Tomato Fruit Nutritional Quality Is Altered by the Foliar Application of Various Metal Oxide Nanomaterials.

Carbohydrates and phytonutrients play important roles in tomato fruit's nutritional quality. In the current study, FeO, MnFeO, ZnFeO, ZnMnFeO, MnO, and ZnO nanomaterials (NMs) were synthesized, characterized, and applied at 250 mg/L to tomato plants via foliar application to investigate their effects on the nutritional quality of tomato fruits. The plant growth cycle was conducted for a total of 135 days in a greenhouse and the tomato fruits were harvested as they ripened. The lycopene content was initially reduced at 0 stored days by MnFeO, ZnFeO, and ZnMnFeO; however, after a 15-day storage, there was no statistical difference between the treatments and the control. Moreover, the β-carotene content was also reduced by ZnMnFeO, MnO, and ZnO. The effects of the MnO and ZnO carried over and inhibited the β-carotene after the fruit was stored. However, the total phenolic compounds were increased by ZnFeO, ZnMnFeO, and ZnO after 15 days of storage. Additionally, the sugar content in the fruit was enhanced by 118% and 111% when plants were exposed to MnO and ZnO, respectively. This study demonstrates both beneficial and detrimental effects of various NMs on tomato fruit quality and highlights the need for caution in such nanoscale applications during crop growth.