Frequency landscape of tip-growing plants

TL;DR

This study used Fourier analysis of voltage measurements in maize coleoptiles to identify a discrete frequency spectrum of ion oscillations, revealing fundamental frequencies and phase relations in plant growth processes.

Contribution

It is the first to demonstrate a discrete frequency spectrum in a living plant using non-invasive voltage measurements and Fourier analysis.

Findings

Identified fundamental frequencies of ion oscillations in maize coleoptiles.

Established phase relations among transport processes in plant cells.

Achieved a quantum-like discrete frequency spectrum in plant growth analysis.

Abstract

It has been interesting that nearly all of the ion activities that have been analysed thus far have exhibited oscillations that are tightly coupled to growth. Here, we present discrete Fourier transform (DFT) spectra with a finite sampling of tip-growing cells and organs that were obtained from voltage measurements of the elongating coleoptiles of maize in situ. The electromotive force (EMF) oscillations (~ 0.1 {\mu}V) were measured in a simple but highly sensitive RL circuit, in which the solenoid was initially placed at the tip of the specimen and then was moved thus changing its position in relation to growth (EMF can be measured first at the tip, then at the sub-apical part and finally at the shank). The influx- and efflux-induced oscillations of Ca$^{2+}$, along with H$^{+}$, K$^{+}$ and Cl$^{-}$ were densely sampled (preserving the Nyquist theorem in order to 'grasp the structure' of the pulse), the logarithmic amplitude of pulse spectrum was calculated, and the detected frequencies, which displayed a periodic sequence of pulses, were compared with the literature data. A band of life vital individual pulses was obtained in a single run of the experiment, which not only allowed the fundamental frequencies (and intensities of the processes) to be determined but also permitted the phase relations of the various transport processes in the plasma membrane and tonoplast to be established. A discrete frequency spectrum (like the hydrogen spectrum in quantum physics) was achieved for a growing plant for the first time, while all of the metabolic and enzymatic functions of the life cell cycle were preserved using this totally non-invasive treatment.