Direction Of Temperature Change Research Articles

Thermal transfer rate is slower in bigger fish: How does body size affect response time of small, implantable temperature recording tags?

AbstractThe recent miniaturisation of implantable temperature recording tags has made measuring the water temperatures fish experience in the wild possible, but there may be a body size‐dependent delay in implanted tag response time to changes in external temperature. To determine whether fish body size affects the response rate of implanted temperature tags, we implanted 20 Salvelinus fontinalis (127–228 mm fork length (FL), 15.1–120.4 g) with temperature recording tags and subjected them to rapid temperature changes (±8°C in less than 2 seconds) in the laboratory. We found that thermal transfer rates, and the lag in temperature tag response rate, was positively correlated with fish size, but the direction of temperature change (colder or warmer) had no significant effect. In fish exposed to a slower rate of temperature change (2°C h−1) implanted tags did not show a response lag. Understanding the limitations of this important technology is crucial to determining the utility of the data it produces and its ability to accurately measure fish thermal experience in the wild.

Impact of Climate Change on the Development of Viticulture in Central Poland: Autoregression Modeling SAT Indicator

Ongoing climate change is having a profound impact on agriculture, which is attracting attention from the scientific community. One of its effects is an increase in average temperature, which is a key factor in grape cultivation. This may increase the popularity of viticulture in central Europe. The aim of this study was to assess the potential for the development of viticulture in central Poland based on SAT changes from 1975 to 2021, in addition to changes in evapotranspiration, occurrence of late spring and early autumn frosts and frosty days in selected years from this period as an important factors relating to climate change. The research utilized data obtained from the Institute of Meteorology and Water Management—National Research Institute. The Bai–Perron test was used to determine the direction of temperature changes. An AR(1) autoregression model was used to predict SAT changes in central Poland for the years 2022–2026, based on the results of the Bai–Perron test. As part of the in-depth research on the SAT index, reference evapotranspiration calculations were also made as a second factor that is considered an important indicator of climate change. The Sum of Active Temperatures from 1975 to 2021 in the provinces of central Poland showed an increasing trend of 0.07% per year. The average SAT in central Poland in 2022–2026 is expected to range from 2700 °C to 2760 °C. Considering the current thermal conditions in central Poland and the forecasts for the coming years, it can be expected that vineyard cultivation will develop in this region. However, the research shows that the observed increasing trend in evapotranspiration, both in total in individual years and in the period of the greatest vegetation, i.e., in the months from May to the end of August, will result in an increasing need in central Poland to ensure adequate irrigation in developing vineyards.

Monitoring Land Surface Temperature Trends in Indonesia

Monitoring Land Surface Temperature (LST) trends helps identify provinces vulnerable to temperature changes and aids in developing appropriate adaptation and mitigation strategies. This research article aims to monitor LST trends in Indonesia from 2000 to 2022 using MODIS Aqua Land Surface Temperature and Emissivity (MYD11A1) imageries. The study utilizes LST Day and LST Night datasets obtained from MYD11A1 datasets to achieve its research objective. Sens’ Slope is employed to identify and measure the magnitude and direction of temperature changes, while the Mann-Kendall trend test detects significant LST trends. GEE is used to process and analyze MODIS LST data. The findings show a significant increase in LST Night during the June-August (JJA) period in most provinces of Indonesia. LST Day data also stresses that some provinces in Indonesia are experiencing a warming trend. Elevation and population increases may contribute to the observed increasing LST trend. Notably, a short-term decrease in LST may occur within the long-term increasing LST trend.

Transient and Steady-State Properties of Drosophila Sensory Neurons Coding Noxious Cold Temperature.

