Mean Water Content Research Articles

Relationships Between Body Condition Indices and Proximate Composition in Adult Walleyes

AbstractRelationships between indices of condition and measures of proximate body composition were examined among and within nine populations of mature walleyes Sander vitreus that varied widely in growth rate and lipid status. Body condition, measured as the residuals from mass versus length regressions, was negatively related to mean water content and positively related to mean lipid content among populations. When the roles of water and lipid content were examined simultaneously within populations, most of the variance in condition was accounted for by lipid content. The strength of the relationships between various condition indices and body proximate composition varied considerably among populations but less between sexes within populations. Furthermore, the strength and nature of these relationships was not strongly influenced by the choice of mass‐at‐length index (residuals, relative condition, relative weight, or Fulton's K). The visceral‐somatic index and muscle lipid content both exhibited slightly stronger relationships with body proximate composition than did mass‐at‐length condition indices for both sexes. The hepatosomatic index was more consistently related to somatic lipid content for females than for males in most populations. Relatively simple condition indices can provide reliable surrogates of body proximate composition in many adult walleye populations, but caution should be exercised in extrapolating from condition‐composition relationships among populations.

Field measurements of topsoil moisture profiles by vertical TDR probes

A recently developed inverse method for the estimation of water content profiles from single time domain reflectometry (TDR) waveforms in laboratory has been adapted and applied to field measurements of topsoil moisture profiles in a pyroclastic sandy loam. Three metallic probes of the lengths of 30 cm, 45 cm and 60 cm were vertically installed in an experimental field for the measurement of vertical water content profiles. One 15 cm long probe was inserted vertically into soil surface and five 10.5 cm long probes were buried horizontally at various depths for the measurement of local values of mean water content by means of the classical TDR approach. The experimental campaign lasted 28 days, during which daily rainfall heights and daily maximum and minimum temperatures were measured at the experimental field. TDR waveforms acquisition was carried out twice a day. The agreement between local volumetric water content measurements and vertical profiles was in general satisfactory, although some of the vertical profiles failed in detecting a layer with systematically smaller water content values indicated by the horizontal probe buried at the depth of 30 cm below soil surface. Such small water content values could be probably ascribed to the presence of a large amount of pumice stones in the soil around that depth, affecting the water content measured by TDR probes and thus increasing estimated moisture spatial variability.

Spatial variation in respiration from coarse woody debris in a temperate secondary broad-leaved forest in Japan

We measured the rates of respiration from snags and logs (“coarse woody debris”, CWD) of Japanese red pine ( Pinus densiflora Sieb. et Zucc.) to examine the rate of decomposition and CO 2 efflux from these materials in a temperate secondary broad-leaved forest in Japan. At this site, a high quantity of CWD of P. densiflora had accumulated as a result of pine wilt disease during the 1970s. Respiration rates were measured using a dynamic closed chamber method combined with an infrared gas analyzer. We measured the respiration rate of 7 samples of snags and 10 samples of logs from August 2003 to January 2004. The responses of the respiration rates of snags ( R snag) and logs ( R log) to changing temperature were both exponential and the responses to water content were quadratic, and the same function could be used to estimate annual values of both R snag and R log. Intensive measurements of water contents of snags and logs showed a marked difference in water content. The mean water content of snags was 20% of log water content. This difference was likely responsible for the observed difference in annual R snag and R log. The decay rate constants estimated from the respiration rates measurement of snags and logs were 0.019 and 0.081 year −1, respectively. Despite being lower than R log, R snag was a significant compartment of the CWD carbon budget at this site.

