Aluminum-Induced Changes In Reactive Oxygen Species Accumulation, Lipid Peroxidation and Antioxidant Capacity In Root Tips of Two Wheat Genotypes Differing In Aluminum Tolerance.

Aluminum (Al) toxicity is a crucial factor limiting crop production on acid soils. However, the associations of Al tolerance with oxidative stress and antioxidant capacity are unclear. The present study investigated the effects of Al on lipid peroxidation, accumulation of reactive oxygen species and antioxidative defense system levels in root tips of Al-sensitive genotype (Yangmai-5) and Al-tolerant genotype (Jian-864) of wheat seedlings. The exposure to 30 mM Al increased levels of malondialdehyde and H₂O₂ and O₂^- and Evans blue uptake in both genotypes, with increases being greater in Yangmai-5 than in Jian-864. In addition, Al treatment increased the activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, glutathione reductase and glutathione peroxidase, and the concentrations of ascorbate (AsA) and glutathione (GSH) in both genotypes. The increments for the activities of the former two enzymes which are responsible for H₂O₂ production, were greater in Al-sensitive genotype than Al-tolerant one, whereas the opposite was true for the activities of the latter five enzymes and concentrations of AsA and GSH. Consequently, the antioxidant capacity in terms of DPPH (2, 2-diphenyl-1-picrylhydrazyl)-radical scavenging activity and FRAP (ferric reducing/antioxidant power) was greater in Jian-864 than in Yangmai-5. The results suggest that Al enhanced the total antioxidant capacity of both non-enzymatic and enzymatic components in wheat seedlings with the enhancement being greater in Al-tolerant than in Al-sensitive genotype. We proposed that the total antioxidant capacity is an important factor conferring Al tolerance in plants.