In-situ root extent measurements by electrical capacitance methods

A conceptual model is presented that provides a rational basis for using plant root capacitance as an in-situ measurement for assessing plant root development. This method is based on measuring the electricla capacitance of an equivalent parallel resistance-capacitance circuit formed by the interface between soil-water and the plant root surface. Nutrient solution studies using tomato (Lycopersicon esculentum Mill.) showed a good correlation between plant root capacitance and root mass. Stage of development studies showed plant root capacitance measurements capable of detecting root development rate and suggested the method to be sensitive to root function. Soil water content was shown to have a significant effect on plant root capacitance measurement. The possibility of using this technique to assess relative root function is discussed. Positioning of the plant shoot electrode was shown to also have a significant effect on measurement of plant root capacitance, demonstrating the need for using consistent measurement techniques. The electrical capacitance method shows considerable promise. More research is needed before it can be used routinely.