Dormancy in Seeds

Dormancy refers to a period of inactivity or suspension of growth and development in seeds. It is an adaptive mechanism that allows seeds to survive unfavorable conditions and ensures their germination occurs under the most favorable circumstances. Dormancy can be categorized into different types based on the causes and mechanisms involved.

Non-dormant and Post-dormant Seeds

Non-dormant seeds are those that have completed their dormancy period and are ready to germinate under suitable conditions. Post-dormant seeds, on the other hand, are those that have undergone dormancy and have been released from it.

Secondary Dormancy

Secondary dormancy is a form of dormancy that occurs in non-dormant or post-dormant seeds. It can be induced by various factors, such as unfavorable environmental conditions or physiological changes within the seed. Secondary dormancy acts as a protective mechanism to prevent premature germination in seeds that have already undergone dormancy and ensures that germination occurs under optimal conditions.

Reasons for Secondary Dormancy
1. Environmental Factors: Seeds may enter secondary dormancy when exposed to unfavorable environmental conditions such as extreme temperatures, lack of moisture, or light conditions that are not conducive for germination.
2. Physiological Changes: Changes in the hormone levels or metabolic activity within the seed can also trigger secondary dormancy. For example, the accumulation of certain growth inhibitors or the depletion of growth-promoting substances can inhibit germination and induce dormancy.
3. Seed Coat Impermeability: Some seeds have hard or impermeable seed coats that prevent water uptake, leading to secondary dormancy until physical or chemical processes break the seed coat and allow water penetration.

Conclusion

In summary, the dormancy observed in non-dormant and post-dormant seeds is referred to as secondary dormancy. It is induced by various factors, including unfavorable environmental conditions and physiological changes within the seed. Secondary dormancy acts as a protective mechanism to ensure that germination occurs under the most favorable circumstances.

Secondary dormancy occurs in some non-dormant and post-dormant seeds that are exposed to conditions that are not favourable for germination, like high temperatures. It is caused by conditions that occur after the seed has been dispersed.