Effect of Photoperiod and Electrical Potentials Applied to Petioles on the Glucose-6-phosphate Dehydrogenase Activity used as Marker of Floral Induction in Shoot Apices of Spinach I

The increase of glucose-6-phosphate dehydrogenase (G-6-PD) activityhas been proposed as an early marker of floral evocation inthe shoot apical meristem of spinach. This induction is obtainedby the transfer of vegetative plants from short days to continuouslight. The exposure of a single leaf to continuous light inducedthe same effect as that produced with the whole plant. In vegetativeconditions (short days), an electrical potential of ten volts(electrical current: 12·5 µA) applied to the petioleof a single leaf induced a weak increase of G-6-PD activityin the shoot apex, while under inductive conditions, this increasewas similar to that of control plants (transferred to continuouslight). Application of an electrical potential to the petioleand the root inhibits the increase linked to the inductive transfer.These results show that an externally applied electrical potentialmay interact with the natural electrical gradients along theshoot and consequently inhibit the normal floral developmentby an as yet unspecified mechanism. Spinacia oleracea, floral induction, interorganic relations, glucose-6-phosphate dehydrogenase, shoot apex, electrical potentials