Germination is a protrusion of radicle or seedling emergence. Germination results in rupture of the seed coat and emergence of seedling from embryonic axis. Factors affecting germination are soil, environment, water, temperature, light, atmospheric gases and exogenous chemicals required for germination of seeds.
Factors affecting germination
Soil: Soil type, texture, structure and microorganism greatly influence the seed germination.
Environment: Generally, the environmental conditions favouring growth of seedling also favours germination. Germination does not occur until the seeds attain physiological maturity.
Water (soil moisture and seed moisture): Imbibitions of water is the prerequisite process for germination. Both living and dead seeds imbibe water and swell. Dead seeds imbibe more water and swell rapidly as compared to good seeds. The amount imbibed is related to the chemical composition of the seed such as proteins, mucilage’s pectins and biochemical components. Cereal grains such as maize imbibe water to approximately 1/3 of its seed weight, soybean seeds to 1/2 of its seed weight. Seed germination will be maximum when the soil moisture level is at field capacity. Slower rate of germination is noticed in places where soil moisture is near or at wilting point.
Temperature: The cardinal temperature (Maximum, optimum and minimum temperature) for germination of some of the crops is given below; The optimum temperature is that one gives the highest germination percentage in the shortest period of time.
Light: The most effective wavelength for promoting and inhibiting seed germination is red
(660 nm) and infrared (730 nm), respectively.
Atmospheric gases: Most crop seeds germinate well in the ambient composition of air with 20% O2, 0.03% CO2 and 78.2% N.
Exogenous chemicals: Some chemicals induce or favour quick and rapid germination.
• Gibberellins stimulate germination in protoplasmic seeds.
• Hydrogen peroxide (H2O2) is used for legumes, tomato and barley.
• Ethylene (C2H4) is used for stimulating groundnut germination.