The dielectric response ofPortulacaceae (Jade) leaves over an extended frequency range

Abstract

Although a number of measurements of the frequency dependence of biological and botanical samples have been reported in the literature and there is agreement that three dielectric dispersion regions are present (Schwann, 1957;Pethig, 1984), it has not been possible to find agreement between the experimental data and the conventional models of dielectric response. This is, in part, due to the limited frequency ranges over which measurements have been made and has resulted in a limited understanding of the basic mechanisms of dielectric response in cellular tissues.Here we report extended frequency measurements of the real and imaginary parts of the complex permittivity of leaves of the succulent Crassula Portulacaceae (Jade), and show that these can be fitted over the frequency spectrum 10 -3 Hz to 10 +9 Hz by an electrical analog model comprised of three series elements.It is shown that these elements represent the electrical properties of individual cells, of imperfect charge transport within the matrix of cells, and of the electrical barrier at the epidermal surface layers of the leaf, in decreasing order of frequency.Elsewhere it will he shown (Hill et al., 1986) that the technique of dielectric response gives quantitative information about the efficiency of charge transport and charge blocking in leaf tissue and hence forms a useful and non-invasive tool for the comparison and detailed examination of biological tissues. Figure 1 shows the measured responses of the permittivities of the Jade samples as functions of frequency on log/log scales.Three different measuring techniques have been used to cover the frequency range and these are indicated in the figure by the use of three different pairs of symbols.The highest frequency data, 106 to 6.10 8 Hz, were obtained using an impedance analyzer (Hewlett Packard model4191A) and the midfrequency range measurements, 80 to 10 7 Hz, by means of a Hewlett Packard network analyzer (model 3570A).

Radiofrequency impedance spectroscopy of biological tissues under heating by homogeneous laser radiation

“…We have performed ex vivo measurements of the electrical impedance temperature dependence as well as its dependence on the degree of thermal damage, for the several samples of aloe parenchyma and broiler chicken liver. The obtained dependences of the impedance spectra (see figure 4(a)) in terms of dielectric permittivity and conductivity are in accordance with the literature data on the order of magnitude for the liver (Gabriel et al 1996) and similar to the parenchyma of succulent Crassula Portulacaceae for the aloe (Hill et al 1986, Broadhurst et al 1987. It is also worth noting the spread of values from sample to sample due to its biological nature.…”

A fractal interpretation of the dielectric response of animal tissues

“…Figure 4. Dielectric response of the leaf tissue of a jade plant (Crassula porfulacaceae)(Hill et al 1986). The slight frequency mis-matching was due, in part, to differences in water content of the three separate…”

Biomonitoring of Environmental Pollution Using Dielectric Properties of Tree Leaves

“…An extensive dielectric investigation of leaves has been performed by Hill et al, covering a wide range of plant and tree types and families (Broadhurst et al, 1987;Hill et al, 1987Hill et al, , 1986. Their results were analyzed in terms of circuit combinations of dispersive dielectric elements.…”

“…Dielectric spectroscopy has been applied successfully to investigate pollution (organic or inorganic), which appears in soils and porous materials, and promising results were obtained concerning the role of ionic strength, moisture content and organic liquids (Kaya, 2001;Kaya & Fang, 1997;Rowe, Shang, & Xie, 2001;Saltas, Vallianatos, Soupios, Makris, & Triantis, 2006;Shang, Ding, Rowe, & Josic, 2004). Dielectric spectroscopy has been also proposed by Hill, Dissado, and Pathmanathan (1987) and Hill et al (1986) as an informative investigative technique in complex systems such as tree leaves, but according to our knowledge, studies that have been carried out to correlate dielectric properties with changes in trace elements concentrations due to environmental pollution, are very limited (Czuba & Kraszewski, 1994). We have to mention that electrical conducting particles incorporated in an insulating material, may affect the electrical behaviour of such mixtures, leading to many interesting applications (Lux, 1993;Roldughin & Vysotskii, 2002).…”