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Nanopesticides are becoming more popular in modern agriculture to improve crop protection product efficacy. However, information on their implications for crop plants is needed. In this study, 3-week-old maize plants were exposed to different doses of Cu(OH)2 nanopesticide (0, 10, and 100 mg) for 7 days via foliar application. Gene expression of 9 antioxidant-related enzymes (CAT1, POD1, GST1, SOD-1A, SOD-B, GPX, APX1, HSP1, PER1) was determined using a quantitative real-time polymerase chain reaction. Using gas chromatography time-of-flight mass spectrometry, levels of 12 low-molecular-weight antioxidant compounds were measured. Results showed that a dose of 100 mg of Cu(OH)2 nanopesticide significantly decreased leaf chlorophyll content and biomass by 17–20%. In addition, potassium and phosphorus were up-regulated (14% and 13%, respectively) in response to this dose. Gene expression of POD1 and GST1 was significantly (p < 0.05) increased by 42.6% and 71.8%, respectively, at a dose of 10 mg, but declined at high dose (100 mg). Precursors of phenolic acids (phenylalanine and tyrosine), 4-hydroxycinnamic acid, and total phenolic content were significantly increased (24–122%) in response to 100 mg, indicating that phenolic acids may also play an important role in antioxidant defense. This study provides important information on maize plant responses to the Cu(OH)2 nanopesticide at genetic, metabolic, and physiological levels and may be applied to other nanoparticle/plant interaction studies.
Zhao et al. (Tue,) studied this question.