Protein hydrolysate-based biostimulants: origin, biological activity and application methods

Protein hydrolysates (PHs) is an important group of plant biostimulants defined as mixtures of polypeptides, oligopeptides and amino acids which are manufactured from protein sources using partial hydrolysis. PHs are generally applied as foliar sprays or near the roots. PHs are widely used in agricultural crops largely for improving plant nutrient uptake, growth, yield and fruit quality and also for their ameliorating effect on crop tolerance to abiotic stresses. In the current paper, we give an update of the chemical characteristics, the timing and frequency of PHs application, the effects of PHs on plant metabolism and physiology, the biostimulant activities on yield and product quality. We report several experimental data on the application of a commercial plant derived-protein hydrolysate ‘Trainer’ on agricultural crops grown under different environmental conditions.