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

Abstract

The increase of glucose-6-phosphate dehydrogenase (G-6-PD) activity has been proposed as an early marker of floral evocation in the shoot apical meristem of spinach. This induction is obtained by the transfer of vegetative plants from short days to continuous light. The exposure of a single leaf to continuous light induced the same effect as that produced with the whole plant. In vegetative conditions (short days), an electrical potential of ten volts (electrical current: ⋍ 12·5 μA) applied to the petiole of a single leaf induced a weak increase of G-6-PD activity in the shoot apex, while under inductive conditions, this increase was similar to that of control plants (transferred to continuous light). Application of an electrical potential to the petiole and the root inhibits the increase linked to the inductive transfer. These results show that an externally applied electrical potential may interact with the natural electrical gradients along the shoot and consequently inhibit the normal floral development by an as yet unspecified mechanism.