Question

Which one of the following growth regulators is known as ‘stress hormone’?

• A. Ethylene
• B. Abscisic acid
• C. Indole acetic acid
• D. GA3

Answer 1

The correct option is B

Abscisic acid

The correct option is B.

Explanation for correct answer:

1. It was discovered that abscisic acid (ABA) controls dormancy and abscission.
2. Both general plant development and plant metabolism are inhibited by it.
3. ABA stops seeds from germinating. It stimulates stomata closure and increases plants' resistance to various stressors. Therefore, it is also called the stress hormone.
4. ABA is crucial for the growth, maturity, and dormancy of seeds.

Explanation of incorrect options:
Option A :

1. Ethylene is a gaseous hormone.
2. Senescent tissues and ripening fruit synthesize it in significant proportions.
3. Ethylene is highly effective in fruit ripening.
4. The senescence and abscission of plant parts, particularly leaves and flowers, are accelerated by ethylene.
5. Ethylene is used to initiate flowering and for synchronizing fruit-set in pineapples Additionally, it causes mangoes to flower.
6. It aids in keeping the leaves and upper portions of the shoot above the water.
7. In deep water rice plants, ethylene stimulates quick internode/petiole elongation.

Option C :

1. They are typically produced at the developing tips of stems and roots, from which they spread out to the areas where they act.
2. IAA or Auxin plays an important role in apical dominance, delaying the abscission of leaves and various responses to light and pathogens.
3. Auxins cause parthenocarpy, such as in tomatoes.
4. They're frequently employed as herbicides.
5. They aid in the process of rooting in stem cutting, which is frequently utilized for plant multiplication.

Option D :

1. Gibberellins promote bolting (internode lengthening immediately before flowering) in beet, cabbage, and several rosette-shaped plants.
2. Gibberellic acid GA3- plays an important role in seed germination, parthenocarpy, and delaying senescence.

Final Answer: Abscisic acid is known as a stress hormone.