Silicon Application Methods Differentially Modulate Nutrient Uptake and Morphophysiology in Passiflora edulis Seedlings Under Salt Stress

Silicon (Si) is a beneficial element that alleviates the adverse effects of salinity in plants, but the efficiency of its application methods remains unclear. This study evaluated two yellow passion fruit cultivars (BRS Sol do Cerrado and BRS Gigante Amarelo) at the seedling stage under five management conditions: irrigation with 1.2 dS m-1 water (control), 4.0 dS m-1 water (salt stress), and salt stress combined with silicon applied via soil, foliar spray, or both (soil + foliar), using silicic acid as the Si source. Leaf nutrient contents, morphophysiological traits, and the Dickson Quality Index (DQI) were assessed. Salinity reduced all parameters, whereas silicon mitigated these effects depending on the application method and cultivar. In BRS Gigante Amarelo, the combined application increased leaf C, N, K, Ca, and Mg contents, as well as dry mass, DQI, and gas exchange. In BRS Sol do Cerrado, it also enhanced plant height and biomass while reducing electrolyte leakage. Principal component analysis confirmed that the combined Si application promoted simultaneous recovery of nutrition, gas exchange, and growth. Overall, the combined soil and foliar application proved to be the most effective strategy to enhance growth, nutrient balance, and seedling quality of Passiflora edulis under salt stress.