NaCl improves the vegetable quality of Mesembryanthemum crystallinum Linn. by increasing betacyanin and nutrient contents

Soil salinization is a growing environmental problem and a major factor limiting crop production. Growing salt-adapted crops may allow farmers to utilize farmland with high salt concentrations. For example, leaves of the halophyte Mesembryanthemum crystallinum (also known as ‘ice plant’) are consumed raw, cooked, or pickled. Here, we examine the mechanism by which salt improved the quality of this vegetable crop and provide theoretical support for planting M. crystallinum in saline soils or growing it in hydroponic facilities. Four-leaf stage M. crystallinum seedlings were treated with 0, 50, 100, 150, 200, 250 and 300 mM NaCl for 4 weeks and then plant growth and ion, nutrient and betacyanin contents were measured. Compared to the control (0 mM NaCl), treatment with 50 and 100 mM NaCl significantly improved M. crystallinum growth and increased the contents of nutrients (protein, dietary fiber, organic acids, and soluble sugars) and betacyanins. By contrast, treatment with 150–300 mM NaCl had the opposite effect. Genes encoding the betacyanin biosynthesis enzymes tyrosinase, DODA, 5-GT, and CYP76AD1 were upregulated in plants treated with 100 mM NaCl. Four betacyanin derivatives were also identified in this species. Treatment with 100 mM NaCl significantly improved the growth, nutrient contents and betacyanin contents of this species, thereby improving its commercial value. These findings thus provide guidance for hydroponic or field growth of this emerging vegetable crop.