چكيده لاتين
Soil salinity is one of the most detrimental abiotic stresses limiting the growth, productivity, and phytochemical quality of medicinal plants, particularly in arid and semi-arid regions. Chitosan nanoparticles (CNs), owing to their biocompatibility, biodegradability, and strong capacity for redox modulation and defense activation, have emerged as promising nano-biostimulants for enhancing plant tolerance to saline conditions. This study aimed to evaluate the mitigating effects of CNs on growth, physiological traits, biochemical parameters, and secondary metabolites of Lallemantia iberica (Syn. Dracocephalum ibericum) under salinity stress. A factorial experiment was conducted using three salinity levels (0, 30, and 60 mM NaCl) and three CN concentrations (0, 75, and 150 mg L-1). Severe salinity significantly reduced biomass, chlorophyll content, relative water content (RWC), and the K⁺/Na⁺ ratio, while markedly increasing oxidative damage indicators, including malondialdehyde (MDA) and hydrogen peroxide (H2O2). Foliar application of CNs alleviated these adverse effects in a concentration-dependent manner, with CN75 performing best under severe stress and CN150 under moderate salinity. CN application enhanced the activities of major antioxidant enzymes (SOD, CAT, POD), increased proline and soluble protein levels, and stimulated the phenylpropanoid pathway by elevating PAL and TAL activities. HPLC profiling revealed a substantial increase in gallic acid and rosmarinic acid in CN-treated plants, indicating an intensified secondary metabolism. Multivariate analyses (PCA, heatmap clustering) demonstrated a coordinated shift in physiological, biochemical, and metabolic attributes, confirming the integrative role of CNs in reprogramming plant defense responses. Overall, CNs effectively improved ionic balance, strengthened the antioxidant machinery, and enhanced phenolic metabolism, thereby increasing L. iberica tolerance to salinity. These findings highlight CNs as eco-friendly, efficient nano-biostimulants for the sustainable production of medicinal plants under saline conditions.
