Light-induced Transients of Bioelectric Potential Difference Across a Chenopodium rubrum L. Plant

An electrical potential difference appears across an intact Chenopodium rubrum L. (Sel. 184) plant, with marked transients induced by light on-off. A study of this potential and the transients was made by means of two electrodes in contact with the bathing solution and the cotyledon of a six-day-old plantlet. We varied the light intensity and wavelength, and worked with green and photobleached (SANDOZ 9789 pretreated) plants. Light intensities below 1.4 W m⁻²2 of white light did not produce any appreciable transients, the amplitude of change of potential difference then increasing to a maximum ≈ 20 W m⁻², where it stayed constant upto light intensities above 100 W m⁻². A maximum in response was obtained at 644 nm and wavelengths>700 nm did not cause any transients. No transients could be observed with bleached or DCMU treated plants. Thus while the participation of the photosynthetic process in the light-induced transients is unequivocal, the participation of a phytochrome coupled component could not be ascertained.