Seed Germination: How Seeds Grow
What is seed germination?
What is a seed?
Structure of a seed
A seed consists of three components: the embryo, the endosperm, and the seed coat.
Radicle: The radicle is the embryonic root that grows and develops the root system of the plant.
Plumule: The plumule is the embryonic shoot that gives rise to the shoot system of the plant.
Endosperm: The endosperm contains the nutrients stored in it. It provides nutrients to the seed for germination.
Seed Coat: The seed coat is a tough outer layer that protects a seed.
Steps of seed germination
Step 1. Seeds absorb water from the ground, which makes them swell and soften. At this stage, the enzymes and nutrients within the endosperm become hydrated. The first step of seed germination is called imbibition.
Step 2. The seed coat splits.
Step 3. A first root grows (called “the radicle”) downward and begins to absorb water and minerals from the soil through the tiny root hairs. Additionally, the roots support the plant and prevent wind or animals from completely tearing it apart.
Step 4. The first shoot breaks through the soil and starts growing upward. The seed leaves supply the seedling with food.
Step 5. As the plant continues to grow, it needs plenty of light, water, air, and nutrients to make its own food through photosynthesis.
Once the process of photosynthesis begins, the cotyledon falls off and becomes part of the soil.
When a seedling emerges into the light, the plant starts to change, such as turning green and producing leaves. This light-dependent development is called photomorphogenesis.
We should not confuse photomorphogenesis with photosynthesis. Photosynthesis is the process of producing energy using sunlight, whereas photomorphogenesis is the transformation of a plant, which is based on a reaction to the light spectrum.
What is seed dormancy?
Factors affecting seed germination
Following are a few environmental factors that affect seed germination:
Water: Sufficient water is extremely necessary for seed germination. Seeds use water to activate enzymes within them. The absorption of water by the seeds is called imbibition, which causes swelling and ruptures the seed coat.
Oxygen: Plants need oxygen for their cells to respire and generate energy for seed development. When there is a lack of oxygen in the soil, it can hinder the germination process.
Light or darkness: Light plays a role as a signal for germination. Some seeds need light to sprout, while others can do so in darkness.
Temperature: The rate of growth and metabolism depends on temperature. Each type of seed has its own temperature requirement for successful germination.