Coding noxious cold signals, such as the magnitude and rate of temperature change, play essential roles in the survival of organisms. We combined electrophysiological and computational neuroscience methods to investigate the neural dynamics of Drosophila larva cold-sensing Class III (CIII) neurons. In response to a fast temperature change (–2 to –6°C/s) from room temperature to noxious cold, the CIII neurons exhibited a pronounced peak of a spiking rate with subsequent relaxation to a steady-state spiking. The magnitude of the peak was higher for a higher rate of temperature decrease, while slow temperature decrease (–0.1°C/s) evoked no distinct peak of the spiking rate. The rate of the steady-state spiking depended on the magnitude of the final temperature and was higher at lower temperatures. For each neuron, we characterized this dependence by estimating the temperature of the half activation of the spiking rate by curve fitting neuron’s spiking rate responses to a Boltzmann function. We found that neurons had a temperature of the half activation distributed over a wide temperature range. We also found that CIII neurons responded to decrease rather than increase in temperature. There was a significant difference in spiking activity between fast and slow returns from noxious cold to room temperature: The CIII neurons usually stopped activity abruptly in the case of the fast return and continued spiking for some time in the case of the slow return. We developed a biophysical model of CIII neurons using a generalized description of transient receptor potential (TRP) current kinetics with temperature-dependent activation and Ca2+-dependent inactivation. This model recapitulated the key features of the spiking rate responses found in experiments and suggested mechanisms explaining the transient and steady-state activity of the CIII neurons at different cold temperatures and rates of their decrease and increase. We conclude that CIII neurons encode at least three types of cold sensory information: the rate of temperature decrease by a peak of the firing rate, the magnitude of cold temperature by the rate of steady spiking activity, and direction of temperature change by spiking activity augmentation or suppression corresponding to temperature decrease and increase, respectively.

Variations in Nitrogen Isotope Composition in Clay Deposits of the Permian–Triassic Boundary Beds in the Verkhoyansk Region (Northeast Asia) and Their Implication for Reconstruction of Marine Environments

The first sediment N-isotope data on the Permian–Triassic boundary transition of the Verkhoyansk region are obtained. Together with the other published materials on other regions of eastern Russia allow us to distinguish a number of N-isotope intervals of various ranks in the Permian–Triassic of eastern Russia. In addition to the well-known method of reconstructing the redox conditions of the marine environment from N‑isotope data (in combination with data on elevated concentrations of redox-sensitive trace metals), the possibility of using N-isotope data also to determine the direction of temperature changes in the marine environment is substantiated. It is assumed that N-isotope signals are primarily a reflection of events associated with denitrification and N2 fixation, the main processes of the global nitrogen biogeochemical cycle (NBC). Deviations in the direction of increasing δ15N values in the considered sections are associated with an increase in upwelling activity and the supply of cool deep waters enriched in the heavy N isotope to the shelf zone; the opposite deviations are associated with a slowdown or cessation of inflow of cool deep waters. The N-isotope data obtained, in combination with the published materials on O-isotope thermometry in the Tethyan Superrealm during the Permian and Triassic, indicate a very likely coincidence of the direction of temperature changes caused by both regional (upwelling) and global (climatic) events of that time. In this regard, the reconstructions of the marine environment that we conduct by the example of the Permian–Triassic sections of Northeast Asia (Verkhoyansk, Kolyma–Omolon, and South Primorye) seem to be appropriate, although they require additional confirmation on the material from other sections of the world. The problems associated with differences in the average δ15N values in the Permian–Triassic sections of different provinces of the Boreal Superrealm, as well as other superrealms, are considered.

Palaeofluid evolution in a fractured basalt hosted reservoir in the Üllés-Ruzsa-Bordány area, southern sector of the Pannonian Basin

Extensive Miocene volcanic activity produced basaltic and pyroclastic successions, which were penetrated by many wells in the area of Ulles-Ruzsa-Bordany, in the western and central part of the Great Hungarian Plain. The Kecel Basalt comprises primary porosity from a high proportion of vesicles and significant secondary fracture porosity, as well. Due to the significant fracture porosity, some depth intervals show good reservoir characteristics, although the fractures crosscutting the rock body are partly or entirely cemented by various minerals. Based on the textural and mineralogical features, four distinct vein types can be distinguished, named after their volumetrically most abundant cement phases, i.e. potassium-feldspar (Kfp-), calcite (Cal-), laumontite (Lmt-) and analcime (Anl-) types. This study focuses on probably the youngest of these vein types, the Anl-type. Based on the study of veins and mineral sequences, the direction of temperature changes cannot be given unequivocally for every stage of cementation, but crystallization of the Anl-type veins might have occurred at lower temperatures than the formation of the Lmt-type veins. Fluid inclusion studies suggest that hydrocarbon migration and accumulation took place after cementation of the first three vein types (Kfp-, Cal- and Lmt-types). In the newly opened fracture system, two types of hydrocarbon (HC1 and HC2)-bearing fluid inclusion assemblages were captured during precipitation of analcime and later zeolites. This refers to two stages of hydrocarbon migration in the fracture system. Observations of the fluorescence colours and low temperature behaviours of the hydrocarbon-bearing inclusions, the earlier HC1 petroleum-inclusions captured heavier (presumably less mature oils), while the later ones (HC2) lighter (presumably more mature) oils. The HC2 petroleum seems to be very similar to the crude oil sampled in a well in the area based on their fluorescence parameters.

