How does a seed germinate? If a seed is viable and does not present damage or evidence of poor development, then it can respond favorably to various environmental factors that will begin the germination process.
Imbibition
At the first stage of seed germination, imbibition corresponds to the absorption of water. In doing so, the seed (which was previously dry) grows due to rehydration. This growth, or swelling, results in the rupturing of the protective coat surrounding the embryo. Effectively, the coat becomes ruptured, and this allows for the radicle to emerge as the primary root of the new plant. This is necessary so the growth of the new plant can begin.
Respiration
The rehydration process made possible via imbibition results in the plant resuming metabolic activity, which at that stage was still anaerobic since the energy was not provided by oxygen, but primarily by glycolysis. Once oxygen is able to enter the seed, reparation becomes aerobic. Some plants can even absorb the oxygen molecules from the water in the initial steps, thus not having to perform anaerobic respiration. Once the radicle emerges from the germinated seed, it does so in order to get access to oxygen above the soil. It is possible to facilitate this stage of germination via ploughing, since doing so may remove the soil just enough for the radicle to breathe.
Cell-Division of Seeds
The final stage of germination corresponds to the division of cells within the seed, and this is due to the seed becoming metabolically active. Due to the aerobic respiration processes, the new plant now has access to energy that may be used for the purpose of cell division. After this, the cells within the embryo become larger and go on to divide further, slowly becoming the seedling.
To unlock this lesson you must be a Study.com Member.
Create your account
There are a few conditions that are necessary in order to germinate a seed, and they are essential to the process of how a seed grows into a seedling and then into an adult plant.
- Water: Water is necessary for the first process to initiate. This is because seeds are very dry and require a lot of water in order to initiate imbibition, in addition to providing some energy via aerobic respiration.
- Oxygen: If the plant is unable to take in oxygen from the water molecules initially, it must be exposed to oxygen at some point after imbibition. Aerobic respiration is essential for the seed to grow into a seedling since oxygen is required for the production of energy, which is necessary for the entire process.
- Light: While some seeds could grow in the dark, most require sunlight as the major trigger.
- Temperature: Seeds are diverse in their temperature requirements, however, most tend to require room temperature in order to germinate (25-30°C; 77-86°F).
To unlock this lesson you must be a Study.com Member.
Create your account
There are several internal and external factors that may aid or halt the germination of a seed.
Internal factors
Seed dormancy occurs when the seed is unable to germinate, even in the presence of all the necessary conditions. In this case, the seed coat may be too resistant to water, the seeds may be immature, or the seeds may require a lot more time in general.
External Factors
Like the necessary conditions for germination, the process may be affected by factors corresponding to the availability of water, the temperature, and the level of oxygen. Temperature is especially important since, in some cases, a lower temperature may promote the growth of fungi.
To unlock this lesson you must be a Study.com Member.
Create your account
Germination is the process whereby a seed or spore grows into a plant according to several key steps and due to several important conditions. A seed is simply the fertilized ovum of a plant, which occurs when pollen meets an ovary in plants. After sprouting, the process of germination involves the following steps:
- Imbibition: This occurs when water hydrates the seed, and in doing so it swells and breaks the outer protective coat.
- Respiration: After puncturing the coat, the radicle is exposed to oxygen and can begin the process of growth.
- Cell Division: Due to the exposure to oxygen, metabolic activity resumes and the radicle grows into a seedling.
The conditions for germination include appropriate water, oxygen, light, and temperature levels. Factors may also affect seed germination, and internal factors correspond to seed dormancy which may occur due to the following reasons:
- The seed coat is too resistant to water
- Seeds are too immature
- Seeds require a lot more time
External factors are similar to the favorable conditions in that irregular levels of water, sunlight, oxygen, and temperature may perturb or facilitate the process. In fact, lower temperatures have been shown to facilitate the formation of fungi instead of plants.
To unlock this lesson you must be a Study.com Member.
Create your account
Video Transcript
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.
 |
Sunlight is also needed to stimulate plant growth. Plants go through phototropism, or movement depending on light. The shoots of the plant grow towards light. This is why when germinating seeds indoors for a garden, an overhead lamp is necessary to keep the shoots growing straight. Otherwise, the shoots tend to turn towards the windows where the sun is.
Some Examples
Seeds are formed and germinate as a natural process of plants in the wild. However, humans also can take advantage of this process to produce food, such as our tasty fruits, vegetables, and other needed products, like cotton or fresh flowers. Humans can grow crops outside, as in traditional farming, or crops can be started inside from seeds in a greenhouse. Seeds are planted in small containers of soil and given the right conditions based on the type of seed. Check out this indoor grow system. Plants are germinated in small cups of soil and water is provided through a plumbing system. The lights overhead ensure that the seeds' shoots grow directly upward.
 |
Lesson Summary
In summary, seed germination is the process of a fertilized plant ovary, or seed, developing into a mature plant. Seed germination starts with imbibition, when the seed takes in water from the soil. This triggers root growth to allow the seed to get more water. Then, the shoots develop and grow towards the sun above ground. After the shoots reach the ground, leaves form, allowing the plant to harvest energy from the sun. Several factors influence this process, such as water availability, temperature and sunlight. Seed germination is important for natural plant growth and growing crops for human use.
The Seed Germination Process
- Step 1: Imbibition: water fills the seed
- Step 2: The water activates enzymes that begin the plant's growth
- Step 3: The seed grows a root to access water underground
- Step 4: The seed grows shoots that grow towards the sun
- Step 5: The shoots grow leaves and begin photmorphogenesis
Learning Outcomes
When you are finished, you should be able to:
- Discuss the process of seed germination
- List the factors that influence seed germination
To unlock this lesson you must be a Study.com Member.
Create your account
