اعظم سیدی

Backround Salinity stress severely limits citrus growth by impairing root development and physiological functions. Therefore, understanding of the mechanisms underlying root system architecture (RSA) adaptation in orange seedlings is crucial for enhancing their resilience to salinity in subtropical regions. The research was conducted to unravel the role of salinity, together with foliar spraying of chitosan/selenium nanoparticles (CS/Se NPs), on nutrient uptake and RSA in Citrus sinensis is examined. Valencia orange seedlings received foliar spraying treatments of distilled water (control), chitosan (CS), selenium nanoparticles (Se NPs), and a CS/Se NPs composite at two levels (10 and 20 mg L−1 ). Following treatment, seedlings were exposed to three salinity regimes: non-saline or control (0 mM NaCl), moderate (50 mM NaCl), and intense (100 mM NaCl). Results Exposure to intense salinity markedly increased sodium (Na) accumulation while reducing potassium (K), the K/Na ratio, calcium (Ca), the Ca/Na ratio, and magnesium (Mg) levels in roots. Additionally, salinity stress negatively affected RSA traits, including total root length, root surface area, and lateral root formation, relative to non-saline conditions. In contrast, treated seedlings with CS, Se NPs, and the CS/Se NPs composite demonstrated lower Na concentrations, enhanced nutrient accumulation, and improved RSA parameters. Remarkably, foliar spraying of CS/ Se NPs at 10 mg L−1 was the most effective under intense salinity stress, significantly reducing Na accumulation and enhancing K, K/Na, Ca, Ca/Na, and Mg content in roots, while also promoting total root length, root volume, root surface area, lateral root number, root perimeter, and maximum root count per plant compared to controls. Conclusions This study demonstrates that CS/Se NPs, with the 10 mg L−1 dose being particularly effective, hold potential as a foliar application to mitigate salinity stress, thereby contributing to better crop performance in harsh growing conditions.