Light-triggered membrane potential oscillations and electric coupling in variegated photosynthetic mutants of Oenothera.

Light-triggered transient oscillations of the membrane potential are recorded with glass micro-electrodes in mesophyll cells of Oenothera. These transients are absent in leaf samples prepared from variegated plastome mutants of Oenothera, in which all cells have a genetically impaired photosystem I or photosystem II. This suggests that co-operation between the two photosystems is responsible for the induction of the transients. Transients are observed in mutated cells when the illuminated leaf sample also comprises normally green cells and there is a symplasmatic connection between the two types of cells. This phenomenon of electric coupling between neighbouring cells is discussed in view of the concept of symplasmatic transport.