Salt Elicitation to Enhance Phytochemicals in Durum Wheat Seedlings

Salt has been identified as an elicitor that can increase the accumulation of phytochemicals in seedlings during the germination process. However, the salinity level required to maximize the yield of phytochemicals, particularly phenolic compounds, needs further investigation for several plant species. To address this issue, we imposed increasing levels of salinity (NaCl solutions) on the sprouting substrate of Triticum durum (var. Platone) grains, at concentrations of 0, 50, 100, 150, 200, 250, and 300 mM (0_S, 50_S, 100_S, 150_S, 200_S, 250_S, and 300_S, respectively). Results: The highest NaCl doses (250_S and 300_S) significantly impacted germination performances and were excluded from further analysis. The seedlings harvested at 8 days after sowing exhibited different growth stages depending on the salinity level, with wheatgrass, early wheatgrass, intermediate between sprout and wheatgrass, sprout, and very early sprout for 0_S, 50_S, 100_S, 150_S, and 200_S, respectively. Furthermore, salinity induced the concentration of phenolic compounds (PhCs) in the seedlings' tissues (i.e., both roots and shoots) in a salinity-dependent manner. The highest values were observed at 200_S, with an increase of 187% of the total investigated PhCs compared to 0_S, averaged over shoots and roots. In particular, in 200_S, the accumulation of phenolic acids was up to 4-fold higher in roots, and that of flavonoids was up to 2-fold higher in shoots. Conclusion: Our findings suggest that the use of 200 mM NaCl applied to the sprouting substrate is excessive for producing edible sprouts but may be suitable for phytochemical extraction purposes.