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

Which of the following statements is/are correct?

a. Plants do not have a nervous system. b. Plants use hormones for coordination. c. Plants respond to stimuli very slowly by growing.

  1. a, b and c

  2. a and b

  3. a and c

  4. b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Plants do not have a nervous system. They use only hormones for coordination. They respond to stimuli very slowly as they do not have a nervous system and their response is reflected by their growth.

Multiple choice

The parthenocarpy has been introduced in egg-plant by inserting a bacterial gene responsible for the synthesis of (1) gibberellins (2) cytokinin (3) auxin

  1. Only 1 and 2

  2. Only 1 and 3

  3. Only 2

  4. Only 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bacterial genes for auxin biosynthesis (such as iaaM and iaaH from Pseudomonas syringae) can be inserted into plants to induce parthenocarpy - the development of fruit without fertilization. Auxin is the primary hormone responsible for fruit set and development. Gibberellins and cytokinins are not the primary hormones for this purpose.

Multiple choice

In 1925, the Japanese biologist Kurosawa showed that the bakanae (foolish seedling) disease of rice was caused by a substance produced by the fungus Gibberella fujikuroi. The substance was named gibberellin and was shown to cause elongation of stem tissues. Which of the following statements about gibberellins is false?

  1. The gibberellins produced by the fungus caused normal healthy rice plants to become unusually tall.

  2. Dwarf pea plants have a mutation in the gibberellin biosynthesis pathway.

  3. If gibberellin is applied to the stems of dwarf pea plants, the stems elongated so that the plant reach normal health.

  4. Pea plants carrying the dwarf mutation would be expected to have higher levels of gibberellin in their stems than normal plants.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The question asks for the FALSE statement. Dwarf pea plants have mutations that REDUCE gibberellin production or sensitivity, which is why they're dwarf. Therefore, they would have LOWER levels of active gibberellin, not higher. Option D correctly identifies this as false by stating they would have 'higher levels' - this is the lie. Options A, B, and C are all true statements about gibberellins.

Multiple choice

Why does a plant appear to bend towards light?

  1. Due to the diffusion of auxins towards the shady side of the shoot

  2. Due to the diffusion of gibberellins towards the bright side of the shoot

  3. Due to the diffusion of cytokinins towards the shady region of the shoot

  4. Due to the diffusion of gibberellins towards the shady region of the shoot
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When light is incident on one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot, which is away from light. Thus, the plant appears to bend towards light.

Multiple choice

Choose the correct match.

 
GROUP I GROUP II
(i) Auxine A. Prevent aging
(ii) Cytokinine B. Change sex of unisexual plant
(iii) Ethylene C. Root regeneration
(iv) ABA D. Stimulate lateral growth

  1. i - B, ii - A, iii - D, iv - C

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

  3. i - A, ii - C, iii - D, iv - B

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

Auxine helps to promote the meristemic tissue, i.e. root. Cytokinine prevents senescence or aging. Ethylene stimulates lateral growth of plant tissue. ABA or abscisic acid is used for changing sex of unisexual plant; it has an economical value.

Multiple choice

Abscisic acid causes _____________.

  1. faster leaf fall

  2. dormancy of tubers

  3. retardation of growth

  4. senescence of leaves

  5. all of the above are correct
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

All the options are correct and reveal the functions of ABA.

Multiple choice

Apical dominance in higher plants is due to _____________.

  1. balance between auxin and cytokinin

  2. enzymatic activity

  3. carbohydrate and nitrogen ratio

  4. photoperiodism

  5. the presence of apical dominance
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It is true that auxin and cytokinin ratio controls morphogenesis in higher plants and thus regulating the apical dominance.

Multiple choice

If a gardener is interested in obtaining a good crop of tea leaves from a single plant, what should he do?

  1. Feed auxin to the plant through soil.

  2. Remove the apical bud of the main shoot and the branches.

  3. Cut off the tip of the plant and then apply auxins to the cut end.

  4. Supply auxin from the tip of the plant as well as through roots.

  5. Not apply auxin at all.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It will relieve the plant of the phenomena called as apical dominance and after removing the apical bud growth will occur vigorously including the lateral buds.

Multiple choice

Gibbrellin is obtained from__________.

  1. gibberella (an algae)

  2. gibberella (a fungus)

  3. basidiolichen

  4. bacterium

  5. virus
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gibberellin is obtained from gibberella fujikuroi, which is a fungus.