Indole-3-acetic Acid (IAA) and IAA Conjugates Applied to Bean Stem Sections

High resolution growth recording techniques and reverse isotope dilution analysis were used to study the relationship between indole-3-acetic acid (IAA) concentration and curvature of excised bean (Phaseolus vulgaris L. cv Bush Burpee Stringless) first internode sections unilaterally treated with hormone. The maximum rate of curvature occurred rapidly (within 25 minutes) and was proportional to the log of the amount of applied IAA recovered in the tissue. The rate of curvature decreased after 30 minutes although little or no lateral migration of applied IAA occurred and tissue levels of IAA increased. The biologic activity of IAA-amino acid conjugates was found to be directly related to the amount of free IAA, resulting from their hydrolysis, which could be recovered from the tissue.