Biology

Plant Growth and Hormones

695 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

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'. 

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

Which one prevents over-ripening of banana and browning of cut fruits?

  1. Gibberellic Acid

  2. Indole-3 Acetic Acid

  3. Ascorbic Acid

  4. Abscisic Acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Lemon juice helps keep the apple from browning, because it is full of ascorbic acid (Vitamin C) and it has a low (acidic) pH level. Ascorbic acid works because oxygen will react with it before it will react with the polyphenol oxidase. However, once the ascorbic acid gets used up, the oxygen will start reacting with the enzyme and browning will occur. Lemon juice's low pH level also helps prevent browning. Polyphenol oxidase works best when the pH level is between 5.0 and 7.0. However, below a pH level of 3.0, the enzyme becomes inactivated. The pH of lemon juice is in the 2.0 range, making it very effective against browning.

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

Abscisic acid controls

  1. Cell elogation and cell wall formation

  2. Shoot elogation

  3. Leaf fall and dormancy

  4. Cell division
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Abscissic acid regulates abscission (the shedding of leaves, flowers and fruits from the living plant) and dormancy. It acts as general plant growth inhibitor and also inhibit plant metabolism. It inhibits closure of stomata in epidermis, and increase tolerance of plant to various kinds of stresses, and therefore called as stress hormone.
ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand dessication and other factors favourable for growth.

Thus, the correct answer is option C.

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

State whether the following statements are true or false.
Dormancy of winter buds in temperate trees is caused by abscisic acid.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid is the hormones also called as stress hormones as they function in stress conditions. They are also known as dormant as they induce dormancy in buds. It mostly induced bud dormancy at the start of the winter season. They are generally growth hormone which inhibits growth normally.

So, the correct statement is 'True'.

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 associated with the closure of the stomata in a plant under water stress?

  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'. 

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

Leaf abscission is caused by

  1. ABA

  2. cytokinin

  3. auxin

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

A plant will abscise apart either to discard a membrane that is no longer necessary, such as a leaf during autumn or a flower following fertilization or for the purpose of reproduction. Most deciduous plants drop their leaves by abscission before winter, whereas evergreen plants continuously abscise their leaves.

So, the correct option is 'ABA'.