Question

Just before flowering, many dicot plants undergo extensive internode elongation. This phenomenon is called

• A. Floral invocation
• B. Bolting
• C. Heading
• D. Floral induction

Hint:

GA + Rosette plants = Bolting.
Applying GA artificially can induce bolting in many plants even without the required environmental stimulus.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
This question describes a specific morphological change in "rosette" plants (where leaves are crowded on a very short stem) when they transition from vegetative growth to reproductive growth (flowering).
Detailed Explanation:

• Bolting (The Correct Term):
Bolting is the rapid elongation of the main stem (internodes) just prior to flowering.
This is commonly seen in plants like Cabbage, Beetroot, and Lettuce.

• Hormonal Control:
Bolting is primarily regulated by Gibberellins (GA).
Under certain environmental cues like long days or exposure to cold (vernalization), GA levels increase, stimulating cell division and elongation in the sub-apical meristem, causing the stem to shoot up.

• Analyzing other options:
Floral induction: The physiological change in the plant that commits it to produce flowers.
Heading: The formation of a compact head of leaves, as seen in cabbage before bolting begins.

Step 2: Final Answer:
The rapid internode elongation preceding flowering is called bolting.