Pretreatment with H2O2 Alleviates Aluminum-Induced Oxidative Stress In Wheat Seedlings.

Hydrogen peroxide (H₂O₂) is a key reactive oxygen species in signal transduction pathways leading to activation of plant defense against biotic and abiotic stresses. In this study, we investigated the effects of H₂O₂ pretreatment on aluminum (Al) induced antioxidative responses in root tips of two Triticum aestivum (wheat) genotypes, Yangmai-5 (Al-sensitive) and Jian-864 (Al-tolerant). Al treatment reduced root elongation and caused elevated accumulation of H₂O₂ and O₂^-, which led to lipid peroxidation and programmed cell death (PCD) in both wheat genotypes. The Al-induced responses, however, were more predominant in Yangmai-5 than in Jian-864. After the plants had been pretreated with H₂O₂, the observed Al-induced responses were alleviated. At the same time, we found an increase in the Al-induced activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and ascorbate (AsA) -glutathione (GSH) cycle-related monodehydroascorbate reductase (MDHAR), glutathione reductase (GR) and glutathione peroxidase (GPX) as well as the concentrations of AsA and GSH. In addition, H₂O₂ pretreatment increased the total antioxidant capacity measured in terms of DPPH (2, 2-diphenyl-1-picrylhydrazyl) activity and FRAP (ferric reducing/antioxidant power) in both genotypes. Interestingly, all the above effects of H₂O₂ pretreatment were more significant in Yangmai-5 than in Jian-864. From these results, we concluded that H₂O₂ pretreatment of wheat seedlings improved Al acclimation process under subsequent Al exposure by enhancing the antioxidative defense system which prevents accumulation of reactive oxygen species with the magnitude of improvement more significant in the Al-sensitive genotype than in Al-resistant one.