ABA Questions in English

(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.

(A) Abscisic Acid $(ABA)$ is a plant growth inhibitor.
Its primary physiological role is to induce stomatal closure in response to water stress,thereby reducing transpiration and conserving water.
It also promotes seed dormancy and abscission of leaves and fruits.

(A) Abscisic acid $(ABA)$ is known as a stress hormone and a growth inhibitor in plants.
It plays a crucial role in promoting the process of senescence (aging) in leaves and other plant organs.
$ABA$ also promotes abscission of leaves,flowers,and fruits,and induces seed dormancy.
Therefore,$ABA$ is the hormone responsible for inducing senescence.

(C) Abscisic acid $(ABA)$ is a plant growth regulator that acts as an inhibitor of plant metabolism.
It is chemically derived from carotenoids,specifically through the cleavage of violaxanthin.

(A) 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.
$ABA$ promotes the closure of stomata to prevent water loss during water-deficit conditions, thereby protecting the plant from desiccation.

(N/A) $Abscisic$ $acid$ $(ABA)$ is known as a stress hormone because it plays a crucial role in helping plants cope with adverse environmental conditions.
$1$. It induces the closure of stomata during water stress,thereby reducing water loss through transpiration.
$2$. It increases the tolerance of plants to various stresses such as drought,salinity,and extreme temperatures.
$3$. It promotes seed dormancy,which ensures that seeds do not germinate under unfavorable conditions and helps them withstand desiccation.
$4$. It induces dormancy in buds and promotes the abscission (shedding) of leaves,fruits,and flowers at the end of the growing season to conserve energy.

(N/A) Abscisic Acid $(ABA)$ is a plant growth inhibitor that acts as a stress hormone. Its key effects include:
$1$. Stomatal Closure: It induces the closure of stomata in response to water stress,thereby reducing transpiration.
$2$. Seed Dormancy: It promotes seed dormancy,which helps seeds withstand desiccation and other unfavorable environmental conditions.
$3$. Growth Inhibition: It acts as a general inhibitor of plant metabolism and growth.
$4$. Abscission: It promotes the abscission of leaves,flowers,and fruits.
$5$. Stress Tolerance: It increases the tolerance of plants to various types of stress,such as drought and salinity.

(N/A) The hormone known as the $Stress \ Hormone$ in plants is $Abscisic \ Acid$ $(ABA)$.
$ABA$ is synthesized in various parts of the plant,including leaves,stems,and fruits,especially under stress conditions.
Its primary functions include:
$1$. It acts as a general plant growth inhibitor and an inhibitor of plant metabolism.
$2$. It stimulates the closure of stomata in the epidermis,which helps the plant conserve water during drought or water stress conditions.
$3$. It promotes seed dormancy and ensures seed development,maturation,and dormancy,which helps seeds withstand desiccation and other unfavorable growth factors.
$4$. It plays a crucial role in seed development and tolerance to various stresses,hence it is called the $Stress \ Hormone$.

(N/A) $ABA$ (Abscisic Acid) is known as a stress hormone because it plays a crucial role in helping plants cope with adverse environmental conditions.
$1$. During water stress,$ABA$ triggers the closure of stomata to reduce water loss through transpiration,thereby conserving water.
$2$. It promotes seed dormancy,which helps seeds survive unfavorable conditions like drought or extreme temperatures.
$3$. It increases the tolerance of plants to various stresses such as salinity,cold,and heat by regulating the expression of stress-responsive genes.

(B) $ABA$ (Abscisic Acid) is primarily synthesized in the leaves,particularly in the chloroplasts,and is transported to the site of action. However,in the context of physiological response to stress,it is known to be transported to the leaves from the root system or synthesized within the leaf tissues. Among the given options,the release or accumulation of $ABA$ in leaves is associated with the leaf tip and mesophyll cells during stress conditions. Therefore,the correct answer is $B$.

(A) $ABA$ (Abscisic acid) is a plant hormone that primarily functions as a growth inhibitor.
It plays a crucial role in inhibiting morphogenesis,which is the biological process that causes an organism to develop its shape.

(B) $ABA$ (Abscisic acid) causes stomata to close by inhibiting an $ATP$-dependent pump in the plasma membrane of guard cells.
The application of exogenous $ABA$ on the leaves of normal plants causes the closing of stomata within a few minutes.
$ABA$ acts in the presence of $CO_2$,which decreases the $pH$ of guard cells.
$ABA$ induces the loss of $K^+$ ions,which decreases the osmotic concentration of guard cells compared to adjacent epidermal cells.
This causes exosmosis,and the turgidity of the guard cells decreases,leading to stomatal closure.

