When the main plant hormones were discovered

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Ethylene

Ethylene (as a plant hormone) was discovered in 1901 by Dimitry Neljubow.

Gibberellic acid

Gibberellic acid was discovered in 1926 by Elichi Kurosawa.

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3

Auxin

Auxin was discovered in 1928 by Fritz W.

Cytokinins

Cytokinins were discovered in 1955 by Skoog, C. Miller and co-workers.

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5

Jasmonic acid

Jasmonic acid was discovered in 1962 by Demole et al.

Abscisic acid

Abscisic acid was discovered in 1963 by Frederick T. Addicott and Larry A. Davis.

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Salicylic acid

Salicylic acid (as a plant hormone) was discovered in 1979.

Brassinosteroids

Brassinosteroids were also discovered in 1979.

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See also:
Plant hormones types
Classification