Free tryptophan and indole-3-acetic acid levels in the leaves and vascular pathways of Ricinus communis L

Levels of free tryptophan in the leaves, phloem and xylem saps of Ricinus communis L. were determined by colorimetric assay. Values of 0.38 μg ml(-1) in root pressure sap and 96.0 μg ml(-1) in phloem sap were recorded. Tryptophan levels were highest in mature and senescing leaves. Levels of indoleacetic acid (IAA) in the phloem sap and leaves were determined by gas chromatography-mass spectrometry using a deuterated internal standard. A mean value of 13.0 ng ml(-1) was recorded in phloem sap. The distribution in the leaves showed an inverse relationship to that of tryptophan, being highest in young leaves.