Effects of Various Concentrations of Iodine as Potassium Iodide on the Growth of Barley, Tomato and Pea in Nutrient Solution Culture

Iodine enhanced the height, number of tillers, fresh and dry weights of barley at concentrations of 0.5 and 1.0 ppm. With 5.0 ppm the plants were indistinguishable from the untreated controls. A dose of 10.0 ppm was inhibitory and induced symptoms of toxicity. In tomato, growth was increased at 0.5 ppm with maximum stimulation occurring at 1.0 ppm. As in barley, 5.0 ppm exerted no effect and 10.0 ppm resulted in decreased growth, with toxicity symptoms evident. With pea, all iodine concentrations used led to reduced growth, the magnitude of the effect and the severity of the toxicity symptoms increasing with concentration. The symptoms of toxicity in barley included general chlorosis, yellow intervenal patches, and brown necrotic spots. The latter tended to coalesce to form streaks. Death of some leaves resulted. Rather similar symptoms developed in tomato and pea, but no necrotic spots were observed in the latter.