Gibberellins
The gibberellins (stress on the penultimate syllable: Gibberell i ne ) are a group of phytohormones . Chemically, they are diterpenes , which are formally derived from ent -Gibberellan.
history
In 1935 the Japanese Teijiro Yabuta isolated a gibberellin as a secondary metabolite for the first time from cultures of the hose fungus Gibberella fujikuroi (now reclassified as Fusarium fujikuroi ), which causes the Bakanae disease in rice plants . The gibberellins formed by this parasitic fungus and named after it lead to strong growth of the infected rice plants; however, these bend off before flowering. Gibberellins were first discovered in 1958 as native phytohormones in higher plants. In the same year, the structural formula of a gibberellin was determined for the first time.
Today, the group of gibberellins includes 136 substances (GA x with x as a running index in the order in which the respective gibberellin was discovered), of which only certain, such as GA 1 , GA 3 ( gibberellic acid ) or GA 7 , are active in plants.
Biological function
Gibberellins are mainly formed in ripening (fruits) and growing parts of plants (leaves, flowers). They are also transported passively via xylem and phloem , but mostly actively via transport proteins ( carriers ) and proton cotransporters.
In rosette plants , they not only determine the growth, but also the sex differentiation of the male flowers . They promote germination by stimulating the storage material mobilization of the seed . The trigger for this can be different environmental influences, in the case of seed germination, for example, water contact, in the budding of flowers z. B. Incidence of light or the like.
The gibberellins, which are formally derived from ent - gibberellan , are, however, synthesized from the diterpene ent - kauren in the plant metabolism . Disturbances in this synthetic pathway become noticeable in the dwarfism of plants (dwarf mutants). If gibberellins are sprayed on plants that do not show any length growth due to a genetic defect (" dwarfs ", see pea mutant little Rhinelander ), the plant grows to normal size. It can be concluded from this that a gene that is necessary for gibberellin synthesis must be defective in Dwarf mutants.
In fruit growing , gibberellins are sprayed onto fruit-forming plants together with auxin . As a result, the fruits are larger, are further apart and have no seeds, so they have no seeds ( parthenocarpy ).
Approval as a growth regulator in agriculture
In Germany, Austria and Switzerland, plant protection products with gibberellin A 4 + A 7 are approved as an active ingredient.
Web links
Individual evidence
- ↑ Teijiro Yabuta (1935): Biochemistry of the "bakanae" fungus of rice. In: Agriculture and Horticulture. Vol. 10, pp. 17-22.
- ↑ Ilse Jahn (Ed.): History of Biology . 3rd edition, Nikol special edition, Hamburg 2004, pp. 524f.
- ↑ P. Hedden, V. Sponsel: A century of gibberellin research . J. Plant Growth Regul. 34, 740-760 (2015).
- ↑ General Directorate Health and Food Safety of the European Commission: entry on gibberellin in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on December 8, 2019.