Abstract
Previous studies have shown the role of silicon (Si) in mitigating the adverse effect of drought stress in different crop species. However, data are lacking on a comparison of drought tolerant and drought sensitive crop cultivars in response to Si nutrition. Therefore, the aim of this study was to elucidate the mechanism (s) by which two contrasting tomato genotypes respond to Si nutrition under osmotic stress condition. Two tomato lines contrasting in their response to drought stress were hydroponically grown under polyethylene glycol (PEG, 6000) and two regimes of Si (0 and 1.5 mM). Metabolite profiling was performed in two lines. Growth and relevant physiological parameters, and expression levels of selected genes were also measured. Si application resulted in improved osmotic stress tolerance in both drought tolerant line LA0147 and drought sensitive line FERUM. In the drought tolerant line, Si enhanced uptake of sulfur (S) and ammonium () which led to a significantly higher production of amino acids arginine, methionine, serine, and glycine. While in the drought sensitive line, Si significantly increased production of amino acids proline and GABA which further lowered the level of GSSG to GSH ratio and thus balanced the redox homeostasis under osmotic stress. The higher significant production of amino acids arginine, methionine, GABA, and proline enhanced production of free polyamines putrescine and spermidine and improved osmotic stress tolerance. Therefore, we conclude that Si distinctively regulated osmotic stress tolerance in two contrasting tomato genotypes by differential accumulation of relevant amino acids which eventually led to enhanced polyamine metabolism.
Highlights
Abiotic stress is estimated to reduce the yield of crops by 51–82% (Cooke and Leishman, 2016)
Application of Si did not change the biomass of tolerant line LA0147 under osmotic stress conditions (OSC), whereas the biomass of sensitive line FERUM significantly increased by Si supply under OSC (Figures 1B,C)
These results showed that under OSC the LA0147 coped better with osmotic stress compared to the sensitive line and Si supply increased the growth level of sensitive line FERUM under OSC
Summary
Abiotic stress is estimated to reduce the yield of crops by 51–82% (Cooke and Leishman, 2016). Several studies have reported that Silicon (Si) application to crops enhances their tolerance to drought (Gong et al, 2008; Chen et al, 2011; Amin et al, 2016), and so plants use Si as a ‘quasiessential’ element in order to alleviate the impacts of drought stress (Ma et al, 2004; Pei et al, 2010) In these studies, the beneficial effects of Si were primarily due to its role through increasing anti-oxidant production, maintaining photosynthetic machinery (Shen et al, 2010) and delaying leaf senescence (Hosseini et al, 2017). It has remained an open question, whether supplemental Si is able to counteract drought stress more effectively in drought-tolerant and/or in drought sensitive genotypes
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