The impact of PGRs applied in the field on the postharvest behavior of fruit crops

In horticulture, Plant Growth Regulators (PGRs) are applied during cultivation in the field to control and regulate different processes with positive effects on stress responses and general performance, including yield, compo-sition, and quality of the harvested produce. Both vegetative and reproductive activities may be affected by PGRs and, considering specifically fruit crops, the effects of these field treatments can also be observed in terms of storage behavior and postharvest physiology. The postharvest effects of inhibitors, antagonists, promoters or releasers of gibberellins, cytokinins, auxins and ethylene depend on the concentration, chemical formulation and plant developmental stage at the time of treatments. Ethylene-related PGRs in particular, applied to control ripening and optimize harvesting, have marked residual effects observed during the storage life. In addition to these hormonal categories, other substances such as salicylic acid, brassinosteroids and jasmonates, recognized as having physiological effects in developing plants and inducing compositional changes in fruits at harvest, are effective in altering specific postharvest ripening processes, such as firmness loss and ethylene physiology. The stimulation of antioxidant enzymes activity and the maintenance of cell membrane integrity during storage, resulting in a reduction of chilling injury incidence, appear to be among the main effects of the field application of these PGRs. This review emphasizes the implications of PGR applications during cultivation on fruit postharvest.