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

Which of the following statements is/are correct?

a. Gibberellin hormone is involved in absission of plants. b. Auxins speed up growth in stems and roots of plants. c. Cytokinins promote the opening of stomata.

  1. Only a

  2. Both a and b

  3. Only b

  4. Both b and c

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

Auxin is a plant hormone responsible for controlling the direction of growth of root tips and stem tips in response to different stimuli including light and gravity.

Multiple choice

Which of the following are the physiological effects of Gibberellins? (a) It induces the formation of parthenocarpic fruits. (b) It delays the ageing process of plants. (c) It promotes bolting and flowering.

  1. (a) and (b) only

  2. (b) and (c) only

  3. (c) and (a) only

  4. (a), (b) and (c)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gibberellins promote bolting and flowering in plants (c), induce formation of seedless parthenocarpic fruits (a), and delay senescence/aging (b). All three effects are well-documented physiological actions of gibberellins.

Multiple choice

The growth hormone 6-Furfuryl amino purine is a/an

  1. Kinetin

  2. Auxin

  3. Gibberellin

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

6-Furfurylaminopurine (kinetin) is a cytokinin, a class of plant growth hormones that promote cell division, delay senescence, and regulate various developmental processes. It was the first cytokinin discovered. Auxins, gibberellins, and abscisic acid are different classes of plant hormones with distinct functions.

Multiple choice

Which of the following is a pair of synthetic auxins used as herbicides?

  1. IAA and IBA

  2. IAA and NAA

  3. 2,4-D and 2,4,5-T

  4. IBA and 2,4-D

  5. IBA and NAA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common systemic pesticide/herbicide used in the control of broadleaf weeds. It is one of the most widely used herbicides in the world and is the third most commonly used herbicide in North America. 2,4-D is a synthetic auxin (plant hormone). 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T), a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants.

Multiple choice

Plant hormones are chemicals that regulate plant growth. Among the following organic compounds which one is a plant hormone?

  1. 1,2-Ethanedithiol

  2. Ethanol

  3. Ethylene

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

Ethylene is a gaseous organic compound with the formula C2H4. It is the simplest alkene because it contains a carbon-carbon double bond. Ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone.

Multiple choice

The growth and elongation of cells in plants is promoted by

  1. γ-butyrolactone

  2. γ-hydroxybutyric acid

  3. geraniol

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

Gibberellic acid is a hormone found in plants. Its chemical formula is C19H22O6. When purified, it is a white-to-pale-yellow solid. Gibberellic acid is a simple gibberellin, a tetracyclic diterpene acid promoting growth and elongation of cells.

Multiple choice

Auxins are plant hormones. Which of the following is a synthetic auxin ?

  1. Dichlorofluoromethane

  2. 2,4-Dichlorophenoxyacetic acid

  3. 2,2-Dichloro-1,1,1-trifluoroethane

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

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common systemic pesticide / herbicide used in the control of broadleaf weeds. 2,4-D is a synthetic auxin (plant hormone), and as such it is often used in laboratories for plant research and as a supplement in plant cell culture media such as MS medium.

Multiple choice

What are anthesins required for?

  1. Growth of stem

  2. Formation of flowers

  3. Dormancy of seeds

  4. Inhibition of elongation of stem
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Anthesins are required for flower formation.

Multiple choice

Which of the following is a major function of cytokinin?

  1. It inhibits elongation of stem.

  2. It causes dormancy of seed.

  3. It stimulate cell division, even in non-meristematic tissues.

  4. It causes parthenocarpy.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytokinin, in presence of auxins, stimulates cell division, even in non-meristematic tissues.