Steps of Seed Germination, Types, and Stages

Introduction to steps of seed germination, types, and stages: Once the seed has been moved to a new location and covered with dirt, it can germinate. It is through Germination that seeds grow into new plants. However, environmental conditions must be present for the seed to germinate. It is usually determined by water availability, depth of planting, and temperature. In a process known as imbibition, seeds fill with water when there is plenty of water available. As a result of the water activating particular proteins, called enzymes, seed growth occurs. Firstly, the seed grows roots below the soil to get water under the earth. Once the roots appear, the seed starts to grow shoots above ground. Next, a seed sends a shoot to the surface and grows leaves to absorb sunlight. In a process known as photomorphogenesis, the leaves grow toward the light source. The Germination of seeds and growth of embryos from seed to seedling under favorable conditions is known as seed germination. The process by which different plant species emerge from a single seed into plants is also known as seed germination.

A guide to steps of seed germination, process, types, and stages

Seed Germination Process
Seed Germination Process (Pic credit: pixabay)

Essentials for seed germination

Water: Water is a primary factor in seed germination. The majority of seeds are dry and require a significant amount of water to germinate, depending on their weight. In addition, the water in a seed coat provides hydration for protoplasmic activities, dissolves oxygen to the growing embryo, and enhances the seed’s permeability. Also, water helps convert insoluble food to a soluble form, translocate food materials, and ripen seeds.

Oxygen: The seeds require oxygen to breathe oxygen-free until they develop leaves. During seed germination for metabolism, oxygen supplies energy for seed growth.

Temperature: A low or very high temperature inhibits protoplasm from carrying out vital activities, so the temperature is also a key element in activating Germination. The temperature requirements are different for different kinds of seeds. They generally need between 25 and 30 degrees Celsius.

Light: A seedling grows mainly from a seed that has been exposed to sunlight.

Different factors affect the Germination of seeds

Seeds need environmental conditions and an optimal internal environment to germinate. Below are the factors that help to Germination:

External factors

Water: Providing the seeds with enough water is essential to their metabolism and enzymatic activity. It is due to the intake of water inside the seed that causes it to rupture, enabling the seedling to emerge.

Temperature: In general, the higher the temperature, the faster the seed will germinate. It is a critical factor in Germination because each seed requires a specific range of temperature. Germination occurs at a wide range of temperatures, including 16°C and 24°C. Certain seeds germinate when the soil temperature is below 0°C, while others require a higher temperature (24°C to 32°C).

Oxygen: Oxygen increases the rate of respiratory activity in germinating seeds. Oxygen is essential for Germination since respiration provides the seed with the majority of its energy. Without oxygen, a seed cannot enter the metabolically active stage and remains inactive or dormant.

Light/Darkness: Lighting is a critical factor in the Germination of seeds. photoblastic seeds are those that sprout when exposed to light. Seeds of plants like lettuce and tobacco, for instance, require light for Germination and are known as positive photoblastic seeds. Conversely, onion seeds and lily seeds germinate when they are dark since they are negatively photoblastic.

Soil: High salt concentrations in the soil prevent the seed from absorbing water, preventing it from germinating. Dormant seeds are the result. Frequent watering of the soil and the use of organic fertilizers can help reduce soil salinity.

Internal Factors

Seed Viability: Gibberellin is a growth hormone that promotes seed germination by shedding the seed coat, resulting in a young plant. An immature embryo can’t germinate until it is completely mature. Depending on the plant species, as many as a week or even many years may pass before seeds germinate.

Dormancy Period: Factors such as the presence of rigid and impermeable seed coats, the presence of growth inhibitors, and the absence or shortage of food supply can cause a seed to remain in an inactive or dormant state. Here, gibberellin plays an essential role in breaking seed dormancy and thus returning the seed to active metabolism.

The process of seed germination

A germination seed absorbs water rapidly, resulting in the swell and softening at an optimum temperature as it absorbs water. The process is referred to as imbibition. It is the activation of enzymes that begins the growth process. Within the seed, physiology is activated, respiration occurs, proteins are produced, and metabolization occurs. During this lag period, Germination takes place. A radicle is formed by rupturing the seed coat and forming a primary root. It then begins to absorb water from the ground. After the radicle and plumule emerge, the shoot starts growing upward. The cells of the seeds are metabolically active in the final stages of Germination, extend, and divide, giving rise to the seedling.

