Gibberellins Questions in English

(B) The Bakanae disease (foolish seedling disease) of rice is caused by the fungus $Fusarium \text{ } moniliforme$.
The perfect stage of this fungus is $Gibberella \text{ } fujikuroi$ (an $ascomycete$).
This fungus produces the plant growth hormone known as gibberellin, which causes excessive elongation of the rice stems, leading to the disease symptoms.

(A) Gibberellins were first extracted from rice seedlings suffering from the 'bakanae disease' (foolish seedling disease), which is caused by the fungus $Gibberella$ $fujikuroi$.

(B) Gibberellins are weakly acidic plant hormones that possess a gibbane ring structure.
They are primarily known for promoting cell elongation in intact plants.
$A$ specific and well-documented property of gibberellins is their ability to induce internodal elongation in genetically dwarf plants,such as dwarf corn or dwarf pea,thereby allowing them to reach a normal height.

(B) $Gibberellins$ are plant hormones that can substitute for the specific light requirements needed for flowering. Specifically,in $long-day$ plants,the application of $Gibberellic$ $acid$ $(GA)$ can induce flowering even when the plants are grown under $short-day$ conditions,effectively bypassing the need for long periods of light.

(A) The $Gibberellins$ are plant growth regulators that primarily induce the elongation of internodes.
This process occurs because $Gibberellins$ stimulate both rapid cell division and cell elongation in the stem tissues.
Therefore,they are responsible for the increase in stem length,particularly in plants that exhibit rosette growth habits.

(B) Gibberellins $(GA)$ are known to substitute for long photoperiods in many long-day plants to induce flowering.
Additionally,$GA$ induces bolting (internode elongation just prior to flowering) in rosette plants like cabbage and beet,which is exploited commercially to induce early seed production.

(B) Gibberellins are plant hormones that can substitute for the requirement of long days in many long-day plants.
When long-day plants are grown under short-day conditions,they fail to flower because the endogenous production of gibberellins is insufficient.
However,if these plants are treated with exogenous gibberellic acid,they can be induced to flower even under non-inductive short-day conditions.

(D) Gibberellins are plant hormones that play a crucial role in breaking seed and bud dormancy.
In winter,potato tubers often remain dormant due to low temperatures.
Applying gibberellins helps in breaking this dormancy and promotes rapid sprouting (germination) of potato tubers.

(D) Gibberellins $(GA)$ are a group of plant growth regulators.
Extensive research in plant physiology has identified more than $100$ different types of gibberellins from various organisms,including fungi and higher plants.
However,in the context of standard textbook questions where $60$ is provided as the highest option,it represents the known count at the time of the source material's publication.
Therefore,the correct option is $D$.

(A) Gibberellins $(GA)$ are plant hormones that play a crucial role in various developmental processes, including the regulation of petal growth and arrangement. Research indicates that gibberellins are present in the petals of certain plants, such as $Cassia \text{ } fistula$ and $Rosa \text{ } indica$, where they help in the tight arrangement and expansion of the petals. Therefore, both $A$ and $B$ are scientifically recognized examples, but in the context of standard botanical $MCQ$, $Cassia \text{ } fistula$ is frequently cited.

(A) $GA$ (Gibberellins) stimulate the activity of intercalary meristem,which promotes the elongation of internodes. This phenomenon is specifically observed in plants like cabbage and beet before flowering and is known as the $Bolting$ effect.

(B) Gibberellins $(GA)$ are known for causing internode elongation,which leads to stem elongation. While both auxins and gibberellins can promote stem elongation,gibberellins are specifically noted for their ability to induce internode elongation in genetically dwarf plants (rosette plants). Auxins primarily stimulate apical dominance and cell enlargement in the apical region,whereas gibberellins stimulate intercalary meristems to increase the length of the axis. Therefore,the most distinct physiological effect often associated with gibberellins in contrast to auxins is significant stem elongation via internode growth.

(C) The 'foolish seedling' disease (bakanae disease) of rice was caused by the fungus $Gibberella$ $fujikuroi$.
Japanese scientists $E.$ $Kurosawa$ reported the appearance of symptoms of the disease in uninfected rice seedlings when they were treated with sterile filtrates of the fungus.
The active substance was later identified and crystallized as $Gibberellic$ $acid$ $(GA_3)$.