Investigation of the yield of X-Ray radiation from pyroelectric sources with cone-shaped targets

The results of experimental studies of the spectral composition and yield of X-ray radiation from pyroelectric sources with cone-shaped targets are presented. A distinct maximum of the yield as a function of the distance between the pyroelectric crystal and the target is found for a single-crystal pyroelectric source with a truncated cone target. It is demonstrated in the experiment involving a source with two pyroelectric crystals and a cone-shaped target that the X-ray parameters are virtually independent of the direction of temperature change in the crystals.

Body size response to warming: time of the season matters in a tephritid fly

Whether shrinking body size is a universal response to climate change remains controversial. Moreover, the mechanisms underlying body size shifts are poorly understood. Here, assuming that life history traits evolve to maximize fitness according to life history plasticity theory, we hypothesized that under global warming temperate multivoltine insects should emerge earlier with a smaller body mass in the early growing season, but emerge later with a larger body mass in the late season. We tested this hypothesis by conducting two field artificial warming experiments in an alpine meadow: 1) with one pre‐dispersal seed predator species (tephritid flies, Tephritis femoralis) and its two host‐plant species flowering in early and late growing seasons, respectively, and 2) with the tephritid flies and one host species with a flowering season that occupies parts of both the early and late growing seasons. These experiments were complemented by a microcosm chamber warming experiment, in which increasing and decreasing temperature trends were set to simulate temperature variation pattern in early and late growing seasons, respectively, but photoperiod was held constant. Warming generally advanced the adult emergence and decreased the body size (adult body mass) in the early season but delayed the emergence and increased the size in the late season in both field experiments, indicating that the seasonally different effects of warming on the fly body size was constant regardless of host‐plant identity. The chamber warming resulted in consistent responses of emerging timing and body size to the simulated seasonal warming, demonstrating that the temperature increase per se and its interaction with direction of temperature change, but not other correlated effects, should be primarily responsible for the observed contrasting shifts of body size at different times of the season. Our results indicate that taking into account temperate seasonal patterns of temperature variation could be of general importance for predicting animal body size changes in the warmed future.

Nuclear magnetic resonance study of sea-water freezing mechanisms: 1. Temperature dependence of relative brine content in sea ice

AbstractThe results of measuring relative brine content (Qlm) in the liquid phase of frozen sea water at temperatures between −2°C and −43°C with variable rate and direction of temperature change are presented. Various pulsed and steady-state nuclear magnetic resonance (NMR) methods are used and the results are compared with data in the literature. Temperature dependences of Qlm in sea water with dry NaCl added are given. Quasi-hysteresis corresponding to the crystallization range of certain seawater salts, mainly NaCl, which partially precipitates as the crystalline hydrate NaCl·2H2O at temperatures below −23°C, is detected in the temperature dependence of Qlm. The reasons why Qlm values, under various experimental conditions, differ from data in the literature are explained. Brine salinity (S) is calculated from the relative intensity of NMR signals of Ql, and agrees well with previously published data over a wide temperature range. It is shown that determining Qlm from base measurements of Ql in ice does not require information about brine salinity. Empirical equations for calculating brine content at different sea-water temperatures and salinity are given.

Nuclear magnetic resonance study of sea-water freezing mechanisms: 2. Temperature dependence of relaxation time of protons in sea-ice brine

AbstractResults of determinations of proton magnetic relaxation time (T1) in the liquid phase of frozen sea water at temperatures between −2°C and −38°C, with variable rate and direction of temperature change, are presented. Temperature hysteresis corresponding to the crystallization range of certain sea-water salts, mainly NaCl which partially precipitates as the crystalline hydrate NaCl.°2H2O at temperatures below −23°C, is detected in the temperature dependence of T1, as in the analogous dependence of brine content. It is shown that formation of crystalline hydrates in brine is preceded by complete solvation of ions at −5 to −6°C. The main causes of hysteresis in temperature dependence of T1 and the extension of loop limits compared with the analogous loop for liquid brine content are indicated. Additional potentialities of using the nuclear magnetic resonance method for investigating sea-ice properties are presented.