Comparison of ground-based and remotely-sensed surface soil moisture estimates over complex terrain during SMEX04

Comparisons to ground-based surface soil moisture estimates are necessary to evaluate the capability of remote sensors to determine soil moisture and its spatiotemporal variability. Soil moisture can be especially variable in regions of complex terrain which exhibit large variations in vegetation, soil properties and hydrologic conditions. The objective of this study is to evaluate the spatiotemporal variability of soil moisture in a mountainous basin in northwestern Mexico. Soil moisture estimates from ground sampling over a topographic transect and high resolution retrievals from the Polarimetric Scanning Radiometer are compared during a two week period in August 2004 as part of the Soil Moisture Experiment 2004. Results indicate that the soil moisture estimates exhibit similar variability with mean water content. Statistical analysis, however, reveals clear differences in soil moisture in the basin, in particular for wet periods and high elevations. Despite these differences, the temporal persistence of soil moisture from the estimates agrees well and indicates locations that capture the basin-averaged conditions. Furthermore, the spatiotemporal soil moisture characteristics from the two products are linked to terrain attributes. As a result, a hypsometric technique is shown to improve comparisons between basin-averaged values derived from ground data and remote sensing, as compared to arithmetic averaging. To our knowledge, this study is the first attempt to evaluate PSR/CX retrievals with respect to ground observations over a region of high topographic and vegetation variability using statistical, time-stability and terrain analysis techniques.

Quantification of the heterogeneity of the unsaturated zone based on environmental deuterium observed in lysimeter experiments

An approach is presented which enables the quantification, in integrative form, of the preferential flow and the heterogeneity in water transport through the unsaturated zone under natural atmospheric conditions. For these purposes, deuterium transport was estimated in seven lysimeters filled with different sediment materials by applying a conceptual model, which consists of preferential and matrix flow paths for each using the lumped parameter approach. The piston flow and dispersion transit time distribution functions were assumed, for preferential and matrix flow paths, respectively. Weekly 2H data measured in precipitation (1984–1991) were taken as the input function. Combining modelling of isotopes and hydrological data enabled the quantification of preferential flow rates. The fraction of preferential flow directly appearing in the outflow within one week varied between 17 and 30%. The fraction of preferential flow was practically independent of the soil texture and flow rates. The crucial parameter influencing the fraction of direct flow was found to be the saturated hydraulic conductivity (Ks ). In the matrix flow, it was found that the apparent dispersion parameter (PD )* is indirectly proportional to the mean water content (). This relationship shows that the heterogeneity of the water flux in the matrix is higher for lower water contents. Finally, the transit time distribution functions, determined for both flow paths and the fractions of preferential flow, were used to construct vulnerability diagrams. Such a diagram gives the amounts of tracer mass (conservative pollutant), which appear weekly in the outflow between 0 and 60 weeks. The vulnerability diagrams showed different patterns for different soils, depending on the saturated conductivity and mean water content. Coarser material with low and high Ks showed a short mean transit time for the matrix flow (about 10 weeks) and mean preferential flow equal to or higher than 20%. Finer sand, with lower Ks and higher , resulted in mean transit times of approximately 30 weeks and preferential flow of 17–21%. These diagrams can be used to estimate the vulnerability of groundwater to pollution for different soil materials of the unsaturated zone.

Water content and other aspects of brittle versus normal fingernails

Previous authors have claimed that dehydration of the nail plate causes brittle nails. Some experts claim that normal nails contain 18% water, and brittle nails contain less than 16%. We sought to test the hypothesis that brittle nails contain 2% less water than normal nails. We also examined the relationship between a number of health and behavioral variables and brittle nails. In all, 102 participants with either brittle or normal nails had two nails clipped and then analyzed for water content by a blinded investigator in the laboratory. Participants filled out a detailed questionnaire designed to reveal information about health and behavior. The mean water content for normal nails was 11.90% and for brittle nails was 12.48%. There was no statistically significant difference between the two groups. The odds of having brittle nails was 3.23 times greater among participants who received a professional manicure (95% confidence interval 1.21, 8.59). The frequency of professional manicures was associated with the likelihood of having brittle nails. Frequency of hand moisturizer use was significantly associated with nail brittleness (95% confidence interval 1.35, 32.10). Family history was significantly associated with the likelihood of having brittle nails (95% confidence interval 1.65, 21.11). Analyzing nails from living participants is limiting because samples can only be collected from the distal unattached nail plate. A small subanalysis was performed and showed that the nails were losing water between the time of clipping and laboratory analysis. Therefore, our water percentage results may not be representative of in vivo nail plate water contents. There was no significant difference in water content of brittle compared with normal nails.

