INDOLE-3-BUTYRIC ACID IN ARABIDOPSIS-THALIANA .1. IDENTIFICATION AND QUANTIFICATION

Indole-3-butyric acid (IBA) was identified by HPLC and GC-MS as an end ogenous compound in plantlets of the crucifer Arabidopsis thaliana (L. ) Heynh. A. thaliana was cultivated under sterile conditions as shakin g culture in different liquid media with and without supply of hormone s. Free and total IBA and indole-3-acetic acid (IAA) were determined a t different stages of development during the culture period as well as in culture media bf different initial pH values. The results showed t hat IAA was present in higher concentrations than IBA, but both hormon es seemed to show the same behaviour under the different experimental conditions. Differences were found in the mode of conjugation of the t wo hormones. While IAA was mostly conjugated via amide bonds, the main IBA conjugates were ester bound. The ethylene concentration derived f rom the seedlings, when they were grown in flasks of different size, s eemed not to influence the auxin content in the same cultures.