Catabolism of 3-indole acetic acid in protoplasts from etiolated seedlings of scots pine (Pinus sylvestris L.)

Protoplasts preparated from dark grown seedlings of Pinus sylvestris L. were incubated with 3-indole (1-¹⁴C) acetic acid and 3-indole (2-¹⁴C) acetic acid (IAA). Three catabolites were consistently produced in the (2-¹⁴C) IAA feeds, one of which co-chromatographed with 3-indole methanol on reversed phase high performance liquid chromatography (HPLC). Protoplasts feed with (1-¹⁴C) IAA produced only one labelled catabolite. The non-decarboxylated compound formed was highly polar on reversed phase HPLC, both in the ion suppression and the ion pair mode. The substance was not hydrolysable at pH 11 and 100° indicating that it is not a conjugated form. Effects of time of incubation, pH and the cofactors hydrogen peroxide and 2,4-dichlorphenol on the catabolic rate of IAA are discussed.Abbreviations BSA bovine serum albumin - DCP 2,4-dichlorophenol - HPLC high performance liquid chromatography - IAA 3-indole acetic acid - IAld 3-indole carboxaldehyde - ICA 3-indole carboxylic acid - IM 3-indole methanol - MES 4-morpholineethane sulfonic acid - MO 3-methyl-oxindol - MnO 3-methylene-oxidol - OxIAA 3-oxindole acetic acid - PEG polyethylene glycol