A step-by-step description of plant growth from Germination  

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Stages of Seed Germination
Stages of Seed Germination (Pic credit: pixaaby)

Plants may live only a few weeks or months, but they undergo distinct changes as they grow, just as people do. Infants, toddlers, adolescents, young adults, middle-aged adults, and senior citizens are the stages of human development. Vegetative, budding, flowering, and ripening stages of plants coincide. The nutritional requirements of people and plants also change as they grow.

1. Sprout: Seeds contain a small parcel of nutrients that they need for Germination and growth.

2. Seedling: The rapidly growing plants absorb and use nutrients efficiently to fuel their rapid growth from spindly seedlings to healthy plants.

3. Vegetative: Nitrogen is a crucial component of chlorophyll in plants, the pigment responsible for plants’ green color. Plants need nitrogen to produce new leaves and stalks as they grow.

4. Budding: The growth of leaves to the formation of buds is when a plant has a high demand for phosphorus.

5. Flowering: Plants use potassium to produce and transport sugars and starches that help them develop healthy flowers and fruit.

6. Ripening: Flowers and fruits need one or two weeks of no nutrients when they are on the verge of full maturation. Flushing is the process of using up all of the nutrients which have already been absorbed.

7. Protect your plant growth: Utilize various tools during the growing stage to protect your plants against pests and diseases to get the best results at the end of the season.

Different types of seed germination

  • Epigeal Germination.
  • Hypogeal Germination.
  • Vivipary.

Epigeal Germination:

By rapid growth of the hypocotyl, these plants germinate when the cotyledons emerge above ground. Epigeal Germination occurs in the seeds of many dicotyledonous plants, including beans, castor, sunflowers, gourds, and cucumbers.  Germination occurs during which the hypocotyl overgrows and becomes curved. A seed emerges from the ground during this stage. Straightening occurs once the hypocotyl rises above the soil surface. The seed coat falls off the cotyledon, and it becomes green. It is now time for the epicotyl to grow and the plumule to produce green leaves. The cotyledons fall ultimately.

Hypogeal Germination: In this type of Germination, seeds remain beneath the soil as the epicotyl elongates rapidly. It occurs in many monocotyledonous seeds as well as dicotyledonous seeds. An epicotyl that is elongated and uncurved evolves during this phase of Germination. These leaves extend above the soil surface. During this phase, the cotyledons remain beneath the soil surface. When planted monocotyledonous seeds, such as maize, the coleoptile (plumule covering) grow straight down into the soil. During the coleoptile, plumbers elongate and emerge from the soil. When they grow further, they rupture the coleoptile. As a result, the coleorhiza (covering of the radicle) and the radicle grow downward. Coleorhiza ruptures after a certain amount of time due to the continued growth of the radicle. As soon as the primary root is formed, a fibrous foot is attached.

Vivipary:  Vivipary is a type of seed germination. At Germination, the seed remains attached to the plant’s parent and is fed by it. Viviparous plants are common in mangroves. In salt marshes that line seashores, mangroves are usually medium-sized trees. Examples are Rhizophora, Sonnenratia, and Avicenna, among others. Marshes have a low oxygen level and excessive salinity, so mangrove plants are unable to germinate. Instead, the seed embryos remain attached to the parent plant while still growing inside of it. As a result, the radicles of plants grow significantly during fruit development.

In some cases, part of the radicle becomes thick and swollen. A dart-like seedling breaks off the parent plant, becoming embedded in the marsh and floating out of the water. A new plant is immediately established from the radicle, which forms new roots.

Stages of seed germination

Five stages of seed germination

  • Imbibition.
  • Respiration.
  • Effect of Light on Seed Germination.
  • Induction of germination reserves by growth regulators, and
  • Embryonic Development into Seedlings.