Projecting annual air temperature changes to 2025 and beyond: implications for vegetable production worldwide

SUMMARYData sets were accumulated of annual average maximum, minimum and mean air temperature from a range of sites worldwide, specifically from non-urban locations such as agricultural research institutes, universities and other rural or island locations for the period 1975–2011 or longer where data were available. The data sets were then analysed using linear regression to determine the rate and direction of change in temperature over the reference periods. This analysis was performed to provide vegetable scientists with likely future temperature change scenarios up to 2025 and 2050 (on the assumption that recent trends are maintained) so that breeding, agronomic and other related research programmes may better respond to potential challenges from abiotic and biotic stresses to vegetable production. Substantial variation was evident between sites and between time runs at specific sites. At some locations rapid increases in air temperature are projected, such as for sites in East Asia, but at other locations little change is evident; in rare cases, local cooling is shown. The implications of variability and change in air temperature in the context of constraints to vegetable production and the opportunities to exploit the range of genetic diversity available in climatically uncertain environments are discussed. It is believed that modern agricultural science can address successfully the problems raised by climate uncertainty, yet the lack of sufficient, immediate investment in horticultural disciplines worldwide places the world at severe risk of failing to attain effective food and nutritional security.

Cooling of Cilia Allows Functional Analysis of the Beat Pattern for Diagnostic Testing

Reports of the effect of low temperatures on ciliary beat frequency (CBF) are conflicting, and the effect on ciliary beat pattern has not been reported. We aimed to clarify this association and determine whether cooling of cilia may allow ciliary function to be assessed without the need of expensive high-speed video microscopy. Fourteen nasal brush biopsy samples were collected, and the CBF and beat pattern of undisrupted ciliated edges were evaluated. Two methods were used to strictly control changes in temperature: One enabled rapid transitory measurements during cooling and warming, and the other was used to maintain accurate low temperatures over longer periods of time. A sigmoid relationship between CBF and temperature was observed. CBF decreased with cooling and increased with warming. Ciliary function was unaffected by the direction of temperature change and was maintained down to 2°C. The percentage of dyskinetic cilia observed at 2°C or 4°C was unchanged from that at 37°C. Contrary to previous research, our data show that cilia continue to beat with a normal pattern at temperatures as low as 2°C. Slowing of cilia by cooling may allow detailed analysis of ciliary beat pattern without the need of expensive high-speed video microscopy.

Using static charge on pyroelectric crystals to produce self–focusing electron and ion beams and transport through tubes

Static charge in and on the surface of pyroelectric crystals of LiNbO 3 and LiTaO 3 in a dilute gas has been shown to ionize gas molecules via electron tunneling. The released electrons and positive ions are focused and accelerated according to the sign of the static uncompensated charge. The uncompensated charge is produced when the temperature of the crystal is changed from any initial temperature between about 500 and about 15 K. It may be either polarization charge that is inside the crystal surface or compensation charge that is on the surface. The direction of temperature change and the polarity of the base of the crystal determine whether electrons or positive ions are accelerated toward or away from the crystal. The ionization, focusing and acceleration may continue for more than 15 days following a single change in temperature from ∼20 to ∼160 to ∼20 °C. Electron and ion transport through tubes is demonstrated.

Two Crossovers in the Pseudogap Regime ofYBa2Cu3O7−δSuperconductors Observed by Ultrafast Spectroscopy

We have investigated the temperature dependence of the optical reflectivity on a femtosecond scale in a near optimally doped YBa 2Cu 3O (7-delta) superconductor. The combined study of the lattice and carrier dynamics at temperatures above T(c) allows us to identify two crossover temperatures in the normal state, giving evidence for an inhomogeneity of the pseudogap regime. These crossovers exhibit a clear hysteresis behavior depending on the direction of temperature change. The carrier and lattice dynamics within the crossover regimes show distinct differences from and similarities to the superconducting state, which may help in choosing between the competing theories for the pseudogap state.

