Current issue: 58(5)
Articles containing the keyword 'impedance'
Category : Article
The ability of one-year old Scots pine (Pinus sylvestris L.) seedlings to reharden during the dehardening period was studied. Naturally hardened quiescent seedlings were preconditioned at 0°C for ten days and then placed in chambers at different forcing temperatures with different light regimes. The forcing periods were followed by cool periods. Changes in frost hardiness were monitored at intervals using freeze tests of whole plants. Frost hardiness was assessed by three methods: impedance, survival and growth retardation. Dehardening seemed to be a partially reversible process, i.e. in some growing conditions slight rehardening was found.
The PDF includes an abstract in Finnish.
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Repo,
E-mail:
tr@mm.unknown
Seven hundred one-year-old Betula pendula Roth seedlings were given different concentrations of potassium fertilizer. Over the study period seedlings were subjected to artificial growing and dormant phases. Frost resistance of the seedlings was assessed by artificial freezing tests and electrical impedance measurements on stem cuttings. In general, high concentrations of potassium fertilizer reflected a low tolerance to frost. Pre-freezing impedance readings decreased with increasing potassium fertilizer dosages. Results from pre-freezing impedance measurements were found to be in broad agreement with the hypothesis that high impedance readings indicate a frost hardy tissue whereas low readings imply the opposite.
The PDF includes an abstract in Finnish.
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Jozefek,
E-mail:
hj@mm.unknown
Electrical impedance characteristics of plant cells are dependent on such physiological factors as physiological condition, developmental stage, cell structure, nutrient status, water balance and temperature acclimation. In the measurements also such technical and physical factors as type of electrodes, frequency, geometry of the object, inter-electrode distance and temperature have an effect. These factors are discussed especially with respect to the impedance method in frost resistance studies of plants.
The PDF includes an abstract in Finnish.
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Repo,
E-mail:
tr@mm.unknown
Category : Research article
The paper aimed at testing the potential of refining tree rot diagnostics carried out by means of electrical impedance tomography (EIT). Examined was the use of EIT datasets with electrical resistance values and sapwood proportion determined on the basis of tomograms. Making use of datasets with resistance values in EIT rot diagnostics is not a default method, although datasets stay unaffected by a fixed colour scale and subsequent subjective evaluation unlike tomograms. Tomography measurement was carried out for 27 individuals of Norway spruce (Picea abies [L.] Karst.) in two stands north-east of Brno, Czech Republic. Once felled down, radial cut-outs were sampled at the measurement site and used for localising rot and determining the extent of the area of decay. The results were subsequently compared with tomograms. EIT datasets containing values of electrical resistance found by measuring were statistically processed and compared with the extent of rot area identified within the cuts. Sapwood proportion values were also detected using the tomograms. The baseline assumption that sapwood proportion decreases as the rot area in the radial cut expands was confirmed. In trees with rot percentage to 35% approximately, sapwood proportion was exceeding 30% except one tree. In trees with rot percentage exceeding 35%, sapwood proportion was below 30%. On the basis of interpreted datasets, the trees can be split into three characteristic groups that correspond to the occurrence, extent and nature of the rot.
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Humplík,
Mendel University in Brno, Faculty of Forestry and Wood Technology, Zemědělská 1665/3, 613 00 Brno, Czech Republic
E-mail:
premysl.humplik@mendelu.cz
- Čermák, Mendel University in Brno, Faculty of Forestry and Wood Technology, Zemědělská 1665/3, 613 00 Brno, Czech Republic E-mail: petr.cermak@mendelu.cz
- Žid, Mendel University in Brno, Faculty of Forestry and Wood Technology, Zemědělská 1665/3, 613 00 Brno, Czech Republic E-mail: tomas.zid@mendelu.cz
- Aphalo, University of Helsinki, Department of Biological and Environmental Sciences E-mail: pja@nn.fi
- Lahti, The Finnish Forest Research Institute E-mail: ml@nn.fi
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Lehto,
University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland
E-mail:
tarja.lehto@joensuu.fi
- Repo, The Finnish Forest Research Institute E-mail: tr@nn.fi
- Rummukainen, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: ar@nn.fi
- Mannerkoski, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: hm@nn.fi
- Finér, The Finnish Forest Research Institute E-mail: lf@nn.fi
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Repo,
The Finnish Forest Research Institute, Joensuu Research Centre, P.O. Box 68, FI-80101 Joensuu, Finland
E-mail:
tapani.repo@metla.fi
- Laukkanen, University of Joensuu, Department of Physics, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: jl@nn.fi
- Silvennoinen, University of Joensuu, Department of Physics, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: rs@nn.fi
