Tetragonia tetragonioides (Pallas) Kuntz. as promising salt-tolerant crop in a saline agricultural context

The lack of natural resources, especially good-quality cropland and renewable water resources is threatening food production potential in marginal agricultural ecosystems, which are already negatively affected by climate change. Since the world's major crops are proving inadequate to supply the calories and nutrients for people in these areas, new crops are sought that can withstand harsh ecological environmental conditions. In the current trial, we assessed the growth and productivity of Tetragonia tetragonioides (Pallas) Kuntz. in a floating hydroponic system supplied with different seawater proportions (i.e. 15% and 30% seawater, EC = 9.8 and 18.0 dS m⁻¹). Moreover, the effects of different salinity levels on mineral elements accumulation, production of osmotic solutes and secondary metabolites were determined, along with the salt removal capacity of the crop. The results indicated that plant growth was not affected by either of the seawater treatments used in this study. The increased leaf succulence and the reduction of both leaf area and specific leaf area with increasing salinity might represent an essential feature of this salt-tolerant species associated to the plants need of limiting transpiration. Low seawater treated plants showed a significantly higher biomass yield per liter of (sea)water used (117%) than the control. Under these conditions plants accumulated the highest amount of Mg (+31% and 48% in medium and high seawater treated plants compared with the control) and Cu (+14% and 30%, respectively) along with increasing proline and decreasing nitrate concentrations. By contrast, we found that seawater supply resulted in a Na-enriched leaf biomass that may represent an issue for human health. We concluded that Tetragonia tetragonioides can be grown in saline agriculture up to a salinity level characterized by an EC of 18 dS m⁻¹ but further investigation is required to address Na accumulation in leaves.