Effect of salt stress on the growth, mineral contents, and metabolite profiles of spinach.

Background: Increased soil salt concentration decreases productivity and changes the physiological and chemical properties of plants. Various omics technologies have been used to understand the salt response in plants but overall changes in the metabolite profiles of spinach (Spinacia oleracea L.) under salt stress have not been studied. In this article, therefore, the changes in mineral and metabolite profiles of spinach plants cultivated with different NaCl concentrations of 0-200 mmol L in the irrigation water were analyzed to investigate the effect of salt stress on nutritional quality.

Results: Increasing NaCl concentration decreased plant growth due to mineral imbalance. The amounts of minerals (K , Ca , and Fe ) were reduced with increasing NaCl concentration, resulting in altered ratios of Na :K and Na :Ca . The change in the mineral ratios due to NaCl irrigation led to a decrease in the height and an increase in the weight of spinach. Moreover, the profiles of 32 metabolites, including flavonoids, amino acids, acidic compounds, sugars, and lipid-related compounds, were altered by NaCl irrigation; most of them showed decreased levels. In particular, at 200 mmol L NaCl, the levels of sucrose, glutamic acid, hexose sugars, and acidic compounds significantly decreased upon NaCl irrigation. Based on these metabolites, a salt-stress-related spinach metabolomic pathway was proposed.

Conclusion: Sodium chloride irrigation increased mineral imbalance, resulting in decreased plant growth, and the levels of most metabolites involved in energy production, sensory quality, and health benefits decreased with NaCl irrigation. The results suggest that NaCl irrigation negatively affects the nutritional quality of spinach. © 2020 Society of Chemical Industry.