Question

Give an account of post-fertilization changes in an angiospermic plant.

Hint:

Post-fertilization changes are essential for the formation of seeds, which are the primary means of reproduction in angiospermic plants. The development of the embryo, endosperm, and fruit ensures that the plant can successfully reproduce and spread.

Answer 1

In angiospermic (flowering) plants, post-fertilization refers to the changes that occur after the fertilization of the egg cell. The main processes that occur after fertilization include the development of the seed and fruit, as well as the formation of the embryo. Below are the key steps involved in post-fertilization changes:
1. Formation of the Zygote:
- During fertilization, the male gamete (sperm) fuses with the female gamete (egg cell) to form a zygote. This fertilized egg cell will later develop into the embryo within the seed.
2. Development of the Embryo: - The zygote undergoes a series of divisions and differentiations to form the embryo. The embryo consists of the following parts: -
Cotyledons: These are the seed leaves and are the first to appear in the developing embryo. They store nutrients and provide energy for the young seedling during germination. -
Radicle: The embryonic root that will later develop into the mature root system of the plant. -
Plumule: The embryonic shoot that will develop into the stem and leaves of the plant.
3. Formation of Endosperm:
- In addition to the zygote, the second male gamete fuses with the two polar nuclei present in the central cell of the ovule to form the triploid endosperm.
- The endosperm acts as a food reserve for the developing embryo and provides nourishment during seed germination.
4. Seed Coat Formation:
- The outer integuments of the ovule develop into the seed coat (testa). The seed coat protects the embryo and provides resistance to desiccation and mechanical damage.

5. Ovary Transforms into Fruit:
- After fertilization, the ovary of the flower matures into a fruit. The walls of the ovary thicken and develop into the fruit's pericarp (fruit wall). The fruit contains the seeds, and its role is to protect the seeds and aid in their dispersal.
- In some plants, the fruit is fleshy (e.g., apples, berries), while in others, it may be dry (e.g., legumes, nuts).

6. Formation of Seed:
- The fertilized ovule develops into a seed, which consists of the embryo, the endosperm, and the seed coat. The seed is the means of reproduction and dispersal in angiospermic plants.
- The seed contains stored food reserves (mainly in the endosperm or cotyledons) that are utilized during germination to nourish the developing plant.

7. Ripening of Fruit:
- After fertilization, the fruit continues to mature, a process known as ripening. This involves changes in the color, texture, and taste of the fruit, making it attractive for seed dispersal.
- In some plants, ripening involves the conversion of starches to sugars, which makes the fruit sweeter and more appealing to animals that will aid in seed dispersal.
8. Dispersal of Seeds:
- Once the fruit has ripened, the seeds are ready to be dispersed. Seed dispersal mechanisms include wind, water, animals, or mechanical forces. Successful seed dispersal ensures that the seeds can grow in new locations, away from the parent plant.
Conclusion:
Post-fertilization changes in angiospermic plants involve a series of steps that lead to the formation of seeds and fruits. The development of the embryo, endosperm, and seed coat, as well as the maturation of the ovary into a fruit, are crucial steps for the successful reproduction and dispersal of the plant.