Technological advancements in nanotechnology have shown promising potential in improving crop protection (Mukhopadhyay, 2011, Pérez-de-Luque, 2017). NPs are advantageous because of their diminutive size, higher surface-to-volume ratio, appropriate delivery of key nutrients to plants, and outstanding physiochemical and structural attributes. These key attributes help significantly in providing safe and nutritive food access in adequate amounts for healthy human life (Tripathi et al., 2017, Ulhassan et al., 2022a, Ulhassan et al., 2022b). These properties also permit the NP’s applications in different industries like engineering, textiles, cosmetics, food, and agriculture (Hazarika et al., 2022). Nanoparticles as carriers have a promising impact and establish themselves as a favorable strategy for the germination of seeds, plant growth, and physiology (Mukhopadhyay, 2011, Sanzari et al., 2019).

Copper is a vital micronutrient for the growth of plants. It is involved in chlorophyll synthesis and the metabolism of proteins. An adequate amount of Cu is necessary for the growth of plants and its deficiency may cause a reduction in yield and decrease resistance against diseases. Copper is required by plants in trace amount, but the increased concentration of Cu exerts toxic effects on plants. CuO-NPs have been used in agriculture as a fertilizer (Liu and Lal, 2015), pesticide, and bactericidal agents on different crops (Rai et al., 2018), however, the excess may cause phytotoxicity. Many findings demonstrate the phytotoxicity of CuO-NPs particularly reduced seed germination, dwarfed plant morphology, and production of low-quality fruit/yield. Phytotoxicity of CuO-NPs has been described in many plants including maize (Raza Khan et al., 2023), rice (Azhar et al., 2022, Thounaojam et al., 2012), and many other species (Da Costa and Sharma, 2016, Rajput et al., 2020, Rajput et al., 2018, Roy et al., 2022, Yang et al., 2020). These reports have revealed that the size, concentration, exposure time, and route of administration are very critical (Naz et al., 2020, Zafar et al., 2020).

Auxins or specifically IAA is one of the most studied phytohormones. IAA has a critical role in the developmental process of plant and defense response. At an adequate amount, IAA causes cell division, tropism, stem elongation, and adventitious root formation (Vernoux et al., 2010). Due to its importance in the developmental processes of plants, it is a tremendously exciting and active area of research (Vieten et al., 2007). Lactuca sativa is a leafy vegetable that is consumed worldwide and is an excellent source of vitamins (A, B, C, E, and K), beta-carotenes, fibers, carotenoids, and phenolic compounds. It has health benefits due to its high-water content (95%) and low caloric content (Noumedem et al., 2017). Lettuce consumption results in a decrease in cholesterol levels (Lee et al., 2009), diabetes (Cheng et al., 2014, Gopal et al., 2017), inflammatory processes (Ismail et al., 2016), and other conditions which bring different health benefits (Kim et al., 2016).

CuO-NPs are known to retard the growth of root plants with a prominent effect on roots but at an appropriate concentration boost the growth that depicts their function as a nano-fertilizer(Ain et al., 2018; Zia et al., 2021). To circumvent the toxic impacts on roots, CuO-NPs can be capped with plant growth regulators. This study aimed to cap the CuO-NPs with IAA and investigate the role in toxicity reduction and plant growth of Lactuca sativa. In this study, we demonstrate the synthesis of CuO-NPs, IAA-capped CuO-NPs as a carrier, and toxicity mitigants and performed their characterization. We screened the concentration-dependent toxicity of CuO-NPs and mitigated their toxicity by IAA-capped CuO-NPs. The physiological parameters and biochemical response of lettuce plantlets grown under the different concentrations of NPs are investigated. The results demonstrate that CuO-NPs can be used as a carrier of hormones for the enhancement of plant growth and IAA on the surface of NPs reduces the toxic effects on NPs.