Gibberellic acid (also called Gibberellin A3, GA, and (GA3) is a hormone
found in plants. Its chemical formula is C19H22O6. When purified, it is a
white to pale-yellow solid.
Gibberellic acid is a simple gibberellin, a tetracyclic diterpene acid
promoting growth and elongation of cells. It affects decomposition of plants
and helps plants grow if used in small amounts, but eventually plants
develop tolerance to it. GA stimulates the cells of germinating seeds to
produce mRNA molecules that code for hydrolytic enzymes. Gibberellic acid is
a very potent hormone whose natural occurrence in plants controls their
development. Since GA regulates growth, applications of very low
concentrations can have a profound effect while too much will have the
opposite effect. It is usually used in concentrations between 0.01 and 10
mg/L.
GA was first identified in Japan in 1935, as a metabolic byproduct of the
plant pathogen Gibberella fujikuroi (thus the name), which afflicts rice
plants; fujikuroi-infected plants develop bakanae ("foolish seedling"),
which causes them to grow so much taller than normal that they die from no
longer being sturdy enough to support their own weight.
Gibberellins have a number of effects on plant development. They can
stimulate rapid stem and root growth, induce mitotic division in the leaves
of some plants, and increase seed germination rate.
Gibberellic acid is sometimes used in laboratory and greenhouse settings to
trigger germination in seeds that would otherwise remain dormant. It is also
widely used in the grape-growing industry as a hormone to induce the
production of larger bundles and bigger grapes, especially Thompson seedless
grapes, and in the Okanagan and Creston Valley, it is used in the cherry
industry as a growth regulator.