Germinação e armazenamento de sementes de Virola surinamensis (Rol.) Warb. (Myristicaceae)

Este trabalho teve como objetivo estudar a germinação e o armazenamento de sementes de Virola surinamensis (Rol.) Warb. em condições de laboratório, no Estado do Amapá, Brasil. Para tanto, frutos foram coletados na Reserva Particular de Patrimônio Natural, "Ekinox", localizada em Macapá. Sementes recém-colhidas do lote original apresentaram teor médio de água de 24% e baixo ganho de água durante a embebição. Devido às diferenças no tamanho e, ou, peso, as sementes colhidas foram divididas em dois grupos: grandes e pequenas. Independentemente do tamanho da semente, a maior porcentagem de germinação e o menor tempo médio de germinação ocorreram a 30 ºC. Sementes armazenadas por 30 dias em condição ambiente (27 ºC ± 3 e 75% ± 5 UR) e em germinador (20 ºC e 58% UR) apresentaram viabilidade abaixo de 2%, ressaltando-se o comportamento recalcitrante de sementes de Virola surinamensis.

Microbial growth on partially saturated rough surfaces: Simulations in idealized roughness networks

A new model is developed to study the effect of aqueous phase configuration on microbial growth on rough surfaces under different hydration conditions. Surface roughness is idealized using a network of conical pits (sites) on a regular lattice connected by v‐shaped channels (bonds) with prescribed geometry that vary spatially. Aqueous phase distribution and connectivity within the surface network are calculated as functions of water potential or relative humidity. Microbial growth on the rough surface network is simulated using a hybrid method coupling the reaction‐diffusion method for the nutrient field with the individual‐based model for microbial activity. The modeling platform links variations in hydration conditions within simple heterogeneous porous media (rough surfaces) with microbial growth rates and expansion patterns. The results demonstrate effects of geometry and spatial distribution of roughness elements on aqueous phase connectivity and on effective diffusion and, consequently, control of microbial growth under different water potentials. The key parameter affecting microbial growth is the effective aqueous diffusion coefficient, which, in turn, is controlled by mean water content of the bonds in the network.

Characteristics and Controlling Factors of Regional-scale Variability in Surface Soil Moisture within Semi-arid Grassland in Mongolia

In this study, we monitored the surface soil moisture at 15 locations within an area of 100 km × 100 km in the Mongolian steppe region. A principal component analysis was used to determine the characteristics and dominant patterns of spatiotemporal variations in the measured surface soil moisture. The results reveal that the predominant pattern of temporal variation is related to large-scale rainfall and that this was spatially uniform over the entire study area. In terms of both temporal and spatial patterns, the spatial heterogeneity of rainfall activity was a minor factor, accounting for less than 33% of the total observed variance. The most dominant pattern in the spatial distribution of surface soil moisture showed a correlation with the spatial distribution of the mean or minimum water content, and the minimum water content was largely equivalent to the wilting point, which is a soil-hydraulic index. Thus, we conclude that the most dominant pattern of surface soil moisture distribution over the study region is regulated by soil-hydraulic properties. Rainfall events acted to disturb or reset this pattern, but the pattern was re-established during drying of the soil.

Improved estimation of soil water retention characteristics from hydrostatic column experiments

The soil water retention characteristic, θ(h), is required for modeling and predicting water and solute transport in unsaturated porous media. Commonly, θ(h) is determined by relating pressure heads, h, to mean water contents, θ, that are measured in column experiments under hydrostatic equilibrium conditions and fitting a parametric retention function to these data pairs. Implicit to this method is the assumption that the mean water content of the column is equivalent to a point measurement in the column center. Dependent on the nonlinearity of the vertical water content distribution, θ(z), in the column, this assumption may be invalid and introduces a systematic error. A sensitivity analysis shows that the magnitude of the error caused by neglecting the nonlinearity of the water content distribution may reach several percent if coarse materials with low air entry values and tall soil columns are investigated. Furthermore, neglecting θ(z) yields a smoothed retention characteristic and thus may lead to wrong conclusions about the most appropriate parametric model for the water retention characteristic. If the hydraulic conductivity function K(h) is predicted from such an incorrect retention function, it can differ greatly from the true function. In this paper, we propose to consider the measured water content of a soil column explicitly as an integral of the equilibrium water content distribution with depth. We show that this eliminates systematic parameter estimation errors and leads to improved estimates of the soil water retention function.

