Seed priming with cold plasma, iron, and manganese nanoparticles modulates salinity stress in hemp (Cannabis sativa L.) by improving germination, growth, and biochemical attributes.

Using cutting-edge technologies such as non-thermal plasma and metallic nanoparticles has shown promise in ameliorating salinity-induced stress in plants. However, there are still knowledge gaps concerning the most effective strategies for mitigating salinity stress in hemp (Cannabis sativa L.) plants. Consequently, this study was undertaken to investigate the impact of seed priming with cold plasma (CP), iron (Fe), and manganese (Mn) nanoparticles (NPs) on salinity modulation in hemp plants, aiming to improve seed germination, plant growth, and biochemical attributes. A pot experiment was conducted with salinity at three levels (0, 60, and 120 mM NaCl) and seed priming at five levels (control, 60 s CP, 90 s CP, 50 mg L^-1 Fe NPs, and 50 mg L^-1 Mn NPs). The results showed that salinity at 120 mM decreased germination percentage (GP, 34%), germination speed (GS, 61%), seedling vigor index (SVI, 47%), shoot weight (38%), root weight (15%), chlorophyll (Chl) a + b (31%), and relative water content (RWC, 24%) while increasing malondialdehyde (MDA, 48%) and proline (39%). Seed priming with CP, Fe NPs, and Mn NPs increased plant weight, GP, GS, SVI, RWC, and Chl but decreased MDA accumulation. Fe NPs and salinity at 60 mM led to high levels of total phenolic content and total flavonoid content, which represent 29 and 44% increases, respectively, compared to the control. The heat map showed that among the treatments, GS and SVI had the highest degrees of variability. Fe NPs at 50 mg L^-1 and CP at 90 s produced the best plant tolerance to salt stress.