Gibberellins are weakly acidic growth hormones having gibbane ring structure which cause cell elongation of intact plants in general and increased internodal length of genetically dwarfed plants (e.g., Pea, Corn), in particular.
The effect of gibberellins had been known in Japan for over a century where certain rice plants were found to suffer from bakanae (foolish seedling) disease. Such rice plants were thin, pale green, spindle shaped, longer by 50% than the healthy plants, and were sterile. The disease was found by Kurosawa (1926) to be caused by a fungus, Gibberella fujikori.
The fungus is the perfect stage of Fusarium moniliforme. The active substance was separated and named gibberellin by Yabuta and T. Hayashi (1935). Gibberellic acid or GA3 was isolated in pure form by Brian et al, in 1955. Cross et al. (1961) worked out the structure of Gibberellic acid, GA3. More than 60 gibberellins have now been discovered in various fungi and plants (31 from seed plants) although no single species contains more than 15 (Phinney, 1971). GA1, GA3-8 and GA17-20 occur rather commonly; the others are found only in certain plants.