Dynamics of phosphatase activities in a cork oak litter (Quercus suber L.) following sewage sludge application     

Sylvie Nèble  Virgile Calvert  Jean Le Petit  Stéven Criquet 《Soil biology & biochemistry》2007,39(11):2735-2742

As part of a study of the processes involved in litter biodegradation following sewage sludge (SS) addition, the variations over 14 months of phosphatase activities in a cork oak litter (Quercus suber L.) were investigated. A field experimental design was carried out using the litter-bag method on both a fertilized plot receiving SS applications (twice ) and a control plot. Acid (APH) and alkaline (BPH) phosphatases were measured, along with several biotic and abiotic variables potentially involved in the regulation of these enzymes. These included moisture, temperature, pH, water-extractable inorganic P (P_W), culturable heterotrophic bacteria and fungi. Sludge addition had significant effects on all the variables measured. Indeed, sludge increased significantly BPH activities, available P_W, microbial densities (i.e. bacteria and fungi) and pH in the fertilized plot. In contrast, APH activities decreased significantly following sludge addition. As a consequence, the BPH/APH ratio increased markedly and immediately in the fertilized plot, but only after the 1st amendment. Following the 1st preconditioning SS amendment, the 2nd fertilization had fewer effects on biological variables, because of summer dryness. The different properties examined varied significantly with incubation time, and most were significantly related to the seasonal patterns of litter moisture in this Mediterranean forest ecosystem. Hence, sewage sludge application modified the intensity of microbial responses to environmental factors, but biological patterns regulating P turn-over were maintained.  相似文献   

Development and validation of a computer program to design and calculate ROPS     

Mangado J  Arana I  Jarén C  Arnal P  Arazuri S  Ponce de León JL 《Journal of agricultural safety and health》2007,13(1):65-82

In Spain, there are more than 250,000 tractors built before 1980, when it became mandatory for all new tractors to be equipped with a rollover protective structure (ROPS). A similar situation is found in the European Union, but the situation is worse in the U.S. and in developing countries. Directive 2003/37/EEC establishes that tractors over 800 kg weight can be homologated by using the OECD standard code for the official testing of protective structures on agricultural and forestry tractors (static test), called Code 4. A ROPS attachable to the rear axle of different tractor models has been designed, and a computer program for the calculation of the ROPS design has been developed. The program, named ESTREMA, is available at: www.cfnavarra.es/insl. Using this program, it has been possible to design a ROPS for the Massey Ferguson model 178 tractor, one of the most common tractor models without a ROPS in Spain. After the tractor was equipped with the designed ROPS, it was tested at the Spanish Authorized Station for testing ROPS and passed the homologation test (OECD Code 4), the main results being a maximum distortion of 21.3 cm when the absorbed energy was 5437 N and the maximum force applied was 34 kN during loading from the side. The ROPS was improved, redesigned, and remounted on the tractor, the tractor was tested in a real overturn, and no part of the structure intruded on the driver's clearance zone during the test. In conclusion, the ESTREMA program worked correctly, and the designed ROPS was able to pass the authorized test and provide adequate protection to the operator during a real overturn.  相似文献   

Changes in red wine soluble polysaccharide composition induced by malolactic fermentation     

Dols-Lafargue M  Gindreau E  Le Marrec C  Chambat G  Heyraud A  Lonvaud-Funel A 《Journal of agricultural and food chemistry》2007,55(23):9592-9599

The polysaccharide content of wine is generally assumed to originate from grapes and yeasts, independent of bacterial metabolism, except for the action of certain spoilage species. This study shows that malolactic fermentation (MLF) significantly modifies the soluble polysaccharide (SP) concentration of various red Bordeaux wines. Wines with the highest initial SP concentration go on to present decreased SP concentration, whereas those with the lowest initial SP concentration rather go on to have a higher SP concentration after MLF. These tendencies were observed whatever the Oenococcus oeni strain (indigenous or starter) used for MLF. Neutral and charged SPs were affected, but to a degree that depended on the microorganisms driving the MLF. The SP modifications were directly linked to bacterial development, because non MLF controls did not present any significant change of SP concentration.  相似文献   

Peptides isolated from in vitro digests of milk enhance iron uptake by caco-2 cells     