Root Water Extraction and Limiting Soil Hydraulic Conditions Estimated by Numerical Simulation

Root density, soil hydraulic functions, and hydraulic head gradients play an important role in the determination of transpiration‐rate‐limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water extraction. The average soil water content at the moment root water potential dropped below a defined critical value was then estimated. The dependence of average water content at the onset of plant water stress on potential transpiration and root density was compared with an analytical solution for hydraulic conditions in the root sphere. The critical value was a function of potential transpiration rate, soil hydraulic properties, and root density. Matric flux potential appears to be a convenient hydraulic property to determine the onset of limiting hydraulic conditions, as numerical simulations showed that, at onset, matric flux potential vs. distance from the root surface is independent of soil type. This was also determined analytically under the constant‐rate assumption. Mean water content occurs at about 0.53 times the half‐distance between roots. This allows calculation of the mean limiting soil water content and pressure head from the matric flux potential at this distance, which is a function of transpiration rate and root density only. A nomogram was developed that—given the transpiration rate, the root density, and the soil hydraulic functions—allows determination of the values of mean water content and mean pressure head that occur at the onset of transpiration reduction.

Soil Profile Water Content Determination: Sensor Accuracy, Axial Response, Calibration, Temperature Dependence, and Precision

Although the neutron moisture meter (NMM) has served the need for accurate soil water content determinations well, increasing regulatory burdens, including the requirement that the NMM not be left unattended, limit the usefulness of the method. Newer methods, which respond to soil electromagnetic (EM) properties, typically allow data logging and unattended operation, but with uncertain precision, accuracy, and volume of sensitivity. In laboratory columns of three soils, we compared the Sentek EnviroSCAN and Diviner 2000 capacitance devices, the Delta‐T PR1/6 Profiler capacitance probe, the Trime T3 tube‐probe, all EM methods, with the NMM and conventional time domain reflectometry (TDR, also an EM method). All but conventional TDR can be used in access tubes. Measurements were made before, during, and after wetting to saturation in triplicate repacked columns of three soils ranging in total clay content from 17 to 48%. Each column was weighed continuously, and thermocouple determinations of temperature were made every 30 min throughout. All of the devices were sensitive to temperature except for the NMM, with conventional TDR being the least sensitive of the EM devices (sensitivity <∣0.0006∣ m3 m−3 C−1). The Trime T3 and Delta‐T PR1/6 devices were so sensitive to temperature (0.015 and 0.009 m3 m−3 °C−1, respectively, in saturated soil using soil‐specific calibration) as to be inappropriate for routine field determinations of soil profile water content. Temperature sensitivity was up to 12 times larger in saturated soils compared with values in air‐dry soils, corresponding to the much larger bulk electrical conductivities of these soils when saturated. All devices exhibited estimation precision better than 0.01 m3 m−3 under isothermal conditions. However, under nonisothermal conditions, estimation precision for the EM sensors worsened as the number of measurements (and time involved in taking readings) increased, and as the soils became wetter, resulting in precision values >0.01 m3 m−3 for the Trime and Delta‐T devices. Accuracy of the devices was judged by the root mean squared difference (RMSD) between column mean water contents determined by mass balance and those determined by the devices using factory calibrations. Smaller values of the RMSD metric indicated more accurate factory calibration. The Delta‐T system was least accurate, with an RMSD of 1.299 m3 m−3 at saturation. At saturation, the Diviner, EnviroSCAN, NMM, and Trime devices all exhibited RMSD values >0.05 m3 m−3, while TDR exhibited RMSD <0.03 m3 m−3 Soil‐specific calibrations determined in this study resulted in RMSE of regression values (an indicator of calibration accuracy) ranging from 0.010 to 0.058 m3 m−3 All of the devices would require separate calibrations for different soil horizons. Of the EM devices, only the Delta‐T PR1/6 exhibited axial sensitivity appreciably larger than the axial height of the sensor, indicating small measurement volumes generally, and suggesting that these systems may be susceptible to small‐scale variations in soil water content (at scales smaller than the representative elemental volume for water content) and to soil disturbance close to the access tube caused during installation.

