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 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

Identify the incorrectly matched pair.

  1. Auxin - Phototropism

  2. Gibberellins - Foolish seedling disease of rice

  3. Ethylene - Induces fruit ripening

  4. Cytokinin's - Promote apical dominance
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cytokinins typically promote lateral bud growth and help overcome apical dominance, rather than promoting apical dominance themselves. Thus, this matched pair is incorrect.

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.

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

Abscisic acid regulates

  1. Shoot elongation

  2. Cell elongation and cell wall formation

  3. Cell division

  4. Leaf fall and dormancy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Abscisic acid regulates leaf fall and dormancy.

Other functions of abscisic acid includes:
  1. It induces bud dormancy in a number of plants. In perennial plants, ABA causes the active axillary buds to become dormant.
  2. It maintains dormancy in many seeds.
  3. It inhibits mitosis in vascular cambium.
  4. It accelerates senescence in leaves.
  5. It functions as a stress hormone by inducing a temporary closure of stomata, to tide over adverse environmental conditions.
  6. It promotes abscission of leaves, flowers and fruits in most of the plants.
  7. It inhibits seed germination.
  8. It delays cell division and cell elongation.
  9. It promotes rooting of stem cuttings in some plants like ivy and bean.
  10. It inhibits flowering except in some short day plants where it promotes flowering.

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

Plant hormone is also known as___________________

  1. Planktohormone

  2. Phytohormone

  3. Photohormone

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Plant hormones are also known as phytohormones, they are chemicals that regulate plant growth. 
  • Plant hormones are signal molecules produced within the plant and occur in extremely low concentrations. 
  • Hormones regulate cellular processes in targeted cells locally and, moved to other locations, in another functional part of the plant. 
Hormones also determine the formation of flowers, stems, leaves, the shedding of leaves, and the development and ripening of fruit. The term 'Phytohormone' was coined by Thimann in 1948. 

Therefore, the correct answer is option B.

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

Hormone which initiates mobilization of storage materials is_________________ 

  1. Gibberellins

  2. Abscisic acid

  3. Cytokinin

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

  • Gibberellins are phytohormones that initiate mobilization of storage materials in seeds during germination. 
  • They also cause elongation of stems, stimulate bolting in biennials stimulate pollen tube growth. 
  • Gibberellins include a large range of chemicals that are produced naturally within plants and by fungi. 
  • Gibberellins are important in seed germination, affecting enzyme production that mobilizes food production used for the growth of new cells. 

Therefore, the correct answer is option A.

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

Plants do not have glands, then how do they secrete hormones?

  1. Each cell is capable of producing hormones

  2. One cell produces hormone and then is transferred to others

  3. Hormones are produced by soil and taken up by the roots

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • In animals, there are various glands that produce different hormones but such glands are absent in the plants. Instead, each cell is capable of producing hormones. 
  • Plant hormones shape the plant, affecting seed growth, time of flowering, the sex of flowers, senescence of leaves, and fruits. 
  • They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity and even plant death. 
  • Hormones are vital to plant growth and lacking them, plants would be mostly a mass of undifferentiated cells. So, they are also known as growth factors or growth hormones.

Therefore, the correct answer is option A.

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 hormones coordinate the root growth process?

  1. Cytokinins

  2. Auxins

  3. Ethylene

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

  • A class of plant hormones called auxins coordinates the root growth process.
  •  Auxins play a key role in bending the plant roots towards the water because they cause one side of the root to grow faster than the other and thus the bending of the root. 

Therefore, the correct answer is option B.

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

Auxins play a key role in tropism

  1. True

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

  • Auxins- play a key role in tropism (controlling the direction of plant growth). 
Geotropism- Under the influence of gravity, auxins accumulate in the lower side of a horizontal stem, causing cells to enlarge faster, turning the stem upright. 
  • Phototropism- The auxin concentration on the shaded side stimulates cell elongation, turning the stem to the sun. 


Therefore, the correct answer is option A.

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

The role of gibberellin is

  1. Inhibits lateral buds

  2. Stimulates fruit ripening

  3. Maintains seed dormancy

  4. Stimualtes rapid stem elongation

  5. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The gibberellins are plant growth hormones which enhance the longitudinal growth of stem when applied to the intact plant. Gibberellins produce extraordinary elongation of stems and leaf sheaths in intact plants. The elongation of the stem is caused due to cell division and cell elongation induced by gibberellic acid. Thus 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

Which of the following regulates phototropism?

  1. Ethylene gas

  2. Abscisic acid

  3. Auxin

  4. Gibberellins

  5. Cytokinins
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The directional growth of organisms in response to light is called phototropism. In plants, aerial shoots usually grow towards the light. The phototropic response is controlled by auxin.