Abstract
Copper (Cu
2+
) toxicity can inhibit plant growth and development. It has been shown that silicon (Si) can relieve Cu
2+
stress. However, it is unclear how Si-nanoparticles (SiNPs) relieve Cu
2+
stress in wheat seedlings. Therefore, the current study was conducted by setting up four treatments: CK, SiNP: (2.5 mM), Cu
2+
: (500 µM), and SiNP+Cu
2+
: (2.5 mM SiNP+500 µM Cu
2+
) to explore whether SiNPs can alleviate Cu
2+
toxicity in wheat seedlings. The results showed that Cu
2+
stress hampered root and shoot growth and accumulated high Cu
2+
concentrations in roots (45.35 mg/kg) and shoots (25.70 mg/kg) of wheat as compared to control treatment. Moreover, Cu
2+
treatment inhibited photosynthetic traits and chlorophyll contents as well as disturbed the antioxidant defense system by accumulating malondialdehyde (MDA) and hydrogen peroxidase (H
2
O
2
) contents. However, SiNPs treatment increased root length and shoot height by 15.1% and 22%, respectively, under Cu
2+
toxicity. Moreover, SiNPs application decreased MDA and H
2
O
2
contents by 31.25% and 19.25%, respectively. SiNPs increased non-enzymatic compounds such as ascorbic acid-glutathione (AsA-GSH) and enhanced superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbic peroxidase (APX) activities by 77.5%, 141.7%, 68%, and 80%, respectively. Furthermore, SiNPs decreased Cu
2+
concentrations in shoots by 26.2%, as compared to Cu
2+
treatment alone. The results concluded that SiNPs could alleviate Cu
2+
stress in wheat seedlings. The present investigation may help to increase wheat production in Cu
2+
contaminated soils.