Q.Write short notes on seed dormancy.
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Seed Dormancy: A Survival Strategy in Plants
Imagine you buy a packet of seeds for your garden. You plant them, water them, and wait. Some sprout in a few days. Others sit in the soil for weeks or months before they finally wake up. That delay is not laziness — it is a deliberate, built-in pause called seed dormancy.
The Everyday Intuition
Think of a seed as a tiny, sleeping baby plant wrapped in a protective coat. If every seed sprouted the moment it fell from the parent plant, what would happen? A seed that lands in the middle of a dry summer would germinate, then die from lack of water. A seed that falls in autumn would sprout just before winter frost kills the tender shoot. Nature avoids this disaster by giving seeds a "pause button." That pause is seed dormancy.
The Precise Meaning
In biology, seed dormancy is a state in which a viable seed (one that is alive and capable of growing) does not germinate even when all external conditions — water, oxygen, temperature, light — appear favourable. The seed is not dead; it is simply refusing to wake up until some internal or external "lock" is released.
Dormancy is not the same as a dead seed. A dormant seed is alive but inactive. A dead seed will never germinate, no matter what you do.
Why Does Dormancy Exist?
The purpose is survival. A seed that germinates at the wrong time will die. Dormancy ensures that germination happens only when the environment is likely to support the seedling's growth. Here are the main reasons:
- To survive unfavourable seasons — Seeds of many temperate plants remain dormant through winter and germinate only in spring.
- To avoid competition — Some seeds lie dormant in the soil for years, waiting for a fire, flood, or clearing that removes competing plants.
- To spread germination over time — Not all seeds from the same plant germinate in the same year. This "bet-hedging" ensures that if one year is disastrous, some seeds remain for the next.
Types of Seed Dormancy (as per NCERT)
The NCERT textbook classifies dormancy into two broad categories:
1. Innate (Primary) Dormancy
The seed is born dormant. It will not germinate even under ideal conditions until a specific trigger occurs. This is further divided into:
- Physical dormancy — The seed coat is hard and impermeable to water or oxygen. The seed cannot absorb water to start germination. Example: seeds of many legumes (peas, beans).
- Physiological dormancy — The embryo itself is immature or contains chemical inhibitors that block germination. Example: seeds of apple, peach, which need a period of cold (stratification) before they can sprout.
2. Induced (Secondary) Dormancy
A seed that was initially capable of germination becomes dormant again because of unfavourable conditions. For example, if a seed starts to germinate but then faces extreme heat or drought, it may re-enter dormancy.
How Is Dormancy Broken?
Nature has evolved several mechanisms to "wake up" dormant seeds:
| Trigger | How It Works | Example |
|---|---|---|
| Scarification | Physical abrasion or cracking of the hard seed coat | Seeds passing through an animal's digestive tract |
| Stratification | Exposure to cold, moist conditions for weeks | Apple seeds need winter cold |
| Fire | Heat or smoke chemicals break dormancy | Many pine species |
| Light | Some seeds need a flash of red light to germinate | Lettuce seeds |
| Leaching | Rain washes away chemical inhibitors from the seed coat | Desert seeds |
Even a viable, mature seed sometimes fails to germinate despite favourable external conditions, because of an in-built resting state. …
Seed dormancy is the failure of a viable seed to germinate under favourable conditions due to internal causes (hard seed coats, chemical inhibitors, immature embryos); it can be broken by scarification, chilling, light and gibberellins, and helps seeds survive bad seasons.
Seed dormancy is a state in which a mature, living (viable) seed does not germinate even when the external conditions required for germination - adequate water, oxygen and suitable temperature - are present. This is because of certain internal (intrinsic) factors.
Causes of seed dormancy:
- Impermeable and hard seed coats that prevent entry of water and oxygen.
- Presence of chemical inhibitors such as abscisic acid (ABA), phenolic acids and para-ascorbic acid in the seed coat.
- Immature or under-developed embryos that need more time to develop.
Methods to break dormancy:
- Scarification: mechanical abrasion or brief treatment with concentrated acids/organic solvents to weaken hard seed coats.
- Stratification: chilling (cold, moist treatment).
- Exposure to light for light-sensitive seeds. …
- CBSE 2026Set ANNUAL1 markMCQQ.Seed dormancy allows the plants to:(a) Reduce viability(b) Overcome unfavourable climatic conditions(c) Prevent deterioration of seeds(d) Develop healthy seeds
›Reveal solutionSolution
Seed dormancy lets a seed 'wait out' harsh or unsuitable conditions and germinate only when the environment becomes favourable.
