Answer»
- The story of the discovery of gibberellins actually began in the last decade of the nineteenth century, when a disease of the rice plants was being studied in Japan. When the rice plants are infected by the ascomycetous fungus, Gibberella fujikuroi (asexual or imperfect stage is Fusarium monoliforme), they become excessively tall and chlorotic with reduced ROOT growth and tillering and eventually die.
- The Japanese farmers called this the ‘bakanae’ (foolish seedling) disease of rice. In 1926, Kurosawa, a Japanese plant pathologist in Taiwan grew the causal fungus in nutrient medium and showed that the cell-free culture medium could itself induce the abnormal elongation of rice seedlings. Yabuta and Sumiki in 1938 isolated the active factor from Gibberella fujikuroi culture filtrates and assigned the NAME ‘gibberellin’ to it.
- The initial research work on gibberellins was published in Japanese language and remained unknown to the western world for about 10 years because of the Second World War. In 1 954-55, American and British scientists like Stodola, Brian, Cross and others isolated and purified the gibberellins and named it gibberellic acid (GA3).
- This was followed by intensive research in 1950s on the effects of gibberellic acid of fungal origin on HIGHER plants. In 1956, West and Phinney in U.S.A. and Radley in England discovered that GAs occur naturally in higher plants. Thus, it became apparent that the plants possess a second group of growth regulators which play an important role in the control of growth and development.
- As of 1990, 84 gibberellins have been discovered in fungi and higher plants. Of these, 73 occur in higher plants, 25 in Gibberella fungus, and 14 in both.
- These are abbreviated as GA with a subscript such as GA1, GA2, GA3, and GA4 and so on of which GA3 is commonly known as gibberellic acid. Gibberellins and GA-like substances have been found in almost all the representatives of the plant kingdom STARTING from bacteria through fungi to angiosperms.
- Besides the fungal sources of GAs, the entire vegetative organs of higher plants, particularly the shoot-tip portion, are the sites of GA synthesis. Fruits and seeds, particularly immature seeds contain an abundant AMOUNT of GAs, much higher than vegetative tissues.
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