Mitigation of Recurrent Water Deficit in Black Pepper (Piper nigrum L.) Using Foliar Applications of Melatonin, Ascophyllum nodosum and Lithothamnium calcareum

Water deficit is one of the main limiting factors in agricultural production, affecting the growth and photosynthetic performance of plants. The aim of this study was to evaluate the effects of foliar applications of melatonin, Baltiko® containing Ascophyllum nodosum and LT Supra® containing Lithothamnium calcareum in black pepper, ‘Bragantina’, subjected to three cycles of water deficit, on physiological performance, carbohydrate allocation and vegetative growth. The results showed that the applied solutions contributed to the recovery of damage caused by water stress. The first cycle of water deficit affected the electron transfer quantum yield, resulting in the reduction of φP0 and PIABS. However, the damage to the photosynthetic apparatus was recovered in subsequent cycles. Water stress reduced chlorophyll indices, possibly as a strategy to minimize photo-oxidative damage. Plants treated with melatonin and L. calcareum maintained a stable leaf expansion rate and showed greater leaf water potential (ΨLea) recovery, standing out in the second and third cycles of water deficit.