Seed priming attenuates the impact of salt stress and enhances lettuce yields

Abstract

Salt stress is a major factor that contributes to reduced lettuce productivity. Seed priming has emerged as a promising technique to improve crop stress tolerance. In this study, Romaine lettuce seeds were primed with calcium chloride (CaCl2), distilled water (hydro), and potassium nitrate (KNO3) to test their effectiveness in improving salt stress tolerance. Lettuce seeds treated with hydro, 50 mM CaCl2, and 0.5% KNO3 were exposed to 0 or 100 mM sodium chloride (NaCl). Priming treatments significantly increased lettuce's fresh mass by 22%–61% under salt stress. Hydro-primed lettuce showed the most significant increase in root mass (109%), a 38% higher root length, a 35% increase in surface area, and a 25%–40% increase in volume, tips, forks, and crossings of roots. The hydro-primed lettuce had higher gas exchange rates than the non-primed control, followed by the KNO3- and the CaCl2-primed lettuce. Furthermore, hydro-primed seedlings exhibited the highest proline accumulation (105%) under salt stress. The accumulation of sugars (up to 50%) in hydro- and CaCl2-primed lettuce led to a 56% decrease in electrolyte leakage and membrane damage. The correlation network analysis of the traits revealed that hydro-primed seedlings exhibited a higher + ve/-ve edge ratio, which indicates their greater resilience to salt stress than other priming techniques. Priming of seeds before planting offers the potential for improving resilience to stress.