Embryo, Development, Monocots And Dicots Plants, Embryogenesis

Embryo: An embryo is a developed form of a zygote formed when male and female gametes fuse. The zygote divides and differentiates into an embryo. In plants, the embryo develops following syngamy, the fusion of pollen grains (male gametes) and egg cells (female gametes). The embryo forms in plants at the micropylar end of the female gametophyte, or embryo sac. Triple fusion leads to the formation of endosperm, which nourishes the developing embryo. The following article describes the development of embryos in monocots and dicots for the NEET Exam .

What is Embryo Development in Plants?

Embryo Development in Dicots

Flower – A Fascinating Organ of Angiosperms

Stages of Developement in Dicots

1. Two Cell Stage: After fertilisation, the zygote divides into a small apical and a large basal cell. These cells are different and give rise to different parts of the plant, establishing polarity in the embryo.
2. Eight Cell Stage: The embryo now consists of eight cells, with distinct domains contributing to different parts of the plant, such as the shoot apical meristem, cotyledons, hypocotyl, and root apical meristem.
3. Sixteen Cell Stage: Additional cell divisions occur, and the four domains become more defined. The protoderm, which forms the epidermis, is introduced during this stage.
4. Globular Stage: The embryo becomes spherical or globular in shape. The ground meristem and procambium, which form the ground tissue and vascular tissue respectively, are initiated during this stage.
5. Heart Stage: The cotyledons start to form and elongate, giving the embryo a heart-shaped appearance.
6. Pro Embryo Stage: The cotyledons continue to grow, and parts of the suspensor complex are terminated to make space for the mature embryo.
7. Maturation: The cells mature, and macromolecules required for germination and seedling growth are stored in the embryo.

Pre Fertilisation – Structures And Events

Embryo Development in Monocots

Sexual Reproduction in Flowering Plants MCQ

Pollen Grain

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Alternative Forms of Embryogenesis

Somatic Embryogenesis

• Somatic embryos are made from plant cells that do not normally develop into embryos.
• They do not have a seed coat or an endosperm.
• This method clones plants, removes viruses, performs genetic transformations, grows plants from single cells (protoplasts), and produces synthetic seeds.
• Plant tissue cells grow into a callus, a mass of undifferentiated cells.
• Plant growth regulators in the culture medium facilitate callus formation and, eventually, embryos.
• The quantity of plant growth regulators required varies according to plant type.
• Somatic embryo development requires asymmetrical cell division, and the failure to form a specific cell (suspensor cell) does not result in the death of the embryo.

Female Gametophyte

Androgenesis

• Androgenesis is when a mature plant embryo forms from an immature pollen grain.
• This usually happens under stressful conditions.
• The embryo develops from a single pollen grain that contains three cells.
• Androgenesis must occur during a specific type of microspore division.
• Androgenesis is impossible once the pollen grain's vegetative cells start producing starch and proteins.
• Androgenesis occurs in three stages: acquiring embryonic potential, initiating cell divisions, and pattern formation.
• After these phases, the rest of the process is like regular embryogenesis.

Pollination