(B) Gibberellic acid $(GA_3)$ is a type of plant growth regulator known as a gibberellin.
It was first discovered by $E$. Kurosawa in the fungus $Gibberella \, fujikuroi$, which causes 'bakanae' (foolish seedling) disease in rice plants.
Therefore, the correct option is $B$.

(C) The bioassay for gibberellin includes the Dwarf maize leaf sheath elongation test and the Barley half-seed endosperm test (also known as the $\alpha$-amylase bioassay).
In the Barley endosperm test,gibberellins induce the synthesis of $\alpha$-amylase,which breaks down starch into sugars.
Therefore,option $C$ is the correct answer.

(B) During seed germination,the embryo releases $Gibberellins$ $(GA)$.
These hormones travel to the aleurone layer of the seed.
$Gibberellins$ stimulate the synthesis of hydrolytic enzymes,specifically $\alpha$-amylase.
These enzymes break down stored starch into simple sugars,providing energy for the growing embryo and thus overcoming seed dormancy.

(B) The correct answer is $B$.
$GA_3$ (Gibberellic acid) is a plant hormone that promotes stem elongation.
In plants like cabbage,which are acaulescent (stemless) or have a rosette habit,the application of $GA_3$ induces 'bolting',which is the rapid elongation of the internodes just before flowering.
This drastically changes the plant's growth habit from a compact rosette to an elongated stem.

(A) Gibberellins are a group of plant growth regulators. The first gibberellin, $GA_3$, was discovered by $E$. Kurosawa from the fungus $Gibberella \, fujikuroi$, which causes 'bakanae' (foolish seedling) disease in rice plants. Therefore, gibberellin is obtained from a fungus.

(A) Gibberellins $(GA)$ are plant growth regulators that primarily promote the elongation of stems and internodes.
They stimulate the activity of the intercalary meristem,which leads to an increase in the length of the plant axis.
Therefore,$GA$ is helpful in the elongation of plants.

(D) The correct answer is $D$. Gibberellins were first discovered in the fungus $Gibberella$ $fujikuroi$ (also known as $Fusarium$ $moniliforme$),which is an ascomycetous fungus. This discovery was made while studying the 'bakanae' (foolish seedling) disease in rice plants.

(D) Gibberellins are plant hormones that play a crucial role in breaking the dormancy of seeds and buds,including potato tubers.
They stimulate the synthesis of hydrolytic enzymes like $\alpha$-amylase,which break down stored starch into simple sugars,providing the energy required for germination and sprouting.
$ABA$ (Abscisic acid) acts as a growth inhibitor and promotes dormancy,whereas Gibberellins act as antagonists to $ABA$ to promote growth.

(B) Gibberellins are plant hormones that play a crucial role in breaking seed dormancy.
They stimulate the synthesis of hydrolytic enzymes,such as $\alpha$-amylase,in the aleurone layer of cereal grains.
These enzymes break down stored starch into simple sugars,providing the energy required for embryo growth and germination.

(D) During the germination of barley seeds,the embryo releases gibberellins.
These gibberellins diffuse to the aleurone layer of the endosperm.
In response,the aleurone layer synthesizes and secretes hydrolytic enzymes,specifically $\alpha$-amylase and protease.
These enzymes break down stored starch into simple sugars,which provide energy for the growing embryo,thereby promoting seed germination.

(C) Gibberellins were first discovered by Japanese scientists $E. Kurosawa$ from the rice seedlings infected with the fungus $Gibberella$ $fujikuroi$. This fungus is a parasitic ascomycete that causes 'bakanae' (foolish seedling) disease in rice plants. Therefore,the correct option is $C$.

(C) $GA$ (Gibberellic Acid) is the hormone that plays a crucial role in the germination of cereal grains.
During germination, $GA$ stimulates the synthesis of hydrolytic enzymes like $\alpha$-amylase in the aleurone layer.
These enzymes break down stored starch into simpler sugars, which provide energy for the growing embryo.
Therefore, $GA$ promotes the metabolism of food material necessary for germination.

(D) Gibberellins $(GA)$ are a group of plant growth regulators that are acidic in nature. They are diterpenes synthesized via the mevalonic acid pathway. Since they are neither sugars,sterols,nor vitamins,the correct option is $(d)$.

(C) Genetic dwarfism is a condition where plants remain short due to their genetic makeup.
Gibberellins $(GA)$ are plant hormones that promote stem elongation.
When $GA$ is sprayed on genetically dwarf plants (such as maize or pea),it stimulates internodal growth,thereby overcoming the dwarfism and allowing the plants to attain a normal height.

