Copper Oxide Nanomaterial Fate in Plant Tissue: Nanoscale Impacts on Reproductive Tissues

A thorough
understanding of the implications of chronic low-dose
exposure to engineered nanomaterials through the food chain is lacking.
The present study aimed to characterize such a response in Cucurbita pepo L. (zucchini) upon exposure to a potential
nanoscale fertilizer: copper oxide (CuO) nanoparticles. Zucchini was
grown in soil amended with nano-CuO, bulk CuO (100 mg Kg–1), and CuSO4 (320 mg Kg–1) from germination
to flowering (60 days). Nano-CuO treatment had no impact on plant
morphology or growth nor pollen formation and viability. The uptake
of Cu was comparable in the plant tissues under all treatments. RNA-seq
analyses on vegetative and reproductive tissues highlighted common
and nanoscale-specific components of the response. Mitochondrial and
chloroplast functions were uniquely modulated in response to nanomaterial
exposure as compared with conventional bulk and salt forms. X-ray
absorption spectroscopy showed that the Cu local structure changed
upon nano-CuO internalization, suggesting potential nanoparticle biotransformation
within the plant tissues. These findings demonstrate the potential
positive physiological, cellular, and molecular response related to
nano-CuO application as a plant fertilizer, highlighting the differential
mechanisms involved in the exposure to Cu in nanoscale, bulk, or salt
forms. Nano-CuO uniquely stimulates plant response in a way that can
minimize agrochemical inputs to the environment and therefore could
be an important strategy in nanoenabled agriculture.