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 life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

To speed up the malting process in brewing industry the growth hormone used is ____________.

  1. auxin

  2. gibberellin

  3. kinetin

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

Gibberellins are used to speed up the malting process in brewing industry. They increase the yield of malt from barley grains.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Read the given statements and identify the plant hormones X, Y and Z.
(i) Hormone Y suppresses flowering in mango and also promotes rapid internode/petiole elongation in deep water rice plants and hence helping leaves or upper part of shoot to remain above water.
(ii) Hormone X promotes root growth and root hair formation.
(ii) Hormone Z inhibits the seed germination, increases the tolerance of plant to various stresses, play important role in seed development maturation and dormancy.

  1. Y-ABA, X-Auxin, Z-GA
  2. Y-$C _2H _4$, X-Auxin, Z-GA
  3. Y-Auxin, X-$C _2H _4$, Z-GA

  4. Y-GA, X-auxin, Z-ABA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

i) Gibberilic Acid (GA) suppresses flowering in mango, GA$ _3$, it is applied periodically to mango plants in their 1-4 yrs of growth to inhibit flowering and promote vegetative growth. GA plays a role in internode elongation in submerged parts of the rice plant.

Auxin along with cytokinin promotes root growth and root hair formation.
ABA is a stress hormones, it protects the plant from unfavorable environmental conditions, by preventing seed germination (due to oxygen deficit, water stress etc).
So, the correct answer is 'Y-GA, X-auxin, Z-ABA'

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Read the given statements and select the option that is/are incorrect ones.


(i) Cytokinin is primarily concerned with cell division.
(ii) $C _2H _4$ breaks seed and bud dormancy.
(iii) ABA stimulates the opening of stomata.
(iv) $C _2H _4$ initiates germination in peanut seeds, sprouting of potato tubers.
(v) ABA is synergistic to GA.

  1. (i), (ii) and (iv)

  2. (iii) and (ii)

  3. (iii) and (v)

  4. (iv) and (v)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

ABA is regarded as the stress hormone or a growth inhibitor. In conditions of water stress ABA initiates closure of stomata to prevent water loss through transpiration. It is antagonistic to GA as the latter promotes seed germination,  while ABA prevents seed germination.

So, the correct answer is ' (iii) and (v)'

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Match the plant hormones listed in column I with their major role listed in column II and select the corret option from the codes given below.

Column I Column II
(A) Auxin (i) Fruit ripening
(B) Cytokinin (ii) Phototropism
(C) Abscisic acid (iii) Suppression of cell division
(D) Ethylene (iv) Stomatal opening and closing
(v) Growth of lateral buds


  1. A - (v), B - (iii), C - (iv), D - (ii)

  2. A - (iii), B - (ii), C - (iv), D - (i)

  3. A - (ii), B - (v), C - (iv), D - (i)

  4. A - (ii), B - (iv), C - (v), D - (iii)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A) Auxin - (ii) Phototropism

(B) Cytokinin - (v) Growth of lateral buds

(C) Abscisic acid - (iv) Stomatal opening and closing

(D) Ethylene - (i) Fruit ripening

So, the correct answer is 'A - (ii), B - (v), C - (iv), D - (i)'.
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

In plant tissue culture experiments, high auxin to cytokinin ratio favours .............. development and high cytokinin to auxin ratio favours .............. development.

  1. Root, shoot

  2. Shoot, root

  3. Root, root

  4. Shoot, shoot
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Callus is an unorganized, undifferentiated mass of diving cells formed during tissue culture which requires both auxins and cytokinins for its growth and differentiation. In callus, shoot regeneration is promoted by a cytokinin, such as BAP (Benzylaminopurine) and root regeneration is promoted by an auxin, such as NAA (Naphthalene acetic acid). Thus, shoot and root regenerations in callus are controlled by auxin-cytokinin balance. Usually, an excess of auxins promote root regeneration and that of cytokinins promote shoot regeneration.
So the correct option is 'root, shoot'.
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Small cut pieces of soft stems are placed in growth medium with following plant hormone. Which combination of plant hormones will show the slowest growth? 

