The correct option is Gibberellins.
Explanation
Bolting is a physiological phenomenon observed in plants with a "rosette" habit (where leaves are clustered near the ground due to very short internodes), such as cabbage and beet. It involves the rapid elongation of internodes just prior to flowering.
Analysis of Options:
- Gibberellins Gibberellins: This is the correct option. Gibberellins (specifically GA3) promote stem elongation. When applied to rosette plants, they induce rapid internodal growth (bolting) followed by flowering, even under conditions that would normally maintain the rosette form.
- Auxins Auxins: This is incorrect. Auxins are primarily responsible for apical dominance, root initiation, and cell elongation at shoot tips, but they do not specifically trigger the bolting response in rosette plants.
- ABA ABA (Abscisic Acid): This is incorrect. ABA is a growth-inhibiting hormone often associated with stress responses (like stomatal closure) and seed dormancy. It acts antagonistically to growth-promoting hormones.
- Cytokinins Cytokinins: This is incorrect. Cytokinins mainly promote cell division, shoot differentiation, and delay leaf senescence. They are not the primary drivers of internodal elongation.
Key Takeaway:
Gibberellins are the plant hormones responsible for inducing bolting (internode elongation) in rosette plants like cabbage and beet.