ABA Questions in English

(D) Abscisic acid $(ABA)$ is a plant growth inhibitor that acts as a stress hormone. During conditions of water stress (drought),$ABA$ is synthesized in the leaves. It triggers the efflux of potassium ions $(K^+)$ from the guard cells,which leads to a decrease in turgor pressure and the subsequent closure of stomata to prevent water loss through transpiration.

(D) Abscisic acid $(ABA)$ is a plant growth inhibitor. It plays a crucial role in the abscission of leaves,flowers,and fruits. Spraying $ABA$ induces rapid leaf fall (abscission). Additionally,it promotes dormancy in buds and seeds,helping plants survive unfavorable environmental conditions.

(B) $IAA$ (Indole$-3-$acetic acid),$NAA$ (Naphthalene acetic acid),and $GA$ (Gibberellic acid) are plant growth promoters.
$ABA$ (Abscisic acid) is a naturally occurring plant growth inhibitor that plays a crucial role in seed dormancy and stress responses.

(A) Dormin, also known as Abscisic Acid $(ABA)$, is a well-known plant growth inhibitor and hormone.
Formalin is a $40\%$ solution of formaldehyde, which is used as a disinfectant or preservative, not a hormone.
Acetylene is a hydrocarbon gas $(C_2H_2)$ often used in welding; while it can induce ripening, it is not a naturally occurring plant hormone like $ABA$ or Ethylene.
Therefore, only Dormin is a plant hormone.

(A) Maleic hydrazide is a synthetic plant growth regulator that acts as a growth retardant. It inhibits cell division in the meristematic tissues of plants. By suppressing growth,it is commonly used to prolong dormancy in crops like onions and potatoes,thereby preventing sprouting during storage.

(C) $Abscisic \, acid$ is also known as the stress hormone or $Dormin$.
$Eagle$ and $Wareing$ $(1963)$ discovered a substance called $Dormin$ from the dormant buds of $Acer$ $(Birch)$ plants, which is capable of inducing seed dormancy.

(D) Abscisic acid $(ABA)$ is a plant growth inhibitor that plays a crucial role in the process of abscission.
It promotes the formation of the abscission zone in leaves,flowers,and fruits,which leads to their shedding from the plant body.
While auxins generally inhibit abscission,$ABA$ acts as a promoter of this process,especially under stress conditions or during senescence.

(B) Abscisic acid $(ABA)$ is a plant growth inhibitor. It plays a crucial role in seed development,maturation,and the induction of seed dormancy. By inhibiting metabolic processes,$ABA$ prevents seeds from germinating under unfavorable conditions,thereby ensuring their survival. In contrast,Gibberellic acid promotes seed germination.

(C) Abscisic acid $(ABA)$ acts as a stress hormone in plants.
When plants experience water stress,$ABA$ is synthesized in the leaves.
It inhibits the $H^+/K^+$ exchange mechanism in the guard cells and promotes the efflux of potassium ions $(K^+)$ and malate.
This reduction in osmotically active solutes causes water to move out of the guard cells,making them flaccid.
As a result,the stomatal pore closes to prevent further transpiration.

(D) Xanthoxin is a naturally occurring growth inhibitor found in plants. It is chemically related to Abscisic Acid $(ABA)$. Historically,Abscisic Acid was also known as Dormin because of its role in inducing dormancy in seeds and buds. Therefore,Xanthoxin is classified as a type of Dormin.

(D) The chemical structure of $ABA$ (Abscisic Acid) is $C_{15}H_{20}O_4$.
In the structure of $ABA$,there is one chiral center at the $C-1'$ position of the cyclohexene ring,which makes it an asymmetric carbon atom.
Additionally,the molecule contains several symmetric carbon atoms within its structure,specifically those involved in the double bonds and the ring structure that do not possess four different groups attached to them.
Therefore,$ABA$ contains one asymmetric carbon atom and multiple symmetric carbon atoms,making option $D$ the most accurate description regarding its carbon configuration.

