Seed Germination: The Impact to Crop Yield and Quality

Seed Germination: The Impact to Crop Yield and Quality
External Guest Writer
June 6, 2022

What is Seed Germination?

Seed germination is the process of viable seeds growing primary roots, breaking out of the seed coat, and starting the growing process. All flowering plant species grow from seeds, and growing seedlings often produce diversified plants as compared to propagated cuttings.

Germination involves the rooting of fully developed seeds once in contact with moisture and soil. Factors like light, water, and temperature affect different crop seed varieties. When a seed activates, it becomes a seedling that starts the delicate growing process.

Seed germination ends the dormancy period of seeds. Seeds can be stored and kept in suspended animation in cold temperatures, similar to the ice-cold facilities of the Svalbard Global Seed Vault where the world's plant varieties are kept in cases of mass extinction. Seeds start the germination process once given the ideal environment to grow.

How Does It Work?

Moisture, temperature, and light all affect seed germination time. Germination starts once a seed comes in contact with enough moisture to break through its hardened exterior. However, without optimal conditions in temperature, light, aeration, and soil nutrients, seedlings will eventually weaken. 

Seeds start to germinate when planted in a seedling mix, potting medium, or with moistened paper towels. The seed coat softens, allowing the seedling inside to push out and germinate. Once the seedlings take root and grow true leaves, they can be transplanted into garden beds, pots, or hydroponic setups to continue their growth into full-grown plants. 

Factors Affecting Seed Dormancy

Light Ends Seed Dormancy

Light requirements differ per plant, and the same goes for seeds. Some seed varieties germinate under total darkness, such as the case with Calendula flowers which germinate best in complete darkness for the first 1-2 weeks. While light may be a beneficial factor in how many seeds activate in certain species of plants, light inhibits germination in other seeds.

Plants like Begonias and Primulas require ample light in germinating seeds. Seedlings can become fragile and leggy when there's not enough light as the plant attempts to reach sufficient light for nutrients, or they may not germinate at all.

Moisture Affects Seed Coats

Moisture is the basic requirement seeds need to germinate. Seeds are covered by a hard shell known as the testa, which protects the plant embryo from harsh temperatures, and from drying out. Moisture softens this shell, allowing the seedlings to develop once the seed coat is removed.

Once moisture has softened the testa, the seed takes in the moisture surrounding it and proceeds to start the germination process beneath the soil surface. Water is needed for the seedling to produce the first seed leaves, called cotyledons, and start to provide for its own food using light and water.

Temperature Affects Seed Growth

The majority of plant species germinate well in warmer soil temperatures as seed germination hastens with warmth. However, a handful of species prefer to germinate in cooler temperatures, albeit slow in the germination process.

Areas with warm climates often have lush flora due to the heat hastening the germination of seeds. Some plants, like verbena and lavender, benefit from the cold treatment to germinate instead. Each plant seedling has its own set of requirements and preferences to grow proper plants

Commercial growers use heat treatments to control soil temperature in cold climates, while urban gardeners would use a soil thermometer and mulch to achieve the optimum temperature for seed germination. Temperature largely affects the speed in germination, so growers tend to manage the amount of heat seeds get.

Soil Depth Affects Rooting

Generally, most seeds are planted in a shallow seedling tray. As the seed grows, the sprouts are transferred into pots or gardens where their roots will continue to grow into the area. The depth of the roots are factors to consider when repotting, as roots can easily take over any container too small for it. 

Roots grow towards moisture, leading the root to travel to the bottom of the pot where the water hasn't evaporated. This leads to deep roots that may weaken if constricted in a small or shallow container, leading to root-bound plants.

Air Circulation Affects Resistance to Disease

Plant roots require good air circulation and oxygenation to fight off fungal and bacterial diseases. In hydroponics, this is done by aerating the water reservoir where the sprouts are planted, but soil-bound seedlings will need a loose soil mix to aerate the roots. Organic farmers typically toss in perlite and pieces of organic material for aeration and soil structure.

Proper air circulation around the roots promotes healthy plants resistant to common diseases brought by waterlogged soil. Aeration also decreases the stress on plant roots, allowing the seedlings to focus energy on the growth of leaves and stronger roots.

The Benefits of Seed Germination

Higher Success Rate

Some plants have strict requirements before they can start rooting from cutting, and in these cases, germinating seeds yields a higher success rate than propagation does. Seeds are formed when pollinators spread pollen from varying plants, causing a diversification in genetic makeup of the seeds.

Healthy seeds grow healthy plants given the optimal conditions to thrive. Seed-borne diseases exist, but seeds are often treated for bacterial and fungal diseases to prevent eradication of the entire crop harvest. Healthy seeds are more viable, and produce plants with larger leaves, vigorous stems, and higher nutritional value. 

Diversified Characteristics

Seed germination can produce characteristics not found in its parent plant as a result of natural pollination, or intentional cross-pollination to achieve specific characteristics in genetically-modified plants.

Common crops such as carrots and bananas are some examples of plants grown with human intervention through seed modification and cross-pollination. These aim to create hybrid crops that may have superior qualities in harvest time, quantity, or plant growth regulators. Modified seeds improve the quality of crops.

Improved Nutritional Quality

Growing crops through seed germination improves the nutritional quality of the crop as gemination decreases Antinutritional Factors (ANFs) such as tannins, lectins, and saponins that reduce nutrient bioavailability.

Germination allows nutrients to pass through the plant, creating crops that contain higher amounts of essential nutrients like B Vitamins and Vitamin C, increasing to approximately 7-20 mg per 100 gm.

Minerals like iron and calcium are converted from complex compounds into simpler ones that make them easier to digest after germination. Plants typically eaten as sprouts provide increased amounts of protein and fibers that are present through seed germination, overall improving the nutritional quality of plants.

The Future of Seed Germination

Research on seed germination is continuously ongoing to produce seeds with higher success rates, crops with better taste and nutrition, and plants that serve purposes other than being ornamental. Multiple studies on seed germination in the past have yielded success in the field of agriculture.

One notable study being the IR64 rice variety introduced by the International Rice Research Institute (IRRI), which produced a rice variety that had favorable cooking texture, early maturity, and disease resistance to gain a high-yielding plant that was grown by cultivating different varieties of rice seeds.

Other studies focus on the success of seed germination in plants noted to have difficulty in keeping their numbers thriving in the current environmental conditions such as the studies done on Bamboo Dendrocalamus strictus, resulting in methods found to increase successful germination survivability by 50% 

Studies on seeds will not cease to exist, as methods and technologies advance along with the changes in the environmental landscape. Researchers are hard at work producing modified seeds that produce better quality crops, and alternative methods that increase the survivability of seeds. Germination is not just a part of horticulture, it has been sustaining lives for millions of years, and will continue to do so.