(B) Gibberellins promote seed germination by inducing the synthesis of hydrolytic enzymes such as $\alpha$-amylase,protease,and lipase in the aleurone layer of the endosperm.
These enzymes break down stored food reserves (starch,proteins,and lipids) into simpler,soluble forms that are transported to the developing embryo to support its growth.
Therefore,the correct option is $B$.

(C) The physiological stimulus of vernalization is known as vernalin.
It has been observed that the application of $Gibberellins$ can replace the requirement of cold treatment (vernalization) to induce flowering in many plants.
Therefore,$Gibberellins$ can effectively substitute for the vernalization process.

(B) Gibberellins are plant growth regulators that influence sex expression in certain plants.
In species like $Cucumis$ (e.g.,cucumber),the application of gibberellins promotes the development of male flowers on genetically female plants.
This is a well-documented physiological effect where hormonal treatment alters the phenotypic expression of sex in dioecious or monoecious plants.

(B) The correct answer is $B$.
Gibberellins $(GA_3)$ are plant hormones that promote stem elongation.
When $GA_3$ is applied to genetically dwarf plants (such as maize or pea),it overcomes the genetic dwarfism by stimulating cell elongation and cell division,causing the plants to grow tall.

(C) Bolting is the phenomenon of internode elongation just prior to flowering in plants like beet,cabbage,and many rosette plants.
Gibberellins $(GA_3)$ are plant growth regulators that promote internode elongation.
Therefore,the application of gibberellins is responsible for inducing bolting in rosette plants.

(C) Gibberellins are a group of plant growth regulators that are primarily responsible for stem elongation and internodal growth in plants.
They promote the elongation of internodes in genetically dwarf plants (rosette plants) by stimulating cell division and cell elongation.
Therefore,$Gibberellin$ is the correct answer for internodal elongation.

(B) The most important physiological effect of $Gibberellins$ $(GA)$ is the reversal of genetic dwarfism in plants.
When genetically dwarf plants (such as dwarf peas or dwarf maize) are treated with $Gibberellic$ $acid$,they grow to attain normal height.
This occurs because dwarf plants typically have lower endogenous levels of $GA$.
Exogenous application of $GA$ stimulates rapid internode elongation,thereby overcoming the dwarf phenotype.
$GA$ does not have a significant effect on the height of normal (tall) plants.

(D) The 'foolish seedling' disease of rice,also known as 'bakanae' disease,was caused by the fungal pathogen $Gibberella$ $fujikuroi$.
$E$. Kurosawa reported the appearance of symptoms of the disease in uninfected rice seedlings when they were treated with sterile filtrates of the fungus.
The active substances were later identified as Gibberellic Acid $(GA)$.
Thus,$GA$ was discovered from the study of this disease.

(A) Gibberellins are plant hormones that play a crucial role in breaking seed and bud dormancy. In the case of potato tubers,the application of gibberellins (specifically $GA_3$) is widely used to break dormancy and stimulate sprouting. $ABA$ (Abscisic acid) acts as a growth inhibitor and promotes dormancy,while $IAA$ (Indole$-3-$acetic acid) is an auxin primarily involved in cell elongation. Therefore,the correct answer is Gibberellin.

(B) In many seeds,$Gibberellins$ promote germination by inducing the synthesis of hydrolytic enzymes,such as $\alpha-amylase$,in the aleurone layer.
These enzymes break down stored starch into simple sugars,which provide the energy required for the growth of the embryo.
Therefore,the primary mechanism for stimulating germination is the production of digestive enzymes that mobilize stored food reserves.

(A) $Gibberellins$ are plant growth regulators that promote various physiological processes. One of the most significant effects of $Gibberellic$ $Acid$ $(GA)$ is the elongation of genetically dwarf plants (like maize or pea). This process is known as 'bolting' or internode elongation. $GA$ does not cause dwarfism in tall plants,nor does it typically initiate root growth (which is a function of $Auxins$). Yellowing of leaves is usually a sign of nutrient deficiency or senescence,not a primary effect of $GA$.

(B) : Gibberellins are plant growth hormones that play a crucial role in seed germination. During germination,gibberellins stimulate the synthesis of hydrolytic enzymes,such as $\alpha$-amylase,in the aleurone layer of cereal seeds. These enzymes break down stored starch into simple sugars,which are then transported to the developing embryo to provide energy for growth. Thus,gibberellins are responsible for the mobilization of food reserves in germinating seeds.

