The uptake of engineered nanoparticles has potential to threaten the growth and safety of harvested food crops. We investigated short-term response of root physiology and function to CuO NP with reference to a Cu2+ control (CuCl2) on two food crop species of contrasting root architecture. In addition to determining germination and root physiology (elongation and diameter), we examined how acute exposure of these crop impacted a critical root function: hydraulic conductivity. CuO NP (10 nm diameter; 1, 10, 100, 500, 1000 mgL-1) had no significant effect on lettuce and carrot germination, but CuCl2 (0.1, 1, 5, 10, 100 mgL-1) decreased germination at concentrations ≥ 10 mg CuL-1 by up to 86% for carrot and 50% for lettuce. Seedling root length decreased with concentration of CuO NP and CuCl2 in a similar manner for both species, with greater inhibition occurred for CuCl2 than for CuO NP. In contrast, a stronger effect of CuO NP than CuCl2 was observed for root diameter. Root thickening induced by CuO NP was greater for lettuce (+52% diameter) than carrot (+26%) at 1000 mgL-1 CuO NP. Root diameter of lettuce was not affected by CuCl2, and carrot root diameter transiently increased by 56% only at 5 mgL-1, with greater mean thickness (0.56 cm) compared to maximum thickness for CuO NP treatments (0.49 cm). Hydraulic conductivity was reduced in acute exposure to CuO NP (1000 mgL-1) for lettuce (-46%) but not carrot. No Cu2+ or CuO NP was observed or detected by TEM-EDS in xylem sap during conductivity measurements. These results indicate the CuO NPs exert acute effects on root physiology and function that are distinct from Cu2+. Finally, experiments to trace nanoparticle uptake in plants over 24 hour period using radiolabeled particles were conducted, with results revealing that uptake is dependent on both size and time. Data suggest a size threshold of &lt;10 nm is most available for plant uptake.

Examining the impact of copper oxide nanoparticles on carrot and lettuce growth and root hydraulic conductivity

253rd National Meeting (2017)

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