用谷朊粉溶涨指数法测定谷朊粉品质

开发了一种新的谷朊粉品质检测方法。对小麦谷蛋白溶涨指数法的参数进行调整，在9种不同离心力条件下，测定从16个小麦品种中分离出的谷朊粉的溶涨指数，根据谷朊粉溶涨指数、面筋吸水率及面粉的蛋白质组分含量之间的关系，提出了用谷朊粉溶涨指数法测定谷朊粉品质的步骤及评价标准。结果认为：加入0.9 mL蒸馏水水化10 min，再加入0.9 mL 0.3%十二烷基磺酸钠(SDS)－乳酸溶液混合30 min，最后用5000×g离心力进行离心是谷朊粉品质测定的最佳技术参数，在此条件下的谷朊粉溶涨指数与面筋吸水率、小麦谷蛋白溶涨指数呈显著正相关(r＝0.541，0.547；P<0.05)，与面筋指数、不溶性谷蛋白含量呈极显著正相关(r＝0.608，0.589；P<0.01)，与单体蛋白含量呈显著负相关(r＝-0.573；P<0.05)。与测定谷朊粉品质的国家标准方法吸水率法相比，谷朊粉溶涨指数法能快速、稳定地反应小麦谷朊粉品质差异。     

沙蒿籽粉和谷朊粉对燕麦全粉食品加工品质的影响

为了探讨全燕麦粉面包、馒头加工品质及燕麦粉冷冻面团品质特性，以燕麦全粉为原料，研究了添加沙蒿籽和谷朊粉对燕麦全粉食品(含冷冻面团食品)加工品质改良效果。试验结果表明，谷朊粉对面包制作影响较大；沙蒿籽粉对馒头制作影响较大；沙蒿籽粉和谷朊粉共同使用的效果优于两者单独使用；加入2.5%沙蒿籽粉和8%谷朊粉对燕麦全粉面包和馒头品质改善效果最好。对冷冻面团加工而言，随着冷冻时间的延长面团品质不断下降，冻藏4 d后燕麦全粉冷冻面团面包、馒头品质显著降低。     

挤压温度对大豆分离蛋白与原花青素复合物结构和功能特性的影响

为了探究不同挤压温度（40、60、80、100和120℃）对大豆分离蛋白（Soy Isolate Protein,SPI）与葡萄籽原花青素（Grape Seed Proanthocyanidin Extract,GSPE）复合物功能性质及结构特性的影响。该研究以溶解度、乳化性、乳化稳定性、ζ-电位、粒度为指标,利用荧光光谱、红外光谱分析该复合体系中大豆分离蛋白功能性质及结构的变化。结果表明：相较于挤压SPI,经过挤压处理的SPI-GSPE复合物的溶解度、乳化活性指数、乳化稳定性指数、ζ-电位绝对值及持水性均显著提高（P<0.05）,其表面疏水性、持油性显著下降（P<0.05）。随着挤压温度的升高,SPI-GSPE复合物的溶解度、持油性及乳化活性均先增大后减小且在80℃达到最大值,而其表面疏水性先减小后增大且最小值在80℃,ζ-电位绝对值、乳化稳定性及持水性均随温度的升高而降低。粒径分析结果表明,挤压处理后SPI与GSPE形成了更加致密的复合物;荧光光谱及红外光谱结果表明,与GSPE的复合及挤压处理使SPI氨基酸残基所处微环境发生变化,蛋白结构发生变化。以上结果表明挤压温度为...     

不同热处理大豆分离蛋白凝胶冻藏特性

为探究冻藏过程中不同加热温度处理大豆分离蛋白(soybean isolate protein,SPI)凝胶特性变化及评估不同热处理对SPI凝胶冻藏特性的影响。该文以65、90和135℃3个不同温度处理所得SPI为研究对象(分别记为65SPI、90SPI和USPI),采用离心法、质构分析法、可溶蛋白含量测定和电泳等方法对其冻藏过程中的凝胶持水性、凝胶硬度、凝胶弹性、可溶蛋白含量及亚基组成和凝胶作用力进行了分析研究。结果表明:随冻藏时间延长,不同温度处理SPI凝胶持水性、凝胶弹性和凝胶可溶蛋白含量呈下降趋势,而凝胶硬度呈增大趋势。凝胶持水性、弹性的下降和凝胶硬度的升高标志着凝胶品质的劣变。不同温度处理对SPI凝胶的冻前凝胶特性和冻藏特性有较大影响,65和90℃的温度处理降低了冻前SPI凝胶的持水性,增强了冻前SPI凝胶硬度,有更多的β和B亚基参与了凝胶形成,冻藏前后的亚基组成没有变化;超高温瞬时加热(ultra high temperature,UHT)处理则降低了冻前SPI凝胶硬度,冻藏过程中可溶蛋白含量大幅下降且可溶蛋白中β和B亚基含量下降。3种温度处理SPI的凝胶劣变程度均高于未处理SPI。加热处理会造成SPI发生部分或完全变性,变性后疏水基团的暴露会加快蛋白凝胶形成过程中聚集速率,进而增大粗糙凝胶结构形成的几率,而粗糙凝胶网络在冻藏过程中其劣变程度更甚于未加热SPI。由此可知,加热处理尽管在一定程度上增大了凝胶硬度,但会加速其凝胶品质冻藏劣变。     