Argyri K  Miller DD  Glahn RP  Zhu L  Kapsokefalou M 《Journal of agricultural and food chemistry》2007,55(25):10221-10225

Milk proteins, during digestion, produce a range of biologically active peptides. Among those are peptides that may enhance iron absorption. The objective of this project was to investigate the effect of isolated milk peptides on iron uptake. Cow's milk, 0% fat, was subjected to a modified in vitro digestion process. The milk digest was further fractionated by gel filtration. All eluted fractions as well as beta-casein synthetic peptides (a tripeptide and a hexapeptide) were subsequently tested for effects on iron uptake with Caco-2 cell monolayers. Fractions of milk digests obtained through Sephadex G-25 gel filtration had a significant enhancing effect on iron uptake in Caco-2 cells compared to nonfractionated milk digests. Two fractions (P = 0) and the hexapeptide (P < 0.0001) enhanced iron uptake by up to 3-fold, whereas others and the tripeptide had no effect. These results suggest that selected peptides produced during the in vitro digestion of milk may enhance iron absorption; however, it remains to be demonstrated whether this effect may be nutritionally significant.  相似文献   

Impact of casein gel microstructure on self-diffusion coefficient of molecular probes measured by 1H PFG-NMR     

Le Feunteun S  Mariette F 《Journal of agricultural and food chemistry》2007,55(26):10764-10772

The translational dynamics of poly(ethylene glycol) (PEG) polymers with molecular weights (Mw) varying from 6x10(2) to 5x10(5) were investigated by pulsed field gradient NMR in casein suspensions and in gels induced by acidification, enzyme action, and a combination of both. For molecules with Mwor=8000, there was strong dependence of diffusion on PEG size and on the casein network structure as revealed by scanning electron microscopy images. The diffusion coefficients of the two largest PEGs were increased after coagulation by amounts that depended on the internal structure of the gel. In addition, the 527,000 g/mol PEG was found to deviate from Gaussian diffusion behavior to greater or lesser extents according to the casein concentration and the sample microstructure. The results are discussed in terms of network rearrangements.  相似文献   

中国主要纸产品国际竞争力综合评价          下载免费PDF全文

李楠  高志强  王鹏  冯艳萍  李乐  夏恩龙 《林草政策研究》2021,1(2):32-40

文中在分析中国主要纸产品出口贸易现状的基础上,选取国际市场占有率、贸易竞争力指数和显示性比较优势指数测算中国主要纸产品2010-2019年的国际竞争力指数,并采用基于主成分分析的定权方法对纸产品国际市场竞争力进行综合评价。结果表明:主要纸产品国际竞争力较强的芬兰、瑞典和德国位居综合评价前3位,中国主要纸产品综合竞争力经过近10年发展已处于中等偏上水平,仍有改进和提升空间。基于上述研究成果,提出推进人工林速生材高效利用、促进科技创新能力提升和探索"出口转内销"等政策建议。  相似文献   

莲雾营养成分及利用价值研究进展     

孙勇  高乐  张先  甘霖  邢宏宝  何海林  何鹏 《安徽农业科学》2021,49(11):23-25,31

莲雾因其具有较高的营养、药用、保健和观赏价值,获得了国内外学者的广泛关注,综述了莲雾营养成分的分析、代谢产物的分离鉴定及其利用价值等方面的研究进展,为莲雾高营养特性的研究和产业的发展提供技术和理论支撑,也为从事莲雾研究的科研工作者提供有效的信息服务.  相似文献   

