ANTAGONISTIC ACTION OF CHLORIDES ON THE TOXICITY OF IODIDES TO CORN

Abstract

During recent investigationis of the relationi of iodine to plant nutritioil, we found iodides to exert toxic effects onl corn at very iuiuch lower conicen- trations than had previously been reported by MAZE (5).MAzE's nutrienit solutions contained 22 p.p.m. of added chlorides.Our solutionis containied only suclh eoncentrations of chlorides as were carried as impurities by the salts and water used in their preparation.We therefore conducted experiments to determiiine whether chlorides antagonize the toxic effect of iodides on corn.Methods Corn seeds were germinated in the basal nutrient solution described below.When 3 to 4 inches high, uniform seedlings were transferred to 4-gallon stoneware jars containing the basal nutrienit solution.Iodide and chloride additions were made 2 to 3 days later.The basal nutrient solution used had the following composition: calcium nitrate, 0.007 M; magniesiumii suLlphate, 0.005 M; miionopotassium phosphate, 0.005 M; dipotassium phosphate, 0.0015 M; boron as boric acid, 0.5 p.p.m.; manganese as sulphate, 0.5 p.p.m.; zinc as sulphate, 0.05 p.p.m.; copper as sulphate, 0.02 p.p.m.; and molybdenum as ammonium molybdate, 0.05 p.p.m.Tap water was used in the preparation of this solution.Ferric tartrate was added twice weekly at the rate of 1 ml. of a 0.5 per cent.solution per liter of nutrient solution.In one experiment, humate iron (3) equivalent to 2 p.p.m. of iron was used in place of ferric tartrate.The initial pH of the basal nutrient solution was approximately 5.8.The pH of the culture solutions was adjusted every 2 weeks, or as needed, while the solutionis were renewed at 30-day intervals.Iodine was added as potassium iodide.Chlorides were added as a mixture of the calcium, magnesium, and potassium salts, in the same cation proportions as these catiolns appeared in the basal formula.The imethods used for iodine analyses varied with the anticipated iodine content.High-iodine samiiples were fused with potassium hydroxide.Low- iodine samiiples were burned in the VON KOLNITZ-REMINGTON (7) oxygen torch.The iodinie was then recovered by the distillation iuethod of BRATTON and MCCLENDON (2), followed by bromine oxidation and thiosulphate titration.