高压均质对油脂预乳化大豆拉丝蛋白素食香肠质构特性的影响

为了将预乳化工艺更好应用于大豆拉丝蛋白（Textured Fibril Soy Protein，TFSP）素食香肠的加工，该研究通过采用不同的蛋白乳化剂和调控均质条件，探究预乳化油脂对TFSP素食香肠流变特性、质构和微观结构的影响。结果发现随着均质压力从0增大到30 MPa，大豆分离蛋白（Soybean Protein Isolate，SPI）乳液和酪蛋白酸钠（Sodium Caseinate，SC）乳液的表观黏度都逐渐增大，SPI乳液粒径为24.80～0.39 μm，SC乳液粒径为12.37～0.12 μm。对TFSP素肉糜进行温度扫描和频率扫描结果发现，所有的素肉糜在蒸煮后都形成了具有黏弹性的乳液凝胶，并且预乳液的均质压力越大，素肉糜的弹性模量越大。沃-布剪切测试和质构特性（Texture Profile Analysis，TPA）测试发现，TFSP素食香肠的剪切力和TPA质构特性都随着预乳液均质压力的增大而增大。采用激光共聚焦显微镜观察分析了不同预乳液和TFSP素食香肠的微观结构，当预乳化的均质压力为0～20 MPa时，SC乳液制备的TFSP素食香肠在蒸煮后发生了明显的乳液滴聚结；然而SPI乳液制备的TFSP素食香肠在蒸煮后表现出对抗乳液滴聚结的能力强。因此，采用SPI对植物油脂进行预乳化过程中，均质压力为20 MPa时，可以有效提升TFSP素食香肠的切片性和质构特性，研究结果为油脂预乳化工艺在素食产品中的开发和应用提供参考。     

适宜物理-酶联合改性提高酸性条件下大豆分离蛋白乳化性

为提高酸性条件下大豆分离蛋白（soy protein isolates,SPI）的乳化性能,该文研究了物理-酶联合改性对SPI（pH值为4）的乳化性能影响,通过对比确定了物理-酶联合改性,即超声波-酶复合改性和挤压膨化-酶复合改性两种改性方法在酸性条件下的乳化性能效果最好;并通过对改性后 SPI（pH 值为4）进行溶解性、游离巯基、二硫键、粒径、扫描电镜（scanning electron microscope,SEM）和激光共焦扫描显微镜（confocal laser scanning microscopy,CLSM）分析,从蛋白结构变化上进一步揭示了乳化性能提高现象的原因。结果表明：超声波联合植酸酶-酸性蛋白酶改性的 SPI （Uphy-aci-SPI）的乳化活性（emulsifying activity index,EAI）为0.53 m2/g,比未改性SPI（0.18 m2/g）显著提高了196%（P<0.05）,乳化稳定性（emulsifying stability index,ESI）为17 min,比未改性SPI（13.5 min）显著提高了25.9%（P<0.05）;挤压膨化联合菠萝蛋白酶改性的SPI（Ebro-SPI）的EAI为0.46 m2/g,比未改性SPI显著增加了155%（P<0.05）,ESI为17 min,比未改性SPI显著增加了25.9%（P<0.05）。在pH值为4的条件下对物理-酶联合改性的SPI的性质分析发现,物理-酶联合改性的SPI与未改性SPI相比,物理-酶联合改性的SPI的溶解性显著增加（P<0.05）;物理-酶联合改性的SPI的乳状液平均粒径减小,CLSM观察乳状液中油与蛋白溶液稳定共融,改善了油滴之间的空间排斥力。物理-酶联合改性的SPI游离巯基的含量显著增加（P<0.05）,二硫键含量显著降低（P<0.05）。SEM观察物理-酶联合改性的SPI为结构松散、破碎均一的微观结构。由此可见,乳化性能的提高是通过深层改变蛋白的结构来实现的。该研究可为探索提高酸性条件下SPI的乳化性能的方法提供理论依据。     

油脂预乳化提高大豆拉丝蛋白素食香肠品质

为了提高大豆拉丝蛋白(Textured Fibril Soy Protein,TFSP)素食香肠的品质,该研究将油脂预乳化工艺应用于TFSP素食香肠的加工,利用响应面试验设计优化了预乳化工艺条件,采用质构分析仪测定分析了产品的质构特性,并进行了感官评价。结果表明优化后的最佳预乳化工艺条件为菜籽油含量445g/L、大豆分离蛋白浓度105g/L、乳化机剪切速率9.0×103r/min。与对照组相比,此条件下制作的预乳化-TFSP素食香肠的凝胶强度、硬度和咀嚼性分别提高了约1倍、10%和26%,且产品口感鲜嫩、富有汁液感,感官评价得分显著提高。采用激光共聚焦显微镜观察分析了不同工艺制作的TFSP素食香肠在煮制前后微观结构的变化,结果发现油脂预乳化工艺可大大提高乳化油脂的稳定性和在香肠凝胶基质中的均匀分布,从而使乳化油脂的‘填充作用’得以发挥,不仅增强了TFSP素食香肠的保水保油能力,降低了蒸煮损失率,而且对香肠的质构和感官特性产生了重要影响。因此油脂预乳化工艺是一种辅助提高素食香肠整体品质行之有效的方法。     

