Physiological indices of sour passion fruit under brackish water irrigation strategies and potassium fertilization

The objective of this study was to evaluate the physiological indices of sour passion fruit under brackish water irrigation strategies and potassium fertilization. The study was carried out under field conditions in Sao Domingos, PB, Brazil, using a randomized block design in a 6 x 2 factorial scheme, with treatments consisting of six brackish water irrigation strategies (irrigation with moderately saline (1.3 dS m-1) water throughout the crop cycle -WS; irrigation with high-salinity (4.0 dS m-1) water in the vegetative stage -VE; flowering stage -FL; fruiting stage -FR; successively in the vegetative/flowering stages -VE/FL; and vegetative/fruiting stages -VE/FR) and two doses of potassium (207 and 345 g K2O per plant per year, corresponding, respectively, to 60 and 100% of recommendation), with four replicates and three plants per plot. Irrigation with water of 4.0 dS m-1 reduced the osmotic and water potentials in the leaf blade, synthesis of chlorophylls a and b, transpiration, and instantaneous carboxylation efficiency of sour passion fruit, regardless of the development stage. Salt stress in the vegetative, flowering, fruiting, and successively in the vegetative/flowering and vegetative/fruiting stages increases intercellular electrolyte leakage in sour passion fruit. Fertilization with 100% of the K recommendation increased stomatal conductance, CO2 assimilation rate, and instantaneous water use efficiency of sour passion fruit cv. BRS GA1 under irrigation with water of 1.3 dS m-1 throughout the crop cycle.