Effects Of Flooding On Cadmium Uptake And Transport In Rice Under Different Soil Cadmium Concentrations

With the continuous development of China’s economy,some environmental problems also arise,among which heavy metal pollution is a focus.Rice is a major food crop in China,and rice is prone to accumulation of cadmium,a heavy metal element,which seriously affects human health.Therefore,the treatment of cadmium pollution in rice has become a hot issue for scholars at home and abroad.Among them,water management,an agronomic control measure that is easy to control and free of secondary pollution,has aroused extensive research.In this paper,pot experiment was conducted to study the effects of two different water management modes,namely,inundated irrigation(F1)and wetting irrigation(F2),on cadmium content,accumulation and transport coefficient among different organs of rice plants at different growth stages and in different organs.The main research results are as follows:(1)Flooding irrigation(F1)can significantly reduce the cadmium content in brown rice and plants,and make the cadmium content in brown rice meet the national safety standard.(2)The root-to-stem Cd transfer coefficient of rice under flooded irrigation was lower than that under wet irrigation,that is,flooded irrigation reduced Cd content in rice aboveground by inhibiting Cd transfer from underground part to aboveground part.(3)Soil available cadmium has a direct effect on cadmium uptake in plants.The results showed that the soil available cadmium content under submerged-irrigation was lower than that under wet-irrigation,thus reducing the cadmium content transferred to plants.(4)The iron membrane on the root surface of rice plays an important role in the absorption of heavy metals and their transport in rice.The iron membrane on the root surface of rice inhibits the transport of cadmium to the aboveground part.The contents of Fe and Mn in root surface iron membrane of both Yuzhixiang and Xiangwanxian cultivar 12 under submerged irrigation were lower than those under wet irrigation,while those under wetted irrigation were higher than those under wetted irrigation.It can be seen that submerged irrigation can reduce the cadmium adsorbed on root surface iron membrane by increasing the content of Fe and Mn in root surface iron membrane,which has obvious antagonistic effect,and the content of Fe in root surface iron membrane is much higher than that of Mn and Cd.In general,Cd content in rice organs,especially in rice grains,can be reduced by long-term flooding irrigation in Cd contaminated paddy fields.