Gibberellin

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Gibberellins are plant growth substances (phytohormones) involved in promotion of stem elongation, mobilisation of food reserves in seeds and other processes. Its absence results in the dwarfism of some plant varieties. Chemically all known gibberellins are gibberellic acids, a family of diterpenoids acids that are synthesized by the terpenoid pathway in plastids and then modified in the endoplasmic reticulum and cytosol until they reach their biologically-active form.

Much of our knowledge of the biosynthesis and molecular mechanisms of gibberellins comes from research on their role in triggering α-amylase release by the aleurone layer in seed germination.

Gibberellin was first isolated in 1926 by Japanese scientist, Teijiro Yabuta (1888-1977). It was derived from the Gibberella fungus lamapitus.

Examples: Gibberellin 452D

[edit] Location, Characteristics and Occasions for Synthesis Induction

Synthesized in the embryo and germinating seeds
Synthesized in the roots
Increased in production in the dark when sugar cannot be manufactured, and decreased in production in the light
Synthesized in apical meristems and young leaves, as well as root tips and seeds.
Transported in non-polar, bidirectional manner, producing general responses
Released in response to root, environmental, pest, and disease stress

[edit] Effects

Stimulates shoot and cell elongation
Delays senescence of leaves
Inhibits root growth
Inhibits adventitious root growth
Produces seed germination
Antagonist promotes root growth and GA reverses this
Promotes root initiation in low concentration in pea cuttings
Stimulates bolting and flowering in biennials
Regulates production of hydrolytic enzymes for digesting starches
Inhibits CK bud growth on calluses
Inhibits bud formation
Inhibits leaf formation
Breaking of dormancy
Used to increase fruit size, increase cluster size (in grapes), delay ripening of citrus fruits, speed up flowering of strawberries, and stimulate starch break down in barley (for beer making).