SEASONAL CHANGES IN DRY MASS AND ENERGETIC CONTENT OF MUNIDA SUBRUGOSA (CRUSTACEA: DECAPODA) IN THE BEAGLE CHANNEL, ARGENTINA

Abstract Munida subrugosa is the most abundant benthic species in the Beagle Channel (55°S, 68°W), Tierra del Fuego. Moreover, this species has two simultaneous but different feeding habits: predator and deposit feeder. Because of its high abundance (100 ind·100 m−2) and trophic position, this species plays a key role in the subantarctic benthic ecosystems. However, little is known about its energetic content and changes in dry mass during its reproductive cycle. Samples of M. subrugosa were obtained in 2000 to 2001 by means of an epibenthic trawl. The relative water content (WC) and the energetic content (EC) (kJ·g−1 ash free dry mass [AFDM]) of whole adult animals, and the relative dry mass (RDM) and EC of tissues and organs of females were measured throughout one year. The EC investment of adults at the time of maximum gonadal development was evaluated. The EC was measured using a bomb calorimeter. The mean WC and EC for M. subrugosa was 59% ± 7% and 19 ± 2 kJ·g−1 AFDM, respectively. WC and EC for whol...

Effect of Planting Density on Grain Yield and Water Productivity of Rice (Oryza sativa L.) Grown in Flooded and Non-flooded Fields in Japan

The effect of planting density on grain yield and water productivity was evaluated in rice (Oryza sativa L.) grown in non-flooded lowland fields in Japan in comparison with flooded fields. One rice cultivar, IR24 was grown both in flooded and non-flooded lowland fields in 2001 and 2002, and only in flooded field in 2003, with different planting densities ranging from 5.6 to 44 hills m-2. Another rice cultivar, Dontokoi was also grown in 2001. Straw mulching treatment was added in non-flooded field in 2002. In non-flooded fields, standing water disappeared from 36 and 8 days after transplanting until maturity in 2001 and 2002, respectively, the mean water content of surface soil during non-flooded period was 72 % g g-1 on a dry basis and 63 % v v-1. Grain yield in flooded fields (637 g m-2; average of 2001 and 2002) was higher than that in non-flooded fields (467 g m-2; average of 2001 and 2002), due to larger spikelet number per panicle in both years, larger 1000 grain weight in 2001, and higher percentage of ripened grains in 2002. Straw mulching tended to increase sink size but reduced percentage of ripened grains, resulting in no yield advantage in 2002. Water productivity in non-flooded fields (0.34 kg m-3; average of 2001 and 2002) was significantly higher than that in flooded fields (0.14 kg m-3). Grain yield increased with higher planting density in flooded fields in 2001 and 2003. In non-flooded fields, however, the effects of planting density on grain yield were little or marginal in both cultivars, due to the trade-off relationship between panicle number and spikelet number per panicle. This study showed that higher planting density would result in higher grain yield in favourable flooded fields, but is not advantageous for higher grain yield under non-flooded lowland fields in Japan in improved cultivars with relatively high tillering and yielding abilities.

Time Domain Reflectometry Laboratory Calibration in Travel Time, Bulk Electrical Conductivity, and Effective Frequency

