Question

Bolting i.e., internode elongation just prior to flowering in beet, cabbage, and many rosette plants, is promoted by
A) Auxins
B) Gibberellins
C) Cytokinins
D) Ethylene

Answer 1

Hint: Plant growth regulators (PGRs) are chemicals used to modify plant growth such as increasing branching, suppressing shoot growth, increasing return bloom, removing excess fruit, or altering fruit maturity.

Complete Answer:
- When broad leaves originate from a constricted length of the stem it is known as rosette growth. In such structures, the internodes are very short, but the leaves are profusely originated.
- Prior to the reproduction stage, the stem elongates and starts flowering. This elongation in the stem is about 5-6 times its original size and flowering is known as Bolting.

1) Ethylene induces apical dominance but reduces the internode elongation therefore we can also say it hinders the gibberellic acid actions.
2) Auxins also promote stem elongation but the auxins are produced mainly in the stem apical i.e. the tips of the stem, moreover, it inhibits the root and lateral bud growth whereas gibberellic acid does not.
3) Cytokinins perform many functions in the physiological development of the plant-like chloroplast differentiation, cell division, nucleic acid metabolism, and protein synthesis, etc.
4) Gibberellins (also known as gibberellic acid), the hormones majorly responsible for the development of most of the plant organs like seed development, stem elongation, and flowering development could be the correct answer.

There the correct choice is B, i.e. Gibberellins.

Note: Gibberellins were first discovered in 1939 by two Japanese scientists Yabuta and Hayashi. The name of gibberellin originated from the fungal species from which this hormone was first extracted, Gibberella fujikuroi.