Foliar applied nanoscale and microscale CeO_2 and CuO alter cucumber (Cucumis sativus) fruit quality

摘要

There is lack of information about the effects of foliar applied nanoparticles on fruit quality. In this study, three week-old soil grown cucumber seedlings were foliar-exposed to nCeO_2, nCuO, and corresponding bulk counterparts at 50,100, and 200 mg/L. Respective suspensions/solutions were sprayed to experimental units in a volume of 250 ml. Net photosynthesis rate (Pn), stomatal conductance (Gs), and transpiration rate (E) were measured 15 days after treatment application and in 74 day-old plants. Yield, fruit characteristics (size, weight, and firmness), Ce, Cu, and nutritional elements were also measured. Results showed a nano-specific decrement on Pn (22% and 30%) and E (11% and 17%) in seedling leaves exposed to nCeO_2 and nCuO at 200 mg/L, respectively, compared with control. nCeO_2 at 50 mg/L, bCeO_2 at 200 mg/L, and all Cu treatments, except nCuO at 100 mg/L, significantly reduced fruit firmness (p ≤ 0.05), compared with control. However, nCuO at 200 mg/L and bCuO at 50 mg/L significantly increased fruit fresh weight (p ≤ 0.05). At 200 mg/L, nCeO_2 and bCeO_2 reduced fruit Zn by 25%, while nCuO and bCuO reduced fruit Mo by 51% and 44%, respectively, compared with control. This study has shown that when the route of exposure is the foliage, differences in particle size are less significant, compared to root-based exposure. To the authors' knowledge, this is the first report on the effect of foliar application of nCeO_2 and nCuO upon yield and nutritional quality of cucumber.