The Impact of Humic Acid and Moringa Treatments on Enhancing Arsenic Tolerance in Broccoli Plants: Modulation of Sulphur Components and Enzymatic Antioxidant Defense

Abstract

Compared with the lowlands of Asia, the ecological exposure to arsenic (As) in Egypt has not received much attention. Recent studies have discovered geogenic As-polluted soil and groundwater in numerous areas in Egypt. The behavior of metals can be affected by the complexation of humic acid (HA), a significant soil organic component, and moringa leaf extract (MLE), a superb source of phytohormones, amino acids, minerals, and antioxidants. This research investigated whether soaking broccoli in HA (0.1%) or MLE (25%) may boost the vegetable’s tolerance to various doses of As (0, 0.75, 1.50, and 3.0 mM Na2HAsO4. 7H2O; AsV). The results of this research demonstrated that HA and MLE enhanced the tolerance index (TI) of shoots, roots, and thiol compounds in leaves (cysteine (Cys), glutathione (GSH), and non-protein thiols (NPTs)) of As-treated plants. The content of hydrogen peroxide (H2O2) and proline in leaves and roots, phenolic compounds (free and bound), and activity of lipoxygenase (LOX), catalase (CAT), and peroxidase (POD) in leaves under As stress were substantially increased while they were decreased by HA and MLE treatments. These results provide insight into the regulation of As pollution by HA and MLE, which is relatively safer and more adaptable to the environment. Further research in this field is necessary to declare that HA and MLE are the most efficient treatments for As stress.