Occurrence and distribution of acidic indole auxins in lucerne at various stages

Abstract The variation of concentration of ‘free’ acidic indole auxins has been studied in different lines of lucerne at various stages of growth. Acidic indole auxins were separated by gas chromatography from the plant ethanolic extract. A large decrease in indole‐3‐acetic acid (IAA) and indole‐3‐carboxylic acid (ICA) was recorded as the plants aged. The trend during the life‐cycle is the same either in open pollinated progenies or in clonal lines. The IAA and ICA contents in various lines, determined in plants at the same stage, differ considerably from each other; this difference may have a genetic basis. The distribution in different parts of a single plant is a falling gradient in auxin concentration from the young to the mature tissues. By comparing root formation with ‘free’ auxin concentration of stem cuttings, evidence is collected which suggests that IAA may have primary action in the regulation of root formation.