A MICROTECHNIQUE FOR THE ANALYSIS OF FREE AND CONJUGATED INDOLE-3-ACETIC-ACID IN MILLIGRAM AMOUNTS OF PLANT-TISSUE USING A BENCHTOP GAS-CHROMATOGRAPH MASS-SPECTROMETER

A microtechnique was developed for the quantification of indole-3-acet ic acid (IAA) in plant samples of one milligram fresh weight or less. The method permitted quantification of both free and conjugated IAA us ing a benchtop gas chromatograph-mass spectrometer. New methods for sa mple purification with high recovery at microscale levels, together wi th simple changes that result in enhanced sensitivity of the instrumen tation, allowed for a significant reduction in the amount of plant mat erial required for analysis; Single oat (A venn sativa L.) coleoptile tips could be studied with this method and were found to contain free and total IAA levels of 137 and 399 pg . mg(-1) fresh weight, respecti vely. A single 5-d-old Arabidopsis thaliana (L.) Heynh. seedling was s hown to contain 61 pg . mg(-1) fresh weight free IAA and 7850 pg mg-l fresh weight of total IAA following basic hydrolysis. This microtechni que provides a way to accurately measure IAA levels in very small stru ctures and individual seedlings, thus making it a valuable research to ol for elucidating the role and distribution of auxin in relation to g rowth and development.