LAUSR

Abstract Iodine (I) has a beneficial effect on plant growth, development and antioxidant activity. The study aimed to compare iodine uptake after the application of iodobenzoates (2-iodobenzoic acid (2-IBeA), 4-iodobenzoic acid (4-IBeA) and 2,3,5-triiodobenzoic acid (2,3,5-triIBeA)) as well as potassium iodide (KI) to tomato seedlings. One of the main tasks was to evaluate how the tested compounds applied in different concentrations (5, 10, 25 and 50 μM) affect the growth and antioxidative potential of tomato seedlings. Negative effect on growth and development of tomato seedlings was noted for 4-IBeA applied in 10–50 μM I concentrations. The 2,3,5-triIBeA application affected shoot deformation. All tested iodine compounds increased iodine level in leaves and roots of tomato seedlings. Iodine after KI application was accumulated mainly in leaves, while after iodobenzoates treatment in roots of tomato seedlings, which is probably related to their weaker transport to the upper parts of the plant. Tested compounds variously modified the content of ascorbic and dehydroascorbic acids in tomato leaves depending on applied concentration. KI treatment improved ascorbate peroxidase activity, but all iodobenzoates decreased APX and catalase activity in leaves. 4-IBeA (5 μM I) and 2,3,5-triIBeA (25 and 50 μM I) increased guaiacol peroxidase activity in leaves. It can be concluded that mechanisms responsible for plant oxidative metabolism were variously affected by the iodine compounds and its concentration in the nutrient solution.