ارزيابي اثر تيمار نانوذرات كيتوزان بر برخي از شاخص¬هاي بيوشيميايي و رشد گياه Dracocephalum ibericum M.Bieb. تحت تنش شوري

eva‎luation of the effect of chitosan nanoparticles treatment on some biochemical indices an‎d growth of Dracocephalum ibericum M.Bieb. under salt stress

زيست شناسي گياهي و جانوري

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.

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