The application of plant growth regulators in modern agriculture.

Six categories of endogenous hormones

1880
Indol-3-ylacetic acid

The discovery of auxin In 1934, Dutch scientist F. Kogl and others isolated and identified the chemical composition of this substance as indole acetic acid. Because it promotes growth, it is named auxin.

From Darwin and his son's coleoptile experiment in 1880 to 1934, when the Dutchman F. Kogl and others isolated and purified the auxin-indoleacetic acid from human urine, Rhizopus, and malt, humans have been researching plant hormones.

1950s
Gibberellic acid and cytokinins

In 1926, Kurosawa of Japan discovered that the leggy and yellowing phenomena of susceptible rice seedlings were related to Gibberella fujikuroi during his research on rice bakanae disease.

In 1935, Yabada and Sumiki isolated a physiologically active substance from the secretion of Gibberellus and named it gibberellin (GA).

Since the 1950s, British and American scientific workers have conducted research on gibberellins. Now more than 60 types of gibberellins have been isolated from gibberella and higher plants, named GA1, GA2, etc. respectively. Later, more than ten kinds of cytokinins were discovered in plants. Gibberellins are widely found in fungi, algae, ferns, gymnosperms and angiosperms. Commercially produced gibberellins are GA3, GA4 and GA7.

GA3, also known as gibberellic acid, is the earliest gibberellin isolated and identified, with the molecular formula C19H22O6. That is 6-furanoaminopurine.

1960s
Abscisic acid and Ethephon

In 1961, W.C. Liu and H.R. Kearns isolated a substance crystal from mature cotton bolls that can accelerate the shedding of petioles after explant leaves are removed, called "abscisin I", but their chemical structure was not identified.

In 1963, Daekuma Kazuhiko, F.T. Adicot and others isolated another substance crystal that accelerates abscission from young cotton bolls, called abscisin II. In the same year, C.F. Eagles and P.F. Wehrling used chromatography to isolate an inhibitory substance from Eurasian maple leaves that could make growing seedlings and buds dormant. They named it dormant.

In 1965, Wehrling et al. comparatively studied the chemical properties of dormantin and abscisin II and proved that the two are the same substance, and the molecular formula is consistent with that proposed by Kazuhiko Ohkuma et al. in 1965. It is collectively named abscisic acid. It is ubiquitous in plants.

1980s
Brassinolide

In 1970, American scholar J.W. Mitchell and others extracted a substance with strong physiological activity from rapeseed pollen, which strongly promoted the elongation of plant stems and cell division. They named it brassinosteroids, also known as brassins. .
In 1979, American scholar Grove harvested 227 kilograms of rape pollen using bee collection methods and purified 4 mg of brassinolide. Through instrumental analysis, it was determined that its chemical structure belonged to sterol lactone, so it was named Brassinolide (BL). About 70 natural brassinolide compounds have been discovered so far, which are collectively called brassinosteroids (BR). BR exists widely in plants. Because their functions are similar to BL, BR has become the name for brassinosteroids, and BL is the most active molecule among the members of the brassinosteroids.
In 1998, it was officially recognized as the sixth category of plant hormones at the 13th International Annual Conference on Plant Growth Substances.

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