two different chemical forms—potassium iodide (I−) and potassium iodate (IO− 3)—in a wide range of wild and cultivated plant species. Pot plants were irrigated with different concentrations of I− or IO− 3, namely 0.05% and 0.1% (w/v) I− and 0.05%, 0.1%, 0.2%, and 0.5% (w/v) IO− 3. Inhibiting effects on plant growth were observed after adding these amounts of iodine to the irrigation water.