Silicon Seed Priming Enhances Salt Tolerance of Barley Seedlings through Early ROS Detoxification and Stimulation of Antioxidant Defence

Seed priming has recently gained considerable attention to induce salt tolerance in several crop plants. In the present study, we evaluated the effect of seed priming with silicon (Si) using different concentrations (10, 20, and 40 mM) on barley (Hordeum vulgare L.) seed germination performance, seedling ion distribution, early growth establishment, and oxidative stress metabolism as grown under salinity (75 mM NaCl). Our results showed that all seed treatments (hydro-priming or Si-priming) improved salt tolerance of barley, relatively to unprimed state. However, specific differences associated with Si concentrations were recorded. At germination stage, a marked increase in germination percentage (100% on the 4th day of sowing) was recorded at 20 mM Si. When germination takes place in a salt-stressed medium, seedlings issued from seeds primed with 20 mM Si exhibited the highest ability to grow under saline conditions. Again, Si at 20 mM was the most beneficial for water adjustment in both roots (70%) and shoots (60%). This response was accompanied with increased root and shoot K+ content (33 and 25%, respectively). Seed priming with 20 mM Si resulted in a decrease in Na+ contents (by 42% in roots and 52% in shoots). This effect paralleled with a marked decline in H2O2 (by 65% in roots and 85% in shoots) and MDA content which together led to a spectacular activation of the overall antioxidant enzymes (SOD, CAT, and GPX). Taking into account these results, we suggest that the marked effectiveness of Si in primed seeds was more associated with ROS-scavenge and early activation of antioxidant defence, recorded in barley seedlings when subsequently grown under salinity stress.