Reaction of Certain Plant Growth Regulators With Ion Exchangers

Abstract

Several investigators have reported that 2,4-dichlorophenoxyacetic acid (2,4-D) and certain other plant growthregulators are readily leached from soils (2, 3, 7). NUTMAN et al. (7) found that leaching equivalent to I.4 inches of water resulted in a loss of 2,4-D from the soil but that far greater volumes of water did not completely remove it. This would indicate that some 2,4-D may be adsorbed by the soil. HANKS (3) studied rates of leaching of 2,4-D and its calcium salt from six types of soil and found that the two compounds were leached from any one soil at about equal rates, as shown by comparative toxicities of the leachatesn but were differentially leached from the various soits. It was recently shown by LUCAS and HAMNER (5) that 2,4-D is inactivated by adsorption on charcoal. Bean plants sprayed with a o. ISo solution of sodium 2,4-dichlorophenoxyacetate, which had been mixed and shaken with I%o activated charcoal? showed little injury. The degree of adsotption of several growth-regulators by certain ion-exchange materials and also the readiness with which the compounds are eluted after having been adsorbed are reported here. Growth of plants in exchanger materials containing an adsorbed growthregulator was also obserrred. Such studies may help to explain why herbicidal growth-regulators vary in toxicity in different soils and why the rates of leaching of the compounds from different soils may vary. A spectrophotometric method developed by BANDURSKI (I) for determining growth-regulators in solution made possible quantitative studies of adsorption and leaching of such compounds which could heretofore be done only with difficulty when using bioassays (6, 8).