germination of seed. list down and explain phases of germination and types of germination ( epigeal and hypogeal ).
Phases of Germination:
1. Imbibition: This is the initial phase where the dry seed absorbs water, triggering biochemical changes. The absorption of water causes the seed to swell and activate enzymes that initiate metabolic activity.
2. Activation: Once the seed has imbibed water, it enters the activation phase. During this phase, enzymes become active, and molecular changes occur, leading to the breakdown of stored nutrients within the seed.
3. Digestion: In this phase, the stored nutrients, such as carbohydrates, proteins, and lipids, are broken down by enzymes into simpler forms that can be utilized by the growing embryo.
4. Radicle and Plumule Emergence: The radicle is the embryonic root, and the plumule is the embryonic shoot. During this phase, the radicle emerges first and grows downwards, anchoring the developing plant, while the plumule emerges and grows upwards, eventually forming the primary leaves.
5. Growth: Once the radicle and plumule have emerged, the plant begins to grow rapidly. The roots extend further into the soil for water and nutrients, and the shoot grows towards the sunlight for photosynthesis.
Types of Germination:
1. Epigeal Germination: In epigeal germination, the cotyledons (seed leaves) are carried above the ground level. As the shoot emerges, the cotyledons are pulled out of the seed coat and become green. Examples of epigeal germination include beans and mustard.
2. Hypogeal Germination: In hypogeal germination, the cotyledons remain below the ground level. The cotyledons stay inside the seed while the shoot elongates and pushes the seed coat upward. The cotyledons usually do not become green and are utilized for nutrient storage. Examples of hypogeal germination include peas and peanuts.
Both types of germination are adaptations to different environmental conditions. Epigeal germination allows the cotyledons to utilize sunlight for photosynthesis, while hypogeal germination provides protection to the sensitive cotyledons underground.