Effects of a pulsing electric signal on the cross membrane potential and the cell division potentiality of a single cell of tobacco

A pulsing electric signal (pulse width 10 a) was applied to a single cell o f cultured tobacco, line BY-2, by inserting a multifunctional microelectrod e (MME) into the cell. The electric voltage (V-ET) was loaded between the e lectrode terminals of the MME and the reference electrode situated in the e xtracellular medium. Since the electrical impedance of the MME was as large as that of the cell membrane, the effective potential acting across the ce ll membrane (V-CMP) should be only some portion of V-ET. The MME enabled si multaneous measurement of V-ET and V-CMP. When V-ET was varied from 0 to -1 V, V-CMP changed linearly in proportion to V-ET. When V-ET variation range was enlarged (from 0 to -2 V), V-CMP changing pattern became a declined cu rve. When V-ET variation range was further enlarged (from 0 to -5 V), the V -CMP changing pattern showed a saturation curve. Under this condition, the cell division potentiality decreased accordingly. Based on these results, t he feasibility of V-CMP as an indicator of the effective intensity of an el ectric stress signal is discussed. In the present case of a BY-2 cell, a pr oper intensity of V-CMP that could cause an appreciable stress and not a le thal signal was estimated as -250 mV. (C) 1999 Elsevier Science S.A. All ri ghts reserved.