INTRACELLULAR POTENTIAL CHANGE OF TRADESCANTIA-VIRGINIANA L LEAF IN RESPONSE TO CO2 STRESS

The response of a Tradescantia virginiana L. leaf to CO2 stress was measured using a double-barrelled microelectrode (a potential recording electrode and an electrode carrying Lucifer yellow CH dye (LY)). After potential measurement, LY was allowed to diffuse out of the microelectrode by iontophoresis. The position of electrode tip was ascertained from the pattern of LY diffusion. The intracellular potential changed markedly in response to CO2 stress. The most typical response pattern obtained during CO2 exposure (ON response) was two-phase, initially changing in the positive direction and then in the negative direction. During the ON response, marked efflux of K+ and slight influx of Cl- occurred initially, followed by efflux of Cl- and influx of H+. On cessation of CO2 exposure, the potential showed a similar two-phase pattern (OFF response) but the ion fluxes reversed. Therefore the effect Of CO2 exposure is not just decrease in intracellular pH owing to dissolution Of CO2.