Some seeds may be exposed to environments conducive to germination but still fail
to germinate. Describe three factors that induce seed dormancy and the strategies
to overcome them.
There are several factors that can induce seed dormancy and prevent germination. Three common factors include:
1. Physical dormancy: Some seeds have a hard seed coat or a thick layer surrounding the embryo that prevents water absorption. This physical barrier inhibits germination. To overcome physical dormancy, seeds can be scarified, which involves breaking, scratching, or weakening the seed coat to allow water penetration. This can be done through processes like soaking the seeds in hot water, mechanically nicking or filing the seed coat, or treating them with chemicals.
2. Chemical dormancy: Some seeds contain chemical compounds, such as inhibitors or growth regulators, that prevent germination until certain conditions, like temperature or moisture levels, are met. Such compounds inhibit the growth of the embryo and keep the seed dormant. To overcome chemical dormancy, seeds can be subjected to techniques like stratification or leaching. Stratification involves subjecting seeds to a specific temperature and moisture regime for a certain period of time to break down the dormancy-inducing chemicals. Leaching, on the other hand, involves removing the inhibitory compounds by soaking the seeds in water or other suitable solutions.
3. Physiological dormancy: This type of dormancy occurs when the embryo within the seed is immature and not fully developed. It may take time for the embryo to fully develop and be able to germinate. To overcome physiological dormancy, seeds can be subjected to a process called after-ripening, which involves storing the seeds under specific conditions, such as temperature and humidity, to allow the embryo to complete its development. Once the embryos are fully developed, the seeds can then germinate normally.
In summary, to overcome seed dormancy caused by physical, chemical, or physiological factors, strategies like scarification, stratification, leaching, and after-ripening can be employed to break down barriers and provide suitable conditions for germination.
Factors that induce seed dormancy are important for the natural survival and propagation of plant species. Here are three common factors that induce seed dormancy and the strategies to overcome them:
1. Physical factors: Seeds may have hard seed coats or impermeable seed coverings that prevent water and oxygen from entering and initiating germination. To overcome this, scarification techniques can be used, such as mechanically nicking or rubbing the seed coat to weaken it and allow for water absorption. Alternatively, soaking in hot water or treatment with weak acid solutions can also break down the seed coat.
2. Chemical factors: Some seeds contain inhibitory compounds, such as chemicals that prevent germination until environmental conditions are favorable. For example, certain compounds called abscisic acid (ABA) can maintain seed dormancy and inhibit germination. Strategies to overcome chemical dormancy include stratification, which involves subjecting seeds to specific temperature and moisture conditions to break the chemical dormancy. Another method is leaching, where seeds are soaked or washed in water to remove or dilute the inhibitory compounds.
3. Environmental factors: Seeds may require specific environmental cues or conditions before they can germinate. These can include temperature, light, water, or a combination of these factors. For instance, some seeds need a period of cold temperatures (cold stratification) to break dormancy, as they have evolved to germinate after experiencing winter conditions. To overcome this, seeds can be subjected to cold stratification by keeping them in a moist, cool environment (refrigerator) for a specific duration. Similarly, exposing seeds to specific light conditions or water availability can also trigger germination.
It's important to note that different seeds have unique dormancy mechanisms, and the strategies to overcome dormancy may vary depending on the particular plant species. Seed dormancy is a complex and adaptive process that helps ensure the survival of plant populations in their natural habitats.