Table 5.

The nanoparticle (NP) toxicity effects in plants under heavy metal (HM) stress

HM	NPs			Plant species	NP-toxicity effects	Ref.
	Type	NP-toxicity concentration	Application method
As	ZnO-NPs	400 mg/L	Aqueous suspension, soil	Pisum sativum	Reduction in germination and plant growth, induction of oxidative stress, decrease in enzyme activity, induction of genotoxic effects, and instability in chromosomes	[278]
		200 mg/L	Seed priming	Vigna mungo	Increase in H2O2, superoxide anion, and MDA accumulation, reduction in relative water content, and induction of oxidative stress.	[279]
		100 mg/L	Hydroponic cultivation	Oryza sativa	Decrease in biomass and total chlorophyll, increase in electrolyte leakage	[14]
	SiO2-NPs	250 and 1000 mg/L	Soil	Solanum lycopersicum	Decreased plant yield	[284]
Cd	ZnO-NPs	10 and 50 µM	Hydroponic cultivation	Carex vulpina	Increase in Cd and Zn accumulation in roots and leaves, reduction in photosynthetic pigments.	[280]
		500 mg/kg	Soil	Phytolacca americana	Damage to root cells, reduction in root and shoot growth, induction of oxidative stress.	[276]
		250 and 500 mg/kg	Soil	Sorghum bicolor	Inhibition of soil enzyme activity, reduction in root and shoot biomass, increase in Zn accumulation in the plant	[286]
		500 mg/kg	Soil	Oryza sativa	Increased Cd in root, shoot, and grain	[285]
	TiO2-NPs	100 and 250 mg/L	Foliar exposure, hydroponic cultivation	Zea mays	Increasing accumulation of Ti and Cd in roots and shoots and induction of oxidative stress	[282]
	CuO-NPs	20 mg/L	Hydroponic cultivation	Brassica	Increase in Cd accumulation, induction of oxidative stress, reduction in nutritional value	[287]
Cu	TiO2-NPs	10 mg/L	Hydroponic cultivation	Glycine max	Increased Cu toxicity at 1–2 mg/L Cu, yet improved plant tolerance at higher Cu concentrations (5–20 mg/L)	[203]
Ni	ZnO-NPs	50 and 100 ppm	Hydroponic cultivation	Sorghum bicolor	Increased Ni accumulation in low Ni concentration, increased Ni accumulation, and improved plant growth under high Ni concentration	[281]
Sb (antimony)	Ag-NPs	1 mg/L	Hydroponic cultivation	Glycine max	Increase in Sb accumulation and production of ROS and induction of oxidative stress, decrease in photosynthetic pigments	[283]