Question

Write any two causes of dormancy in the seed.

Answer 1

Dormancy is hibernation in seeds.

Complete answer: Seed dormancy is defined as the state/ condition in which seeds are prevented from germinating even under suitable/ favorable environmental conditions for germination. It includes temperature, water, light, gas, seed coats, and other mechanical restrictions.
The causes of dormancy in seeds include:
1. Hard seed coats: In many seeds, dormancy is caused by the hard seed coat. This hard seed coat is impermeable to water, gases, or other essential nutrients that are a requisite for plant growth and development. In some seeds, the seed coat is so hard that it does not break even by the emergence of an embryo.
2. Immature embryo: Some seeds are of apparent health, but they do not germinate as they have an immature embryo. This is because the development of the embryo is not completed in these seeds due to various unknown factors. Hence, these seeds remain dormant until the embryo develops to its mature form.

Additional information: Other reasons for seed dormancy are light, temperature, the time period after ripening, germination inhibitors, impermeability of seed coat to water, impermeability of seed coat to oxygen, mechanically resistant seed coat, presence of high concentrate solutes in the matrix, etc.

Note: There are the following types of seed dormancy:
1. Innate dormancy: Here, the seeds are incapable of germination even if the conditions suitable for seedling growth are supplied. This inability to germinate may be due to the immature embryo at the time of dispersal.
2. Enforced dormancy: Here, the seeds are incapable of germination due to an environmental restraint that includes an adequate amount of moisture, oxygen, light, and suitable temperature.
3. Induced dormancy: Here, the seed has imbibed water, but it has been placed under extremely unfavorable and hostile conditions for germination.