Reports indicate that silver nanoparticles (nAg) are toxic to vegetation, but little is known about their effects in crop plants. This study examines the impacts of nAg on the physiology and nutritional quality of radish (Raphanus sativus) sprouts. Seeds were germinated and grown for 5 days in nAg suspensions at 0, 125, 250, and 500 mg/L. Seed germination and seedling growth were evaluated with traditional methodologies; the uptake of Ag and nutrients was quantified by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and changes in macromolecules were analyzed by infrared (IR) spectroscopy. None of the nAg concentrations reduced seed germination. However, the water content (% of the total weight) was reduced by 1.62, 1.65, and 2.54% with exposure to 125, 250, and 500 mg/L, respectively, compared with the control. At 500 mg/L, the root and shoot lengths were reduced by 47.7 and 40%, with respect to the control. The seedlings exposed to 500 mg/L had 901 ± 150 mg Ag/kg dry wt and significantly less Ca, Mg, B, Cu, Mn, and Zn, compared with the control. The infrared spectroscopy analysis showed changes in the bands corresponding to lipids (3000–2800 cm-1), proteins (1550–1530 cm-1), and structural components of plant cells such as lignin, pectin, and cellulose. These results suggest that nAg could significantly affect the growth, nutrient content and macromolecule conformation in radish sprouts, with unknown consequences for human health.

Little is known about the effects of surface coating on the interaction of engineered nanoparticles (ENPs) with plants. In this study, basil (Ocimum basilicum) was cultivated for 65 days in soil amended with unmodified, hydrophobic (coated with aluminum oxide and dimethicone), and hydrophilic (coated with aluminum oxide and glycerol) titanium dioxide nanoparticles (nano-TiO) at 125, 250, 500, and 750 mg nano-TiO kg soil. ICP-OES/MS, SPAD meter, and UV/Vis spectrometry were used to determine Ti and essential elements in tissues, relative chlorophyll content, carbohydrates, and antioxidant response, respectively. Compared with control, hydrophobic and hydrophilic nano-TiO significantly reduced seed germination by 41% and 59%, respectively, while unmodified and hydrophobic nano-TiO significantly decreased shoot biomass by 31% and 37%, respectively (p ≤ 0.05). Roots exposed to hydrophobic particles at 750 mg kg had 87% and 40% more Ti than the pristine and hydrophilic nano-TiO; however, no differences were found in shoots. The three types of particles affected the homeostasis of essential elements: at 500 mg kg, unmodified particles increased Cu (104%) and Fe (90%); hydrophilic increased Fe (90%); while hydrophobic increased Mn (339%) but reduced Ca (71%), Cu (58%), and P (40%). However, only hydrophobic particles significantly reduced root elongation by 53%. Unmodified, hydrophobic, and hydrophilic particles significantly reduced total sugar by 39%, 38%, and 66%, respectively, compared with control. Moreover, unmodified particles significantly decreased reducing sugar (34%), while hydrophobic particles significantly reduced starch (35%). Although the three particles affected basil plants, coated particles impacted the most its nutritional quality, since they altered more essential elements, starch, and reducing sugars.

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