Ionic Currents Generated by Tip Growing Cells

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Abstract
A new mechanism for the generation of ionic currents around tip growing cells is presented. Because of the absorption of a nutrient by the cell tip, its concentration decreases along the cell sides. As a nutrient molecule enters the cell with a well defined number of protons via a channel called a symport, the influx of protons decreases when one moves away from the tip. Then the balance between influx and efflux of protons is broken and a proton current loop is generated, entering the cell tip and leaving farther back. Using typical values for symport membrane current, pH, and nutrient concentration, we obtain an order of magnitude of the current intensity in agreement with the vibrating electrode measurements.