Radioimmunoassay for pmol-quantities of indole-3-acetic acid for use with highly stable [(125)I]- and [ (3)H]IAA derivatives as radiotracers.

A radioimmunoassay for the detection of as little as 0.5-1 pmol indole-3-acetic acid (IAA) in unpurified or partially purified plant extracts is described. The assay makes use of either IAA[(125)I]tyrosine methyl ester or [(3)H]IAA methyl ester as radioactive antigens and IAA methyl ester as the assay standard (measuring range: 1-200 pmol). Levels of extractable IAA in a number of biological samples have been estimated.