  1. Auxin+Cytokinin

  2. Gibberellins+Auxin

  3. Gibberellins+Cytokinin

  4. Abscisic Acid+Auxin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Abscisic acid is growth inhibiting hormone whereas auxin, gibberellin and cytokinin are growth promoting hormones. Options A,B, and C include all growth promoting hormones whereas option D includes both growth promoting and growth inhibiting hormones. Therefore, this combination of hormones will show slowest growth.

So option D is the correct answer.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Cytokinin and auxin are antagonistic in which of the following function?

  1. Cell division

  2. Phototropism

  3. Apical dominance

  4. Geotropism
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • The main function of Auxin is to promote stem elongation and inhibition of growth of lateral buds to maintain apical dominance.
  • It is produced in the stem tips, buds and root tips to promote growth and it also helps to repair wounds in plants.
  • The function of cytokinins is to increase the cell division by stimulating the process of mitosis which helps in plant growth and formation of shoots and buds.
  • Cytokinins promote sprouting of lateral buds and overcome apical dominance.
  • Cytokinin and auxin are antagonistic for apical dominance.
  • So the correct answer is 'Apical dominance'.
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Which of the following plant hormones is not acidic in nature?

  1. Gibberellin

  2. Auxin

  3. Cytokinin

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

Gibberellins are diterpenoid acids, Auxins are indole derivatives (often acidic), and ABA (Abscisic acid) is acidic. Cytokinins are adenine derivatives and are generally basic or neutral in nature.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Match the names of the phytohormones with the roles listed. 

   List I    List II
 A  Auxin  p  Internodal elongation
 B  Gibberellin  q  Cell division
 C  Cytokinin  r  Ripening of fruits
 D  Ethylene  s  Abscission
     t  Apical dominance

  1. A- t, B- p, C- s, D- q

  2. A- t, B- p, C- q, D- s

  3. A- t, B- p, C- q, D- r

  4. A- t, B- s, C- p, D- q
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Auxin hormone causes apical dominance. Apical dominance is referred to the growth of plants attaining height. As a result of this, the plant will grow tall. Cytokinin is the phytohormone which is responsible for the multiplication if cells or cell division. 
  • In other words, cytokinin influences mitosis. Gibberellin is the hormone that induces internodal elongation. It is also called as bolting. This is commonly found in cabbage when this hormone is more in amount.
  •  The ethylene hormone is responsible for the ripening of fruits. Spraying of ethylene will promote early fruit ripening.
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Consider the statements A -D.
A. Ethephon is widely used in agriculture for the source of ethylene.
B. Auxin stimulates the stem to bent towards the source of light. 
C. Carbohydrates are produced in mature leaves and transported to other plants parts. 
D. Gibberellins promote the growth of plumule and radicle in seed germination.

Which of these statements are correct?

  1. A , B and C

  2. A, C and D

  3. A, B and D

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

Etheophon is the most widely used growth regulator for the source of ethylene, Auxins used to promote shoot elongation and carbohydrates are produced in mature leaves and will get transported to other parts of the plants. but gibberellins won't promote the growth of plumule and radicle in seed germination.

So the correct option is 'A, B and C.'

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Auxin inhibits the growth of

  1. Apical buds

  2. Fruits

  3. Lateral auxillary buds

  4. Roots of cuttings
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Auxin induces shoot apical dominance. The axillary buds are inhibited by auxin, as a high concentration of auxin directly stimulates ethylene synthesis in lateral buds, causing inhibition of their growth and potentiation of apical dominance. When the apex of the plant is removed, the inhibitory effect is removed and the growth of lateral buds is enhanced. Auxin is sent to the part of the plant facing the light, and this promotes growth towards that direction. 

Therefore, the correct answer is option C.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Which of the following plant hormones is incorrectly paired with its function?

  1. Auxins- Responsible for apical dominance

  2. Abscisic acid- Regulates the rate of transpiration

  3. Gibberellins- Promotes bud and seed dormancy

  4. Ethylene- Promotes ripening
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gibberellins regulate the cell growth and influence various developmental processes, including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, and leaf and fruit senescence. Ethylene promotes ripening. Auxins are responsible for apical dominance. Abscisic acid regulates the rate of transpiration. 

Therefore, the correct answer is option C.