Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants.

The application of nanomaterials as a method to overcome plant stress and increase crop yield is relatively new as compared to the use of fertilizers and pesticides in agricultural production. In the present study, manganese (III) oxide nanoparticles (MnNPs) were investigated as a nanopriming agent to alleviate salinity stress in Capsicum annuum L. during germination at 100 mM NaCl. In general, the root growth in both nonsalt and salt-stressed seedlings was significantly improved by MnNPs (0.1, 0.5, 1 mg/L). Scanning electron microscopy and energy-dispersive spectroscopy showed the penetration of MnNPs through the seed coat and the formation of nanoparticle–corona complex. MnNPs have different surface chemistries when present in water or NaCl, which may lead to their different affinities to proteins and alter the N–H bonding according to Fourier transform infrared spectroscopy. Salt stress inhibited root growth, induced proteins and lignin pattern changes, and redistributed the manganese, sodium, potassium, and calcium contents between the shoot and root. However, neither the redistributions nor manganese superoxide dismutase expression were affected by MnNPs but by MnSO4. This study describes how nanopriming elicits compositional changes and molecular interactions among key biomolecules and implies the role of MnNPs in plant salt stress management in order to promote sustainable agriculture.

The environmental impacts of Cu-based nanoparticles (NPs) are not well understood. In this study, cilantro (Coriandrum sativum) was germinated and grown in commercial potting mix soil amended with Cu(OH)2 (Kocide and CuPRO), nano-copper (nCu), micro-copper (μCu), nano-copper oxide (nCuO), micro-copper oxide (μCuO) and ionic Cu (CuCl2) at either 20 or 80 mg Cu per kg. In addition to seed germination and plant elongation, relative chlorophyll content and micro and macroelement concentrations were determined. At both concentrations, only nCuO, μCuO, and ionic Cu, showed statistically significant reductions in germination. Although compared with control, the relative germination was reduced by ∼50% with nCuO at both concentrations, and by ∼40% with μCuO, also at both concentrations, the difference among compounds was not statistically significant. Exposure to μCuO at both concentrations and nCu at 80 mg kg(-1) significantly reduced (p≤ 0.05) shoot elongation by 11% and 12.4%, respectively, compared with control. Only μCuO at 20 mg kg(-1) significantly reduced (26%) the relative chlorophyll content, compared with control. None of the treatments increased root Cu, but all of them, except μCuO at 20 mg kg(-1), significantly increased shoot Cu (p≤ 0.05). Micro and macro elements B, Zn, Mn, Ca, Mg, P, and S were significantly reduced in shoots (p≤ 0.05). Similar results were observed in roots. These results showed that Cu-based NPs/compounds depress nutrient element accumulation in cilantro, which could impact human nutrition.

Little is known about the effects of surface modification on the interaction of nanoparticles (NPs) with plants. Tomato (Solanum lycopersicum L.) plants were cultivated in potting soil amended with bare and citric acid coated nanoceria (nCeO nCeO+CA), cerium acetate (CeAc), bulk cerium oxide (bCeO) and citric acid (CA) at 0-500 mg kg. Fruits were collected year-round until the harvesting time (210 days). Results showed that nCeO+CA at 62.5, 250 and 500 mg kg reduced dry weight by 54, 57, and 64% and total sugar by 84, 78, and 81%. At 62.5, 125, and 500 mg kg nCeO+CA decreased reducing sugar by 63, 75, and 52%, respectively and at 125 mg kg reduced starch by 78%, compared to control. The bCeO at 250 and 500 mg kg, increased reducing sugar by 67 and 58%. In addition, when compared to controls, nCeO at 500 mg kg reduced B (28%), Fe (78%), Mn (33%), and Ca (59%). At 125 mg kg decreased Al by 24%; while nCeO+CA at 125 and 500 mg kg increased B by 33%. On the other hand, bCeO at 62.5 mg kg increased Ca (267%), but at 250 mg kg reduced Cu (52%), Mn (33%), and Mg (58%). Fruit macromolecules were mainly affected by nCeO+CA, while nutritional elements by nCeO; however, all Ce treatments altered, in some way, the nutritional quality of tomato fruit. To our knowledge, this is the first study comparing effects of uncoated and coated nanoceria on tomato fruit quality.

No abstract