Imbibition: The first stage in seed germination is imbibition, which is absorbing seed water. Imbibition causes the seed to swell as the cellular constituents become rehydrated. There is a great deal of force involved in the swelling process. Seed coats are ruptured, allowing radicles to emerge as primary roots.Cell walls rehydrate structural and storage macromolecules, especially polysaccharides and proteins, during imbibition. Many seeds are also rich in polysaccharides, which are uncommon in vegetative tissues. As a result, seeds packed in a bottle dry could crack when they swell up when they absorb water.

Respiration: As the seed is rehydrated, its metabolism starts to resume after being ingested with water. During anaerobic reproduction, bacteria use glycolysis to generate energy before their respiration becomes aerobic in the presence of oxygen. Thus, in the presence of dissolved oxygen, water plants and rice can germinate.To germinate underwater, plants need more excellent oxygen than they do on land. The air in the soil provides the oxygen for these seeds to germinate. In loose soil near the surface, most seeds are sown, so they are most widely distributed. The act of plowing and hoeing aerates the soil and facilitates seed germination. Due to insufficient oxygen, seeds planted deeper in waterlogged soil often do not germinate.

Effect of light on seed germination: In terms of seed germination, plant responses to light vary greatly. Light-responsive seeds are referred to as photoblastic there are positive photoblastic, negative photoblastic, and non-photoblastic. The seeds of photoblastic plants (lettuce, tobacco, mistletoe, etc.) do not germinate in darkness, but they do need exposure to sunlight (maybe for a brief period) to germinate.If exposed to sunlight, negative photoblastic seeds (onion, lily, amaranths, nigella, etc.) will not germinate. A non-photoblastic seed germinates regardless of exposure to light.Seeds with red-sensitive characteristics are most effectively germinated by the red region of the visible spectrum.

Nevertheless, the far-red region (the region immediately after the visible red region) reverses the effect of red light and makes the seed dormant. It is due to the phytochrome pigment, which is a blue-colored pigment, that the seeds are red and far-red sensitive. A phycobiliprotein is widely distributed within plants.It also controls Germination in light-sensitive seeds, besides many other light-dependent developmental processes in plants. For example, a variety of plants are capable of photomorphogenesis (light-regulated development) and flowering.

Control of seed germination by phytochrome and red-far-red- Plant phytochrome is found in two interconvertible forms, Pr and Pfr. Phytochrome Pr has no metabolic activity. In the presence of red light (660 nm.), it is transformed into metabolically active Pfr. A phytochrome-controlled process such as Germination is promoted by the latter. Once the far-red is absorbed (730 nm), it becomes Pr again. As well, Pfr gradually changes into Pr in the dark. This oscillation of phytochrome between Pr and Pfr states has led to the system being called a “reversible red-far-red pigment system” or, in short, the phytochrome system.

On the other hand, far-red light (FR) treatment inhibits seed germination. Thus, red light (R) is a stimulator, and Far-red light (FR) is an inhibitor. Let the US study seed germination in plants with positive photo elasticities, like lettuce (Lactuca sativa). Brief exposure of red light (660 nm.) followed immediately by brief exposure of far-red light (720 nm.) determines the response of soaked seeds in close succession. The red light (R) stimulates the Germination of seeds. Thus, red light (R) is stimulatory, but it loses its effect if we follow it up with far-red light (FR). There is no limit to how many times this trick is used. For seeds to germinate, they need to be exposed to the best light. This result indicates that red light (R) induces reversible responses, whereas far-red light (FR) does not. Seeds can be germinated even without light when gibberellins or cytokinin are present. Also, hormones given singly or in combination with other hormones at the correct time can mimic several development processes of plants controlled by phytochrome.

