Question

Which hormone is responsible for bolting in rosette plants?

• A. Auxin
• B. Cytokinin
• C. Gibberellin
• D. Ethylene Correct Answer: (C) Gibberellin

Hint:

To easily remember this on an exam, use this simple sound-association trick: Gibberellins make things Giant! Whether it is making individual grape stalks longer, stretching out sugarcane stalks, or causing a flat cabbage rosette to bolt upward into a tall tower, Gibberellin is always your go-to hormone for stem elongation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Certain plants, such as cabbage, beet, and lettuce, exhibit a compressed growth habit known as a rosette. In these plants, the internodes are highly reduced, causing the leaves to grow clustered together tightly near the soil surface. Under specific environmental conditions (like changes in day length or temperature) or upon targeted chemical treatment, these plants undergo a dramatic developmental shift where their stems suddenly stretch out just prior to flowering. This rapid, premature elongation of internodes is biologically termed bolting.

Step 2: Detailed Explanation:
Let's look at the hormonal mechanism that triggers this dramatic elongation: - Gibberellins (GAs) are plant growth regulators that primarily target internodal regions by stimulating both rapid cell division and cell elongation. - In rosette plants, the natural production of gibberellin is genetically restricted during regular vegetative growth, keeping the plant compact. - When gibberellin is applied artificially to a rosette plant, it overcomes this genetic restriction, causing the compressed internodes to expand. The stem shoots upward rapidly, inducing bolting and triggering immediate flowering. Therefore, Gibberellin is the specific phytohormone responsible for this process. This matches option (C).

Step 3: Final Answer:
The hormone responsible for bolting in rosette plants is Gibberellin.