Eustress with H₂O₂ Facilitates Plant Growth by Improving Tolerance to Salt Stress in Two Wheat Cultivars

In this study, the positive role of hydrogen peroxide (H₂O₂) pretreatment in mitigating the adverse impacts of seawater stress has been evaluated in two wheat (Triticum aestivum L.) cultivars, namely Gemmiza 11 as a salt-sensitive and Misr 1 as a salt-tolerant cultivar, with contrasting phenotypes in response to the salinity stress. Under normal conditions, wheat seeds eustress with H₂O₂ have shown significant effects on the improvement of plant growth parameters, such as dry weight and root and shoot lengths. Under salt stress conditions, seeds eustress with H₂O₂ have shown a reduction in damage to plant growth and physiological parameters as compared to the seeds kept as un-primed in both wheat cultivars. In addition, eustress of seeds with H₂O₂ has induced an increment in the pigments content, proline level and mineral uptake (K⁺, Ca²⁺ and Mg²⁺). Moreover, seeds eustress with H₂O₂ have shown significant decrement in Na⁺ content uptake in plants and that subsequently reduced lipid peroxidation. Seawater stress has increased the activity of the antioxidant system based on catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in both cultivars, except POD in Gemmiza 11. Similarly, the application of H₂O₂ has further enhanced the activity of the antioxidant system in stressed plants and this enhancement of the antioxidant system further reduced Na⁺ content in plants and subsequently increased the growth parameters. Results of inter-simple sequence repeat (ISSR) markers have shown clear differentiation among the treatments and have provided strong evidence in support of the hypothesis proposed in this study that H₂O₂ eustress improves seed tolerance and enhances plant growth parameters under seawater stress.