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981.
The aroma compounds in broccoli stored in different modified atmospheres were studied. The packaging materials used were oriented polypropylene (OPP), poly(vinyl chloride) (PVC), and low-density polyethylene (LDPE) containing an ethylene-absorbing sachet. All samples were stored for either 1 week at a constant temperature of 10 degrees C or for 3 days at 4 degrees C, followed by 4 days at 10 degrees C. The atmospheres that developed inside the packaging materials differed significantly. The broccoli samples were analyzed raw and after cooking, with regard to volatile compounds, using gas-phase (headspace) extraction followed by gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), hexanal, 3-cis-hexen-1-ol, nonanal, ethanol, and a group of thiocyanates were selected for a detailed study because these compounds cause off-odor and can be used as indicators of stress. Significant differences were found in the aroma profiles of the broccoli samples relative to the packaging materials used for storage. Storage in OPP (14% O(2), 10.5% CO(2)) resulted in most of the off-odors, while storage in LDPE (6% O(2), 7% CO(2)) and PVC (17.9% O(2), 4% CO(2)) was found to maintain the concentration of DMS, DMDS, and DMTS during storage. Heat treatment of the broccoli increased the content of aroma compounds as well as the number of compounds containing sulfur. 相似文献
982.
983.
Spatial distribution of soil nematode populations in Antarctic terrestrial ecosystems is tightly controlled by environmental factors and thus highly sensitive to changes in soil properties. Increases in the magnitude and frequency of episodic warming events as well as eventual warming trends are likely to result in increased water availability due to glacial melting and permafrost thaw, and may also incite changes in soil physical and chemical characteristics that determine nematode habitat suitability. We hypothesized that climate warming would result in new suitable soil habitats leading to heightened diversity and activity in nematode communities. In order to test this hypothesis, we compared nematode populations in patches of soil wetted by naturally enhanced permafrost thaw versus adjacent soils unaffected by thaw. We found that thaw sites had significantly lower nematode abundances and living to dead ratios, contradicting our hypothesis. We also observed significantly altered soil texture (finer particle size), lower pH and higher salinity in permafrost seeps. These observations suggest that current and future changes in climate may alter soil properties and result in significant changes in nematode population structure, distribution and function. 相似文献
984.
Henrik Bak Topbjerg Kacper Piotr Kaminski Kirsten Kørup Kåre Lehmann Nielsen Hanne Grethe Kirk Mathias Neumann Andersen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(5):400-411
A drought screening experiment focusing on intrinsic water use efficiency (WUEi) was carried out among 132 clones belonging to a dihaploid potato mapping population. The clones were exposed to progressive soil drying during a five-day period in a greenhouse pot experiment. Analysis of the underlying variables was done based on a multivariate data analysis strategy. The strategy successfully divided the clones into WUEi performance categories. Differences between clonal WUEi responses were traced back to differences in the net photosynthetic rate. Stomatal conductance (gs) did not vary significantly between the clones. Leaf abscisic acid (ABA) concentration and leaf water potential were found to reflect known isohydric behaviour for potato, and a non-linear relationship could be established for gs and leaf ABA concentration across the WUEi groups. Similarly, a common non-linear relationship between leaf ABA concentration and soil water potential was found. The latter findings suggest that the investigated population did not harbour significant genetic variation as to ABA production as function of soil desiccation level or with respect to the sensitivity of stomatal aperture vis-à-vis leaf ABA concentration and soil water potential. 相似文献
985.
R. Markfoged L. P. Nielsen T. Nyord L. D. M. Ottosen N. P. Revsbech 《European Journal of Soil Science》2011,62(4):541-550
Emission of nitrous oxide (N2O) from soils is the net result of N2O‐producing and consuming processes within the soil, and studying the regulation of these processes in the real soil environment is essential to the understanding of the factors governing N2O emission. In this study, microscale distributions of O2 and N2O in the soil were investigated to describe how N2O production within, and emission from, soils are regulated by anoxic volumes created by injection of liquid manure. An application device simulating field injection methodology was developed and liquid pig manure was injected at a depth of 5 cm into boxes containing soil. Microsensors with <0.12 mm tip diameter were used to measure high‐resolution vertical N2O and O2 concentration profiles though the centre of the horizontally positioned soil‐manure core and up to 4 cm laterally away from the centre. Both microsensor measurements and N2O emission rate determinations, with a closed chamber, were performed daily. Injected manure filled the original air‐filled pore space of a 6‐cm‐wide cylindrical core and created anoxia. Nitrous oxide was detected in the anoxic part of the core, indicating N2O production by denitrification in the entire anoxic volume. Although anoxia was present in the core during all 3 days of the experiment, a peak rate of net N2O production was detected after 1 day, with a maximum N2O accumulation of 500–700 Pa in the core. Comparison of the cumulated N2O net production and emission revealed a delay of N2O emission, as N2O was trapped inside the saturated core. 相似文献
986.
