Seed Dormancy Questions in English

(D) Seed dormancy is a state in which seeds are prevented from germinating even under favorable environmental conditions.
Inhibitory substances such as abscisic acid $(ABA)$ are responsible for maintaining this dormancy.
Methods to break dormancy include exposure to chilling temperatures (stratification),application of gibberellins $(GA)$,and treatment with nitrates.
Conversely,ascorbic acid acts as an inhibitor that promotes or maintains seed dormancy rather than removing it.

(D) Stratification is a process of exposing seeds to low temperatures $(5-10^{\circ}C)$ in the presence of moisture to break seed dormancy and promote germination.
Scarification involves physical or chemical damage to the seed coat to make it permeable to water and gases.
Vernalisation refers to the promotion of flowering by a period of low temperature exposure to the plant.
Chelation is a chemical process involving the formation of complex structures with metal ions.

(C) Water is essential for seed germination. It initiates the metabolic processes by activating enzymes,softening the seed coat,and allowing the embryo to expand and emerge. While nutrients and light are necessary for the subsequent growth of the seedling,water is the primary requirement for the initial germination process.

(D) Stratification involves the treatment of seed at low temperature $(5^{\circ} C - 10^{\circ} C)$ under sufficiently moist conditions to break its dormancy and to induce germination.

(A) Dormancy is a physiological state in which seeds or buds fail to germinate or grow even when environmental conditions (such as water,temperature,and oxygen) are favorable for growth. This temporary suspension of metabolic activity allows the plant to survive unfavorable conditions.

(C) Quiescence is the condition of a seed or plant organ where growth is suspended due to the lack of suitable external environmental conditions (such as water,temperature,or light) required for germination or growth. Once these conditions are provided,the organism resumes growth. In contrast,dormancy is often controlled by internal factors.

(C) In tomato,seed dormancy is primarily caused by the presence of chemical inhibitors in the fruit pulp. Specifically,the presence of ferulic acid in the tomato pulp acts as a germination inhibitor,which prevents the seeds from germinating while still inside the fruit. This mechanism ensures that seeds do not germinate prematurely before being dispersed.

(D) Seed germination is the process by which a seed develops into a seedling.
During this process,the radicle emerges to form the root system.
The metabolic activity increases significantly,leading to an increase in the rate of respiration to provide energy.
Stored food reserves like polysaccharides and proteins are hydrolyzed into simpler forms to support growth.
However,photosynthesis does not occur during the initial stages of germination because the seedling is typically underground or lacks fully developed,functional photosynthetic machinery in the cotyledons at the very start.

(D) Seed dormancy is a state in which seeds are prevented from germinating even under environmental conditions normally favourable for germination.
$1$. Hard seed coats can physically restrict water uptake and gas exchange,preventing germination.
$2$. Unfavourable environmental conditions (such as lack of water or extreme temperatures) naturally induce dormancy to ensure survival.
$3$. Abscisic acid $(ABA)$ is a plant growth inhibitor that plays a crucial role in inducing and maintaining seed dormancy.
Since all these factors contribute to the state of dormancy,the correct answer is $D$.

(C) Some seeds are sensitive to light and are known as photoblastic seeds.
Positively photoblastic seeds are those that germinate only in the presence of light,for example,$Viscum$,$Lactuca$,and $Rumex$.
Conversely,negatively photoblastic seeds are those that do not germinate in the presence of light,such as onion and tomato.

(N/A) Causes of Seed Dormancy:
$1$. Underdeveloped embryo: The embryo may not be fully mature at the time of seed dispersal.
$2$. Impermeable seed coats: The seed coat may be impermeable to water or oxygen,preventing the necessary metabolic processes for germination.
$3$. Mechanically resistant seed coats: Hard seed coats physically restrict the expansion of the embryo.
$4$. Presence of germination inhibitors: Chemicals like Abscisic acid $(ABA)$ inhibit germination by suppressing gene transcription and enzyme synthesis.
$5$. Absence of growth promoters: $A$ lack of sufficient Gibberellins $(GA)$ in dormant seeds prevents the initiation of germination.
Methods to Remove Seed Dormancy:
$1$. Natural removal: When the concentration of Gibberellins increases and exceeds that of $ABA$,the inhibitory effect is neutralized,and the embryo becomes active.
$2$. Mechanical scarification: Lightly scraping the seed coat with sandpaper or other abrasive materials makes it permeable to water and gases.
$3$. Chemical scarification: Using specific chemicals to soften or break down the hard seed coat.
$4$. Temperature treatment: Exposing soaked seeds to specific high or low temperatures for a defined period can break dormancy.
$5$. Oxygen availability: Providing an oxygen-rich environment to soaked seeds can also help in overcoming dormancy.

