What Is Gibberellic Acid?

by Kay Phillips; Updated September 26, 2017

Gibberellic Acid, commonly referred to as GA3, is a naturally occurring plant growth hormone that is harvested from fungus and produced commercially for the agriculture and home gardening industries. Because of its low toxicity, the Environmental Protection Agency has approved the use of Gibberellic Acid to help hasten germination and growth in food crops.


Gibberellic acid was discovered in Japan by plant pathologists studying bakanae (foolish seedling) disease in rice. In this diseased plant, seedlings grew so elongated that they would be unable to support their own weight, causing the plant to die. In 1898 Shotaro Hori discovered that a fungus, now known as Gibberrella fujikuroi, was responsible for causing the disease. In 1926, Eiichi Kurosawa found that the disease was caused by a heat-resistant chemical produced by the fungus. In 1935 Teijiro Yabuta isolated this chemical and named it Gibberellin.


There are currently more than 100 known Gibberellins. GA3 is the most commonly used Gibberellin and is extracted from the Gibberella fujikuroi fungus. It is grown in large vats and then purified. It is produced in tablet form, liquid concentrate and soluble granules. GA3 was first registered with the United States Environmental Protection Agency in 1947 and was re-registered in 1995.


Gibberellic Acid is applied directly to growing crops which include fruits, field crops and vines. The hormone stimulates cell division and cell elongation that affect the leaves and stems in plants. Gibberellic Acid is commonly used in the seedless grape industry to increase both grape and bunch size. It may be applied via aircraft, ground spray equipment, irrigation, seed treatment, or soil incorporation.


Gibberellic Acid works on germination by promoting growth in the embryo of a seed. Gibberellin is released by the embryo, where it travels to the endosperm region of the seed. It then allows the enzyme induction of amylase, breaking down starch into a sugar for use by the embryo. Sugar is then used to synthesize proteins in the plant and break dormancy.


The Environmental Protection Agency classifies Gibberellic Acid as a biochemical pesticide with a Toxicity Category III, or slightly toxic. The Agency has determined that its usage does not pose an unreasonable risk to humans or the environment. The Agency states that the small amounts of Gibberellin applied to crops does not noticeably increase exposure to humans who consume the harvested food.