E. W. Bruun C. T. Petersen E. Hansen J. K. Holm H. Hauggaard‐Nielsen 《Soil Use and Management》2014,30(1):109-118
Crop yields and yield potentials on Danish coarse sandy soils are strongly limited due to restricted root growth and poor water and nutrient retention. We investigated if biochar amendment to subsoil can improve root development in barley and significantly increase soil water retention. Spring barley (Hordeum vulgare cv. Anakin) was grown in soil columns (diameter: 30 cm) prepared with 25 cm topsoil, 75 cm biochar‐amended subsoil, and 30 cm un‐amended subsoil lowermost placed on an impervious surface. Low‐temperature gasification straw‐biochar (at 0, 0.50, 1.0, 2.0, and 4.0 wt%) and slow pyrolysis hardwood‐biochar (at 2 wt%) were investigated. One wt% can be scaled up to 102 Mg/ha of char. After full irrigation and drainage, the in‐situ moisture content at 30‐80 cm depth increased linearly (R2 = 0.99) with straw‐biochar content at a rate corresponding to 0.029 m3/m3/%. The lab determined wilting point also increased linearly with char content (R2 = 0.99) but at a much lower rate (0.003 m3/m3/%). Biochar at concentrations up to 2% significantly increased the density of roots in the 40–80 cm depth interval. Addition of 1% straw‐biochar had the most positive effect on root penetration resulting in the highest average root density (54% coverage compared to 33% without biochar). This treatment also resulted in the greatest spring barley grain yield increase (22%). Improving the quality of sandy subsoils has global potentials, and incorporation of the right amount of correctly treated residues from bioenergy technologies such as straw‐biochar is a promising option. 相似文献
987.
988.
989.
To suit the purpose of composting, an optimal control of the composting process will be advantageous. Modeling may be useful for predicting how a composting process will proceed, both for the purpose of dimensioning a process plant and for planning the process runs. It may also be applicable for process control. If an applicable mathematic model can be created from a reasonably simple theoretic basis, it may have advantages compared to an empirical model. An equation for the temperature dependency of decomposition rate is proposed for modeling thermophilic composting processes. The equation is derived from a simple chemical model, including enzyme activity applying the Arrhenius equation. 相似文献
990.
Jane E. Kelly Jane C. Quinn Sharon G. Nielsen Paul Weston John C. Broster Leslie A. Weston 《Weed Research》2020,60(3):221-231
Hordeum spp. (barley grass) and Bromus spp. (brome grass) are annual weed species that achieve long-distance seed dispersal via attachment to sheep, but also lead to sheep carcass damage due to the penetration of seeds into animal tissues. Range expansion of invasive weed populations predicted as a consequence of climate change may be associated with an increase in seed contamination incidence globally. An examination of Australian abattoir data (2006–2012), along with recent weed distribution patterns, indicates carcass contamination was associated with rainfall and abundance of key annual grass weeds, primarily Bromus spp. and Hordeum spp., although other factors may play a contributing role. Significant differences in seed contamination in slaughtered sheep were noted between states and regions, with widespread contamination occurring throughout all agro-ecological zones. Abattoir, sheep age and sex significantly influenced incidence, with contamination highest in adult males. Incidence increased with mean monthly rainfall, but declined with mean elevation, and significant interactions were noted between mean monthly temperature and state, and between mean elevation and year. Results show the need for vigilant recording of seed injuries in sheep to enhance weed surveillance efforts and effective integrated weed management of contributing annual grass weeds. 相似文献