Gibberellin
Encyclopedia : G : GI : GIB : Gibberellin
Gibberellins are a plant growth substance (phytohormone) 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 scientists. It was derived from the Gibberella fungus lamapitus.
Examples: Gibberellin 452D
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 all cells (more particularly root and mature cells) when they do not have enough sugar and oxygen to support both themselves and any dependent cell ([speculative])
- Released in response to root, environmental, pest, and disease stress
- Directly induced by high levels of CK ([speculative])
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
- Induces extra Chlorophyll production or more efficient methods of photosynthesis (C4 Photsynthesis). ([speculative])
- Stimulates root senescence ([speculative])
- Directly or indirectly induces CK at high levels ([speculative])
- Inhibits the rate of metabolism of cells in the roots so as to funnel resources to the shoot for better acquisition of sugar and gases. ([speculative])
- Is a general indication of poor shoot health. May be released when the plant or plant part does not have enough shoot derived nutrients (sugar and gases) to continue existing at the present size, let alone growing. Action in general may be to increase sugar and gases, by either releasing stores, lowering root metabolism or inducing less needed root senescence. ([speculative])
- May work with Brassinosteroid to produce its effects. ([speculative])
External links
- [Phytohormones (Plant Hormones) and other Growth Regularors: Gibberellin]
- [Plant Hormones - Gibberellin]
- http://www.biology-online.org/3/6_gibberellin.htm
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
| Plant hormones | [edit] |
| Abscisic acid - Auxins - Cytokinins - Ethylene (Ethene) - Gibberellins |
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