Effect of graphene oxide-glyphosate nanocomposite on wheat and rape seedlings: Growth, photosynthesis performance, and oxidative stress response

Recently, nanomaterials have been increasingly applied to improve the bioactivity of pesticides for plant protection. However, the incorporation of nanomaterials into nano-herbicides is still in the early stage of development. In this study, the effect of GO–GLY nanocomposites was tested on wheat and edible rape seedlings in terms of growth parameters, photosynthises, the activity and gene expression of antioxidant enzymes. The results showed that compared with GO or GLY alone, GO–GLY nanocomposite more significantly inhibited the growth of wheat and rape seedlings, decreased the net photosynthetic rate, stomatal conductance, transpiration rate, primary maximum photochemical efficiency of photosystem II, actual quantum yield and photosynthetic electron transport rate, while significantly increased the intercellular CO2 concentration. These changes may be related to increases in oxidative stress, as indicated by the higher accumulation of O2.− and H2O2 under GO–GLY treatment. Furthermore, GO–GLY treatment increased the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) in both plant species compared with GO or GLY alone. In addition, gene expression analysis revealed that GO–GLY treatment upregulated the transcription of CATs, APXs, MDHAR, and DHAR genes in wheat seedlings, and elevated that of CATs, APXs, MDHAR, DHAR, and GR genes in rape seedlings compared with GO or GLY alone. Ultimately, in response to GO–GLY stress, a preliminary regulatory mechanism was proposed for the self-protective mechanism of wheat and rape seedlings, which lays a theoretical foundation for the wide application of nano-herbicides.