Imre Cseresnyés

Role of phase angle measurement in electrical impedance spectroscopy

Abstract Importance of phase angle measurement during the application of electrical impedance spectroscopy was studied by executing pot experiments with maize. Electrical impedance, phase angle (strength of capacitive character), and dissipation factor in the plant-soil system were scanned between 100 and 10 000 Hz current frequency. The frequency-dependent change in the phase angle could be described by optimum curves culminating within 920-3 650 Hz. Since the rate of energy dissipation is independent of root extent, the higher phase angle and lower energy dissipation were associated with the higher coefficient of determination achieved for the root electrical impedance - root system size (root dry mass and root surface area) regressions. The characteristic frequency selected on the basis of phase angle spectra provided a higher significance level at statistical comparison of plant groups subjected to stress conditions influencing root development. Due to the physicochemical changes observable in aging root tissue, the apex of phase angle spectra, thus the characteristic frequency, shifted continuously toward the higher frequencies over time. Consequently, the regularly repeated phase angle measurement is advisable in time-course studies for effective application of the electrical impedance method, and the systematic operation at the same frequency without determination of phase angle spectra should be avoided.

Monitoring of herbicide effect in maize based on electrical measurements

Monitoring of herbicide effect in maize based on electrical measurements The effect of the herbicide acetochlor on root growth was studied by a non-destructive electrical impedance and capacitance method in pot experiments on maize. Acetochlor was applied both as single active ingredient and mixed with safener AD-67 in two dosages. Without safener addition, acetochlor had a permanent inhibiting effect on plant root expansion. The safener AD-67 was capable of providing protective effect against herbicide application. High correlations between root electrical impedance or capacitance and the root dry mass or surface area under our laboratory conditions were confirmed by plant harvest method. Root electrical impedance and capacitance measurements proved to be valid for monitoring the effect of the herbicide influencing root development and for distinguishing plant groups subjected to different stress conditions.

Simultaneous monitoring of electrical capacitance and water uptake activity of plant root system

Abstract Pot experiments were designed to test the applicability of root electrical capacitance measurement for in situ monitoring of root water uptake activity by growing cucumber and bean cultivars in a growth chamber. Half of the plants were inoculated with Funneliformis mosseae arbuscular mycorrhizal fungi, while the other half served as non-infected controls. Root electrical capacitance and daily transpiration were monitored during the whole plant ontogeny. Phenology-dependent changes of daily transpiration (related to root water uptake) and root electrical capacitance proved to be similar as they showed upward trends from seedling emergence to the beginning of flowering stage, and thereafter decreased continuously during fruit setting. A few days after arbuscular mycorrhizal fungi-colonization, daily transpiration and root electrical capacitance of infected plants became significantly higher than those of non-infected counterparts, and the relative increment of the measured parameters was greater for the more highly mycorrhizal-dependent bean cultivar compared to that of cucumber. Arbuscular mycorrhizal fungi colonization caused 29 and 69% relative increment in shoot dry mass for cucumbers and beans, respectively. Mycorrhization resulted in 37% increase in root dry mass for beans, but no significant difference was observed for cucumbers. Results indicate the potential of root electrical capacitance measurements for monitoring the changes and differences of root water uptake rate.

Soil seed bank of the invasive Robinia pseudoacacia in planted Pinus nigra stands

Abstract - Pinus nigra and Robinia pseudoacacia are exotic trees used for afforestation in Hungary. Pinus nigra was non-invasive, however R. pseudoacacia escaped from cultivation and invaded several vegetation types including pine plantations. It has recently been planned to cut P. nigra plantations and replace them by native tree stands, especially in nature reserves. The scattered presence of R. pseudoacacia specimens in pine stands might place constraints on planned tree replacement because of their vegetative resprouting and recolonization from an established seed bank. The aim of this study was to investigate the soil seed bank under the canopy of solitary R. pseudoacacia specimens found in P.nigra plantations. Altogether 250 soil samples were collected from the 0-6 and 6-12 cm soil layers under solitary Robinia trees of varying ages (with basal areas between 62.4 and 1089.3 cm2). Seeds were separated by sieving then scarified and germinated. Seed bank density ranged between 640 and 2285 seedsm-2 with an average distribution of 82.7% and 17.3% in the upper and lower soil layer, respectively. Total density of the seed bank and also the seed bank ratio of the lower soil layer increased with tree age. The accumulated seed bank of R. pseudoacacia should be considered in the careful planning of tree replacement operations in Pinus nigra stands.