Effects of temperature and moisture on carbon respired from decomposing woody roots

Controls of temperature and moisture on root decomposition have not been well studied despite their direct relevance to climate change impacts on root carbon flux. The main objective of this laboratory study was to examine the respiration response of Sitka spruce, Douglas-fir, western hemlock, ponderosa pine, and lodgepole pine decomposing roots (1–3 cm in diameter) to temperature and moisture change. Roots of Sitka spruce, Douglas-fir and western hemlock, and ponderosa pine and lodgepole pine were collected from Cascade Head, H.J. Andrews, and Pringle Falls site, respectively. Dead root respiration increased with temperature and reached the maximum at 30–40°C, and then decreased. Analysis of covariance indicated that the Q 10 of root decomposition rate was influenced significantly ( p<0.01) by incubation temperature range 5–40°C, but not by species, decay class or the direction of temperature change. At 5–10°C, Q 10 averaged 3.99 and then decreased to 1.37 at 30–40°C. Over a range of 5–60°C, Q 10 could be predicted by a single-exponential model using temperature as the independent variable. Analysis of variance showed that the respiration rate of dead roots was significantly ( p<0.01) influenced by root moisture, species, and decay class as well as temperature. Dead root respiration increased with root moisture, reached the optimum range when moisture was between 100 and 275% and then decreased. Moreover, there were apparent interactions of root moisture and temperature on root respiration. Our study showed the direction of temperature and moisture change did not significantly influence root respiration, indicating that hysteresis may not occur for the temperature and moisture ranges examined. To better model global climate warming effects on root carbon flux, we suggest a temperature dependent Q 10 function should be incorporated into current root dynamics models. The short-term laboratory incubation approach provided a good way to examine temperature and moisture controls on root decomposition, although we are cautious about long-term mass-loss extrapolations based on these short-term results.

Temperature Tolerances of North American Freshwater Fishes Exposed to Dynamic Changes in Temperature

Traditionally lower and upper temperature tolerances of fishes have been quantified in the laboratory via three different experimental approaches: the Fry or incipient lethal temperature (ILT), critical thermal (CTM) and chronic lethal (CLM) methodologies. Although these three experimental laboratory approaches generate endpoints which are quantitatively expressed as a temperature, are determined experimentally with random samples of fish acclimated to specific temperatures, and involve both time and temperature as major test variables, they do not quantify the same response. All three approaches generate valuable, albeit different, information concerning the temperature tolerance of a species. In this review we have summarized published research concerning the tolerance of North American freshwater fishes to dynamic changes in temperature, i.e., tolerance is tested by methods that gradually change temperatures until biological stress is observed. We found more than 450 individual temperature tolerances listed in 80 publications which present original dynamic temperature tolerance data for 116 species, 7 subspecies and 7 hybrids from 19 families of North American freshwater fishes. This total represents about 1/3 of the families and 1/6 of the known North American freshwater species. Temperature tolerance data were partitioned by experimental approach, i.e., critical thermal method (CTM) and chronic lethal method (CLM), and direction of temperature change. Although both CTM and CLM expose fish to dynamic changes in water temperature, these two methods differ in temperature change rates and test endpoints, and hence measure different aspects of thermal stress. A majority of the 80 studies employed CTM to assess temperature tolerance, in particular determination of CTmaxima. One or more CTmaxima has been reported for 108 fishes. Twenty-two fishes have reported highest CTmaxima of 40°C or higher. Several species in the family Cyprinodontidae have generated some of the highest CTmaxima reported for any ectothermic vertebrate. For a variety of reasons, data concerning tolerance of low temperatures are less plentiful. Low temperature tolerance quantified as either CTminima or CLminima were found for a total of 37 fishes. Acclimation temperature exerts a major effect on the temperature tolerance of most North American fish species and it is usually strongly linearly related to both CTmaxima and CTminima. Although we uncovered dynamic temperature tolerance data for 130 fishes, only a single dynamic, temperature tolerance polygon has been published, that for the sheepshead minnow, Cyprinodon variegatus.

Fluidity of Neuronal Membranes of Crayfish ( Astacus astacus L.) Acclimated to 5°C and 20°C

The fluidity of microsomal membranes from nerve cords of eurythermal freshwater crayfish Astacus astacus acclimated to 5°C or to 20°C was measured by steady-state fluorescence polarization. Membrane fluidity was measured at 4–24°C during a cyclic temperature change (0.2°C/min) using 1,6-diphenyl-1,3,5-hexatriene (DPH) or 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) molecule as probes. The fluidity of neuronal membranes depended on temperature but not on the direction of temperature change. Thermal dependence of fluidity was higher with DPH than with TMA-DPH. Neuronal microsomal membranes of cold-acclimated crayfish were more fluid than those of warm-acclimated animals. Except at the lowest experimental temperatures, in both microsomal and plasma membranes, the TMA-DPH polarization values were higher than the DPH polarization values, indicating the anchorage of TMA-DPH to the more rigid hydrophilic surface of the bilayer at these temperatures in both membranes. Neuronal plasma membranes were more rigid than microsomal membranes measured with DPH. With TMA-DPH plasma membranes were more fluid than microsomal membranes.