Accurate soil water content measurements to considerable depth are required for investigations of crop water use, water use efficiency, irrigation efficiency, and the hydraulic properties of soils. Although the soil moisture neutron probe has served this need well, it cannot be used unattended. Newer methods, which respond to the electrical properties of soils, typically allow data logging and unattended operation, but with uncertain precision, accuracy, and volume of sensitivity. In laboratory columns of three soils, we calibrated a conventional time domain reflectometry (TDR) system for use as a reference system for a companion study of water content sensors that are used in access tubes. Measurements were made before, during, and after wetting to saturation in triplicate repacked columns of three soils: (i) a silty clay loam (30% clay, 53% silt), (ii) a clay (48% clay, 39% silt), and (iii) a calcic clay loam (35% clay, 40% silt) containing 50% CaCO3. Each 75‐cm‐deep, 55‐cm‐diameter column was weighed continuously to 50‐g precision on a platform scale. Conventional TDR measurements of water content and thermocouple measurements of temperature were made at eight depths in each column every 30 min. Accuracy of the TDR system was judged by the root mean squared difference (RMSD) between column mean water contents determined by mass balance and those determined using the Topp equation as a standard calibration. Smaller values of the RMSD metric indicated more accurate standard calibration. Although the TDR system exhibited RMSD <0.03 m3 m−3 using the Topp equation, there were differences in accuracy between the three soils, and there was some temperature dependency at the saturated end, although not at the dry end. This paralleled the temperature dependency of the soil bulk electrical conductivity (BEC). Incorporation of bulk electrical conductivity and effective frequency of the TDR measurement into the calibration model reduced the calibration RMSE to <0.01 m3 m−3 and practically eliminated temperature effects. Because the temperature effects on the TDR measurement are embedded in the BEC and effective frequency, a measurement of temperature is not needed to apply the calibration to these soils.

Water content and porosity estimated from ground-penetrating radar and resistivity

Both ground-penetrating radar and the resistivity method have proven to be useful tools for exploring water content variations, since related parameters such as dielectric constant and the resistivity of rocks and sediments are highly dependent on moisture content. These methods were used independently to estimate volumetric water content in the unsaturated zone and porosity in the saturated zone in a 100-m sandy section. Two sample sites along the profile were also chosen for a shallow geophysical investigation and soil sampling, to enable the calibration and verification of the indirect geophysical methods. The grain distribution at these sites is dominated by medium-sized sand (0.25–0.5 mm). The water content was 6.9 vol.% and calculated porosities are 37% and 40% respectively. At each of these sites the mean water content values calculated from resistivity are within one percentage unit of measured water content while those calculated from ground-penetrating radar give higher values by as much as 2.9 percentage units. The water contents in the unsaturated zone in the section, estimated from resistivity and ground-penetrating radar, show very similar trends, although that deduced from ground-penetrating radar is generally somewhat larger, consistent with the results from the sample sites. The mean porosity values obtained from the two methods in the saturated zone are in good agreement.

Changes in water content of high plus hydrogel lenses worn on an extended wear basis in a geriatric aphakic population

Purpose: To investigate the water content of hydrogel lenses of relatively high plus power hydrogel lenses after 3 months extended wear and compare values with unused lenses. Method: Geriatric aphakic extended wear soft lens patients were fitted with one of four different brands of hydrogel lenses (A) Incanto 78 (Cantor and Nissel, UK), (B) PSL72 (Prospect lenses, UK), (C) ES70 (Ocular Sciences), (D) Proclear (Coopervision). After 3 months continuous wear the lens was removed and water content (WC) was determined at both lens surfaces using an Abbé refractometer. The water content was also measured for 40 unused lenses (+10 to +20 D, 10 lenses per brand). Results: One hundred and thirty-two lenses were checked after 3 months extended wear. Mean (±S.D.) WC values for front (f) and back (b) surfaces of worn and unworn lenses were, respectively, (A) Worn ( n = 45): f 73.2(4.13) b 73.8(4.33); unworn f 80.5(0.68) b 81.1 (0.80). (B) Worn ( n = 37); f 70.5(4.49) b 70.9 (3.89); unworn f 72.5(0.94) b 72.3 (0.89). (C) Worn ( n = 34); f 68.3(3.18) b 68.4(3.63); unworn f 70.6 (0.48) b 71.1 (0.55). (D) Worn ( n = 16); f 63.4(3.68) b 63.3(3.19); unworn f 60.9 (1.56) b 61.5 (1.92). There was a significant correlation between WC measured from front and back surfaces ( p < 0.01). In worn A–C lenses, front surface WC tended to be lower than back surface WC. For lenses A and C at both surfaces the WC of worn lenses was significantly lower than unworn lenses ( p < 0.05). For lens D, mean WC of worn lenses was significantly higher than unworn lenses ( p < 0.05). In 80% of B lenses, surface WC of worn lenses were significantly lower than WC of unworn lenses ( p < 0.05). There was no relationship between WC and lens power. Conclusion: On average, A and C lenses tended to desiccate but D lenses tended to swell as did 20% of B lenses. The front surface of worn lenses measured lower water content than the back surface suggesting the front surface is drier than the back. This apparent difference in water content between the surfaces could be an artefact emanating from differential rates of surface deposition.

