The Bioaccumulation and Detoxification Mechanism of Neodymium on the Shoot of Rice Seedlings

Abstract

Neodymium (Nd) potentially pollutes environment for its wide usage in agriculture and industry. In this study, the chemical forms of Nd and effect of Nd on rice shoots were studied after rice seedlings were exposed with 0, 1, 10, 100 and1000 μM Nd. The higher concentration of Nd inhibited shoot growth, but the lower concentration of Nd induced shoot growth. Six different chemical forms of Nd were present in shoot and the major forms of Nd were the insoluble phosphate and oxalate Nd. The content of Nd was further detected in the soluble fractions, organelles and cell wallsof rice shoot, respectively. Nd was mainly accumulated in the cell wall of shoot. The higher concentration of Nd decreased the content of Ca, K, Mg, Fe, Mn, Cu and Zn in shoot. Moreover, the activities of antioxidant enzymes and the contents of Reactive Oxygen Species (ROS) were elevated by Nd treatments. Our results showed that the inactive oxalate or phosphate Nd was the major forms of Nd in rice shoot and the efficient sequestration into cell wall was a key detoxification pattern of Nd in the shoot of rice seedlings.With the wide usage of Rare Earth Elements (REEs) in agriculture, the detoxification mechanism of Nd in rice shoot was helpful for assessing the environmental safety of REEs.