Induction of germination reserves by growth regulators: Embryonic cells resume metabolic activity and undergo division and expansion during Germination. Moreover, starch, protein, or fats stored in the body need to be digested. Aerobic respiration provides the energy necessary for these cell conversions. Some monocotyledon plants (such as cereal grains, legumes, and oats) and some dicotyledon plants (such as peas and beans) contain food reserves. In addition, numerous studies have been conducted on reserving reserves via the shield-like cotyledon (scutellum) in several cereal grains. In the outer layer of the endosperm, called the aurone layer, hydrolyzing enzymes (such as amylases and proteases) are produced and secreted. An enzyme causes digestion or the breakdown of food stored in the inner endosperm cells, such as starch and protein. As a result, insoluble foods are made soluble, and complex foods are simplified. Cotyledons transfer sugars and amino acids to the epicotyls, hypocotyls, and roots of the plant. Gibberellic acid plays a crucial role in the synthesis of hydrolyzing enzymes. Gibberellin, therefore, encourages Germination and growth of young seedlings. The seedling assumes its ultimate form as soon as the growing organ absorbs this food. Abscisic acid (ABA), a dormancy-inducing hormone, has been found to prevent Germination. In several different kinds of seeds, ABA levels increase as the embryo enters dormancy during seed development. Growing cotton embryos in culture do not cause them to be dormant but instead causes them to continue growing without stopping. Thus, a crucial stage in growth can be induced by adding ABA to induce dormancy in such cases.

Embryonic Development into Seedlings: The cells in the growing regions are metabolically active after being transferred with food and later assimilated. During this process, the cells divide to form seedlings.

A few tips for improving seed germination

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Tips for improving seed germination
Tips for improving seed germination (Image credit: pixabay)

Here are some tips you can use to improve seed germination:

  • Seeds need to be appropriately stored, preferably in a cool, dark place that is free of moisture, to be viable
  • Before planting the seeds in shallow water, soak them in the water ahead of time. Seeds will absorb more water and grow faster if soaked beforehand.
  • Make sure to water the soil beforehand by soaking it for at least 24 hours.
  • Maintain a regular seed-environment monitoring schedule. Feel the soil for moisture.
  • Follow germination progress daily and adjust conditions if necessary.
  • Using seed trays is also a fail-safe way to start your seeds. In addition, sowing seeds in seed trays allows for more accurate control of soil moisture depth for each seed/seedling separately.

The following tips should help you improve the Germination of your seeds. The process of Germination is straightforward and can be followed by any plant. However, understanding the seed’s growing needs is essential for you to plan your planting. In that case, you’ll be able to complete the germination process in one go with the additional steps.

Commonly asked questions about seed germination

1. How does seed germination occur in plants?

Germination is when a seed begins to grow into a seedling. All seeds require water, oxygen, and a temperature that is right for Germination. In a state of suspended animation, dormancy occurs when seeds wait until the right conditions are met for sprouting.

2. Which seeds germinate quickly?

The quickest germinating seeds are the cabbage family, including Bok choy, Broccoli, Kale, Cauliflower, and Lettuce. Pepper, Eggplant, Fennel, and Celery seeds take the longest to germinate, taking an average of five days. Most of the rest will take three days, including Tomatoes, Beets, Chard, Squash, and Onions.

3. Is light necessary for seeds to germinate?

Most seeds should germinate in darkness. Some seeds are even inhibited by light (e.g., Phacelia and Allium species). Make sure you don’t confuse seed light requirements and seedling light requirements. Both require sunlight to grow.

4. How is seed germination affected by various factors?

Germination can be affected by both internal and external factors. For example, several external factors affect seed germination, including light, water, temperature, and oxygen. Similarly, the viability of seeds, dormancy, and maturity of seeds are also internal factors.

5. How do you force the Germination of seeds?

The easiest way to make seeds germinate faster is to soak them in hot water for 24 hours. In the presence of water, seed coats will penetrate, and the embryos inside will plump up. However, make sure you don’t soak them longer than 24 hours, as they could rot. Instead, place the seeds in moist soil immediately after soaking.

6. What are the three requirements for Germination?

  • Germination refers to the process of transforming a seed into a plant.
  • The correct temperature and water are necessary for seed germination.
  • During dormancy, seeds delay Germination, waiting for the right conditions to sprout.

7. What is the germination time for seeds?

As a general rule of thumb, you should begin to see signs of germination 3 to 5 days after introducing moisture to the seed, depending on the seed and the environment. You should see a white root tip during this period, assuming you used a germination method that permits it.

8. How do I take care of germinating seeds?

Make sure there are no gaps between the soil and the containers. Almost all mixes contain little if any, nutrients, so make sure you feed the seedlings liquid fertilizer a few weeks after they germinate until the seeds are transplanted into the garden.

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