Effects Of Arbuscular Mycorrhizal Fungi Inoculation On Physiological Ecology And Absorption And Accumulation Of Antimony In Rice Under Antimony Stress

Antimony?Sb?is a heavy metal element with potential carcinogenicity and long distance transport capability.In recent years,the demand of antimony increased rapidly with the rise of antimony production and related industries.Most of Antimony released to the environment transports in terrestrial ecosystems and accumulates in human body through food chains,and ultimately affects the metabolism of protein and sugar,causing diseases of the respiratory,urinary and nervous systems.China has the most abundant antimony resource in the world and contributes almost 80%of the world's annual output of antimony.China also faces a serious threat of antimony pollution due to mining,smelting,coal combustion and wide application of antimony products.Studies showed that rice in the five provinces of Guangxi,Hunan and Guizhou is seriously polluted by antimony.Therefore,it is important to control the antimony pollution and protect the diet safety.The research on antimony is relative few compared with other toxic metals?such as arsenic and cadmium?.There is a lack of systematic understanding of the biogeochemical cycle of antimony.Especially the mechanism of transformation in soil-plant system is still not clear.The research on antimony absorption and transport of plant remains at the stage of inference and hypothesis.In the interaction between rice and antimony,present research is mainly focused on the hazards of antimony in rice.The migration and transformation mechanism of antimony in soil-rice system is still not clear,which seriously restricts the research and innovation of risk control of antimony pollution in rice.Arsenic and antimony belong to the same element clan and have similar properties.Previous studies found that,symbiotic relationship can be formed between arbuscular mycorrhizal fungi and rice under arsenic stress,which resulted in the inhibition of the absorption of arsenic in rice shoot and reduction of the arsenic content in rice.It is also reported that symbiotic relationship can be found between arbuscular mycorrhizal fungi and ramie,Bermuda grass and maize under antimony stress,respectively,which promotes the antimony absorption.Therefore,it can be inferred that that arbuscular mycorrhizal fungi may play an important role in the accumulation of antimony in rice under antimony stress.In this study,a pot cultural experiment of antimony exposure was conducted using rice as host plant and Mose tube glomus as inoculum.Comparison tests are made on rice treated by inoculation and control group.The physiological ecology and accumulation of antimony in rice were studied.The purpose of this study is to provide a theoretical basis for controlling antimony pollution in rice.Following results are obtained:?1?Symbiotic relationship can be formed between arbuscular mycorrhizal fungi and rice,and the average infection rate was 21%+6.2%.?2?Gradient of antimony concentration experiment was applied to study the effect on rice growth.The results showed that plant height,biomass and seed yield decreased with the increase of antimony content.The result indicated that antimony can inhibit the growth of rice.Comparison test was carried out to find the influences of arbuscular mycorrhizal fungi on rice growth.Compared with control group,the shoot biomass and root biomass of rice inoculated decreased by 3.12%-11.25%and6.14%-22.58%,respectively.Plant height and seed yield decreased by 1.44%-7.54%and 2.63%-11.57%.The result indicated that arbuscular mycorrhizal fungi inhibited the growth of rice under antimony stress.?3?Gradient of antimony concentration experiment was applied to study the effect of antimony on antioxidant enzyme activity and MDA content in rice.The results showed that SOD,POD and CAT activity and MDA content in rice leaves increased gradually with the increase of antimony content,which indicated that antimony could promote the activity of SOD,CAT,POD and increase of MDA content.The effects of arbuscular mycorrhizal fungi on antioxidant enzymes in rice were studied by comparative experiments.Compared with control group,the SOD,CAT and POD activity of rice inoculated increased by 15.57%-28.70%,17.89%-26.06%and 4.47%-9.70%,respectively.The result indicated that inoculation of arbuscular mycorrhizal fungi promoted antioxidant enzyme activities and increase MDA content in rice under antimony stress.?4?Gradient of antimony concentration experiment was applied to study the absorption and enrichment of antimony by rice.The results showed that the content of antimony in various organs of rice increased,while the enrichment coefficient of rice decreased with the increase of antimony concentration.The results indicated that the increase of antimony concentration promoted the absorption of antimony by rice organs,and inhibited the transfer of antimony from soil to plant.The influence of arbuscular mycorrhizal fungi on absorption of antimony antioxidant was studied by comparative experiments.The contents of antimony in root,stem,leaf,bran and grain from rice inoculated increased by 13.89%-23.43%,0.66%-19.41%,5.16%-15.30%,3.16%-20.15%and0.43%-7.42%,respectively.Meanwhile,the enrichment coefficients increased by18.29%-26.78%.This indicated that inoculation of arbuscular mycorrhizal fungi promoted the uptake of antimony by rice and the transfer of antimony from soil to plants.?5?The effect of arbuscular mycorrhizal fungi on pH values in rhizosphere soil of rice was studied.The results showed that the rhizosphere soil pH values of the inoculated group decreased by 0.18-0.35 compared with control group.The decrease of soil pH promotes the precipitation of antimony ions in soil.This may be one of the reasons for arbuscular mycorrhizal fungi promoting the uptake of heavy metals.The effect of inoculating arbuscular mycorrhizal fungi on the valence of antimony absorbed by rice was also studied.The results showed that the proportion of Sb³⁺in roots of inoculation group increased by 8.31%-22.35%,which indicated that arbuscular mycorrhizal fungi could promote the transformation of Sb⁵⁺to Sb³⁺.