Ion Uptake by Soybean Root Tissue Depleted of Calcium by Ethylenediaminetetraacetic Acid

Abstract

Treating soybean root tissue with ethylenediaminetetraacetic acid for 30-40 minutes removes 2/3 of the Ca and results in increased labeled K accumulation. Longer treatment depresses accumulation. The effectiveness of the EDTA treatment is temperature-dependent. The increased accumulation appears in the initial phase of a biphasic curve and is interpreted as an activated exchange of radioactive label for cytoplasmic cations. The 2nd linear phase of accumulation, presumably into the vacuole, is unaffected. The initial phase of labeled Ca accumulation is promoted, but the 2nd phase is inhibited. Phosphate and chloride accumulation are depressed by Ca removal, but the amount of freely exchangeable anion is increased. Ca or Mg will reverse the inhibition and actually increase accumulation. Anion uptake appears to be critically linked to the presence of divalent ions. Ultraviolet irradiation or ribonuclease treatment of root tips will produce effects similar to Ca removal.