The extremely low frequency electrical properties of plant stems

Area of Science:

• Plant Physiology
• Dielectric Spectroscopy
• Biophysics

Background:

• Plant stem electrical properties are crucial for understanding physiological processes.
• In vivo measurement of these properties presents challenges, particularly regarding electrode effects.
• Time domain dielectric spectroscopy offers a potential solution for accurate in vivo measurements.

Purpose of the Study:

• To measure the in vivo electrical properties (capacitance and conductance) of plant stems as a function of frequency.
• To develop and validate a method for eliminating electrode effects in dielectric measurements of plant tissues.
• To compare the dielectric properties of plant stems with those of bone and inorganic materials.

Main Methods:

• Applied time domain dielectric spectroscopy to Poinsettia and Coleus stems.
• Measured polarization current in response to a voltage step.
• Utilized microprocessor sampling and Fourier transformation to obtain dielectric spectra.
• Analyzed capacitance and conductance variations with frequency and electrode separation.
• Eliminated electrode effects through least-square fitting of inverse capacitance and conductance versus separation.

Main Results:

• Determined effective dielectric constant and conductivity of plant stems over a frequency range of 0.35 to 350 Hz.
• Observed a two-stage linear decrease in dielectric constant versus frequency for both plant species.
• Found that conductivity was primarily DC (direct current) in nature.
• Noted a smooth decrease in dielectric loss with increasing frequency for Coleus.

Conclusions:

• Time domain dielectric spectroscopy is an effective method for in vivo measurement of plant stem electrical properties.
• The dielectric properties of plant stems are frequency-dependent and can be modeled using a cooperative, many-body approach.
• Comparison with bone and hollandite suggests unique dielectric characteristics of biological tissues.