Synergistic effects of multi-walled carbon nanotubes (MWCNTs), MgO, and Fe3O4 nanoparticles promoting growth, physiological performance, and artemisinin production in Artemisia annua L.

Using the nanomaterials is a novel method to improve plant products. This study investigated the potential of multi-walled carbon nanotubes (MWCNTs), magnesium oxide nanoparticles (MgO-NPs), and iron oxide nanoparticles (Fe 3 O 4 -NPs), to improve the biochemical and physiological traits of Artemisa annua . The nanomaterials applied at 0-100 mg L -1 and sample collected up to 120 hours. Results demonstrated that combined treatments, MWCNTs with Fe 3 O 4 -NPs or MgO-NPs, exerted significant positive effects on the growth indices, inducing an increase in relative water content, leaf area, fresh and dry weight (≤1.16-, ≤1.3-, ≤1.62- and ≤2.02-fold, respectively). Nanoparticles at low concentrations triggered a mild elicitation of reactive oxygen species (ROS), which stimulated the biosynthesis of photosynthetic pigments, chlorophyll b content (with MWCNTs) and carotenoid contents (with Fe 3 O 4 -NPs) increased by more than 1.66- fold and 1.56-fold, respectively. ROS burst activated antioxidant defense and metabolic alternations. Superoxide dismutase (SOD) and peroxidase (POX) activities increased 6.14- and 6-fold, respectively. While, catalase (CAT) activity was enhanced (≤14.79-fold) after 120 h except with MWCNTs treatments. The contents of soluble protein (≤2.87-fold), proline (≤7.67-fold), polysaccharides (≤1.6-fold), reducing sugars (>1.85-fold), and artemisinin (> 6-fold) were markedly elevated. In silico analyses revealed that MWCNTs interact with the catalytic sites of the antioxidant enzymes via the hydrogen bonding and steric interactions. Furthermore, Fe 3 O 4 -NPs exhibited strong binding interactions, likely releasing Fe 2+ /Fe 3+ ions as the cofactors to boost enzymatic activity. The combined nanoparticle treatments promoted effective adaptation to oxidative stress, particularly at 120 hours post-treatment. These findings propose an efficient strategy for enhancing growth and defense responses in A. annua .