The plant hormone, gibberellins was discovered by E. Kurusawa in 1926 as the active substance produced by the fungus Gibberella fvjikuroi. It causes Bacanae or foolish disease of rice in Japan.
The disease induces excessive increase in the height of infected plants. Cross et al (1961) isolated 6 gibberellins from the fungus Gibberella and they were termed as GA^ GA2, GA3 etc. Many of the hormones are found in the same plant. They are synthesized in different parts, particularly in growing tissues.
Their transport is nonpolar and occurs both in xylem and phloem. Some of the important physiological properties of this hormone are:-
(1) Stem elongation
Elongation of the stem is a very important character of this hormone. It occurs through elongation of internodes.
(2) Dwarf plants
Stimulation of cell division in subapical meristem and cell expansion occur due to gibberellins.
(3) Flower development
In long day plants and in cold-requiring plants, flowering can be promoted by this, hormone.
(4) Parthenoearpie fruits
Gibberellins have been observed to be more effective than auxins in the parthenoearpie fruit development.
(5) Breaking dormancy
The use of the hormone has been observed in breaking dormancy of evergreen deciduous plant buds.
(6) Activity of enzymes
Certain enzymes like L-amylase and several other hydrolass are made active due to the hormone.