Development and Application of Zn2+ Selective Microelectrode for Non-invasive Micro-test Technology

Abstract

Non-invasive Micro-test Technology（NMT） has been widely applied in the study of plant root growth and development as well as the response of plant cell and tissue to abiotic stresses. Due to the limitations of its microelectrodes types for different heavy metals, its application in the study of toxicological effects of heavy metals in plant is also limited. Based on our previous work, a NMT Zn2+ selective microelectrode was constructed and for the first time was used for real-time monitoring Zn2+ flux at plant rhizosphere under living condition. The developed microelectrode has a Nernstian response(30.1 mV/decade of Zn2+ activity) to Zn2+ within the concentration range of 10-6 to 10-1 mol/L in DI water. The response time of the microelectrode is less than or equal to 1 s and the microelectrode can work well within a wide pH range of 3.5 to 7.0. While in simple simulated soil solution（containing 0.1 mmol/L Ca（NO3）2, 0.1 mmol/L KNO3, 0.1 mmol/L Mg（NO3）2 and 0.1 mmol/L NaNO3）, it displayed a Nernstian response within Zn2+ concentration range of 5.0&times;10-5 to 10-1 mol/L with slope of 28.1 mV/decade, which indicates that the microelectrode has good anti-interference performance to the coexisting cations in soil solution. The developed Zn2+ selective microelectrode was then used to monitor Zn2+ flux at the rhizosphere of Zn/Cd hyperaccumulator Sedum plumbizincicola. This developed technique provides a powerful method for understanding the process and mechanism of Zn2+ at the micro-interface of plant rhizosphere under living conditions.</p