(B) Abscisic acid $(ABA)$ is a plant growth inhibitor.
It promotes the formation of an abscission layer in leaves and fruits,which leads to leaf fall and fruit drop.
Therefore,it is also known as the stress hormone.

(D) $ABA$ (Abscisic Acid) is a plant growth inhibitor.
It is widely distributed in plant tissues,including the fruit pulp,seed coat,and resting buds.
It plays a crucial role in seed dormancy,bud dormancy,and the inhibition of growth,helping the plant survive unfavorable conditions.

(D) Abscisic acid $(ABA)$ is known as a stress hormone in plants. When a plant experiences water stress or scarcity,$ABA$ is synthesized in the mesophyll cells of the leaves. It triggers the closure of stomata to reduce the rate of transpiration,thereby helping the plant conserve water and survive under drought conditions.

(A) $ABA$ (Abscisic acid) acts as a plant growth inhibitor. It plays a crucial role in inducing dormancy in seeds and buds,which helps plants survive unfavorable environmental conditions such as winter or drought. Therefore,it inhibits growth rather than promoting it.

(A) $ABA$ (Abscisic Acid) is a plant growth inhibitor that plays a major role in the abscission of leaves,flowers,and fruits. During leaf senescence and the process of leaf fall,the concentration of $ABA$ increases in the plant tissues to promote the formation of the abscission layer.

(B) $ABA$ (Abscisic acid) stimulates senescence of leaves by causing the destruction of chlorophyll and the inhibition of protein and $RNA$ synthesis.

(B) $Abscisic$ $acid$ $(ABA)$ is a well-known plant growth inhibitor.
It plays a crucial role in regulating seed dormancy by inhibiting the process of germination.
$Gibberellic$ $acid$ acts as an antagonist to $ABA$ and promotes seed germination.
Therefore,$Abscisic$ $acid$ is the correct answer.

(A) $ABA$ (Abscisic acid) acts as a plant growth inhibitor.
It plays a crucial role in inducing bud dormancy,especially as winter approaches,to protect the plant from harsh environmental conditions.
Therefore,$ABA$ is responsible for the induction of dormancy in buds.

(D) Abscisic acid $(ABA)$ is known as a stress hormone because it increases the tolerance of plants to various kinds of stresses.
One of its primary physiological roles is to induce the closure of stomata in response to water stress,thereby reducing the rate of transpiration and conserving water.
Therefore,it is correctly described as mediating stomatal closure.

(D) $Abscisic$ $acid$ $(ABA)$ is known as the stress hormone in plants.
It plays a crucial role in helping plants cope with adverse environmental conditions such as drought, waterlogging, and extreme temperatures.
When a plant faces such stress, the synthesis of $ABA$ is stimulated, which leads to responses like stomatal closure to prevent water loss.

(D) Abscisic acid $(ABA)$ is known as a stress hormone in plants.
It plays a crucial role in promoting the abscission of leaves and fruits,which is the shedding of these parts from the plant body.
Additionally,$ABA$ acts as an inhibitor of plant metabolism and promotes bud dormancy,allowing plants to survive unfavorable environmental conditions.
Therefore,the correct phytohormone responsible for these processes is Abscisic acid.

(C) The correct answer is $ABA$ (Abscisic Acid).
$ABA$ is known as a stress hormone in plants.
When applied to leaves,even in minute quantities,it induces the partial closure of stomata.
This action significantly reduces the rate of transpiration,thereby helping the plant conserve water during periods of water stress or drought.

(D) $ABA$ (Abscisic Acid) is a stress hormone that induces the closure of stomata to prevent water loss during water stress conditions.
Cytokinin,on the other hand,promotes stomatal opening by stimulating the synthesis of enzymes that increase the osmotic potential of guard cells,thereby facilitating water uptake and turgor pressure increase.

(D) The phytohormone $ABA$ (Abscisic Acid) is known to be situated at its site of synthesis. Unlike other hormones like Auxin or Gibberellin,which are transported from their site of production to the site of action,$ABA$ often acts locally within the tissues where it is synthesized,particularly in response to stress conditions like water deficit.

