Question

The substance that triggers the fall of mature leaves and fruits from plants is due to

• A. auxin
• B. gibberellin
• C. abscisic acid
• D. cytokinin

Answer 1

The correct option is C

abscisic acid

The correct answer is option C.

Explanation of the correct option:

1. Abscisic acid a plant growth inhibitor is responsible for the shedding of leaves.
2. The shedding of cotton balls in cotton plants found that the shedding of cotton balls was induced due to the secretion of the chemical substance abscisic acid.
3. Abscisic acid is synthesized in leaves.
4. Besides falling leaves of mature plants, Abscisic acid is responsible for bud dormancy, increasing resistance of plants to cold, and stomatal closing.

Explanation of the incorrect options:

Option A:

1. The group of chemicals synthesized in the apex of the plant promotes the growth of the stem called auxin.
2. The naturally occurring auxins in plants are Indole -3- acetic acid responsible for elongating the stem, initiating root growth at a lower concentration, and preventing abscission of leaves.

Option B:

1. The plant growth hormone synthesized in young leaves, immature seeds, and roots is responsible for the elongation of stems of plants by promoting cell division in regions of the plant where it is synthesized.
2. The gibberellins also promote seed germination and break seed dormancy

Option D:

1. The plant growth substances primarily help in the formation of leaves, adventitious shoot, and lateral shoot by promoting cell division.
2. The cytokinins are also responsible for delaying senescence in mature leaves.

Final answer: The substance that triggers the fall of mature leaves and fruits from plants is abscisic acid.