Studies on 3-Indoleacetic Acid Metabolism. V. Effect of Calcium Ions on 3-indoleacetic Acid Uptake and Metabolism by Pea Roots

It has previously been shown that indoleacetic acid (IAA) applied to pea roots is in part degraded and in part conjugated with aspartic acid to form indoleacetylaspartic acid (IAAspA) (2, 6). While other workers (9) have reported that IAA applied to pea roots is metabolically bound to tissue protein to give a Salkowski reactive derivative, we have found no evidence of such a complex, almost all the Salkowski material in the tissues being accountable for in our studies as IAAspA or IAA itself (3). During the present studies on IAA miietabolism by roots, it was found that whereas tips of intact roots accumulated IAAspA at a rate considerably greater than epicotyl segments, excised root tips almost entirely lost this ability. This decreased accumulation of IAAspA was paralleled by a decreased loss of IAA from solution. The addition of Ca+ + or certain divalent ions in combination with sucrose completely restored the ability of roots to accumulate IAAspA but had no effect on this process in epicotyls.