Redistribution of the Potential Geographical Ranges of Mistletoe and Colorado Beetle in Europe in Response to the Temperature Component of Climate Change

1. Following the method of Jeffree & Jeffree (1994), mean temperatures of the coldest (x) and warmest (y) months of the year in the geographical ranges of Viscum album and Leptinotarsa decemlineata were used to construct ellipsoidal probability regions for the range of each species in temperature space. 2. Assuming that species responsiveness to temperature remains constant, the temperature probability ellipsoids may be used to interpret both the potential geographical range of the species and its potential redistribution in response to the temperature component of past or future climatic changes. 3. Temperature changes Δx and Δy for UKHI and UKTR GCM scenarios for a double CO 2 were plotted as vectors in two-dimensional (x, y) temperature space, enabling the magnitude and direction of temperature change at each geographical location to be visualized. 4. Interactions in x, y temperature space between the temperatures of geographical locations and the temperature probability ellipsoids were used to map those areas of Europe in which the combination of summer and winter temperatures would be suitable for the species in various temperature change scenarios. 5. The direction of potential migration of each species was found to be sensitive to seasonality both of existing temperatures and of the increments Δx and Δy, and cannot therefore be interpreted from annual mean temperature change alone. 6. Under the increasingly oceanic temperature regimes in Europe indicated by the UKHI and UKTR GCM scenarios the potential range of Viscum album is only likely to extend north and east into parts of Europe currently with a regime that is both cooler and more continental than in the present species distribution. 7. UKHI and UKTR scenarios of climatic warming are likely to be unfavourable to northward extension of the range of Viscum album in Britain, and may result in the loss of the species where current annual temperature range is reduced. 8. By contrast, in the same temperature change scenarios, the potential geographical range of summer and winter temperatures suitable for Leptinotarsa decemlineata may extend into Britain as far as the north of England.

Symptoms and rate of temperature change in febrile outpatients

Although patient comfort is a frequent rationale for antipyretic therapy, there have been few systematic studies of relationships between temperature and comfort. In this study, adult outpatients with febrile illnesses were asked to complete a symptom diary at multiple time points at which temperature was recorded. Temperature readings showed modest correlation (0.316) with scores of “feeling better or worse” and moderate correlation (0.586) with aggregate symptom scores. Rate of temperature change showed low levels of correlation (<0.25) with both measurements. Direction of temperature change was not significantly associated with overall subjective score of “feeling better or worse” although aggregate symptom scores were slightly higher with rising than falling temperature. These findings suggest that temperature is a partial determinant of morbidity in minor febrile illnesses but contribution of temperature change to well being may be small. Further study is needed to determine the appropriate priority of temperature reduction in symptomatic therapy.

Measurement of heat injury in plant tissue by using electrical impedance analysis

Electrical impedance spectra (100 Hz to 800 kHz) were measured in pieces of potato (Solanum tuberosum L.) tuber tissue that had been heat stressed. Analysis of the impedance data based on equivalent circuits showed that tissue injury was revealed as decreases in membrane capacitance and extracellular resistance. By using a single piece of tissue, membrane thermostability (in relation to heat stress temperature or time of heat stress) was measured. Nonstressful temperature changes produced changes in tissue parameters that were fully reversible when the direction of temperature change was reversed. Stressful temperature changes produced irreversible changes in parameters. During heat injury, decrease in extracellular resistance always preceded a decrease in tonoplast capacitance. It is suggested that two stages may be involved in heat injury to membranes: functional injury leading to electrolyte leakage to extracellular space, and structural damage leading to membrane disintegration. It is concluded that electrical impedance analysis is useful in plant heat stress physiology. Key words: potato (Solanum tuberosum L.) tuber, electrical impedance, membrane capacitance, heat injury, membrane thermostability.