The Construction And Preliminary Application Of Electrochemical Sensors For Proline And Indole-3-acetic Acid

Plants produce a series of small molecules with biological activities in the process of life,such as amino acids,plant hormones.These small molecules play an important role in plant growth and environmental adaptation.Therefore,it is necessary to accurately detect the content of these small molecules in plants.Electrochemical sensors have the characteristics of high sensitivity,strong specificity,simple operation,easy portability and low experimental cost,and have important potential in agricultural field and in vivo detection.In this thesis,two kinds of active small molecules,proline and indole-3-acetic acid（IAA）,were taken as examples to construct their electrochemical sensors,and the free proline content in cucumber young leaves and IAA content in cucumber stems and fruits were measured in vivo.The results and conclusions are as follows:1.The construction and application of proline molecularly imprinted electrochemical sensor.Proline is an important amino acid,which is crucial to plant growth and development.Accurate analysis of proline content is of great significance for understanding its physiological mechanism in plants.In this thesis,according to the requirements for in vivo detection in plants in precision agriculture,an electrochemical molecularly imprinted（MIP）sensor for determining proline in living plants was developed.Polypyrrole（PPy）was used as the functional monomers.To improve the performance of the MIP sensor,Au nanoparticles（NPs）were electrodeposited on the SPEs electrode.Thionine（Thi）were then electropolymerized on the SPEs to be used as an internal reference signal molecule.The MIP-based proline sensor has the widest detection range of 1×10^-16-1×10^-2 M,the correlation coefficient was R²=0.989,and its detection limit is the lowest（9.18 a M）so far.It was also used for measuring free proline in leaves of living cucumber seedling under salt stress.The MIP-based proline sensor has an important prospect for detecting the physiological status of plants in vivo and will play an important role in smart agriculture.2.The construction and application of IAA electrochemical sensor.As an important plant hormone,IAA plays a crucial role in the whole process of plant growth and development.In this thesis,according to the actual needs of in vivo detection in plants,a four-array electrode suitable for plant stem and a six-array electrode for plant fruit were developed.Platinum nanoparticles（Pt NPs）and reduced graphene oxide（ERGO）nanocomposite film were electrodeposited on the platinum wire working electrode by one-step method,thereby enhancing the catalytic effect and improving the sensitivity of the biosensor.The experimental results show that the four and six array electrochemical sensors have good linear relationships in the IAA concentration range of0.1μM-150μM and 0.1μM-200μM,respectively.The correlation coefficients are R²=0.977 and R²=0.986,respectively.The detection limits are 0.03μM（S/N=3）and 0.01μM（S/N=3）,respectively.The prepared sensor was further used to detect the IAA content in cucumber stem and cucumber fruit in vivo,indicating that the sensor has important application prospects in the in vivo detection of plant physiological states.Compared with the traditional detection methods,the proline and IAA electrochemical sensor prepared in this thesis has a wider linear range and a lower detection limit.It is of great significance in regulating plant growth and achieving continuous high quality and high yield of crops,and has high practical application potential.