Abstract
Alkalinity is a known threat to crop plant growth and production, yet the role of exogenous silicon (Si) and salicylic acid (SA) application has been largely unexplored. Here, we sought to understand the beneficial impacts of Si and SA on tomato seedlings during high-pH (9.0) stress. Results showed that Si- and SA-treated plants displayed higher biomass, chlorophyll contents, relative leaf water and better root system than none-treated plants under alkaline conditions. Both Si and SA counteracted the alkaline stress-induced oxidative damage by lowering the accumulation of reactive oxygen species and lipid peroxidation. The major antioxidant defence enzyme activities were largely stimulated by Si and SA, and these treatments caused significantly increased K+ and lowered Na+ concentrations in shoot and root under stress. Moreover, Si and SA treatments modulated endogenous SA levels and dramatically decreased abscisic acid levels in both shoot and root. Additionally, key genes involved in Si uptake, SA biosynthesis, the antioxidant defence system and rhizosphere acidification were up-regulated in Si and SA treatments under alkaline conditions. These results demonstrate that Si and SA play critical roles in improving alkaline stress tolerance in tomato seedlings, by modifying the endogenous Na+ and K+ contents, regulating oxidative damage and key genes and modulating endogenous hormone levels. These findings will help to broaden our understanding regarding the physiological and molecular mechanisms associated with the alkaline soil tolerance in plants.
Highlights
Alkalinity is a known threat to crop plant growth and production, yet the role of exogenous silicon (Si) and salicylic acid (SA) application has been largely unexplored
The results showed that the shoot length, diameter, fresh (FM) and dry masses (DM) were significantly lowered by high-pH compared with pH 6.0
A similar prospect was shown by SA treatment, where the shoot DM was significantly higher at pH 6.0 than at pH 9.0 (Fig. 1D)
Summary
Alkalinity is a known threat to crop plant growth and production, yet the role of exogenous silicon (Si) and salicylic acid (SA) application has been largely unexplored. Key genes involved in Si uptake, SA biosynthesis, the antioxidant defence system and rhizosphere acidification were up-regulated in Si and SA treatments under alkaline conditions These results demonstrate that Si and SA play critical roles in improving alkaline stress tolerance in tomato seedlings, by modifying the endogenous Na+ and K+ contents, regulating oxidative damage and key genes and modulating endogenous hormone levels. These findings will help to broaden our understanding regarding the physiological and molecular mechanisms associated with the alkaline soil tolerance in plants. In addition to SA, Si has been implicated in conferring similar beneficial impacts on plant growth physiology during stress conditions
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