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 are the examples of natural plant growth hormones?

i. IAA ii. GA3 iii. Zeatin iv. 2,4-D v. IBA

  1. i, ii and iii

  2. i, iv and v

  3. ii and iv

  4. iii and v

  5. iii, iv and v
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All are natural plant growth hormones. Indole-3-acetic acid (IAA) is the most common, naturally-occurring, natural plant growth regulator hormone of the auxin class. Gibberellic acid (GA3) is an important natural plant growth regulator that is used commercially to increase plant growth and crop yields. Zeatin is a member of the plant growth regulator hormone family known as cytokinins.  

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

Correct answer. 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

Which of the following is not a plant growth hormone?

  1. Auxin

  2. Gibberlin

  3. Ascorbic acid

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

Auxin, gibberellin, abscisic acid, and cytokinins are the five major plant hormones that regulate growth and development. Ascorbic acid (Vitamin C) is an antioxidant and enzyme cofactor in plants, but it does not function as a growth hormone like the others.