Zinc oxide nanoparticles and polyethylene microplastics affect the growth, physiological and biochemical attributes, and Zn accumulation of rice seedlings

Metal nanoparticles and microplastics are becoming important pollutants in agricultural fields, but there are few studies on the interaction of zinc oxide nanoparticles (ZnONPs) and polyethylene (PE) microplastics with rice seedlings. The two rice cultivars Xiangyaxiangzhan and Yuxiangyouzhan were grown at three ZnONP levels (0 mg L-1, 50 mg L-1, and 500 mg L-1) and three PE levels (0 mg L-1, 250 mg L-1, and 500 mg L-1), and the growth, physiological attributes, and Zn uptake of rice seedlings were measured. Result showed that the ZnONPs and PE treatment effects on the investigated parameters differed between the cultivars, whilst Yuxiangyouzhan produced 6.98% higher in mean total dry biomass than Xiangyaxiangzhan. The mean total dry biomass in Xiangyaxiagnzhan and Yuxiangyouzhan changed by 10.22-30.85% and -11.74-25.58% under ZnONPs, respectively. The PE treatments reduced growth parameters in Xiangyaxiangzhan, whilst the 250 mg L-1 PE treatment reduced the growth parameter of Yuxiangyouzhan. Besides, the ZnONP treatment had a stronger effect on rice seedling growth than the PE treatment. Furthermore, the ZnONPs modulated the physiological parameter in plant tissue of the two rice varieties. ZnONP treatment lead to the accumulation of Zn in plant tissue and the shoot Zn content was strongly related to shoot cellulose content. Overall, ZnONPs and PE treatments modulated the growth, physiological and biochemical attributes, and Zn uptake of rice seedlings, and the cultivars and dose effects could not be ignored.