Plant biostimulants in greenhouse horticulture: Recent advances and challenges ahead.

Interest in plant biostimulants is on the rise, compelled by the growing interest of greenhouse growers and private industries in natural substances and beneficial microorganisms able to boost vegetables and ornamentals productivity in a sustainable way. Protein hydrolysates (PHs) and arbuscular mycorrhiza fungi (AMF) are two important groups of plant biostimulants. PHs are generally applied as foliar sprays or near the roots, whereas, AMF are applied as powder, pellet, gel and seed coating. PHs and AMF are widely used in greenhouse crops largely for improving plant nutrient uptake, growth, yield and fruit quality, and also for their ameliorating effect on crop tolerance to abiotic stressors. In the current review article, we give an update about the recent advances in the biostimulant properties of PHs and AMF on vegetables, flower and ornamental crops performance. The agronomical and physiological processes conferring tolerance and/or resistance to several environmental stresses in biostimulant-treated plants will be also elucidated.