Study On The Mechanism Of Non-metallic Nanoparticles Regulating The Growth,Yield And Nutritional Quality Of Arsenic Contaminated Rice

Arsenic（As）is a congener element with phosphorus,which makes it easily absorbed by cells and causes cell poisoning.It is considered to be a non-threshold,first-class potent carcinogen.The increasing soil arsenic pollution caused by geological（volcanic eruptions,As-containing minerals）and man-made（mineral mining,smelting,coal,fossil fuel combustion,arsenic-containing pesticides and herbicides）activities has become a global environmental problem.Moreover,the increase in global temperature caused by climate change in the future will further increase the accumulation of As in rice tissues,aggravating the threat of As to rice quality and human health.To deal with As pollution in rice,the agronomic measures（application of mineral fertilizers,reduction of sewage irrigation,bioremediation strategies）that have been adopted have little effect and are labor-intensive and cost-intensive.Therefore,it is urgent to develop an efficient and sustainable As pollution control strategy.In recent years,nanotechnology has shown great application potential in controlling heavy metal pollution in farmland,but the relevant mechanism is still unclear.Therefore,silica（Si-based）,hydroxyapatite（P-based）,elemental sulfur（S-based）,and zerovalent selenium（Se-based）nanoparticles（NPs）were chosen for this study.To explore the mechanism of regulating the growth of arsenic-contaminated rice by applying four kinds of non-metallic NPs,the main research results are as follows.（1）The application of four non-metal-based NPs significantly promoted the growth of arsenic-contaminated rice and reduced the accumulation of arsenic in rice,with a concentration effect.The optimal application concentrations of the four NPs were:50 mg kg^-1（Si）,100 mg kg^-1（P）,50 mg kg^-1（S）,5 mg kg^-1（Se）.Application of four NPs significantly increased the plant height of As-contaminated rice by 7～13%,and restored biomass and photosynthesis to68～88%and 84～171%of the healthy control group.And the Se and P-based NPs had the best effect;the four NPs significantly reduced the arsenic accumulation by 9-75%,and the Se-based NPs had the best effect.The mechanism of regulating the growth of As-contaminated rice by non-metal-based NPs was elucidated,including:（1）Provide nutrients directly.（2）Reduce the uptake of As by plant roots and its translocation to shoots.（3）Promote the absorption of trace elements（Mn,Fe,Cu,Zn）by plant roots and improve the symptoms of plant deficiency.（4）Improve plant stomatal conductance,transpiration rate and chlorophyll content,and enhance plant photosynthesis.（5）Improve plant TCA cycle and amino acid metabolism level.（2）The mechanism of four non-metal-based NPs regulating rice As resistance was revealed.Application of four non-metal-based NPs significantly increased the activity of antioxidant enzymes（SOD,POD,CAT）by 1.5-3.9 times and the concentration of thiol substances（cys,GSH,PC3）by 14-96%.The relative expression of Os Lsi1 and Os Lsi2 genes was significantly down-regulated by 5-54%,and the relative expression of Os ABCC7 and Os GST genes was significantly up-regulated by 11-146%,and the effects of Si,S,and Se-based NPs were better than those of P-based NPs.Under the condition of optimal application concentration,the effects of four non-metallic NPs on regulating the growth of As-contaminated rice were Se NPs>Si NPs>P NPs>S NPs.The mechanism of the four NPs regulating rice As resistance was clarified,including:（1）The soil microbial community was improved（the phylum Chlorobacteria was replaced by Acidobacteria,and the abundance of Firmicutes increased）.（2）Down-regulate As uptake and transport genes,up-regulate plant detoxification genes,reduce As uptake and translocation to shoots.（3）Enhance the activity of plant antioxidant enzymes and alleviate the ROS stress caused by As.（4）Strengthen the JA signaling pathway and enhance plant stress resistance.（3）The application of four non-metal-based NPs significantly increased the yield of As-contaminated rice by 67-91%,and significantly reduced the accumulation of As by 17-64%.Among them,the effect of Si,S and Se-based NPs is better than that of P-based NPs,and P,S and Se-based NPs can increase the starch content of rice by 12-25%.In summary,this study provides a novel As resistance strategy in rice,and found that four non-metal-based NPs can reduce As accumulation,improve plant detoxification ability,improve plant metabolism level and plant rhizosphere microbial community.Directly or indirectly regulate the growth and arsenic resistance of As-contaminated rice.At the same time,this study provides more theoretical basis for the rational use of nano-fertilizers in crops to enhance stress resistance,increase yield and quality,and is of great significance to the development of nano-agricultural technology and the response to world food security.