Question

Write any four physiological effects of gibberellins.

Answer 1

Hint: Physiological effects in gibberellins appear in stem, seed, fruit, flower and height, as well.

Complete Answer:
- Gibberellin had been first identified by Kurusowa in Japan. From his field he found that some rice seedlings had become much taller than the others.
- He noted, on further inspection, that certain taller rice plants had exhibited abnormal internodal elongation. This internodal elongation is recognized as the rice disease of 'bakanae,' or 'foolish seedling.'
- Recent evidence shows that the elongation was due to the action of Gibberella fujikuroi, a material produced by a fungus. Successfully isolated from the fungus this compound was called gibberellic acid.
- There are more than 90 different gibberellins extracted from higher plants and the fungi. Gibberellins exist in different organs of the plants. They are called GA1, GA2, GA3, etc. Such phytohormones exist in all plant groups.

Let us now answer the question regarding four physiological effects of gibberellins-
- Gibberellins offer exceptional stem elongation. The stem elongation is induced by the gibberellic acid by occuring cell division and cell elongation.
- One of the gibberellins' most noticeable results is the reversal of dwarfism in several genetically dwarf plants.
- The plant rosettes typically display lower internodal growth. When treated with gibberellin, these plants show excessive internodal growth. This abrupt stem elongation accompanied by flowering is termed as bolting.
- In many plants, seedless fruit formation without fertilisation can also be caused by treatment with gibberellin.

Note: Student should know that Gibberellins are slightly acidic growth hormones with gibbane ring structure that typically induce intact plant cell elongation and, in particular, increased internodal length of genetically dwarfed plants (e.g., corn, pea).