Altering growth and antioxidant responses of basil cultivars with aluminum oxide nanoparticles in vitro

• High aluminum nanoparticle or bulk particle exposure hinders basil growth in vitro . • Excessive aluminum exposure heightened oxidative stress in red rubin or sweet basil tissues. • Aluminum exposure disrupted the non-enzymatic defense system of basil cultivars. • Different aluminum forms altered the enzymatic defense mechanisms in basil plant organs. • Aluminum exposure affected the production of secondary metabolites in basil cultivars. The rapid advancement of nanotechnology has resulted in a significant increase in the production of metal oxide nanoparticles, which are increasingly released into the environment. Due to their widespread distribution, evaluating the potential toxicity of these particles is essential. Aluminum oxide nanoparticles (Al 2 O 3 NPs), in particular, are widely used in various industries and consumer products. Basil, a valuable medicinal herb known for its essential oils and antioxidants, has numerous health benefits. The impact of Al 2 O 3 NPs on plants remains largely unexplored. This study investigated the effect of different concentrations of Al 2 O 3 NPs and their bulk form (AlCl 3 ; BP) on the growth of red Rubin and sweet basil cultivars in vitro , focusing on the induction of non-enzymatic and enzymatic antioxidant responses. Growth parameters were adversely affected by variations in cultivar, Al particle size, and concentration. The highest reductions occurred at 200 mg L −1 NPs or BPs, with decreases of up to 69.34 % for red Rubin and 63.33 % for sweet basil. Al NPs and BPs reduced chlorophyll a, b, and carotenoid levels. These pigments showed the highest decreases at 200 mg L −1 , with reductions of up to 81.92 % for red Rubin and 75.96 % for sweet basil. Al NPs and BPs compromised membrane integrity, inducing oxidative stress, as evidenced by increased electrolyte leakage, UV-absorbing compounds, malondialdehyde (MDA), and hydrogen peroxide (H 2 O 2 ) levels. The phenolic and amino acid concentrations in red Rubin basil leaves and roots decreased in response to increasing NP concentrations, while the opposite trend was observed for BPs. Conversely, sweet basil showed a consistent upward trend in phenolic and amino acid levels as Al concentrations increased, irrespective of particle form. The content of soluble proteins in basil leaves and roots declined as the concentrations of NPs and BPs increased. Enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO), increased in basil leaves and roots when exposed to rising concentrations of NPs and BPs. Catalase (CAT) activity increased in red Rubin leaves and roots but decreased in sweet basil leaves and roots, with rising concentrations of NPs and BPs. The observed variations in leaf and root growth between the two basil cultivars exposed to different concentrations of Al NPs and BPs suggest that cultivar physiology and particle characteristics play a role. Additional studies are required to clarify these mechanisms.