Exogenous pig blood-derived protein hydrolysates as a promising method for alleviation of salt stress in tomato (Solanum lycopersicum L.)

Abstract

Soil salinity is one of the major environmental threat for sustainable agriculture. Animal protein hydrolysates, as plant biostimulants, have received increasing attention because of their positive impacts on crop performances. However, their functions in crop tolerance to salt stress are unknown. We investigate the feasibility of pig blood-derived protein hydrolysates (Pp) in improving salt tolerance in tomato and the underlying mechanism. Pp application effectively ameliorated the salt stress-induced reduction in plant growth, chlorophyll levels, and photosynthetic efficiency. Salt-induced osmotic stress was indicated by lower relative water content, where higher Na+/K+ ratio indicated the ionic toxicity, whereas these phenomena were alleviated by Pp application, which might be due to the increased proline, soluble protein, sugars, K+, Ca2+, and Mg2+ contents. Salt stress also caused a significant increase in oxidative stress, as indicated by the enhanced H2O2 and O2− generation, malondialdehyde content and electrolyte leakage, which were mitigated significantly by Pp application via enhanced antioxidant enzyme (CAT, POD, and SOD) activities and the levels of non-enzymatic antioxidant including GSH and phenolic compounds. Pp application effectively enhanced tomato salt tolerance by regulating osmolytes biosynthesis, ion homeostasis, and antioxidant system responses. Thus, Pp may be proposed as effective methods to help plants overcome salt stress situations in agriculture.