(B) Abscisic acid $(ABA)$ is a natural growth inhibitor.
It promotes stomatal closure,acting as a stress hormone that helps the plant cope with adverse environmental conditions,especially drought.
It also induces dormancy in seeds and buds,ensuring they remain inactive until favorable conditions return.
These seeds sprout only when the inhibitory effect of $ABA$ is overcome by $GA$ (Gibberellic Acid).

(B) Abscisic acid $(ABA)$ is known as the stress hormone or dormin because it induces dormancy and helps plants overcome stress conditions,such as drought. Its primary function during water stress is to induce stomatal closure to prevent water loss through transpiration.

(D) Abscisic acid $(ABA)$ is a naturally occurring plant growth inhibitor. It is known as a 'stress hormone' because it helps plants cope with adverse environmental conditions. It promotes the abscission of leaves, fruits, and flowers, and accelerates senescence. It does not act as a general flowering hormone; in fact, it often inhibits growth and development. Therefore, the pair 'Abscisic acid - Flowering hormone' is incorrect.

(D) During the mid-$1960$s,three independent research groups reported the purification and chemical characterization of three different kinds of inhibitors,which were named Inhibitor $B$,Abscission $II$,and Dormin.
Later,all three were proven to be chemically identical.
Consequently,they were collectively named Abscisic Acid $(ABA)$.

(C) The hormone that performs all these functions is Abscisic acid $(ABA)$.
$1$. $ABA$ acts as an antagonist to Gibberellic acid $(GA)$ in various physiological processes.
$2$. It promotes bud and seed dormancy,which helps plants survive unfavorable conditions.
$3$. It induces stomatal closure during water stress to prevent transpiration.
$4$. It promotes the formation of the abscission layer,leading to the shedding of leaves,flowers,and fruits.
Therefore,the correct option is $C$.

(B) $ABA$ (Abscisic acid) acts as an antagonist to gibberellins.
Gibberellins promote seed germination and stem elongation,whereas $ABA$ inhibits these processes.
Due to this antagonistic effect on the physiological activities induced by gibberellins,$ABA$ is commonly referred to as an anti-gibberellin.

(C) Abscisic acid $(ABA)$ is known to possess viral inhibitory properties. It functions by inhibiting the synthesis of $RNA$ and proteins,which are essential for viral replication. Additionally,$ABA$ regulates the expression of specific genes during seed maturation and under various stress conditions,such as heat shock,cold adaptation,and drought tolerance.

(C) Abscisic acid $(ABA)$,also known as the stress hormone or dormin,is found in all vascular plants,as well as in some mosses,green algae,and fungi. It is completely absent in bacteria.
$ABA$ is primarily synthesized within the chloroplasts of plant cells. The biosynthetic pathway involves the conversion of carotenoids,such as violaxanthin,which are present in the chloroplasts.
While leaves are the primary site of synthesis due to the abundance of chloroplasts,$ABA$ can also be synthesized in other plastids like chromoplasts,leucoplasts,or proplastids found in roots,fruits,and seeds.

(B) $ABA$ (Abscisic acid) is a derivative of carotenoids.
Its biosynthetic pathway involves the cleavage of carotenoids,specifically violaxanthin,which acts as a precursor for the synthesis of $ABA$ in plants.

(A) Seed dormancy is a state in which seeds are prevented from germinating even under environmental conditions normally favourable for germination.
Abscisic acid $(ABA)$ acts as a general plant growth inhibitor and plays a crucial role in seed development,maturation,and dormancy.
It promotes seed dormancy and inhibits germination,thereby helping the seed survive unfavourable conditions.
In contrast,hormones like ethylene and gibberellic acid are known to break seed dormancy and promote germination.

(D) $ABA$ (Abscisic acid) is known as the stress hormone in plants. It plays a crucial role in regulating the opening and closing of stomata. During stressful conditions,such as water deficit or drought,$ABA$ is synthesized in the leaves,which triggers the closure of stomata to prevent excessive water loss through transpiration.

(A) During the germination of cereal grains,$Gibberellins$ $(GA)$ stimulate the synthesis of the enzyme $\alpha$-amylase in the aleurone layer,which helps in the breakdown of starch into sugars.
$Abscisic$ $acid$ $(ABA)$ acts as a physiological antagonist to $Gibberellins$.
Therefore,$ABA$ inhibits the $Gibberellin$-mediated synthesis of $\alpha$-amylase,thereby preventing or delaying seed germination.

(D) Abscisic acid $(ABA)$ is a plant growth inhibitor that acts as an antitranspirant by closing stomata,is synthesized in chloroplasts from carotenoids,and helps plants increase tolerance to various stresses.
Epinasty (the downward bending of leaves or other plant parts) is primarily induced by the gaseous plant hormone ethylene,not by $ABA$.

(A) Abscisic acid $(ABA)$ is known as the stress hormone in plants. It stimulates the closure of stomata in the epidermis to reduce water loss through transpiration,thereby acting as an antitranspirant. Additionally,it increases the tolerance of plants to various kinds of stresses,such as drought or salinity.

