Seed germination is the fundamental process whereby various plant species are grown from a single seed. It is the initial and first phase of the growth cycle in plants. The seed germination process has many physiological and biochemical changes that result in the activation of the embryo that gives the plant life and allows it to grow and mature.
The Process of Seed germination
The initial step of seed germination is referred to as the incubation period. In this step, the seed absorbs the water rapidly resulting in swelling of the seed. The swelling results in the softening of the seed coat and this step causes the activation of the enzymes. At this stage, the seed starts to metabolize its stored food and produce protein so that it can respire easily. It is the lag phase in the process of seed germination.
At this level, the seed coat finally ruptures, emerging the radicle that forms the primary root. The seed absorbs more water and the shoot starts to grow after the radicle has emerged.
The final stage causes the cells to become metabolically active, elongate, and divide to form the seedling.
Essential Requirements for Seed Germination
These are the following requirements for the seed germination process:
Water is the most essential requirement for seed germination. The seeds are dry and require the uptake of water so that the seed coat softens. The water causes the seed coat to rupture and it is necessary for the growth of the plant. For the vital activities of the protoplasm, hydration is necessary. The water helps in the translocation of the food to the embryo by converting the insoluble food into a soluble form.
Oxygen is an important component of aerobic respiration as it provides energy to the seed for germination. The oxygen is available in the pores of the soil particles. Oxygen is not available if the seeds are buried too deep in the soil.
The seeds germinate in favorable conditions and require mostly an optimum temperature to germinate. Different seeds require different temperatures. The seeds germinate at either low or higher temperatures between 5 to 40 degrees.
- LIGHT: It plays a major role in the germination process. Many seeds do not germinate until a sufficient amount of light is provided to them.
Factors Affecting Seed Germination
There are certain factors that affect the germination of seeds.
The external factors include Water, oxygen, temperature and, light. If there is not a sufficient supply of water then the seed will not be able to germinate because water helps in the rupture of the seed coat as it is an initial and most important step of seed germination. The excess amount of water can also disturb the germination process. Therefore, an adequate amount of water is required.
Oxygen is the source of energy for the seeds and helps germination. The deficiency of oxygen will disturb the germination process.
The optimum temperature is required for germination. Very hot or very cold temperatures may also not favor the germination process.
Seed dormancy is the condition in which a seed despite getting favorable conditions does not germinate. It happens because the coat of the seed gets thick and does not allow the water uptake or oxygen exchange preventing the seed from germinating. The seed may have an undeveloped embryo that also hurdles the process of seed germination. In some cases, seed germination is inhibited because the seed contains plant growth regulators.