Effects of sequential hydrogen peroxide applications on salt stress tolerance in bread wheat varieties

Salinity is one of the factors affecting plant growth and development. In the literature, low concentration of hydrogen peroxide (H2O2) has shown to be effective against various abiotic stress factors. In this study, the effects of superoxide dismutase (SOD) on salt (NaCl) tolerance in early development period of some wheat varieties in H2O2 pre-treated before sowing in November 2017 and H2O2 re-pretreated to the seeds harvested in June 2018 were investigated. NaCl (0, 80, 160 mM) applied gradually to 100 µM H2O2 applied wheat seedlings (-H2O2: - control; H2O2: + control; 1xH2O2: H2O2 applied 1 year ago; 2xH2O2: H2O2 applied second time after one year) before the sowing. The morphological, physiological and biochemical changes of thrity five and fourty nine days old wheat seedlings were investigated. According to the results, only germination rate increased in 2xH2O2 group compared to H2O2 group, while other growth parameters decreased in the early development period. It was determined that growth parameters except root fresh and dry weight increased in 2xH2O2 group in 35 days old seedlings in seedling development stage. Biochemical results in 35 days old seedlings showed that the lowest amount of H2O2 was in NKU Lider cultivar and in groups treated with -H2O2 and 1xH2O2. The lowest TBARS amount was in Tosunbey variety and 2xH2O2 group. The highest SOD activity was in NKÜ Lider variety, all H2O2 pre-treatment caused an increase in SOD activity and 2xH2O2 pre-treatment caused the highest SOD activity. However, H2O2 and TBARS amounts increased in all application groups except 2xH2O2 group, while H2O2 amount increased and TBARS amount decreased in 2xH2O2 group. In this study, it was found that H2O2 pretreatment better tolerated the stress caused by salt stress on 35 days seedlings, and second-applied H2O2 pretreatment eliminated the stress and improved plant growth. In conclusion, it was determined that H2O2 re-pre-treatment to wheat seeds resulted in improvement of plant growth in tolerant wheat varieties exposed to salt stress.