After fertilization, the ovule develops into a seed. The zygote grows into an embryo, which is the baby plant inside the seed. The surrounding tissues provide food, while the seed coat protects it until conditions are right for germination.

Seeds are very important because they allow plants to reproduce and spread to new places. They ensure the survival of plant species and provide food for humans and animals.


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