Have you ever wondered why some seeds fail to growth after sowing?
After tedious pre-planting operations, it is sadden to notice the seeds sown fail to germinate even when the conditions to favor germination are favorable. However, as a farmer, it is crucial you know the state of any seed before planting and if modification is required, it is best done to enhance rapid seed and uniform growth.
The period between seed harvesting and sowing is called dormancy period; this period is of great importance and consideration as it determines the tendency of seed germination and growth. This condition has to be eliminated before a seed grows.
What is seed dormancy?
Seed dormancy is the inability of a viable seed to germinate even when the conditions to facilitate growth are available and conducive. It is also the physiological state of rest in plants especially when environmental conditions are not favorable. During this period, the seed awaits conditions to facilitates its growth. For germination to take place, the seeds have to overcome dormancy. Germination is initiated after the elimination of dormancy. However, there are different types of seed dormancy; they are:
• Immature embryo: This occurs when the embryo of the seed is not fully matured at the period of seed shedding. Such seeds cannot germinate.
• Dormancy as a result of excessive salt: There are some seeds that contain high concentration of salt that do not allow the seeds to germinate.
• Dormancy as a result of hard seed coat: There are some seeds with hard seed coat; this hard seed coat prevents the exchange of water and gases between the seed and the environment as a result of the impermeability of the seed coat.
• Inhibitory dormancy: Dormancy as a result of growth inhibitors present in the seed. Such as abscisic acid.
What are the causes of dormancy?
Seed dormancy is usually caused by:
• Hard seed coats that desist the permeability of water and gases to facilitates growth.
• Immature or underdeveloped embryo: seeds with immature embryo do not germinate.
• Period after ripening: some seeds have a period of ripening, such seeds only germinate after the completion of this period.
• Germination inhibitors: Some seeds contains some chemicals, like abscisic acid, which inhibit germination.
To help seed resume germination, the dormancy has to be broken or eliminated; the following ways are how to break seed dormancy:
This is the process of softening seed coats to aid water and gases permeability, thus, enhancing seed germination. There two types of scarification, they are:
• Mechanical scarification: This is the softening of the seed coat through abrasion on a hard surface; it can be achieved through passing the seeds through machine that scratches the surface, rubbing the seed surface with sand paper, through filing and notching of the seeds to make the seed permeable to water and gases.
• Chemical scarification: This is the softening of the seed coat through soaking in concentrated acids, like sulphuric acid for a few period. After soaking, the seeds are washed with clean water to make them free from acid before planting. This process hastens germination.
2. Boiled water treatment
in this process, boiled water is poured over seeds and getting it cool gradually, to soften the coats of hard shelled seeds. It can be done for small seeded plants like vegetables.
3. Soaking of seeds in water:
Seeds are soaked in water to soften the seed coat, remove inhibitors, remove excess salt and hasten germination. Examples of such seeds are: peas, beans, etc.
4. Stratification or moist chilling:
This is when seeds are exposed to low temperature to bring about prompt and uniform germination. It also softens the seed coat.
Any of these should be done on seeds before planting, to allow seeds resume growth and hasten germination, also bringing about uniform growth. Care must be taken during scarification to avoid total damage of the seeds