Ar+ beam implantation causes enhancement of salt stress tolerance in highland barley

This study examines the effects of ionizing radiation (control, 4 × 1016, 6 × 1016, 9.5 × 1016, and 15 × 1016 Ar+/cm2) on some physio-biochemical and molecular responses of highland barley (Hordeum vulgare L. ssp. vulgare) under salt stress for 0, 24, 48, and 96 h. The growth parameters of highland barley were the highest at the dose of 9.5 × 1016 Ar+/cm2, but the lowest at 15 × 1016 Ar+/cm2 dose. The malondialdehyde (MDA) content increased with increasing irradiation dose and peaked at 15 × 1016 Ar+/cm2 during stress treatments. The activities of antioxidant enzymes and proline accumulation showed different changes than MDA following ion beam irradiation toward stress conditions, at the dose of 15 × 1016 Ar+/cm2, antioxidant enzyme activities and proline content were the lowest compared with their corresponding controls, while at the dose of 9.5 × 1016 Ar+/cm2 antioxidant enzyme activities and proline content were the highest. Moreover, the expression of salt-related gene followed the same pattern as that of the antioxidant enzymes. Our results suggest that the dose of 9.5 × 1016 Ar+/cm2 alleviates salt stress by modulating the physio-biochemical responses and eliciting the stress signal transduction in plants.