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 ethylene plant hormones plants and animal hormones

Which hormone is used to induce ripening in banana?

  1. Cytokinin

  2. Ethylene

  3. ABA
  4. GA$ _{3}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ehtylene is a simple gaseous plant growth regulator. It is synthesized in large amounts by tissues undergoing senescence and ripening of fruits. It enhances the respiration rate during ripening of fruit. This rise in rate of respiration is called as respiratory climacteric. 
Exposure of plants to ethylene causes drooping of leaves and flowers, a phenomenon known as epinasty.

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants ethylene plant hormones plants and animal hormones

Flowering in Pineapple is promoted by

  1. GA

  2. IAA

  3. Ethylene

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Flowering in pineapple is not only based on external factors like temperature, daylength but also is based on internal factors like phytohormones. Pineapple flowering can be artificially induced by activity of the ethylene and IAA (indoleacetic acid). During flowering of pineapple, low temperature stimulates ethylene biosynthesis. Other hormones which are involved in initiating pineapple flowering are a-naphthalene acetic acid (NAA), indolbutiric acid (IBA), 2,4-dichlorofenoxiacetic acid (2,4-D). 

Thus, the correct answer is option D.

Multiple choice biology chemical coordination in plants ethylene plant hormones plants and animal hormones

Choose the correct answer from the alternatives given.
Which of the following plant hormones stimulates the ripening of fruit and inhibits plant growth?

  1. Abscisic acid

  2. Cytokinin

  3. Ethylene

  4. Gibberellin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Ethylene is a simple gaseous PGR. 
  • It is synthesised in large amounts by tissues undergoing senescence and ripening fruits. 
  • Influences of ethylene on plants include horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings. 
  • Ethylene promotes senescence and abscission of plant organs, especially of leaves and flowers. 
  • Ethylene is highly effective in fruit ripening
  • So, the correct option is 'Ethylene'.
Multiple choice biology life within the seed developmental journey of seed introduction to plant organs and germination seed to plants

At the time of seed germination, digestive enzymes are induced to be formed under the influence of

  1. Cytokinin

  2. Gibberellins

  3. Ethylene

  4. Auxin
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gibberellin is a plant hormone which breaks the seed dormancy. Before the germination, starch nourishes seedling. It stimulates the synthesis of digestive enzymes like amylase in the aleurone cells of certain cereals. Amylase hydrolyzes starch into glucose which is used to provide nourishment to the seed embryo. 

Thus, the correct answer is option B.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

The cause of dormancy for sometime in fertilized ovule is 

  1. Presence of Auxin hormone

  2. Zygote divides only after certain amount of endosperm is formed

  3. Presence of growth inhibitor ABA

  4. Presence of least amount of water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The fertilized ovule is got dormant so that the adequate amount of endosperm is formed as for division and for further survival, it is very necessary that ample amount of food is present in the seed.

So the correct option is 'Zygote divides only after a certain amount of endosperm is formed'.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

Which of the following breaks the dormancy of potato tubes?

  1. IAA

  2. ABA

  3. Zeatin

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

Dormancy of seeds could be broken by the activation of digestive enzymes like alpha amylases. It is being done by phytohormones like gibberellic acid. It also helps in cell elongation, division of lateral meristem and many more.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

Which of the following is used to break the seed dormancy?

  1. ABA

  2. Cytokinin

  3. Auxin

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

ABA, abscisic acid was discovered for its role in regulating abscission and dormancy. It acts as a general plant growth inhibitor and an inhibitor of plant metabolism. It inhibits seed germination, stimulates the closure of stomata in the epidermis and increases the tolerance of the plant to various kind of stresses. 

Gibberellins cause fruits like apple to elongate and improve its shape. They also delay senescence.
Auxins promote stem elongation, inhibit the growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips. Ethylene is highly effective in fruit-ripening, it promotes senescence and abscission of plant organs especially leaves and flowers. Ethylene breaks the seed and bud dormancy and initiates seed germination.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

Dormancy of seed is broken by 

  1. Auxin

  2. Gibberellin

  3. Abscisic acid

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

Gibberellin are involved in seed germination in certain plants. They break seed dormancy by promoting mobilisation of reserve food material. In a classic experiment involving barley seed germination, researchers showed that the release of gibberellin from the embryo triggers the synthesis of $\alpha$-amylase, an enzyme that digests starch in the endosperm. As a result, glucose becomes available for absorption by the embryo. Although enzymes mobilize starch reserves in many types of seeds, gibberellin control of seed enzymes appears restricted to cereals and other grasses. 

Thus, the correct answer is option B.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

Common cause of seed and bud dormancy is the presence of

  1. Ethylene

  2. Cytokinins

  3. Abscisic acid

  4. Both B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dormancy is defined as the condition of seed when it fails to germinate even though the envoirnment condtions, usually considered favourable for active growth, are present.

A. Ethylene serves as a hormone in plants. It acts at trace levels throughout the life of the plant by stimulating or regulating the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves.

B. Cytokinins are plant hormones that cause increased celldivision by stimulating the process of mitosis. 

C. Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in terminal buds. This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season.

So, the correct answer is 'Abscisic acid'.

Multiple choice biology plant growth seed dormancy fruit plants: structure and function

Among the following which compound can induce seed dormancy?

  1. Gibberellins

  2. Caffeine

  3. ABA

  4. Potassium nitrate
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Abscisic acid (ABA) is the primary plant hormone responsible for inducing and maintaining seed dormancy to prevent premature germination.