Why are so many stages involved in germination?
Answers
How Do Plants Reproduce?
I don't know about you, but I love fruit! Sweet, delicious fruit, though, is actually ripened plant ovaries, or female reproductive organs. The seeds inside the fruits are designed to spread throughout the environment and grow into new plants in a process called seed germination. So if you're a fan of ripened plant ovaries, too, check out this lesson to learn how they grow from tasty snacks into full grown plants.
Seed Formation
Plants reproduce using eggs and sperm, just like people. However, they don't have physical sex! Male plants release pollen, which fertilize ovaries. The fertilized ovaries develop into seeds, which can then be distributed to make new plants. As the fertilized ovaries develop, a surplus of carbohydrates and proteins are stored inside the seed. This will serve as food for the plant until it can develop leaves. Next, the fertilized plant ovaries develop the hardened coat we see as the outside of seeds to protect them against harsh environmental conditions. The seeds then can be carried away by wind or animals to create new plants.
Seed Germination
After the seed has made it to a new location and is covered with dirt, it can begin germination. Germination is the process of seeds developing into new plants. First, environmental conditions must trigger the seed to grow. Usually, this is determined by how deep the seed is planted, water availability, and temperature. When water is plentiful, the seed fills with water in a process called imbibition. The water activates special proteins, called enzymes, that begin the process of seed growth. First the seed grows a root to access water underground. Next, the shoots, or growth above ground, begin to appear. The seed sends a shoot towards the surface, where it will grow leaves to harvest energy from the sun. The leaves continue to grow towards the light source in a process called photomorphogenesis.
Influencing Factors
Several factors influence if, and how, seeds germinate. The most important factors are water availability, temperature and sunlight. Water is crucial to seed germination. The seed must go through imbibition to activate root growth. However, too much water can be a bad thing, as most gardeners know. When a plant is still growing underground, during root formation, it cannot use the sun to make food like most grown plants do. It must rely on the stored food inside the seed, and oxygen from the environment to make energy. If the soil is too soggy, there will not be enough oxygen and the plant will not thrive. Think about a person being kept underwater. We wouldn't last too long!
Temperature is also an important factor. Some seeds germinate when it is cold, such as plants in northern environments. Other seeds only germinate when the weather reaches spring temperatures, which is why we see so much plant growth in the spring in temperate climates. Other seeds only germinate after extreme temperatures, such as after a fire in the grasslands.