Development of Embryo in Angiosperms

In angiosperms, the development of the embryo occurs within the ovule, which is located within the ovary of the flower. The process of embryo development in angiosperms involves several distinct stages, each leading to the formation of a fully developed embryo. Let's explore the different stages of embryo development in angiosperms:

1. Fertilization:
- Fertilization is the initial step in embryo development, which occurs following the pollination process.
- After successful pollination, the pollen grain germinates on the stigma and develops a pollen tube.
- The pollen tube then grows down through the style and reaches the ovary, where it enters the ovule.
- Once inside the ovule, the pollen tube releases two sperm cells.

2. Double Fertilization:
- Double fertilization is a unique characteristic of angiosperms, where two fertilization events occur simultaneously.
- One sperm cell fuses with the egg cell to form the zygote, which is the primary cell that develops into the embryo.
- The other sperm cell fuses with the polar nuclei to form the endosperm, which provides nourishment to the developing embryo.

3. Zygote Development:
- The zygote undergoes a series of mitotic divisions known as embryogenesis.
- These divisions give rise to a multicellular embryo, which goes through different stages of development.
- The first division of the zygote leads to the formation of a basal cell and a terminal cell.

4. Formation of Embryo Proper:
- The basal cell gives rise to the suspensor, a structure that anchors the embryo to the maternal tissues and provides nutrients.
- The terminal cell forms the embryo proper, which goes through several stages, including the globular, heart-shaped, torpedo-shaped, and mature embryo stages.
- During these stages, different tissues and organs of the embryo, such as the shoot apical meristem, root apical meristem, cotyledons, and embryonic leaves, develop.

5. Maturation of Embryo:
- As the embryo develops, it undergoes maturation processes, such as cell differentiation and tissue specialization.
- The cotyledons, which are the embryonic leaves, play a crucial role in nutrient storage and absorption.
- The embryo also develops protective structures, such as the seed coat, which surrounds and protects the developing embryo.

6. Seed Formation:
- After the embryo has reached maturity, it becomes surrounded by endosperm and seed coat, forming a seed.
- The seed is a dormant structure that allows the embryo to survive unfavorable conditions until germination.
- The endosperm provides nourishment to the developing embryo, and the seed coat protects the embryo from mechanical damage, desiccation, and pathogens.

In conclusion, the development of the embryo in angiosperms involves several stages, starting from fertilization and culminating in the formation of a mature seed. This process ensures the successful reproduction and dispersal of angiosperms.