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

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Abstract
Excised roots submerged in IAA solution accumulated indoleacetylaspartic acid to the same extent as roots of intact seedlings, with the greatest accumulation in both cases occurring in the root tips. Excised root tips, on the other hand, almost completely lost the ability to accumulate indoleacetylaspartic acid. This activity could be restored by certain divalent cations, notably Ca, in the presence of sugar or sugar alcohols. It was not clear whether the absence of these substrates affected the ability to take up IAA from solution or the ability to conjugate IAA with aspartic acid. Ca had no effect on the accumulation of indoleacetylaspartic acid by tips suspended on the surface of the solution, where, under optimum conditions, indoleacetylaspartic acid accumulation was only one third that of submerged root tips; Ca had no effect on indoleacetylaspartic acid accumulation by epicotyls. It was concluded that on incubation in water factors were lost from the submerged root tips which were essential for the accumulation of indoleacetylaspartic acid and that Ca and sucrose prevented this loss.