A dormant seed is fully viable (alive and capable of germinating) but is prevented from germinating immediately, either by an internal block (e.g., presence of germination inhibitors like abscisic acid, an impermeable/hard seed coat, or an immature embryo) or by external unfavourable conditions. This delay is biologically adaptive: if a seed germinated the instant it matured, a seedling might emerge just before winter, during a drought, or in some other unsuitable season and die. Dormancy allows the seed to remain protected and inactive through such unfavourable periods and to germinate later, once temperature, moisture, and light conditions become suitable for seedling establishment. It is not primarily about reducing viabi …
- CBSE 2026Set ANNUAL1 markMCQQ.In seed, inactivity state of embryo is called:(a) Polyembryony(b) Vernalization(c) Dormancy(d) Apomixis
›Reveal solutionSolution
The resting, inactive state of the embryo in a seed is called dormancy.
A mature seed usually contains an embryo whose growth is temporarily arrested. In this state, called seed dormancy, the embryo's metabolism is very low and it does not germinate even if some conditions are met, allowing the seed to survive unfavourable periods and germinate later when conditions are suitable. Polyembryony is the formation of more …
- CBSE 2025Set ANNUAL1 markMCQQ.Which one of the following methods are used to break the seed dormancy?(a) Impaction(b) Stratification(c) Scarification(d) All the above
›Reveal solutionSolution
Seed dormancy caused by a hard, impermeable seed coat or by physiological immaturity of the embryo can be overcome by more than one treatment — mechanical weakening of the coat (impaction/scarification) and cold/moist pre-treatment (stratification) are all standard, valid methods, so the answer is "all of the above".
Seed dormancy is a resting state in which a viable seed fails to germinate even under favourable conditions, usually because of a hard/impermeable seed coat, presence of germination inhibitors, or an immature/dormant embryo. Different treatments break dormancy in different ways:
- Scarification — deliberately damaging or thinning the hard seed coat (by abrasion, chemical treatment with acid, or nicking) so that water and oxygen can penetrate and reach the embryo.
- Impaction — mechanically striking or abrading the seed coat (a form of physical/mechanical scarification) to crack or weaken it, again allowing water and gas exchange. …
- CBSE 2023Set 57/3/11 markMCQQ.Which of the following seeds have remained alive for the longest period ?(a) Phoenix dactylifera(b) Striga asiatica(c) Mangifera indica(d) Yucca gigantea
›Reveal solutionSolution
Seed longevity records belong to Phoenix dactylifera (date palm), with documented viability exceeding 2000 years from archaeological sites. The answer is (a).
Why seed longevity matters
Seeds vary enormously in how long they can remain dormant yet viable. This longevity depends on the seed's structure, moisture content, storage conditions, and inherent dormancy mechanisms. Some seeds lose viability within weeks, while others can survive centuries under the right conditions—a phenomenon that fascinates both ecologists and archaeologists.
The question asks about documented longevity records, not theoretical maximum lifespans. We need to compare what's actually been observed for each species.
Comparing the candidates
Let's examine each option:
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Phoenix dactylifera (Date palm)
This holds the record for verified seed longevity. Seeds recovered from archaeological excavations at Masada (Israel) and other ancient sites have been successfully germinated after approximately 2000 years. The most famous case is "Methuselah," a date palm grown from a seed carbon-dated to around 2000 years old, germinated in 2005. The seed's low moisture content, protective seed coat, and the dry storage conditions of the region all contributed to this remarkable preservation.
-
Striga asiatica (Witchweed)
This parasitic plant produces tiny seeds that can remain dormant in soil for 10–20 years, waiting for chemical signals from host plant roots. While impressive for an agricultural pest, this is nowhere near the date palm's record.
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Mangifera indica (Mango) …
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- CBSE 2023Set A1 markMCQQ.Inactive state of embryo is -(a) Dormancy(b) Morulla(c) Excited state(d) None of these
›Reveal solutionSolution
Dormancy is a resting/inactive phase in which a seed's embryo suspends its metabolic activity and growth until favourable conditions arise.
Seed dormancy is a state in which the embryo inside a mature seed remains metabolically inactive and does not germinate, even under otherwise favourable conditions, until internal or environmental cues (like a period of cold, light, or breaking of a hard seed coat) trigger germination. This is a survival adaptation t …
- CBSE 2017Set ANNUAL1 markQ.A date palm seed discovered during archeological investigation retained viability even after 10000 years. The retention of viability is due to the state of inactivity of embryo called ________.
›Reveal solutionSolution
A seed's embryo can stay alive without growing for thousands of years because it enters a resting, low-metabolism state called dormancy.
After fertilisation, the zygote develops into an embryo and the ovule matures into a seed. Under favourable conditions a seed germinates soon after dispersal, but many seeds instead enter a resting phase called dormancy, in which the embryo's metabolic activity is drastically reduced (very low water content, minimal respiration) and growth is suspended until external conditions (moisture, temperature, oxygen, light) become favourable again. This dormant state protects the embryo from desiccation and other stresses and is what lets seeds remain viable for exceptionally long periods — the classic examples cited are date palm seeds recovered from an ancient (~2,000-year-old, sometimes reported as much older) archaeological site that still germinate …
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