Reaction of Certain Plant Growth-Regulators with Ion Exchangers

Abstract

1. Studies were made on the adsorption by and elution from several ion exchangers of six plant growth-regulators. Cation exchangers in the hydrogen cycle adsorbed much 2,4-dichlorophenoxyacetic acid (2,4-D) and its ammonium, calcium, and cupric salts, and in about equal amounts. Anion exchangers adsorbed much 2,4-D and its salts, but not always in equal amounts. Little or no 2,4-D or its salts was adsorbed by cation exchangers in the sodium or calcium form. 2,4,5-Trichlorophenoxyacetic acid was adsorbed in amounts similar to those of 2,4-D except that less of the former was adsorbed by the cation exchangers. 2. Isopropyl N-phenylcarbamate was more strongly adsorbed than 2,4-D by cation exchangers in the hydrogen, sodium, or calcium form. Much less was adsorbed by the acid exchangers. 3. Much less 2,4-D was adsorbed by Amberlite IR-100 H when the pH of the solution was 3.3 than when it was 2,5 or lower. The amount of 2,4-D adsorbed by ion exchangers from solutions varying in concentration from 20 to 200 p.p.m, was in about direct proportion to the concentration of 2,4-D in the initial solution. 4. Solutions of NaC1, CaC2, or AlCl3 6H2, O of 0.75 normality caused less elution of 2,4-D adsorbed on Amberlite IR-100 H than did water. The amounts eluted by hydrochloric acid and water were approximately equal. Solutions of NaCl, Na,2SO4, and Na3PO4.12 H2O of 0.685 normality also eluted less 2,4-D from Amberlite IR-100 H than did water. Isopropyl N-phenylcarbamate, however, was eluted from IR-100 H by sodium chloride solution. 5. Hydrochloric acid eluted 2,4-D from anion exchangers, probably in typical anion- or acid-exchange reactions. 6. 2,4-D was mixed with Decalso and Zeo-Dur, respectively, at rates of 19.4 or about 64 mg. per pound. The mixtures were leached with three 2-inch columns of water. Much 2,4-D was removed by the first leaching, a smaller amount at the second leaching, and practically none at the third leaching. 7. About 93 micro-equivalents of six different growth-regulators were mixed with Decalso and Zeo-Dur and the mixtures were leached with a, 2-inch column of water. One-half or more of each compound was usually leached from the exchanger materials, and the different compounds were usually removed in about equivalent amounts. 8. Growth of plants in soils containing ion exchangers upon which NH42,4-D was adsorbed showed that much of adsorbed growth-regulator is nontoxic. Barley and white mustard plants: grew well in gravel-Zeo-Karb H mixtures containing NH42,4-D at concentrations of 100 and 10 mg., respectively, per pound of mixture. The growth-regulator may not have come into contact with the roots growing around the adsorbent or perhaps could not diffuse into or enter the plants.