(N/A) $1$. Water brings about the activation of the dormant protoplasm. The activation of cells requires about $75-95 \%$ of water for carrying out their metabolism.
$2$. It is essential for respiration because oxygen reaches the protoplasm only when dissolved in water.
$3$. Water softens the seed coat (testa),causing the seeds to swell. This allows the embryo to break through the softened seed coat and emerge easily.

(N/A) $1$. Water is essential for the metabolic activities required for seed germination.
$2$. Dry seeds have a very low water content,typically ranging from $5-15\%$.
$3$. This low water content results in a highly concentrated protoplasm and reserve food material.
$4$. At such high concentrations,the enzymatic activities necessary for breaking dormancy and initiating growth cannot occur,thus preventing germination.

(N/A) $1$. Germination is an active metabolic process that requires a significant amount of energy.
$2$. During germination,the embryo resumes growth,which leads to a sharp increase in the rate of cellular respiration.
$3$. This process requires a continuous and adequate supply of oxygen $(O_2)$.
$4$. Seeds sown too deeply in the soil or in water-logged soils face a deficiency of oxygen because the air spaces in the soil are filled with water or are too far from the surface.
$5$. Due to the lack of oxygen,aerobic respiration cannot occur,and the seed fails to produce the energy required for the emergence of the radicle and plumule,thus failing to germinate.

(N/A) Germination is the biological process by which a seed develops into a new plant. It encompasses the entire sequence of events starting from the sowing of the seed in the soil,followed by the absorption of water (imbibition),activation of metabolic processes,and culminating in the emergence of the young sapling (seedling) from the soil surface.

(D) Seed germination is a complex process that depends on several factors:
$1$. Favourable environmental conditions such as appropriate temperature,water,and oxygen are essential for seed germination.
$2$. In the absence of favourable conditions,the seed remains in a dormant state,and the metabolic activities of the embryo are minimal or suspended.
$3$. Seed germination is influenced by both internal factors (e.g.,seed maturity,hormones) and external factors (e.g.,temperature,moisture,light).
Therefore,all the given statements are correct.

(B) Seed dormancy is a state in which seeds are prevented from germinating even under environmental conditions normally favourable for germination.
Factors responsible for seed dormancy include:
$1$. Hard and tough seed coat $(I)$ which prevents water and oxygen uptake.
$2$. Presence of growth inhibitors like Abscisic Acid $(ABA)$ $(II)$,Phenolic acids,and Para-ascorbic acid $(IV)$.
$3$. Immature embryo $(V)$ which requires time to develop before germination can occur.
Gibberellic Acid and Nitrates $(III)$ are actually growth promoters that help in breaking seed dormancy,not causing it.
Therefore,the factors responsible for seed dormancy are $I, II, IV,$ and $V$.

(D) Seed dormancy is a state in which seeds are prevented from germinating even under favorable environmental conditions. Various methods can break this dormancy:
$1$. Mechanical or physical abrasion (scarification) using sandpaper or other methods helps to break or weaken the hard seed coat,allowing water and oxygen to enter.
$2$. In nature,the action of microorganisms (bacteria and fungi) can degrade the seed coat,thereby breaking dormancy.
$3$. Passing seeds through the digestive tract of animals exposes them to digestive enzymes and acidic conditions,which softens the seed coat and breaks dormancy.
Therefore,all the given options are correct methods for breaking seed dormancy.

(B) Certain chemicals such as $GA_3$ (Gibberellic Acid) and nitrates are known to be effective in breaking seed dormancy.
Seed dormancy is a state in which seeds are prevented from germinating even under favorable environmental conditions.
Gibberellins are plant hormones that promote seed germination by counteracting the effects of abscisic acid,which is responsible for maintaining dormancy.
Therefore,these chemicals are used to overcome dormancy and initiate the germination process.

(A) Statement $I$ is correct: Seed dormancy is a physiological state where the seed's metabolic activity is significantly reduced or arrested,allowing it to survive harsh environmental conditions.
Statement $II$ is correct: Even if environmental factors like moisture,temperature,and oxygen are optimal,a seed will not germinate until its internal dormancy period is over,which is a survival mechanism to ensure germination occurs at the most suitable time.