Extraction of meat juices for isotopic analysis

So far no standard procedure exists to obtain water of meat for isotopic 18O/ 16O-water analysis. Fast extraction via heating the tissues is possible when considering certain boundary conditions. A specially designed vessel was tested with water and was then used for meat juice extraction. The reproducibility ( σ) of δ 18O-values was 0.12‰. Meat samples of six different species were analysed. Water of pork samples was extracted after open storage. Here, decreases in meat weight correspond to decreases in extract yield and to an increase in the 18O/ 16O-ratio. The mean water contents in extracts was almost constant [93.2 ± 0.05 wt% ( p > 0.05)]. The technique offers an opportunity to develop an automatic, mobile extraction device and to obtain extracts with no further influences on their quality. This method could also be useful for the determination of meat quality attributes as cooking loss or drip without evaporative losses.

Effects of different drying rates on the physiological quality of Coffea canephora Pierre seeds

Desiccation tolerance in seeds depends on the species, development stage and drying conditions, especially the water removal rate. Coffea seeds are considered of intermediate performance, because they tolerate relative dehydration compared to orthodox seeds and are sensitive to low temperatures. The objective of this study was to verify the effect of different drying rates on the viability and storability of Coffea canephora seeds. A complete randomized experimental design was used, in a factorial 3 x 5 x 2 design, with three drying rates (fast, intermediate and slow), five final mean water contents after drying (51, 42, 33, 22 and 15 %) and two storage temperatures (10 and 20°C). The germination and seed vigor assessments, using radicle protrusion, cotyledon leaf opening, seedling emergence and emergence speed index, were performed shortly after drying and after two and four months storage. It was observed that with reduction in the water content there was reduction in the germination values and seed vigor, for all the drying rates. The greatest reductions in physiological quality occurred when the seeds were dried quickly and the best results were obtained at the intermediate drying rate. There was an effect of drying rate and storage temperature on the physiological quality of the seeds, and lower germination and vigor values were observed in seeds with lower water content stored at 20°C. C. canephora seeds were tolerant to desiccation down to 15 % water content and can be stored for four months at 10°C. A temperature of 20ºC can be used to store C. canephora seeds, as long as the water content is not reduced to values below 22 % water content.

Effects of Carex rostrata on soil oxygen in relation to soil moisture

Many wetland plants are faced with severe edaphic problems. Long term flooding effects a sequence of chemical processes that result in soil anoxia and production of several phytotoxic compounds. In order to maintain an aerobic root respiration wetland plants produce aerenchyms that enable oxygen conduction through the plant body to underground organs. Moreover wetland plants are able to release oxygen into the soil. This aeration effect of wetland plants in turn can influence soil chemistry considerably and protects roots by an aerobic rhizosphere. Oxygen release by underground organs of aerenchymous plants has been well documented in laboratory investigations but not under field conditions. In this study, dynamics of oxygen saturation were measured together with soil water content and microclimatic parameters. Measurements were carried out on some lowland peat covered by Carex rostrata Stokes from July to October 2001. Oxygen saturation was quantified using novel optical sensors (microoptrodes). The presence of C. rostrata significantly increased oxygen content in the soil. Mean oxygen saturation under Carex rostrata (56.0%) was significantly higher than in a control plot without vegetation (26.6%). Due to fluctuating water content, oxygen saturation in both plots was characterized by pronounced time variation. Increasing soil water content caused an extreme decline of oxygen saturation in both plots and led to anoxia in the control plot. In the presence of C.rostrata, the decline in soil oxygen took place at significantly higher water content (68.5% compared to 67.5% in the control plot) which is substantial as the mean water contents varied between 67 and 69% during the measurement period.