Fire risk in Austrian pine (Pinus nigra) plantations under various temperature and wind conditions

Fire risk in Austrian pine (Pinus nigra) plantations under various temperature and wind conditions The Austrian pine (Pinus nigra), an introduced conifer in Hungary, forms a highly flammable vegetation type. The fire risk of such stands was examined using McArthurs empirical forest fire danger model. Our study focused on the effects of temperature and wind speed on fire behaviour. By keeping the input parameters of the model constant while changing temperature andwind speed within a specified interval the resulting fire danger index (FDI) and fire behaviour were examined. The applied fixed parameters were: 30 °C temperature, 30% relative humidity, 30 km h-1 wind speed, 30 degree of slope and drought factor value 10. The annual trends of the Byram-Keetch drought index (BKDI) and the drought factor were also calculated. Our results show that increasing temperature and wind speed raises the FDI, flame height, rate of fire spread (ROS) and spotting distance. The amount of fuel does not influence the FDI, but increasing the amount promotes the ROS and raises the flame height. Wind speed was the most important factor in the ROS. A serious fire risk of these plantations was determined. The reliability of McArthurs model was proved by comparison of our results with experimental laboratory data based on literature.

Application of Electrical Capacitance Method for Prediction of Plant Root Mass and Activity in Field-Grown Crops

The root electrical capacitance (CR) method is suitable for assessing root growth and activity, but soil water content (SWC) strongly influences the measurement results. This study aimed to adapt the method for field monitoring by evaluating the effect of SWC on root capacitance to ensure the comparability of CR detected at different SWC. First a pot experiment was conducted with maize and soybean to establish CR–SWC functions for the field soil. Ontogenetic changes in root activity were monitored under field conditions by simultaneously measuring CR and SWC around the roots. The CR values were normalized using SWC data and experimental CR–SWC functions to obtain CR*, the comparable indicator of root activity. The effect of arbuscular mycorrhizal fungi (AMF) inoculation on the CR* and biomass of field-grown soybean was investigated. The pot trial showed an exponential increase in CR with SWC. CR–SWC functions proved to be species-specific. CR showed strong correlation with root dry mass (R2 = 0.83–0.87). The root activity (CR*) of field-grown crops increased until flowering, then decreased during maturity. This was consistent with data obtained with other methods. AMF inoculation of soybean resulted in significantly higher CR* during the late vegetative and early flowering stages, when destructive sampling concurrently showed higher shoot biomass. The results demonstrated that the root capacitance method could be useful for time course studies on root activity under field conditions, and for comparing single-time capacitance data collected in areas with heterogeneous soil water status.

Szójafajták gyökérnövekedésének és szárazságtűrésének in situ vizsgálata elektromos kapacitás mérésével

Munkank soran tenyeszedeny-kiserlettel teszteltuk az elektromos gyokerkapacitas (EC) meres alkalmazhatosagat szojafajtak gyokernovekedesenek es szarazsagtűresenek in situ vizsgalata celjabol. A kontroll es a szarazsagstressznek kitett novenyek EC-jet rendszeresen mertuk, vegul biomasszajukat destruktiv eljarassal meghataroztuk. Az EC meresevel jol detektalhato volt a fajtak elterő gyokernovekedesi dinamikaja es biomassza-produkcioja. Az EC — fajtatol es kortol fuggő intenzitassal — a viragzas kezdeteig folyamatosan emelkedett, majd kozel allandova valt. A fajtak EC-je es gyokertomege szoros korrelaciot mutatott a kontroll (R2=0,844) es a szarazsagkezelt (R2=0,936) novenyeknel egyarant. A vizhiany 28,8–50,5%-kal csokkentette az egyes fajtak EC-jet, ami osszhangban allt azok hajtastomegeinek 25,5–49,1%-os, es levelfeluleteinek (transzspiraciojanak) 23,6–51,5%-os csokkenesevel, ugyanakkor tobb fajtanal lenyegesen meghaladta a gyokertomegben mutatkozo veszteseget (12,6–47,3%). Ennek oka, hogy a szarazsag hata...