Biology

Plant Growth and Hormones

727 Questions

Plant growth and hormones is a vital topic in biology that covers the physiological effects of different plant regulators like auxins, gibberellins, and cytokinins. These concepts are frequently tested in various general science sections of competitive exams. Practicing these questions helps clarify complex mechanisms like vernalisation, senescence, and tropism for test takers.

Abscisic acid effectsCytokinin functionsAuxins and tropismPlant tissue cultureSenescence in plantsNatural plant hormones

Plant Growth and Hormones Questions

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

In the extreme drought condition, which of the following plant hormone is produced, due to which stomata closes?

  1. ABA

  2. IAA

  3. Gibberellin

  4. Ascorbic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ABA is a plant hormone which is inhibiting in nature. It causes the closure of stomata, in order to reduce the rate of transpiration and the loss of water thereby. It is also well known for its dormant activity. ABA promotes early aging in the plant and also inhibits flowering, fruiting, germination, etc. 

Thus, the correct answer is option A.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in 

  1. Annual plants

  2. Floral parts

  3. Vessels and tracheid differentiation

  4. Leaf abscission
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Senescence is a programmed developmental process. Leaf abscission is a classic example of programmed cell death and senescence in plants, allowing the plant to shed older or damaged leaves.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Which one is not a growth promoter?

  1. ABA

  2. GA

  3. IAA

  4. CK
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are various plant hormones which act as growth regulators. Hormones like gibberellic acid (GA), Indoleacetic acid (IAA), a type of auxin, cytokinin (CK) are growth promoter. Hormones like Abscisic Acid (ABA), ethylene are growth inhibitor. These hormones accelerate abscission process.

Thus, the correct answer is option A.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Abscisic acid causes

  1. Stomatal closure

  2. Stem elongation

  3. Leaf expansion

  4. Root elongation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 It inhibits root elongation, stem elongation and seed germination. It brings out the stomatal closure when soil water is insufficient to keep up with transpiration. It binds to receptor present on the guard cells and hence closes stomata.

So, the correct answer is 'Stomatal closure'

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Abscisic acid causes

  1. Seed dormancy

  2. Apical dominance

  3. Root initiation

  4. Phototropism
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid is a plant hormone. It is involved in various physiological processes of the plant. It acts as a plant growth inhibitor. It is also called as stress hormone as its concentration increases during stress condition. Under the unfavourable condition, it induces seed dormancy. When favourable condition returns, seed dormancy is broken. 

Thus, the correct answer is 'Seed Dormancy'.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

During drought, plants develop hormone

  1. Indole acetic acid

  2. Naphthalene acetic acid

  3. Indolebutyric acid

  4. Abscisic acid

  5. Ethylene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stress hormone is a hormone produced during adverse environmental conditions. Abscisic acid (ABA) is called as stress hormone. Due to this hormone, plants respond to stresses conditions like cold, drought. It increases the tolerance of plants toward various stresses. It is found in high concentration in roots during drought and later translocated to leaves. It causes stomatal closure during water stress. It also promotes seed dormancy under adverse condition.

Thus, the correct answer is option D.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Which one is wrongly matched?

  1. Auxins - to grow

  2. Gibberellins - Gibberella fujikuroi

  3. Cytokinins - Herring sperm DNA

  4. ABA - flowering hormone

  5. Ethylene - gas hormone
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Auxin is a plant hormone that is involved in growth and development of plant. Kinetin, a type of cytokinin was isolated from autoclaved herring sperm DNA by Miller and Skoog. Gibberellin hormone was first isolated from fungus Gibberella fujikuroi. Ethylene is a gaseous hormone which helps in ripening process and hence also called as ripening hormone. ABA is responsible for abscission of leaves, fruits and flowers. Florigen is a flowering hormone that is responsible for flowering in certain plants.

Thus, the correct answer is option D.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Leaf abscission is brought about by

  1. Auxin

  2. Cytokinin

  3. Gibberellin

  4. ABA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Leaf abscission is a detachment or fall of older leaves.It occurs at the base of the petiole. During abscission, high synthesize of abscisic acid is observed along with decrease in the concentration of auxin. ABA loosens the cell wall and cells separate which ultimately leads to leaf abscission. 

Thus, the correct answer is option D.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Hormone antagonistic to ABA is

  1. Gibberellin

  2. Auxin

  3. Ethylene

  4. Cytokinin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid is a plant hormone. It causes abscission of leaves. It induces dormancy of seed under unfavorable condition. Gibberellin is a plant hormone that is an antagonist to the abscisic acid hormone. It regulates plant growth. It stimulates stem elongation, germination, flowering. it breaks the seed dormancy and initiates germination process. 

Thus, the correct answer is option A.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Which one demonstrates process associated with abscission of a leaf?

  1. In the leaf concentration of both auxin and ABA decreases

  2. In the leaf concentration of both auxin and ABA increases

  3. Reduction in ABA concentration and increase of auxin concentration in the leaf

  4. Reduction in concentration of auxin and increase of concentration of ABA in the leaf
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Auxin is a plant hormone which prevents the abscission of leaves and fruits. Young leaves and fruits produce auxin and thus remain attached to the stem. When the level of auxin declines in leaves, leaves the drop. ABA induces abscission of leaves. Hence, during abscission of a leaf, there is the reduction in auxin concentration and increase in ABA concentration in the leaf.
Thus, the correct answer is option D.
Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Hormone antagonist to gibberellins is

  1. IAA

  2. ABA

  3. Zeatin

  4. Ethylene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Gibberellin or Gibberellic Acid (GA) is produced in embryos, roots, and young leaves and it enhances growth. Abscisic acid is a naturally occurring growth inhibitor found in wide variety of plants, synthesised in leaves. Gibberellin delays senescence in plants. Abscisic acid promotes the senescence of leaf, i.e., fall of leaves happens due to abscisic acid. Gibberellin breaks dormancy of seeds and as opposed to Abscisic acid, which induces dormancy of buds and seeds.
Hence, due to their opposite effect on plant growth, Gibberellins and Abscisic acid can be said to be an antagonist to each other.
So, the correct answer is 'ABA'
Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Choose the correct answer from the alternatives given.
Which of the following statements is false?

  1. Auxins and gibberellins promote stem elongation.

  2. Cytokinins promote cell division but retard leaf ageing

  3. Abscisic acid promotes water loss and dormancy

  4. Ethylene promotes fruit ripening and abscission
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

ABA helps seeds to withstand desiccation and other factors unfavorable for growth.

So, the correct option is 'Abscisic acid promotes water loss and dormancy'.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Choose the correct answer from the alternatives given.
Which of the following plant hormones is called the stress hormone because it produces dormancy in seeds and buds?

  1. Abscisic acid

  2. Auxin

  3. Cytokinin

  4. Ethylene
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid inhibits seed germination and 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.

So, the correct option is 'Abscisic acid'.