Light-dependent variations in the plant electropotential (PEP) in Mangifera indica.
Rajasekar S., Rajasekar R., Gnanasekaran K. S. A.
Author Affiliation: Central Electrochemical Research Institute, Karaikudi 623 006, India.
Proceedings of the Indian National Science Academy, B (Biological Sciences) 53 : 425-433
Abstract : On inserting a thin Pt wire electrode into the soft green pulvinus of the leaf, the PEP measured was about -95 mV and this rose to +200 mV in about 5 h. When the wound was fully healed, in about 3 days, the electrode was able to sense the rise or fall in potential, induced by dark -> light and light -> dark transitions, respectively. Within the intensities of light studied, i.e. up to 7800 lx, the rise in PEP was proportional to light intensity. Under all light intensities, the maximum potential was reached in about 10 minutes. With the onset of darkness, the values came to the original level in about 20 minutes. Under constant and continuous illumination, the potential rose slowly but continuously, though with fluctuations. Under continuous darkness, irregular variation in potential was observed. The pulvini of younger leaves were more sensitive to the photoelectric changes than those of older leaves. The rise and fall in potential were attributed to the removal and influx of H+ ions, respectively, in the vicinity of the electrode.