Drought stress markedly affects plant growth and crop production. In turn, treatment with some metal-based nanoparticles (NPs) such as TiO2-NPs could improve the plant tolerance against drought stress. In the present study, the effects of different levels of moisture regime (40%, 60%, and 90% field capacity [FC]) in conjunction with various concentrations of TiO2-NPs (0, 5, 10, 20, and 40 mg. L−1) on chickpea were studied. Exposure of drought-challenged chickpea plants to TiO2-NPs raised antioxidant enzyme activity compared with plants grown under drought without TiO2-NP treatment. The highest activity of ascorbate peroxidase (APX) was observed at 40% FC and application of 40 mg. L−1 TiO2-NPs. Moreover, peroxidase (POX) activity has increased with the enhancing concentration of TiO2-NPs to 20 mg. L−1 at 90% FC. In comparison, the application of 40 mg. L−1 TiO2-NPs and decreasing levels of FC caused a rise in the activity of superoxide dismutase (SOD). Exposure to TiO2-NPs raised the amount of total phenols and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) at different levels of moisture regime. The content of malondialdehyde (MDA) at 60% FC has decreased by 22% after treatment with 20 mg. L−1 TiO2-NPs compared with control plants. Also, treatment with TiO2-NPs heightened the proline content, and the highest amount of proline was obtained at 40% FC by applying 20 mg. L−1 NPs. The treatment with TiO2-NPs in the moisture regimes led to higher chlorophyll and carotenoid production in chickpea plants. Taken together, the application of TiO2-NPs could raise the defense potential of chickpea plants against oxidative stress caused by the generation of reactive oxygen species.

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