Metabolism of Auxin in Pine Tissues: Naphthaleneacetic Acid Conjugation

Incubation of sections of various tissues of Pinus pinea L. and Pinus halepensis Mill, with α‐naphthaleneacetie acid‐1‐¹⁴C (NAA) resulted in two metabolites which proved to be l‐O‐(α‐naphthylacetyl)‐β‐D‐glucose (NAGlu) and α‐naphthylacetylaspartic acid (NAAsp). NAGlu was purified by means of insoluble polyvinyl‐polypyrrolidone (Polyclar AT) column chromatography and preparative thin layer chromatography and identified by its ‘H‐nuclear magnetic resonance and mass spectra. NAAsp was partially purified by means of preparative thin‐layer chromatography and identified by co‐chromatography with a synthetic standard and hydrolysis to the parent compounds. NAA and L‐aspartic acid. Needles and shoot bark rapidly converted NAA mainly to NAGlu. In contrast, woody roots and shoot wood showed a much slower rate of conjugation with the formation of both NAGlu and NAAsp. Preincubation of wood sections in NAA increased the formation of NAGlu, whereas the formation of NAAsp was almost unaffected.