Labeled Indole-Macromolecular Conjugates from Growing Stems Supplied with Labeled Indoleacetic Acid

Pea (Pisum sativum var. Alaska) and bean (Phaseolus vulgaris var. Red Kidney) stem sections treated with indoleacetic acid-1-(14)C, indoleacetic acid-2-(14)C, and indoleacetic acid-5-(3)H were homogenized, extracted with phenol, and the water-soluble, ethanol-insoluble material subjected to further fractionation. Following an 18-hour incubation period in indoleacetic acid-1-(14)C, most of the label was found as nonindole-(14)C in high molecular weight polysaccharide, as phenol extraction is specific for both RNA and polysaccharides. With indoleacetic acid-2-(14)C and -5-(3)H, and to a lesser extent with indoleacetic acid-1-(14)C, radioactive indoles were obtained by hydrolysis from a heterogeneous fraction between about 500 and 30,000 molecular weight, possibly polysaccharide in nature. Indoleacetic acid accounted for 8% and indole aldehyde accounted for 21% of the total radioactivity in the extract.