Studies on plant growth-regulating substances. XXVII. The growth-regulating activity and metabolism of 2,4-dichlorophenoxyethylamine and related compounds in higher plants.

Abstract

SUMMARY2‐(2,4‐Dichlorophenoxy)ethylamine (2,4‐D ethylamine) was converted to 2,4‐dichlorophenoxyacetaldehyde (2,4‐D acetaldehyde) by extracts of pea cotyledons. The 2,4‐D acetaldehyde was further converted to 2,4‐dichloro‐phenol and 2,4‐dichlorophenoxyacetic acid (2,4‐D). Under the same conditions, 2‐(2,6‐dichlorophenoxy)ethylamine was converted to 2,6‐dichloro‐phenoxyacetaldehyde and 2,6‐dichlorophenol, although at a relatively slow rate.In pea stem segments and wheat coleoptiles the main products of 2,4‐D ethylamine metabolism were 2,4‐dichlorophenol, 2,4‐D acetaldehyde and 2,4‐D. In comparison with the wheat coleoptiles, larger amounts of these products were found in the pea stem segments. Metabolism of 2,4‐D acetaldehyde gave 2‐(2,4‐dichlorophenoxy)ethanol (2,4‐D ethanol) and 2,4‐D in both pea and wheat tissues.Pretreatment with the amine oxidase inhibitor, 2‐hydroxyethylhydrazine (HEH) completely prevented the extension of pea stem segments and substantially prevented the extension of wheat coleoptiles on subsequent treatment with 2,4‐D ethylamine. No such protection was found against 2,4‐D acetaldehyde or 2,4‐D after pretreating the tissues with HEH.In pea, radish, and tomato plants, epinasty resulted from treatment with 2,4‐D ethylamine, 2,4‐D acetaldehyde and 2,4‐D. Prior treatment with HEH prevented the epinasty due to the 2,4‐D ethylamine, but no protection was given by HEH against 2,4‐D acetaldehyde or 2,4‐D.