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为了解冬季土壤干旱对紫花苜蓿(Medicago sativa L.)越冬的影响,本研究在实验室内通过控温和更换表土试验模拟低温干旱环境,结合抗冷冻测试、细胞损伤、根颈组织含水量和渗透调节物质变化等,研究低温干旱环境对‘WL440HQ’和‘肇东’苜蓿根颈耐寒性的影响及原因。研究结果表明:低温干旱环境降低苜蓿根颈的耐寒性;与‘肇东’苜蓿相比,低温干旱环境下‘WL440HQ’苜蓿根颈具有较低的耐寒性,根颈组织含有较少的可溶性糖和较高的失水速率,细胞受到不可逆损伤,细胞液相对渗透率超过50%;在低温干旱环境下,根颈内的脯氨酸和可溶性蛋白含量在2个苜蓿品种间差异显著,2种物质可能与‘肇东’苜蓿在低温环境下耐寒性更强有关。综上,为提高苜蓿的越冬能力,建议除在初冬季节灌冻水外,冬季还应适时补水。 相似文献
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The microalgae Chaetoceros sp. and Phaeodactylum tricornutum were grown in semicontinuous 15 1 cultures, a volume commonly used for mid-scale inocula in aquacultural practices. The daily yields were concentrated and stored by freezing and freeze-drying for up to 1 month. After slow or fast freezing without the protective agents glycerol or Me2SO, neither of the microalgae was capable of active growth, while with the cryoprotectants slow freezing gave good results after 7 days of storage at −20°C. After 15 and 30 days, however, microalgae growth was poor, probably due to bacterial contamination. Freeze-drying gave even worse results, which we attribute to severe losses of storage products after this treatment. 相似文献
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分析了微波真空冷冻干燥中容易出现的干燥不均匀、微波泄漏、制冷量不足、真空系统的抽真空能力不足以及整个系统的安全操作问题等典型的理论、工艺和设备问题,并提出了解决这些问题相应的设计、工艺、合理的操作规程等基本技术方法和手段。为改进和优化微波真空冷冻干燥工艺和设备提供了依据。 相似文献
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Filip Coppens Gonzague Alavoine Olivier Delfosse Sylvie Recous 《Soil biology & biochemistry》2009,41(6):1335-1337
Lyophilisation of K2SO4 soil extracts has been proposed as a sample preparation technique before elemental analysis of carbon or nitrogen. However, previous measurements, based on wet oxidation or catalytic combustion, indicated that C measurements in lyophilised samples not always proved to be accurate. To determine whether the C analysis was affected by the lyophilisation process, an exploratory study was conducted to investigate the potential effects of the sample pre-treatment and of the lyophilisation process itself. This paper puts forward that the use of soil extracts, previously stored at −20 °C, may affect the recovery of salt in the samples and that contamination of the soluble carbon with exogenous C during lyophilisation is feasible. Therefore we recommend to use freshly prepared soil extracts for lyophilisation and always to include an internal standard among the unknown samples to account for a possible contamination. 相似文献
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保加利亚乳杆菌优良菌种的筛选 总被引:1,自引:0,他引:1
[目的]筛选保加利亚乳杆菌优良菌种。[方法]对选出的5株菌(ADR、S-1、SY、TX-B、MS2)在液体MRS中培养时的生长特性、OD值和pH值和对数生长末期的活菌数进行比较,以TX-B活菌数最高,确定TX-B为后续发酵试验的目标菌株,将其与现有的优良的球菌进行优化搭配,组成发酵剂,通过鲜奶发酵试验,选育出可生产优质酸奶的乳酸菌种(株)。[结果]TX-B杆菌在42℃的脱脂乳中培养,其生长速率和产酸速率均很快,发酵3 h可凝乳,凝乳时的活菌数和酸度值分别达到7.35×108cfu/m l和94.3°T,发酵10 h,活菌数最高,达1.36×109cfu/m l。TX-B与球菌搭配,通过鲜奶发酵试验及后酸化特性的检测,制得的产品具有酸奶特有的香气,酸甜适宜。[结论]TX-B杆菌是制备酸奶的优良菌种。 相似文献
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介绍了微生物冷冻干燥保藏方法的原理,探讨了影响微生物冷冻干燥保藏的因素,并就冻干微生物样品存在的问题提出了解决措施,以期为提高微生物冷冻干燥保藏技术提供参考。 相似文献
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A new method for the measurement of microbial biomass C by direct extraction of freeze-dried soil with either 0.5M K2SO4 or 0.5M NaHCO3 was evaluated. The underlying principle of the method is that rehydrating a freeze-dried soil releases cytoplasmic organic
compounds from desiccated and disrupted microbial cells. Nineteen soils under various management regimes were sampled to test
the proposed method, in which each soil sample was split into two subsamples. One subsample was kept in the field-moist condition
at 4°C. The other subsample was brought to 100% water-holding capacity and frozen at –20°C for 24h. The frozen soil was then
freezedried. Both subsamples were extracted with 0.5M K2SO4 or 0.5M NaHCO3 at a soil-to-extractant ratio of 1-to-4 (w/v) and organic C determined in the extract (CK2
SO4 or CNaHCO3). The net freeze-dry stimulated increase in extracted C was correlated (r
2=0.98 for CK2
SO4 or 0.93 for <$>\rm C_{NaHCO_3})<$> more closely with microbial biomass C (CMB) measured as net evolution of CO2–C by chloroform fumigation incubation (CFI) than with total C (r
2=0.42 for CK2
SO4 or 0.47 for CNaHCO3). Based on linear regression equations, extraction efficiency coefficients (K
EC) were used to calculate CMB from CK2
SO4 or CNaHCO3 as follows:
CMB=CK2
SO4/0.152±0.004
CMB=CNaHCO3/0.257±0.01
The relationship between the CMB and the flushes of C extracted after rehydration of freeze-dried soil showed that the K
EC values were more consistent for CK2
SO4 than CNaHCO3. The freeze-dried soil extraction was a fast, precise, reliable and safe method for measuring microbial biomass C in soil.
Received: 27 May 1996 相似文献
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