大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响

针对速溶豆腐花粉的制备工艺中需要对大豆进行热处理,热处理过程中大豆蛋白的热变性程度对豆腐花粉凝结的凝胶强度与凝结所需的时间具有显著影响,而现在速溶豆腐花粉的工业生产中还没有对豆浆热处理程度较为合适的标准。该文以大豆、大豆分离蛋白(soybean protein isolate,SPI)、大豆球蛋白(glycinin,11S)、β-伴大豆球蛋白(beta-conglycinin,7S)为原料,研究大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响。研究表明11S比7S更难发生完全变性,SPI中的7S和11S比单独存在的7S、11S更难发生完全变性。传统制备方式、前热处理后喷雾干燥或冷冻干燥制备方式、先喷雾干燥或冷冻干燥后热处理制备方式对豆腐花凝结成型影响不同,其中传统方式制备的豆腐花凝胶效果最好,先干燥后热处理制备的豆粉凝胶效果比前热处理后干燥的豆粉好,引起豆腐花凝胶强度差异的主要原因是大豆蛋白中7S和11S热变性程度不同。制备同一凝胶强度的豆腐花,热处理温度越低,所需的热处理时间越长;制备高凝胶强度的豆腐花比制备低凝胶强度的豆腐花所能进行的热处理温度与时间范围小。大豆蛋白的7S处于完全变性而11S处于未完全变性的状态时,适合制备速溶豆腐花粉的大豆蛋白变性程度应控制热处理温度与时间范围为80℃时热处理20~65 min,85℃时热处理15~50 min,90℃时热处理10~35 min,95℃时热处理5~20 min。该研究结果为调控速溶豆腐花粉的凝胶特性提供理论依据。     

羟自由基导致肉类肌原纤维蛋白氧化和凝胶性降低

为研究羟自由基（·OH）氧化体系中肌原纤维蛋白（myofibrillar protein,MP）氧化及其凝胶特性的变化,试验分析了羟自由基氧化体系中不同H2O2浓度对蛋白氧化程度及MP凝胶白度、持水力、质构特性（texture profiles analysis,TPA）与弹性模量等特征指标的影响。结果表明：随H2O2浓度的增加,MP中羰基值上升,蛋白氧化程度加剧,凝胶白度、保水性、硬度、咀嚼性及弹性模量则与H2O2浓度呈显著负相关。与对照组相比,当H2O2浓度增加至20 mmol/L时,羰基含量增加至2.82 nmol/mg蛋白（p＜0.05）,凝胶白度、持水性及硬度则分别下降了2.83%、14.65%及52.77%（p＜0.05）。扫描电镜（scanning electron micrograph,SEM）观察表明,MP氧化导致凝胶微观结构破坏,形成空隙较大且分布不均的网络;低场核磁共振分析（nuclear magnetic resonance,NMR）结果显示,随 H2O2浓度的增加,MP 凝胶中的一部分不易流动水“态变”为自由水,凝胶持水力降低。综上所述,·OH氧化体系中肌原纤维蛋白氧化会影响其凝胶形成,破坏蛋白凝胶结构,降低凝胶功能,这为肉类生产加工过程中蛋白氧化控制提供理论参考。     

广西德保猪MC1R基因的克隆与分析

近年来含有天然黑色素的动植物黑色食品得到青睐,为探讨广西地方品种德保猪全黑毛色形成的分子机制,本文克隆了广西德保猪MC1R基因并进行了系统生物信息学分析。根据NCBI已公布的猪MC1R基因序列（GI：347618788）设计特异性引物,以从德保猪血液中提取的基因组DNA为模板,通过PCR扩增克隆获得长1 519 bp的MC1R基因序列片段。多重序列比较结果显示克隆片段与已公布的猪、牛、人、狗、绵羊、小鼠和鸡的相似性依次分别为99%、87%、86%、85%、84%、81%和77%,表明MC1R基因在不同哺乳动物间具有较高的保守型。德保猪MC1R蛋白结构预测结果显示,其理论分子质量为34.65 ku,等电点为8.70,为弱碱性蛋白,N-末端不存在信号肽,定位于细胞质膜,具有1个低复杂度结构域和7个跨膜结构域,具有典型的细胞膜受体蛋白结构。多项研究报道表明MC1R基因是动物毛皮颜色重要的决定基因,德保猪MC1R基因克隆为揭示其全黑色形成的分子机制奠定了较好的实验基础。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.