Hydrogen Peroxide Mitigates Cu Stress in Wheat

Abiotic stress imposed by heavy metals (HMs) adversely influences plant growth. In crop plants, such stresses penalize grain yield and ultimately could have enduring connotations for sustainable food security. Although copper (Cu) is an essential micronutrient for crop life, excessive availability of copper impairs plant growth and/or reproductive performance. Anecdotal evidence suggests that hydrogen peroxide (H₂O₂) is produced in plants under either biotic or abiotic stresses to mitigate oxygen-derived cell toxicity, although the influence of H₂O₂ remains to be definitively quantified. Here, our aim was to investigate the effects of hydrogen peroxide (H₂O₂) on the growth, grain yield, and yield components, as well as copper uptake of stressed wheat grown in sandy soil. We found that applications rates of 150 or 300 mg Cu kg⁻¹ soil significantly reduced net photosynthesis, leaf area, chlorophyll, and grain yield. Foliar application of H₂O₂ to plants grown under 150 and 300 mg Cu kg⁻¹ soil had improved growth, physiological, and yield traits. For instance, foliar application of H₂O₂ Cu-stressed plants grown under 300 mg Cu kg⁻¹ soil reduced detrimental effects of Cu toxicity by −12% in terms of grains per spike and −7% for 1000-grain weight in comparison to the control treatment. Foliar application of H₂O₂ on wheat grown under copper stress reduced accumulation of other heavy metals such as cadmium. We suggest that the potential for foliar application of H₂O₂ in mitigating heavy metal stress in crop plants has large global potential; however, further work is required to elucidate the environmental conditions and application rates required to attain optimal benefit.