MITIGATION OF SALINITY STRESS ON PISTACHIO (Pistacia vera L.) SEEDLINGS THROUGH THE APPLICATION OF CARBON NITRIDE MODIFIED WITH IRON (FE/C3N4) NANOSTRUCTURES

Salinity has a global impact on plants by inducing biochemical and metabolic changes that lead to oxidative stress, impairing growth, yield, and productivity. The pistachio tree (Pistacia vera L.) is a salt-tolerant species. This study aims to investigate the effectiveness of carbon nitride nanostructures modified with iron (Fe/C3N4) on the Akbari pistachio variety under salinity stress levels (0, 50, 100, and 150 mM) and foliar applying (distilled water as a control, Fe2O3 (0.2 g L–1), C3N4 (0.2 g L–1), and carbon nitride modified with iron or Fe/C3N4 (0.2 g L–1). The findings showed that salinity decreased relative water content (RWC), SPAD index, membrane stability index (MSI), maximum fluorescence (Fm), and variable fluorescence (Fv), and increased hydrogen peroxide (H2 O2). However, foliar application with Fe2O3, or Fe/C3N4, improved all traits. Nevertheless, there was no significant interaction between the applied mitigating treatments and salinity levels on RWC, MSI, SPAD index, Fm, Fv, and H2O2. Salinity stress increased malondialdehyde (MDA), phenol, and flavonoid levels, and reduced leaf number, height, photosynthetic pigments, vitamin C, and total protein. The application of foliar treatments, especially Fe/C3N4, improved the influence of salinity stress. Additionally, the activity of antioxidant enzymes increased under salt stress and foliar application. Fe/C3N4-treated seedlings consistently exhibited higher growth and photosynthetic traits and lower oxidative damage than untreated controls across salinity levels, indicating a stable physiological benefit rather than a salinity-specific effect.