Dormancy: Do living organisms take a break from their metabolic activity? What is dormancy? It involves remaining inactive for a brief amount of time since we all know that all living creatures require a favourable environment in order to develop. However, plants experience various temperatures and conditions throughout the year. Animals have the luxury of movement and bodily insulation, while plants do not.

Dormancy is a state in which living organisms do not grow or develop. For a brief while, they stop or slow down their metabolic activity. It is also possible to claim that living creatures go into a profound slumber during times when they are not actively growing. Plants, as we all know, are unable to protect themselves or live in the absence of water. As a result, they become dormant. Let us learn more about dormancy, seed dormancy, types and causes of dormancy.

What is Dormancy?

Dormancy is a period in an organism’s life cycle when growth, development, and (in animals) physical activity are temporarily suspended for a specific period. Dormancy had derived from the word ‘Dormant’ meaning sleeping.
Dormancy can be defined as the inactive state of the seed in which the growth of the embryo is temporarily suspended for a specific period of time. 
Torpor is a similar term to dormancy, meaning inactivity or lethargy.

What is Seed Dormancy?

Seed dormancy is defined as a resting condition in which seeds cannot germinate even under optional environmental conditions.

What is Bud Dormancy?

Bud dormancy is a temporary suspension of most physiological activity and growth, which can be reactivated.
This may be a response to environmental conditions such as seasonality, extreme heat, drought, or extreme cold. The exit from bud dormancy is marked by the resumed growth of the bud.

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Types of Dormancy

Dormancy can be classified on various basis. Two important bases of classification are
(i) source and
(ii) nature.
Type of dormancy based on source:

Type of dormancy	Description
1. Exogenous	Exogenous dormancy is caused by external conditions outside the embryo.
1.a Physical	Physical dormancy is also called seed coat dormancy. In this type of dormancy, the seed coat is hard which does not allow the seed to absorb water and gases. Example: olive, peach, plum, apricot etc.
1.b Mechanical	In Mechanical dormancy, radicle growth of the seed is restricted by seed covering, resulting in the dormancy of seeds. Example: walnut
1.c Chemical	Chemical dormancy can occur due to the presence of inhibitors within the seed coat. Example: abscisic acid, coumarin, tomato juice etc.
2. Endogenous	1. Endogenous dormancy is caused by the internal conditions within the embryo.

Types of dormancy depending on nature:

Type of dormancy	Description
1. Primary dormancy	1. In primary dormancy, the seed is released from the plant, which is already in a dormant state.
2. Secondary dormancy	2. In secondary dormancy, the released seed from a plant becomes dormant due to environmental conditions.

Fig: Primary and Secondary Dormancy

One other way to classify Dormancy is:

1. A condition of seeds that are incapable of germination even if the conditions are suitable or perfect for suitable conditions for seedling growth are supplied externally is called Innate Dormancy. The probable cause for this may be an immature embryo at the time of dispersal.
2. A condition of seeds that are incapable of germination due to an environmental restraint. This is called Enforced Dormancy. This could be moisture, light, suitable temperature, etc., which are essential for germination.
3. A condition of seeds that fail to germinate when they have sufficient water absorbed but are naturally or artificially placed under extremely unfavourable conditions. This is termed Induced Dormancy.

Causes of Seed Dormancy

Seed dormancy is caused due to the following methods:

Methods of causing Seed Dormancy	Description
1. Mechanically resistant seed coat	Due to the tough and mechanically seed coat, the growing embryo fails to come out of the seed coat. Example – Mustard (Brassica), peppergrass (Lepidium), etc.
2. Impermeable seed coat	Many plants have hard seed coats so, they cannot be permeable to the entry of water, gases, chemicals. As a result, the seed fails to germinate and lies dormant. Example – Chenopodium, Xanthium, Brassica alba, etc.
3. Rudimentary and poorly developed embryos	The embryos of some seeds are still immature and rudimentary at the time of seed germination. Example – Ginkgo biloba, Eranthis hyemalis, etc.
4. Dormant embryos	In many species of apple, peach, cherry, pines, peas, etc., although the embryos are completely developed in ripe seed, the seeds fail to germinate even when the environmental conditions are completely favourable.This is caused due to physiological immaturity of the embryo.They can germinate when they undergo the “after-ripening” process.
5. Germination inhibitors	Germination of seeds considerably changed by the presence of compounds known as inhibitors.Some natural germination inhibitors are found in the pulp of the fruits, seed coat, endosperm and embryos or structures surrounding them, etc., (e.g., in tomatoes, in glumes of Oats, etc.)The important chemical germination inhibitors abscisic acid, phenolic acids, short-chain fatty acids, coumarin, etc.
6. Specific light requirement	The seeds of certain plant species such as Lactona sativa, Nicotiana tabacum, etc., have specific light requirements for germination.

Breaking of Dormancy

Generally, during favourable conditions, seed dormancy is broken. Seed dormancy can break naturally and artificially.

Artificial Breaking of Seed Germination

When the embryo is exposed to an adequate environment, such as adapted moisture and temperature, dormancy is broken. The smoothing action of natural agents such as microorganisms, temperature, and abrasion by the digestive tract of birds and animals that eat these seeds causes the seed coat of many species to become transparent. Other natural options are:

• The over-ripening phase is ended.
• Inhibitors contained in the seed coat are leached.
• The use of cold, heat, and light to inactivate inhibitors.
• Excess and extremely concentrated solutes are leached from the seeds.
• Production of growth hormones that can counteract inhibitory effects.

Natural Breaking of Dormancy

The following are some of the artificial methods for breaking seed dormancy:

• Waxes, surface inhibitors, and other substances are terminated with hot water.
• Seed coatings are ruptured by filing, chipping, or threshing in machines.
• Heat, cold, or light exposure, depending on the kind of seed dormancy.
• Hydraulic pressure is applied for 5 to 20 minutes to weaken the strong seed coverings.
• To remove all remnants of the mineral acid, seed coats are treated with strong sulphuric acid.

FAQs based on Dormancy in Plants

Below here we have provided frequently asked questions related to Dormancy:

Q.1: What is seed dormancy in plants?

Ans: The difficulty of intact viable seeds to complete germination under favourable environmental conditions is known as seed dormancy.

Q.2: What is dormancy for example?

Ans: When organisms are in unfavourable conditions, they slow down their metabolic activities to the bare minimum in order to conserve resources until the situation improves. Plants may do this in the absence of water, whereas mammals, such as the garden dormouse, hibernate, which is a sort of dormancy.

Q.3: What are the factors affecting seed dormancy?

Ans: A variety of factors might lead an organism to go into a dormant condition during periods of environmental stress. Changes in temperature and photoperiod, as well as the availability of food, water, oxygen, and carbon dioxide, are all important factors in the start of dormancy.

Q.4: Is it necessary to water the plants while they are dormant?

Ans: Dormant plants do not need frequent watering as they don’t show active growth during their dormancy. So avoid watering blindly and do check for the moisture level of the soil, if it’s dry then water the soil thoroughly, if it is not avoid watering.

Q.5: In the winter, why do plants go dormant?

Ans: We are all aware that sunshine is essential for plant growth. However, because the days are shorter and the nights are longer in the winter, the amount of daylight is reduced. If the plants continue to grow in this circumstance, the stored water willze and injure the plants. As a result, they go dormant in the winter.

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