Conclusion on seed germination, phases of germination and types of germination
Seed germination is the process by which a seed develops into a new plant. It begins when a viable seed, which has the potential to grow into a plant, comes into contact with favorable conditions such as moisture, proper temperature, and oxygen. Over time, the seed absorbs water, initiates metabolic activities, and eventually undergoes germination.
The phases of seed germination can be categorized into three main stages: dormancy, activation, and growth.
1. Dormancy: Many seeds go through a period of dormancy before they can germinate. During this phase, the seed is in a dormant state and remains metabolically inactive. Dormancy allows the seed to withstand unfavorable conditions, such as extreme temperatures or lack of water, until conditions become suitable for germination.
2. Activation: Activation is the stage where the seed breaks dormancy and prepares for germination. It typically occurs when the seed is exposed to favorable environmental conditions, such as sufficient moisture and temperature. At this point, biochemical changes occur within the seed, including the breakdown of stored nutrients and the synthesis of growth-promoting substances.
3. Growth: Once activated, the seed enters the growth phase. The embryo inside the seed starts to enlarge, and root and shoot structures begin to emerge. The radicle, which will develop into the primary root, emerges first, followed by the emergence of the shoot or plumule. This process may involve the extension of roots into the soil for nutrient and water uptake, while the shoot system grows above the ground to carry out photosynthesis.
Regarding types of germination, there are three common types:
1. Epigeal Germination: In this type of germination, the cotyledons (seed leaves) are brought above the soil surface, exposing them to light for photosynthesis. The hypocotyl (region between radicle and cotyledons) elongates, lifting the cotyledons and the tiny stem above the ground. Examples of plants exhibiting epigeal germination include beans, peas, and sunflowers.
2. Hypogeal Germination: Hypogeal germination is the opposite of epigeal germination. Here, the cotyledons remain below the ground, and only the plumule emerges and grows above the soil surface. The hypocotyl elongates, pushing the plumule upward. Plants like maize, wheat, and rice show hypogeal germination.
3. Vivipary: Vivipary occurs when the seed germinates while still attached to the parent plant, resulting in the embryo growing directly into a new plant. This is observed in certain plant species, such as mangroves and some aquatic plants, where seeds germinate while still on the tree or in water.
To summarize, seed germination involves the stages of dormancy, activation, and growth. The types of germination include epigeal germination (cotyledons above the ground), hypogeal germination (cotyledons below the ground), and vivipary (germination while attached to the parent plant).