Raimo Silvennoinen

Analysis of the willow root system by electrical impedance spectroscopy

Information on plant roots is increasingly needed for understanding and managing plants under various environmental conditions, including climate change. Several methods have been developed to study fine roots but they are either destructive or cumbersome, or may not be suitable for studies of fine root functionality. Electrical impedance, resistance, and capacitance have been proposed as possible non-destructive measures for studying roots. Their use is limited by a lack of knowledge concerning the electrical circuit of the system. Electrical impedance spectroscopy (EIS) was used for hydroponically raised willows (Salix schwerinii) to estimate the root system size. The impedance spectra were investigated in three experimental set-ups and the corresponding appropriate lumped models were formulated. The fit of the proposed lumped models with the measured impedance spectra data was good. The model parameters were correlated with the contact area of the roots and/or stems raised in the hydroponic solution. The EIS method proved a useful non-destructive method for assessing root surface area. This work may be considered to be a new methodological contribution to understanding root systems and their functions in a non-destructive manner.

Determination of wood grain direction from laser light scattering pattern

Laser light scattering patterns from the grains of wood are investigated in detail to gain information about the characteristics of scattering patterns related to the direction of the grains. For this purpose, wood samples of Scots pine (Pinus sylvestris L.) and silver birch (Betula pubescens) were investigated. The orientation and shape of the scattering pattern of laser light in wood was found to correlate well with the direction of grain angles in a three-dimensional domain. The proposed method was also experimentally verified.

An appraisal of the electrical resistance method for assessing root surface area

Electrical resistances of roots and stems of hydroponically raised willows (Salix schwerinii) were studied and related to root morphology. Willow cuttings with and without roots were set in a constant electric field (effective voltage of 0.1 V, sine-AC, 128 Hz) in a hydroponic solution. The electrical resistance of different components in the measurement system was measured and analysed in relation to root surface area in contact with the cultivation solution. Axial resistivities of single root segments and of stems were measured. The results showed that the resistance decreased in relation to an increase in the contact surface area of the roots with the solution. The resistance depended strongly on the contact area of the stem with the solution, however, thus causing bias in the evaluation of root surface area. This work is a new contribution for the understanding of current pathways in the root system as exposed to an external electric field and for developing a non-destructive method to study plant roots accordingly. It may be concluded that the electrical resistance method is a useful non-destructive method to study roots and their physiological properties. Electrical analogues for roots and stem comprising resistors are discussed in relation to in situ measurements.

On the adsorption and kinetics of phase transients of adenosine at the different carbon electrodes modified with a mercury layer

Abstract Optical roughness of a pyrolytic graphite electrode with basal (PGEb) and edge orientation (PGEe), a glassy carbon electrode (GCE), and the same electrodes modified with mercury (MFE) was studied by an optical diffractive element (DOE) based sensor. Electrochemical characterisation of these electrodes used was performed by cyclic voltammetry (CV) and capacitance measurements ( C – E curves and electrochemical impedance spectroscopy, EIS). The kinetics of phase transients of adenosine adsorbed on PGEb, and GCE modified with mercury layer of different thicknesses (thickness was changed from 0.02 to 2 μm) was studied by chronoamperometry ( j – t curves) and capacitance measurements ( C – E curves). In acidic (pH 5) solution adenosine forms two different two-dimensional (2D) physisorbed condensed layers on the MFE. The first of these (region I) is located at more positive potential; the centre of this adlayer is situated around −0.4 V. The second 2D physisorbed film (region III) is formed at more negative potentials; the centre of the region III is around −1.3 V. The 2D condensed films (adlayer I and III) of adenosine still exist on the PGEb substrate modified by 0.02 μm thick mercury layer. Adlayers III and I of adenosine exist on the GCE modified with mercury layer down to 0.02 and 0.2 μm, respectively. The kinetics of phase transients of the adenosine films taking place by a potential jump from dilute adsorption region (state II and IV) to the 2D physisorbed film (region I and III) at the PGEb and GCE substrates modified with mercury (Hg–PGEb and Hg–GCE) were studied, respectively. During both of the phase transients of IV→III and II→III of adenosine a polynucleation and growth process on both the Hg–PGEb and Hg–GCE was detected. The phase transients of II→I are characterised by an exponential decay of the current without the current maximum (the adsorption process took place only). It was observed that the phase transients of IV→III are the fastest at the HMDE and gradually slow down on 2 μm Hg–GCE and 2 μm Hg–PGEb, respectively.

CLASSIFICATION OF THE REFLECTANCE SPECTRA OF PINE, SPRUCE, AND BIRCH

Statistical pattern-recognition methods are applied to the classification of the reflectance spectra of growing trees (Scots pine, Norway spruce, and birch). We show by using large training sets that it is possible to develop classification filters that are able to discriminate the tree types with a very high probability. Our approach may offer a reference coordinate system for multispectral remote sensing of different levels of forest damage.

Sensing of human plasma fibrinogen on polished, chemically etched and carbon treated titanium surfaces by diffractive optical element based sensor

Adsorption of human plasma fibrinogen (HPF) on 6 differently treated titanium samples (polished, polished and etched, and 4 titanium carbide coatings samples produced by using plasma-enhanced chemical vapour deposition (PECVD) method) is investigated by using diffractive optical element (DOE) sensor. Permittivity (susceptibility) change and fluctuation in optical roughness (R(opt)) of treated titanium surface in the presence of background electrolyte without and with HPF molecules are sensed by using DOE sensor and optical ellipsometry. Correlation between transmitted light and thickness of molecule layer was found. The findings allow to sense temporal organization and severity of adsorption of nano-scale HPF molecules on polished, on polished and etched, and on titanium carbide surface.

On measurement of complex refractive index of liquids by diffractive element-based sensor

A sensor for measurement of the complex refractive index of absorbing liquids was developed. The sensor exploits diffractive element and machine vision.

On the optical inspection of the surface quality of pharmaceutical tablets

The optical surface quality of pharmaceutical tablets was investigated using a computer-generated hologram as a sensor. The optical surface quality was related to the porosity of the tablets.

Electrical Impedance Spectroscopy and Roots

This chapter reviews studies dealing with the characterization of the plant root system by the electrical impedance method, i.e., with resistance and capacitance at a single frequency or at multifrequencies, according to the approach used in electrical impedance spectroscopy (EIS). Several studies have shown a correlation between electrical capacitance and resistance at a single low frequency with root biomass and morphology (e.g., surface area). It has not been possible to define clearly which part of the root system the electrical parameters represent. The circuitry in the stem–root–soil continuum has been analyzed in more detail by means of EIS. Using this approach, lumped and distributed models have been formulated that consider the role of roots in the context of other components in the circuitry. By means of EIS, a parameter referring to root capacitance was found to correlate positively with root biomass and root surface area. Several open questions remain with regard to the applications of the method. More studies are needed for the evaluation of longitudinal and radial electric field distribution between root interior and soil along the root system from root collar to root tips. In addition, further studies are needed under standardized measurement conditions with soils of different ionic composition and texture as the growing substrate, and also by taking into account the role played by mycorrhizas.

Investigation of microcracks in wood with laser speckle intensity

Microcracking of wood caused by drying was investigated by detecting the intensity variations of a speckle pattern induced by a focused laser beam scattered from the surface. Two trials were carried out to test the usefulness of this method. The trials were used to compare the severity of different drying treatments and to follow the development of cracking during drying. The data gathered from these experiments revealed clear correlation between the amount of cracking on a wood surface and severity of the drying treatment. Furthermore, an increase in the amount of cracks was observed as drying proceeds.