Comparative physiological and biochemial effects of CuO NPs and bulk CuO phytotoxicity onto the maize (Zea mays) seedlings

Plant nanotoxicology is an emerging and less-explored area of research for the plant stress biologists. The present study assesses the toxicity of bulk-CuO and nano-CuO (size <50 nm and surface area = 29 m² g^-1) on maize (Zea mays cv. hybrids triple white Hi Tech.) seedlings. Five successive levels of stress (25, 50, 100, 150 and 200 mg L^-1) suspensions of CuO and CuONP were imposed and seedling growth performance was studied along control at 8 days of experiment. Modulation of enzymatic antioxidants (SOD, CAT, APX and POD) and non-enzymatic antioxidants (total phenolics and total flavonoids) activities under both-CuO stresses were investigated in detail to get an overview of their-stress response of maize. Seed germination was completely stopped under 150 and 200 mg L^-1CuONP. Generally, CuONP stress was most violent and 100 mg L^-1CuONP showed the same or more drastic effect in 150 and 200 Cu bulk. Photosynthetic pigments, shoot and root lengths reduced under both stresses by about 50% of control. Soluble proteins and total antioxidants increased gradually till it reached about 200% of control at 150 mg L^-1CuO and about 200-300% at 100 mg L^-1CuONP. In addition, increased reducing power activity coupled with both stresses which reached to 400% of control at 150 mg L^-1CuO and 100 mg L^-1CuONP. Moreover, superoxide dismutase increased by 800% of control at 100 mg. L^-1CuONP.