Chitosan Increases the Sensitivity of Soybean Under Iron Deficiency by Impairing the Antioxidant Mechanisms and Nutrient Balance

Iron (Fe) deficiency is a common problem, especially in alkaline soils, and large yield losses are experienced in sensitive plants such as soybean (Glycine max L.) when they are grown on alkaline soils. Natural and organic products can be used as fertilizer alternatives to complex with a small amount of Fe in the soil and make it available for the plant roots for effective uptake. For this reason, the effectiveness of chitosan application in different doses was studied in two soybean cultivars (tolerant-Ar & imath;soy and sensitive-Ataki & scedil;i) under Fe deficiency. Plants were grown in hydroponic media containing 60-mu M (Fe-sufficient) or 6-mu M (Fe-deficient) Fe-EDTA supplemented with chitosan in different concentrations (0.5, 1, 1.5, and 2%) until the V2 stage. An increase in Fe deficiency symptoms was observed in plants due to the increased chitosan concentration. Iron deficiency-related genes were induced after chitosan application. Fe, Mn, Zn, and Mg concentrations were altered significantly in the sensitive cultivar after chitosan application. Therefore, chitosan application cannot rescue Fe deficiency; on the contrary, it impacts the availability of other divalent metals to plants. These alterations resulted in increased H2O2 and MDA, and decreased proline levels. All these changes were more drastic in IDC-sensitive soybean cultivar. Antioxidant enzyme activities varied between cultivars, with Ar & imath;soy relying on catalase and superoxide dismutase, while Ataki & scedil;i favored ascorbate peroxidase. Overall, chitosan application from the roots leads to oxidative stress due to the altered nutrient balance under Fe deficiency.