Cold plasma, Fe and Mn nanoparticles modulate antioxidant activity, cannabinoids gene expression, and fatty acid profile in salt-stressed hemp

Soil salinity threatens global agriculture, yet sustainable strategies for high-value crops like hemp (Cannabis sativa L.) remain underexplored. While seed priming with physical and nano-technologies offers promise, their potential to enhance hemp's resilience under salt stress is unknown. This study investigates the comparative efficacy of cold plasma (CP; 60 and 90s) and metal nanoparticles (Fe NPs and Mn NPs; 50 mgL⁻¹) seed priming to mitigate salinity stress in hemp (0, 60, and 120 mM NaCl). Severe salinity (120 mM) compromised non-primed plants, reducing shoot fresh weight (39%), root fresh weight (17%), and cannabinoids; cannabidiol (CBD; 22%) and tetrahydrocannabinol (THC; 20%). Crucially, specific priming agents counteracted this stress and enhanced performance. Fe NP priming under moderate salinity (60 mM) was most effective, triggering upregulation of biosynthetic genes-CBDAS and THCAS expression increased by 102% and 170% relative to stressed controls-leading to improved cannabinoid levels and fatty acid profiles. The 90s CP treatment similarly bolstered salt tolerance. This work provides the first evidence that Fe NPs and 90s CP are effective priming strategies modulating antioxidant activity, gene expression, and lipid metabolism. These findings offer a novel approach to sustainably enhance resilience and pharmaceutical value of industrial hemp cultivated on salinized lands.