Response Mechanisms Of Arbuscular Mycorrhizal Fungi-reed Symbiosis System To AgNPs Stress

In recent years,the development of nanotechnology has made more and more applications in life.Among them,Ag nanoparticles?AgNPs?is one of the most widely used nano materials.As of 2015,the global annual consumption is about 500 tons,and there is an increasing trend.Considering that AgNPs may accumulate in the environment through surface water circulation in daily applications.Therefore,in recent years,there have been more and more studies on its accumulation phenomena and ecological effects in the water environment.In the surface water environment,functional plants and micro-organisms are the main body of water environment pollution assessment and remediation.Among them,the reed-arbuscular mycorrhizal symbiosis system is a typical biological system for fixed growth at the water-land interface.It is of great significance to study its response process and mechanism to nano-silver stress,and to assess and control the ecological risk of nano-silver release.In summary,this experiment set up six concentration gradients?0,1,5,10,50,100 mg/kg?based on the published environmental nano silver concentration as a reference basis.Under different concentrations of AgNPs stress,the arbuscular mycorrhizal fungus-Glomus mosseae?GM?was inoculated.To explore the effects of AMF on the growth and development of reeds,antioxidant system and photosynthetic physiological response under the AgNPs stress.And under the symbiotic conditions of AMF,the reeds absorption and distribution characteristics of AgNPs.On the one hand,taking reed as the research object to evaluate the phytotoxic effect of AgNPs;it also provides a theoretical basis for the use of AMF-reed coupling system to repair AgNPs pollution.Studies have shown that GM bacteria can effectively infect the roots of reeds and promote the growth and development of various organs of reeds under adverse conditions.GM infection rate is negatively correlated with AgNPs stress concentration.At 100 mg/kg concentration,the infection rate is stable at about 20%,indicating that GM bacteria have a certain tolerance to AgNPs and can form a stable symbiotic structure with reeds under adverse conditions.In addition,inoculation of GM promotes the development of aboveground organs of reeds at low concentrations;at high concentrations,GM acts on root organ development,resulting in changes in the root-to-shoot ratio of reeds adapted to AgNPs stress.Under AgNPs stress,AMF can increase the antioxidant enzyme activity of reed leaves,promote the synthesis of proline,and inhibit the synthesis of malondialdehyde;improve the operating efficiency of the leaf photosynthetic system,increase the leaf photosynthetic rate,CO₂ absorption process,and gas exchange capacity.In addition,GM can also improve the water use capacity of leaves,stabilize the photosynthesis and transpiration process of leaves under stress of AgNPs,enhance the efficiency of light use?Pmax?,AQY?,LCP?,LSP??,and promote the effective improvement of reed material assimilation under adversity The process is manifested by the increase of biomass quality and the improvement of the adaptability of reeds to the stress stress of AgNPs,thus ensuring the benign development of reeds under stress.GM can promote the absorption and enrichment of AgNPs in reed roots(Ag_max can reach up to 34.75mg/kg),and the type of enrichment tends to be fixed to the root system.GM can promote the fixation of AgNPs in the plant root system(BCF_0-5mg/kg?,)and inhibit its transport to the aerial parts(TF_root?stem?,TF_stem?leaf?)at high concentration,by adjusting Ag organs in the reed Distribution characteristics to improve the overall tolerance of reeds to AgNPs.In addition,inoculation of GM bacteria can stabilize the fluctuation range of P,Ca,Mg and Fe elements in reed organs and improve the nutritional status of reeds.Overall,the construction of AMF-reed coupling system has good AgNPs tolerance and repair efficiency.It can be seen that the construction of reed-mycorrhizal symbiosis system can not only evaluate the phytotoxic effect of AgNPs,but also improve the tolerance and absorption mechanism of reeds to AgNPs by inoculating AM fungi,which provides theoretical support for the remediation strategy of environmental AgNPs pollution.