Developmental Research for Constructing an Equipment to Measure Electrical Potential Generating in Crops

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An experimental apparatus on a trial basis designed for measuring electrical potential on a plant surface was made to estimate water stress of crops under field conditions, and tested with several crops grown under various nutritional and soil water conditions.The apparatus was made up from an Ag-AgCl electrode connecting with a preamplifier of a high impedance circuit (10^<12>OMEGA). A pair of two electrodes was contacted on the different parts of stem surface in one plant. The difference in electrical potential between the two parts was detected and recorded with a pen-recorder and/or a data-logger. The apparatus was tested with rice plants cultured in various nutritional solutions, and with potatoes and kidney beans grown under different soil water conditions.As a result of the preliminary observations with this apparatus, we detected relatively large differences, large than 100 mV,in electrical potential between the plants with different treatments. A circadian rhythm of electrical potential in the crops was also indicated in some measurements. However, the reliability of the measurements was still inadequate for common usage under field conditions. We further need some improvement of the present apparatus and of the method, especially how to make contact the electrode on a plant surface.