Plant biostimulants from seaweeds or vegetal proteins enhance the salinity tolerance in greenhouse lettuce by modulating plant metabolism in a distinctive manner

•PH and SWE application effects on lettuce at 0 or 40 mM NaCl was explored.•PH treatment reduced Na and Cl contents while increased those of S, K and Mg.•Glucosinolates, phytoalexins and jasmonates were modulated by the biostimulants.•The protein hydrolysate and the seaweed elicited distinct metabolic processes.