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.