Studies On The Dynamic Changes Of Mg²⁺ Ion Concentration In MgO NPs Suspension And Its Effects On The Growth Of Wheat?Triticum Aestivum L.? Under Different PH Values

MgO NPs have wide applications in life and production as adsorbents,antibacterial agents,flame retardant materials and electrical insulation materials.During use,MgO NPs will enter the ecosystem in the form of factory sewage and waste,threatening the safety of the ecosystem.Studies have shown that MgO NPs can have toxic effects on organisms.It is generally believed that its biological toxicity is not only related to the characteristics of MgO NPs,but also closely related to the release of Mg²⁺.But so far,in the research on the biotoxicity of MgO NPs,there is a lack of real-time and dynamic measurement and analysis of Mg²⁺ concentration.In this thesis,wheat?Triticum aestivum L.?,a large crop planted in China,was selected as the test plant and cultivated in MgO NPs suspension to study the effect of MgO NPs on wheat growth.At the same time,the magnesium ion selective microelectrode was used to continuously measure the Mg²⁺ concentration in the MgO NPs suspension in real time to make up for the deficiencies of the existing research.MgO NPs with a particle size of 50 nm were formulated into 20?100 mg/L MgO NPs suspension,and wheat in rooting stage was cultivated for 3 d.Magnesium ion selective microelectrode was used to detect the change of Mg²⁺ concentration in MgO NPs suspension within 48 h.It was found that the release of Mg²⁺ is a dynamically changing process.In addition to increasing with the increase of MgO NPs concentration,the concentration of Mg²⁺ is also increasing with time.The change of Mg²⁺ concentration slowed down after 32 h,and reached the maximum after 48 h.In addition,compared to the case of uncultivated wheat,the MgO NPs suspension increased rapidly during the first 4 h during wheat cultivation,which may be related to the wheat root exudates.When the concentration of MgO NPs is 40 mg/L,the growth of wheat roots begins to be inhibited.The greater the concentration,the more pronounced the inhibition.Combined with the detection results,the corresponding concentration of Mg²⁺ solution was used to treat wheat at the rooting stage.It was found that when the Mg²⁺ concentration was 5?20 mg/L,it had a significant promotion effect on wheat root growth.When the Mg²⁺ concentration was 50 mg/L,it began to inhibit root growth.The upper limit of Mg²⁺ concentration released by MgO NPs suspension within 48 h is 24.31 mg/L,which is much less than 50 mg/L.It showed that the toxic effects of MgO NPs on wheat growth are mainly caused by its own nano-characteristics,not the released Mg²⁺.In addition,the pH of the growth environment will also affect the release of ions in the nanoparticles and their interaction with plants.This thesis adjusted the pH value under hydroponic conditions to simulate different growth environments,and further explores the dynamic changes of Mg²⁺ concentration in MgO NPs suspension at different pH values and the effect of MgO NPs on wheat.Considering that the most suitable pH value for wheat growth is 6.5,pH<5 or pH>8 is not conducive to its growth.In this thesis,50 m L of aqueous solutions of pH 6.5,6 and 5.5 were formulated into 80 mg/L MgO NPs suspension to cultivate wheat at rooting stage for 3 days as the experimental group,and 80 mg/L MgO NPs suspension treatment was used as the control group.The magnesium ion selective microelectrode was used to detect the Mg²⁺ concentration in the MgO NPs suspension within 48 h in real time.It was found that under the condition of adjusting the pH,the Mg²⁺ concentration released in the MgO NPs suspension increased with time,and the released Mg²⁺ concentration increased significantly compared with the control group.When cultivating wheat,the Mg²⁺ concentration curve measured by the experimental group increased first and then decreased slightly over time.The Mg²⁺ concentration curve measured in the control group gradually stabilized after rising.Measuring the root length of wheat found that the root length of wheat in the experimental group increased slightly compared with the control group.When the pH was adjusted,the release of Mg²⁺ in the suspension of MgO NPs increased,and the absorption of Mg²⁺ by wheat also increased,thereby reducing the inhibitory effect of MgO NPs on wheat roots to a certain extent.In this thesis,the Mg²⁺ concentration in the interaction process of MgO NPs and wheat was detected in real time by magnesium ion selective microelectrode,to explore the variation rule of Mg²⁺ concentration in MgO NPs suspension at different pH values and the effect of MgO NPs on wheat growth.The results of this study are of great significance for the in-depth study of the role of Mg²⁺ in the biological effects of MgO NPs.