(N/A) Abscisic acid $(ABA)$ was discovered for its role in regulating abscission and dormancy.
Like other plant growth regulators $(PGRs)$,it has wide-ranging effects on plant growth and development.
It acts as a general plant growth inhibitor and an inhibitor of plant metabolism.
$ABA$ inhibits seed germination.
$ABA$ stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses.
Therefore,it is also called the stress hormone.
$ABA$ plays an important role in seed development,maturation,and dormancy.
By inducing dormancy,$ABA$ helps seeds to withstand desiccation and other factors unfavourable for growth.
In most situations,$ABA$ acts as an antagonist to gibberellins $(GAs)$.

(N/A) With the progression in research on plant growth regulators,three independent researchers reported the purification and chemical characterization of three kinds of inhibitors during the mid-$1960$s,namely: inhibitor-$B$,abscission-$II$,and dormin.
Later,all three were proved to be chemically identical in nature and were collectively named Abscisic Acid $(ABA)$.

(N/A) Abscission is the natural process of shedding or separation of plant parts such as leaves,flowers,fruits,or branches from the main plant body.
This process occurs at a specific region known as the abscission layer or abscission zone.
It is primarily regulated by the balance between plant hormones,specifically the increase in $ABA$ (Abscisic Acid) and ethylene,and the decrease in auxins.

(D) During the mid-$1960$s,three independent researchers reported the purification and chemical characterization of three different kinds of inhibitors: Inhibitor-$B$,Abscisin-$II$,and Dormin. Later,it was discovered that all three of these substances were chemically identical and were collectively named Abscisic Acid $(ABA)$.

(B) 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.
$ABA$ promotes the closure of stomata to reduce water loss during water stress conditions,thereby protecting the plant.

(B) Abscisic acid $(ABA)$ acts as a general plant growth inhibitor. It functions as an antagonist to gibberellic acid $(GA)$ in many physiological processes,such as seed germination and bud dormancy. While $GA$ promotes seed germination and breaks dormancy,$ABA$ inhibits germination and induces dormancy.

(A) Abscisic acid $(ABA)$ acts as a general plant growth inhibitor and an inhibitor of plant metabolism.
It plays a crucial role in seed development,maturation,and dormancy.
$ABA$ helps seeds withstand desiccation and other factors unfavorable for growth by inducing dormancy.
Therefore,the correct option is $A$.

(D) Plant growth regulators (PGRs) are classified into two categories: growth promoters and growth inhibitors.
Abscisic acid $(ABA)$ is the primary growth inhibitor.
Apart from inhibiting growth,$ABA$ plays a crucial role in plant responses to various biotic and abiotic stresses,such as drought,salinity,and wounding.
Therefore,it is often referred to as a stress hormone.

(B) $ABA$ (Abscisic acid) acts as a stress hormone that promotes stomatal closure to reduce transpiration.
It functions by inducing the efflux of $K^+$ ions from the guard cells.
This loss of ions decreases the osmotic pressure within the guard cells,causing water to move out,which makes the guard cells flaccid (hypotonic).
Therefore,making the guard cells turgid is the opposite of the action of $ABA$,as turgidity leads to stomatal opening.

(C) Abscisic acid $(ABA)$ is a plant growth inhibitor that maintains seed dormancy and inhibits germination.
In contrast,auxins,gibberellins,and cytokinins are growth-promoting hormones that help in breaking seed dormancy and stimulating germination.

(A) Abscisic acid $(ABA)$ is a plant growth inhibitor.
It acts as a stress hormone and is primarily responsible for the closure of stomata during water stress conditions.
When a plant experiences water deficiency,$ABA$ is synthesized in the leaves,which triggers the efflux of potassium ions $(K^+)$ from guard cells,leading to a decrease in turgor pressure and subsequent closure of stomata to prevent transpiration.

(B) Abscisic acid $(ABA)$ is known as the stress hormone in plants.
It is synthesized in response to adverse environmental conditions such as drought, salinity, or extreme temperatures.
It helps the plant survive these conditions by promoting the closure of stomata to reduce water loss and by inducing dormancy in seeds and buds.

(B) Abscisic acid $(ABA)$ is a plant hormone known as a stress hormone.
When a plant experiences water stress,$ABA$ is synthesized in the leaves.
$ABA$ acts on the guard cells of the stomata to induce the efflux (outward movement) of $K^{+}$ ions.
This loss of $K^{+}$ ions decreases the osmotic potential of the guard cells,causing water to move out of the cells via osmosis.
As a result,the guard cells lose turgor pressure and become flaccid,which leads to the closure of the stomata to prevent further water loss.

(B) Abscisic acid.
Abscisic acid $(ABA)$ is a plant growth inhibitor that promotes leaf fall (abscission) by inducing senescence in plant tissues.