Abstract
Drought and salinity are major abiotic constraints that compromise photosynthesis and crop yield. This study aimed to investigate how Lilium LA Hybrid ‘Serrada’ responds to drought and salinity stresses, individually and in combination, with a particular focus on photosynthetic performance, nutrient uptake, and biomass accumulation. Plants were subjected to four volumetric water contents (VWCs; 0.25, 0.35, 0.45, and 0.55 m³·m⁻³) and three sodium chloride (NaCl) concentrations (0, 200, and 400 mM) over a 23-week period. Substrate pH, electrical conductivity (EC), photosynthetic parameters, ion balance, and growth traits were monitored to assess the interactive effects of water and salinity stress. Higher VWC moderated substrate pH and reduced NaCl accumulation, with EC reaching 25.1 dS·m⁻¹ at 0.25 m³·m⁻³ with 400 mM NaCl, approximately 36 times higher than at 0.55 m³·m⁻³. Elevated VWC and lower salinity supported greater net photosynthetic rates (An) and higher light saturation points. In contrast, combined stress markedly reduced stomatal conductance (gs), quantum yield of PSII (ΦPSII), and maximum quantum efficiency (Fv/Fm), while increasing nonphotochemical quenching (NPQ). Substrate EC negatively correlated with photosynthetic efficiency and biomass but positively correlated with Na⁺/K⁺ ratio and NPQ. Combined stress exacerbated Na⁺ accumulation, K⁺ depletion, and growth inhibition. The interplay between water availability and salinity strongly influenced substrate EC, ion homeostasis, photosynthetic efficiency, and biomass in Lilium. These findings provide insights into plant adaptive responses under simultaneous drought and salinity, offering implications for improved irrigation and salinity management strategies in Lilium cultivation.