Bolting, i.e. internode elongation just prior to flowering in beet, cabbage and many rosette plants, is promoted by

Options

A. auxins
B. gibberellins
C. cytokinins
D. ethylene

Explanation

**Step-by-Step Solution:**

1. **Understanding Bolting**: Bolting refers to the rapid elongation of the internodes in certain plants just before they flower. This phenomenon is particularly observed in rosette plants like beet and cabbage.

2. **Characteristics of Rosette Plants**: Rosette plants typically have a short stem with broad leaves that grow close to the ground. Due to their growth habit, these plants exhibit reduced internodal growth during their vegetative phase.

3. **Transition to Flowering**: As these plants prepare for reproduction, they undergo a significant change where the stem elongates dramatically, often increasing in height by five to six times. This elongation is crucial for the plant to transition from vegetative growth to flowering.

4. **Role of Gibberellins**: Gibberellins are a class of plant hormones that play a vital role in promoting growth and development. When rosette plants are treated with gibberellins, it stimulates the internodal elongation process, leading to bolting.

5. **Conclusion**: Therefore, bolting in plants like beet and cabbage is promoted by the application of gibberellins, which trigger the necessary growth changes for flowering.

**Final Answer**: Bolting is promoted by gibberellins.

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