(B) The correct answer is $(b)$.
Germination is the process by which a dormant embryo in a seed resumes active growth to form a seedling.
The initial step in the germination process is the uptake of water and rehydration of seed tissues through imbibition.
Upon imbibition,the embryo releases gibberellins,which signal the aleurone layer to synthesize and secrete hydrolytic enzymes,most notably $\alpha$-amylase.
$\alpha$-amylase hydrolyzes the starch stored in the endosperm into simple sugars like glucose.
These sugars are essential as a respiratory substrate for energy production and as a source of carbon skeletons for the synthesis of new molecules required for growth.

(D) The 'foolish seedling' disease (bakanae disease) of rice plants is caused by the fungal pathogen $Gibberella$ $\text{fujikuroi}$.
In $1926$, $E$. Kurosawa reported that rice seedlings infected with this fungus grew abnormally tall and became thin, leading to the name 'foolish seedling'.
He observed that the symptoms were caused by a substance secreted by the fungus.
Later, this substance was identified as Gibberellic Acid $(GA)$, which is a type of gibberellin.

(B) Gibberellins are plant growth regulators that exhibit several physiological effects:
$1$. $(b)$ Delaying senescence: Gibberellins delay the aging of leaves and fruits,allowing fruits to remain on the tree for a longer duration.
$2$. $(e)$ Inducing parthenocarpy: Gibberellins can induce the development of seedless fruits (parthenocarpy) in species like tomatoes.
$3$. $(f)$ Promoting female flowers: In plants like cucumbers,gibberellins increase the number of female flowers.
Apical dominance is primarily controlled by auxins,not gibberellins. Increase in axis length is a characteristic effect,but the combination $(b, e, f)$ is a standard set of physiological responses attributed to gibberellins in $NCERT$ textbooks. Therefore,the correct option is $(b)$.

(C) Gibberellins were first discovered by $E$. Kurosawa in the fungus $Gibberella$ $\text{fujikuroi}$.
$GA_3$ (Gibberellic acid) was the first gibberellin to be isolated and identified chemically.
It remains the most extensively studied and widely used gibberellin in research and agriculture.
Therefore, $GA_3$ is considered the first discovered gibberellin.

(B) Gibberellins are a group of plant hormones that promote stem elongation.
In genetically dwarf plants, the application of $Gibberellic$ acid $(GA)$ can overcome the genetic dwarfism by stimulating internode elongation, thereby allowing the plant to grow to a normal height.
This phenomenon is known as the reversal of dwarfism.

(D) The 'foolish seedling' disease (bakanae disease) of rice plants is caused by the fungus $Gibberella fujikuroi$.
$E$. Kurosawa reported the appearance of symptoms of this disease in uninfected rice seedlings when they were treated with sterile filtrates of the fungus.
The active substance responsible for this effect was later identified as $Gibberellic Acid$ $(GA)$.
Thus, the discovery of $GA$ is linked to the study of this disease.

(B) $E$. Kurosawa $(1926)$ reported the appearance of symptoms of the 'bakanae' (foolish seedling) disease in rice seedlings when they were infected with the fungus $Gibberella$ $fujikuroi$.
He discovered that the active substance responsible for this disease was Gibberellic acid $(GA_3)$.
This was the first gibberellin to be discovered.

(B) $GAs$ (Gibberellins) are a group of plant growth regulators that are chemically acidic in nature. They are diterpenes synthesized via the terpenoid pathway. Because they contain carboxyl groups,they exhibit acidic properties.

(D) Bolting refers to the internode elongation just prior to flowering in plants that exhibit a rosette habit,such as beet and cabbage.
Gibberellins $(GA)$ are plant hormones known to promote this internode elongation,thereby inducing bolting.
$IAA$ and $NAA$ are auxins,which are primarily involved in cell enlargement and apical dominance.
Kinetin is a type of cytokinin,which promotes cell division.
Therefore,the correct answer is Gibberellin.

(D) The 'foolish seedling' disease (bakanae disease) of rice is caused by the fungal pathogen $Gibberella fujikuroi$.
This disease was observed by $E. Kurosawa$ in rice seedlings that grew abnormally tall and became thin.
It was later discovered that the fungus secretes a chemical substance, which was identified as Gibberellin, responsible for this excessive growth.