(A) $ABA$ (Abscisic acid) is known as a stress hormone in plants.
During extreme drought conditions,$ABA$ is synthesized in the leaves.
It acts on the guard cells of the stomata,triggering the efflux of potassium ions $(K^+)$ and water,which leads to the loss of turgor pressure.
As a result,the stomata close to prevent excessive water loss through transpiration.

(B) Abscisic acid $(ABA)$ acts as a stress hormone that promotes the closure of stomata during water stress conditions.
It functions by inhibiting the active uptake of $K^+$ ions into the guard cells.
As the concentration of $K^+$ ions decreases,the osmotic potential of the guard cells increases (solute concentration decreases),leading to the efflux of water from the guard cells into the surrounding subsidiary cells.
This loss of water causes the guard cells to become flaccid,resulting in the closure of the stomatal pore,thereby reducing transpiration.

(A) $ABA$ (Abscisic Acid) is known as a plant growth inhibitor.
It plays a crucial role in inducing bud dormancy,which helps plants survive unfavorable conditions such as cold or drought.
By inhibiting metabolic activities and growth,$ABA$ ensures that the bud remains inactive until favorable conditions return.
In contrast,Gibberellic acid $(GA)$ generally promotes growth and breaks dormancy.

(D) Abscisic acid $(ABA)$ is known as a stress hormone in plants.
It acts as a general plant growth inhibitor.
It plays a crucial role in seed development,maturation,and dormancy.
$ABA$ helps seeds withstand desiccation and other factors unfavorable for growth.
Therefore,it promotes dormancy and inhibits plant growth.

(C) Gibberellins are plant growth promoters that stimulate seed germination,stem elongation,and flowering. $ABA$ (Abscisic Acid) is a plant growth inhibitor that acts as an antagonist to gibberellins. For example,gibberellins promote seed germination,while $ABA$ inhibits it and promotes seed dormancy. Therefore,$ABA$ is considered the primary antagonist to gibberellins.

(A) $ABA$ (Abscisic Acid) is the primary plant growth inhibitor that promotes senescence and abscission in plants.

(B) Abscisic acid $(ABA)$ acts as a general plant growth inhibitor. It plays a crucial role in the abscission of leaves and fruits. Additionally,it induces dormancy in buds and seeds,helping plants survive unfavorable environmental conditions.

(C) Abscisic acid $(ABA)$,also known as dormin,is a plant hormone.
It plays a role in several growth-inhibiting processes,such as seed dormancy.
Abscisic acid is a derivative of carotenoids.
It was previously known as Abscisin-$II$ because it was believed to play an important role in the abscission of fruits.
At the same time,it was identified as dormin by another group due to its role in seed dormancy.
Eventually,the name Abscisic acid was adopted as a compromise between the two groups.

(B) Abscisic acid $(ABA)$ is a plant growth regulator that acts as a potent inhibitor of seed germination. It promotes seed dormancy and helps the seed withstand desiccation and other unfavorable growth factors. Therefore,it is considered the most common natural inhibitor for seed germination.

(D) Abscisic acid $(ABA)$ is known as the stress hormone in plants.
It plays a crucial role in helping plants cope with various environmental stresses such as drought,salinity,and extreme temperatures.
$ABA$ induces stomatal closure to prevent water loss during water stress conditions,which is why it is primarily associated with stress responses.

(A) $Abscisic$ $\text{acid}$ $(ABA)$ is known as the stress hormone.
It prepares plants to cope with adverse environmental conditions such as drought, salinity, or extreme temperatures.
It induces stomatal closure to reduce water loss through transpiration.
Therefore, it is commonly referred to as the stress hormone.

(C) $ABA$ (Abscisic acid) acts as an antagonist to gibberellins. This is illustrated in the table below:

Abscisic acid	Gibberellic acid
It inhibits growth.	It promotes growth.
It promotes the dormancy of seeds,buds,and tubers.	It overcomes the natural dormancy of seeds,tubers,etc.
It inhibits the synthesis of $RNA$ and proteins.	It promotes the synthesis of $RNA$ and proteins.
Causes abscission of flowers and fruits.	Promotes development of fruits.
Promotes leaf senescence.	Prevents leaf senescence.
Promotes stomatal closure.	Promotes stomatal opening.
Prevents amylase activity.	Promotes amylase activity during seed germination.

