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excitation mode and at 35.8% for the voltage mode.
The biological application study aimed at
discriminating between different pine tree
physiological states.
The obtained results suggest that the
implemented method may constitute a first
innovative approach to the early diagnosis of plant
diseases. In fact, the achieved impedance parameters
allow discriminating three different physiological
states: healthy trees, trees with PWD and trees in
hydric stress.
The trees with PWD present Z
1
/Z
50
ratio with
high values of reactance, suggesting that the current
flows preferably trough the cytosol. In fact, the
action of the nematodes inside the tree may destroy
cell membranes. This means that membranes
capacitor effect becomes less significant in the
impedance measurement.
It was also shown that the number of nematodes
and Z
1
/Z
50
impedance parameter are related. The
higher the number of nematodes is, the higher the
reactance of the ratio is.
The action of bark beetles seems not to interfere,
at least in measurable terms, in the level of hydric
stress of pine trees.
Healthy trees, with high values of hydric stress
(decays above 80 %), and also trees with PWD at
advanced stages, revealed low reactance and high
resistance for the same studied parameter. The high
values of resistance are justified due to the water
loss in the tree. Consequently, it means that for this
specific case, the method cannot distinguish between
trees with PWD or trees with high level of hydric
stress but with no disease. However, it is known that
advanced stages of PWD promote high levels of
hydric stress. This means that both cases represent,
in practical terms, the same situation, i.e., the tree
presents high probability to die. In addition, in the
stages where the method is able to distinguish
between healthy trees and trees with PWD, the
decay was determined to round the 40 %. Therefore,
if a cure is available, this diagnosis could help to
administrate a treatment and reverse the disease
evolution.
Hence, the main conclusion of the developed
study is that the studied method could be used to
assess physiological states of living pine trees, and
that the Z
1
/Z
50
impedance parameter could be
applied as a risk factor.
ACKNOWLEDGEMENTS
We acknowledge support from Fundação para a
Ciência e Tecnologia, FCT (scholarship
SFRH/BD/61522/2009).
REFERENCES
Bauchot, A. D., Harker, F. R. and Arnold, W. M., (2000).
The Use of Electrical Impedance Spectroscopy to
Assess the Physiological Condition of Kiwifruit.
Postharvest Biology and Technology, 18 9-18.
Callegaro, L., (2009). The Metrology of Electrical
Impedance at High Frequency: a Review. Meas. Sci.
Techno, 20 022002.
Dean, D. A., Ramanathan, T., Machado, D. and
Sundararajan, R., (2008). Electrical Impedance
Spectroscopy Study of Biological Tissues. J
Elesctrostat, 66 (3-4): 165-177.
Dejmek, P. and Miyawaki O., (2002). Relantionship
between the Electrical and Rheological Properties of
Potato Tuber Tissue after Various Forms of
Processing. Biosci. Biotechnol. Biochem., 66 (6),
1218-1223.
Fang, Q., Liu, X. and Cosic, I., (2007). Bioimpedance
Study on Four Apple Varieties. IFMBE Proceedings,
17, 114-117.
Fukuma, H., Tanaka, K. and Yamaura, I., (2001).
Measurement of Impedance of Columnar Botanical
Tissue Using the Multielectrode Method. Electronics
and Communications in Japan, 3, 84, 2.
Giouvanoudi, A. C. and Spyrou N. M., (2008). Epigastric
Electrical Impedance for the Quantitative
Determination of the Gastric Acidity. Physiol. Meas.,
29 1305-1317.
Grimnes, S. and Martinsen, O. (2008). Bioimpedance &
Bioelectricity Basics, 2
nd
Edition. Academic Press of
Elsevier.
Harker, F. R. and Maindonald, J. H., (1994). Ripening of
Nectarine Fruit – Changes in the Cell Wall, Vacuole,
and Membranes Detected Using Electrical Impedance
Measurements. Plant Physiol, 106: 165-171.
Hayashi, T., Todoriki, S., Otobe, K., Sugiyama, J., (1992).
Impedance Measuring Technique for Identifying
Irradiated Potatoes. Biosci. Biotechnol. Biochem., 56
(12), 1929-1932.
He, C., Zhang, L., Liu, B., Xu, Z. and Zhang, Z., (2008).
A Digital Phase-sensitive Detector for Electrical
Impedance Tomography. IEEE proceedings.
Ivorra, A., (2003). Bioimpedance Monitoring for
Physicians: an Overview. Centre Nacional de
Microelectrònica, Biomedical Applications Group.
Kyle, U. et al., (2004). Bioelectrical Impedance Analysis –
Part I: Review of Principles and Methods. Clinical
Nutrition, 23, 1226-1243.
Pliquett, U., (2010). Bioimpedance: A Review for Food
Processing. Food Eng Rev, 2:74-94.
Rafiei-Naeini, M., Wright P. and McCann, H., (2007).
Low-Noise Measurements for Electrical Impedance
Tomography. IFMBE Proceedings, 17 324-327.
Repo, T., Zhang, G., Ryyppö, A. and Rikala, R., (2000).
BioimpedanceParameterasaRiskFactortoAssessPineDecay-AnInnovativeApproachtotheDiagnosisofPlant
Diseases
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