The Mechanism Of Selenium Nanoparticles And Selenite Regulating Cadmium Uptake And Transport In Rice (Oryza Sativa L.)

In recent years,due to the impact of human activities such as industrial mining,the content of cadmium,a toxic heavy metal in farm Land,has increased greatly,resulting in cadmium pollution.Cadmium(Cd)pollution not only affects the growth and development of crops in farm Land,but also poses great threat to human health as being ingested through the food chain.Selenium is one of the essential trace elements for animals and human,which has been proved to strengthen human immunity and anti-tumor activity.On the other hand,selenium can promote the growth,the resistance to drought and heavy metals of crops.Many papers have reported that selenite and selenate application can effectively reduce the stress of cadmium on rice.It has been reported that selenium nanoparticles(Se NPs)has better bioavailability,higher biological activity and lower toxicity than selenite and selenite.To investigate the toxicity of exogenous Se NPs to rice and the mechanism of Se NPs on affecting cadmium absorption and transport in rice,we conducted the following experiments:(1)The effect of root application with Se NPs to rice growth;(2)The mechanism of root application with Se NPs on regulating cadmium absorption and transport in rice seedlings;(3)The alleviating effect and mechanism of Se NPs and selenite under cadmium exposure(0.2,1,5 μM)in rice were compared.The main results were summarized briefly as following:1.Se NPs of 10 μM boosted the rice seedlings most.Root application with 1,10 μM Se NPs improved the growth and chlorophyll content of rice,while 50,100 μM Se NPs suppressed the rice growth to some degree.Among all these treating concentrations,10 μM Se NPs promotes the rice growth and resistance most.2.Root application with 10 μM Se NPs effectively mitigated the toxicity of Cd to rice seedlings.Cd treatment at all concentrations inhibited the growth and the synthesis of chlorophyll of rice.Root application with 10 μM Se NPs alleviated the suppression of Cd on rice,by regulating the Cd-related genes and forming Se-Cd compounds,which significantly reduced the uptake and translocation of Cd in rice and promoted the compartmentation of Cd into rice vacuoles.Under 1μM and 5 μM Cd exposure,the accumulation of Cd in rice root,stem and leaf was significantly decreased by 31.47% and 54.29%,79.86% and 59.00%,75.27% and 43.15% respectively.3.Compared with Se NPs,foliar spraying with selenite can better effect on alleviating the toxicity of cadmium to rice.The rice growth,chlorophyll content,Cd and Se content,distribution and formation were determined.Foliar spraying with Se NPs and selenite could both regulate gene expression,inhibiting the uptake of Cd into the rice roots and reducing the cadmium accumulation in rice.The percentage of cadmium decreased by 62.41% with Se NPs treatment and by 85.01% with selenite treatment.Compared with nano-selenium,leaf application of sodium selenite can effectively alleviate the stress of cadmium on rice growth and reduce the content of cadmium in rice rhizomes and leaves.Foliar spraying with selenite has better effect on alleviating the inhibition of Cd on rice growth and reduce Cd accumulation in rice.