Silicon and potassium synergistically alleviate salt stress and enhance soil fertility, nutrition, and physiology of passion fruit seedlings

Alicia Camila Zeferino da Silva¹Rennan Fernandes Pereira¹Raquel da Silva Ferreira¹Samuel Barbosa Alves¹Franklin Suassuna de Sousa¹Samuel Saldanha Rodrigues¹José Felix de Brito Neto¹Alberto Soares de Melo¹Roseano Medeiros da Silva¹Evandro Franklin De Mesquita^2*

• ¹Universidade Estadual da Paraiba, Campina Grande, Brazil
• ²Department of Biology, State University of Paraíba, Campina Grande, Brazil

Yellow passion fruit (Passiflora edulis) is widely cultivated in Brazil but suffers adverse effects when irrigated with saline water, a common condition in the Brazilian semiarid region. Silicon and potassium have been extensively studied as salt stress mitigators, yet little is known about the synergistic effects between these two elements. Therefore, we evaluated the synergistic effects of silicon and potassium on alleviating salt stress in yellow passion fruit seedlings. Five Four doses of silicic acid (1.26, 2.52, 3.78, and 5.04, and 6.30 g dm-3) and two potassium doses (150 and 600 mg dm-3) were tested. Two controls were included: one irrigated with saline water (Control 1) and another with non-saline water (Control 2). The experimental design was completely randomized in a 4 × 2 + 2 factorial scheme, with five replicates. Soil fertility parameters (pH, electrical conductivity, macro-and micronutrients) and the following plant variables were assessed: foliar concentrations of macro-and micronutrients, biochemical traits (chlorophylls and proline), gas exchange, relative water content, electrolyte leakage, growth, and biomass accumulation. Results showed that the silicon-potassium combination linearly reduced substrate pH and electrical conductivity, while increasing the availability of P, K, Ca, Mg, S, Fe, Mn, Zn, and Cu. These improvements in soil fertility translated into greater foliar accumulation of these nutrients and lower Na⁺ levels in the leaves. Biochemically, there was a significant increase in chlorophyll a, b, and total, along with reduced proline levels, indicating lower osmotic stress. Physiologically, plants exhibited higher CO2 assimilation rates, stomatal conductance, and relative water content, with reduced electrolyte leakage. Morphologically, plant height and shoot and root dry masses increased in response to silicon doses, with gains of up to 133% compared to the saline control. Thus, the combined application of silicic acid and potassium is an effective practice to enhance soil fertility, optimize mineral nutrition, reinforce plant physiology, and promote seedling growth under high-salinity conditions.