Silicon‐mediated changes in polyamines participate in silicon‐induced salt tolerance in Sorghum bicolor L.

Abstract

Silicon (S i) is generally considered a beneficial element for the growth of higher plants, especially under stress conditions, but the mechanisms remain unclear. Here, we tested the hypothesis that Si improves salt tolerance through mediating important metabolism processes rather than acting as a mere mechanical barrier. Seedlings of sorghum (Sorghum bicolor L.) growing in hydroponic culture were treated with N a C l (100 m m) combined with or without S i (0.83 m m). The result showed that supplemental S i enhanced sorghum salt tolerance by decreasing N a+ accumulation. Simultaneously, polyamine (PA) levels were increased and ethylene precursor (1‐aminocyclopropane‐1‐carboxylic acid: ACC) concentrations were decreased. Several key PA synthesis genes were up‐regulated by S i under salt stress. To further confirm the role of PA in S i‐mediated salt tolerance, seedlings were exposed to spermidine (S pd) or a PA synthesis inhibitor (dicyclohexylammonium sulphate, DCHA) combined with salt and S i. Exogenous S pd showed similar effects as S i under salt stress whereas exogenous DCHA eliminated S i‐enhanced salt tolerance and the beneficial effect of S i in decreasing N a+ accumulation. These results indicate that PA s and ACC are involved in S i‐induced salt tolerance in sorghum and provide evidence that S i plays an active role in mediating salt tolerance.