Improvement of Physiological Features and Essential Oil Content of Thymus vulgaris after Soil Amendment with Chitosan Nanoparticles under Chromium Toxicity

: An excessive amount of chromium in soil has detrimental effects on plant processes, and impairs food security, and public health. The application of nanoparticles may be a suitable solu‐ tion and an innovative strategy by which to reduce plant abiotic stresses and pollution in the ag‐ ricultural ecosystems. This research focuses on the effects of chitosan nanoparticles (CS‐NPs) on thyme (Thymus vulgaris L.) plants grown in Cr‐contaminated soil. The effects of CS‐NPs as a soil amendment at four concentrations were investigated on plant nutrient uptake, photosynthesis parameters, antioxidant system, and essential oil (EO) content under soil Cr stress. The results show that chromium stress reduced fresh and dry weight of shoots, the uptake of macro‐, and mi‐ cro‐elements, chlorophyll and carotenoids. The application of CS‐NPs improved the antioxidant enzyme activity, reduced malondialdehyde, and increased the content of nutrients, EOs, photo‐ synthetic pigments, and chlorophyll fluorescence parameters. The intermediate dose of chitosan nanoparticles (0.1% w/v) best valorized the content and yield of thyme EOs under chromium stress. These results are indicative that the application of CS‐NPs can represent a supportive approach for plant production in soils contaminated with heavy metals.