Hydro-Electrochemical Integration of the Higher Plant – Basis for Electrogenic Flower Induction - Communication in Plants: Neuronal Aspects of Plant Life - page 369

25 Hydro-Electrochemical Integration

of the Higher Plant - Basis
for Electrogenic Flower Induction
Edgar Wagner, Lars Lehner, Johannes Normann,
Justyna Veit, Jolana Albrechtová

Abstract The integration of activity of Chenopodium plants on a hydraulic-electrochemical
level is expressed by a diurnal rhythm in the resting membrane potential measured with
contact electrodes. The membrane state could be gated by the energy state of cells. From
earlier studies we compiled evidence in favour of a circadian rhythm in overall energy trans-
duction producing a circadian rhythm in energy charge and redox state (NADPH 2 /NADP).
The ratio of metabolic coupling nucleotides would be relatively temperature independent
and thus could fulfil the requirements for precise temperature-compensated time-keeping.
The phytochrome photoreceptors, involved in photoperiodic control of development, could
via changes in pyridine nucleotide pool sizes and changes in nucleotide ratios regulate
transcription-translational loops by redox and phosphorylation controlled transcription
factors. Spontaneous action potentials (APs) have been shown to correlate with turgor-
controlled growth movements. The accumulation of spontaneous APs at specific times
during daily light-dark spans were recorded, giving specific electrophysiograms, represen-
tative for flower-inducing and vegetative conditions. It is anticipated that hydraulic changes
at the apex leading to flower initiation are mediated by a specific hydro-electrochemical
communication between leaves, the shoot apex and the root system. These results have been
used to substitute a flower-inducing photoperiod by specific timing of electric stimulation
via surface electrodes.

25.1
State of the Art in Photoperiodic Control
of Flowering in Short- and Long-Day Plants

Photoperiodic control of flowering involves perception of the critical pho-
toperiod by the leaves, the production of the flower-inducing stimulus in
the leaves, and its transduction to the shoot apex, where flower induction
and evocation takes place. There is substantial evidence that the communi-
cationbetweenleavesandtheshootapexinvolvesfrequency-codedsignals
in both organs and the change in their phase relationship upon flower
induction.
To develop a coherent view on photoperiodic control in long- and short-
day plants, the observations in Table 25.1 have to be considered, not least
for the development of a hypothesis on electrogenic flower induction in
short- and long-day plants.
To study interorgan communication between the signal-perceiving organ
(leaf) and the target tissue (stem/apex) implied in the control of flowering,