(C) $Abscisic$ $acid$ $(ABA)$ is a plant growth inhibitor.
Its biosynthesis in most plants occurs indirectly through the degradation of certain carotenoids,specifically violaxanthin,which are present in chloroplasts or other plastids.
The biosynthetic pathway involves the mevalonic acid pathway for the synthesis of its precursors.
The primary sites of $ABA$ synthesis include fruits,leaves,roots,and seeds.

(A) $ABA$ (Abscisic Acid) is a plant growth inhibitor.
It plays a crucial role in regulating plant responses to stress.
It promotes the abscission of leaves,flowers,and fruits by accelerating senescence.
Additionally,it induces seed dormancy,which helps seeds withstand desiccation and other unfavorable growth conditions.

(A) Abscisic acid $(ABA)$ is a plant growth inhibitor. It plays a crucial role in the process of senescence (aging) of leaves and other plant parts. It promotes the abscission of leaves and fruits and induces dormancy in seeds,helping plants survive unfavorable conditions.

(A) $ABA$ (Abscisic acid) is a plant growth inhibitor.
It plays a crucial role in the induction of seed dormancy,which helps seeds withstand desiccation and other unfavorable growth conditions.
It also promotes the closure of stomata and inhibits growth-promoting hormones like auxins and gibberellins.

(D) The discovery of plant growth regulators involved various researchers identifying substances with similar physiological effects.
Abscisic acid $(ABA)$ was discovered independently by three different groups of researchers,who named it differently:
$1$. $ABA$ was named 'Dormin' by one group.
$2$. It was named 'Abscisin-$II$' by another group.
$3$. It was named 'Inhibitor-$B$' by a third group.
Since all three names refer to the same chemical compound,Abscisin-$II$ and Dormin are chemically identical.

(A) $ABA$ (Abscisic Acid) is known as the stress hormone in plants.
It plays a crucial role in helping plants cope with various environmental stresses such as drought,salinity,and extreme temperatures.
It induces stomatal closure to prevent water loss during water stress conditions.

(A) Plant growth regulators are classified into two main groups: plant growth promoters and plant growth inhibitors.
$1$. Plant growth promoters: These include auxins (e.g.,$IAA$),gibberellins (e.g.,$GA$),and cytokinins (e.g.,Kinetin). They promote cell division,cell enlargement,and flowering.
$2$. Plant growth inhibitors: Abscisic acid $(ABA)$ is the primary plant growth inhibitor. It plays a crucial role in seed dormancy,bud dormancy,and the abscission of leaves and fruits,and it helps the plant withstand stress conditions.

(D) $ABA$ (Abscisic acid) is a plant growth inhibitor. It acts as an antagonist to $GAs$ (Gibberellins) in various physiological processes. For example,in seed germination,$GAs$ promote germination,while $ABA$ inhibits it. Similarly,$ABA$ promotes bud dormancy,whereas $GAs$ break dormancy.

(B) Abscisic acid $(ABA)$ is a plant growth inhibitor that plays a crucial role in the closure of stomata during water stress conditions.
When a plant experiences water stress,$ABA$ is synthesized in the leaves,which triggers the efflux of potassium ions $(K^+)$ from the guard cells.
This loss of ions leads to a decrease in the turgor pressure of the guard cells,causing them to become flaccid and resulting in the closure of the stomatal pore.
Therefore,$ABA$ acts as a stress hormone to prevent water loss through transpiration.

(B) Abscisic acid $(ABA)$ is a plant growth inhibitor.
It plays a crucial role in the abscission of leaves and fruits.
It also induces dormancy in seeds and buds,which helps plants survive unfavorable environmental conditions.
Therefore,$ABA$ is primarily associated with the regulation of leaf abscission and dormancy.