GA3介导miR171s及其靶基因VvSCLs调控葡萄种子发育的作用分析     

王文然  解振强  诸葛雅贤  白云赫  管乐  吴伟民  张培安  郑婷  房经贵  王晨 《中国农业科学》2021,54(2):357-369

【目的】鉴定vvi-miR171s成员及其靶基因,明确vvi-miR171s成员及其靶基因在葡萄种子发育中的重要作用及其响应赤霉素（Gibberellin,GA）调控种子发育的表达模式。【方法】以‘魏可’葡萄（‘Wink’）果实为试材,利用miR-RACE技术鉴定vvi-miR171a/b/e/f/g/h的成熟体序列;通过PsRNATarget软件预测vvi-miR171s的靶基因,利用生物信息学软件对其进行染色体定位、系统进化树、基因结构、保守结构域及motif分析;通过启动子作用元件分析预测vvi-miR171s及其靶基因的潜在功能;采用RLM-RACE和PPM-RACE验证vvi-miR171s对靶基因的裂解作用;利用qRT-PCR鉴定其应答外源GA₃在葡萄种子区中的表达模式。【结果】从‘魏可’葡萄果实中鉴定并克隆了6条葡萄vvi-miR171s成熟体序列,并用RLM-RACE和PPM-RACE鉴定到3条靶基因VvSCL6/15/22。靶基因的生物信息学分析显示,VvSCL6/22与苹果、桃子和樱桃同源基因遗传距离较近,而VvSCL15则与拟南芥、苹果、桃子和樱桃中的同源基因遗传距离相同,且VvSCLs的基因结构也与进化树中亲缘关系较近的基因相似;SCLs蛋白均具有GRAS结构域,鉴定到5个与GRAS结构域对应的保守motif,且它们含有的motif元件类型及排列顺序均相似,表明SCL家族结构较为保守。vvi-miR171s及靶基因的启动子均具有大量的GA、水杨酸（Salicylic acid,SA）和种子发育相关作用元件,表明它们可能参与响应GA、SA和种子发育过程;qRT-PCR表达分析显示,GA₃强烈抑制了种子区vvi-miR171a的表达,但同时显著上调种子区的VvSCL15和VvSCL22表达;vvi-miR171a和VvSCL15在对照组和GA₃处理后的种子/种子区均呈强烈的负相关,表明GA₃可能在葡萄种子/种子区显著增强vvi-miR171a对VvSCL15的负调控作用,从而介导葡萄种子发育。【结论】在‘魏可’葡萄中鉴定到vvi-miR171a/b/e/f/g/h 6个成员;均可裂解VvSCl6/15/22 3个靶基因;vvi-miR171a-VvSCL15可能作为主要的调控途径响应赤霉素并参与调控葡萄种子发育。  相似文献   

基于SCoT分子标记的黄河鲤抗嗜水气单胞菌不同群体遗传多样性分析          下载免费PDF全文

张岚  姜淑泓  陈玉函  常乐  管俊翔  林强  于淼  乔志刚  王磊 《南方农业学报》2022,53(10):2748-2755

【目的】基于SCoT分子标记探讨黄河鲤遗传多样性与其抗嗜水气单胞菌能力的关系,为黄河鲤的抗病育种提供理论依据。【方法】通过腹腔注射对300尾黄河鲤进行人工感染嗜水气单胞菌,按死亡顺序分为最先死亡群体（FP）、最后死亡群体（LP）和存活群体（SP）,每个群体选取30尾。从80条SCoT引物中筛选出多态性好、重复性高、条带清晰的引物,对3个黄河鲤群体进行多态性扩增,采用PopGene32和Arlequin 3.5计算3个群体的等位基因数（Na）、有效等位基因数（Ne）、Nei’s基因多样性指数（H）及Shannon’s信息指数（I）等遗传参数,基于Nei’s遗传距离（Ds）利用MEGA 7.0中的非加权组平均法（UPGMA）构建系统发育进化树,并以Structure 2.3进行群体间的遗传结构分析。【结果】黄河鲤感染嗜水气单胞菌的死亡率为40.0%。从80条SCoT引物中筛选出18条扩增条带清晰、多态性好的引物,从3个黄河鲤群体中共扩增出103条条带,其中多态性条带97条,占94.17%。3个黄河鲤群体的Na范围为1.7961~1.8155,Ne范围为1.3828~1.4029,H范围为0.2258~0.2467,I范围为0.3453~0.3804;群体间的遗传分化指数（Gst）为0.0972,即90.28%的遗传多样性分布在群体内部。3个黄河鲤群体的遗传分化指数（Fst）为0.1299,属于轻度遗传分化;群体间的Ds分布在0.0248~0.0835,其中FP群体与SP群体的遗传距离最大。基于Ds的UPGMA聚类分析结果显示,FP群体和LP群体聚为一支,SP群体单独聚为一支;遗传结构分析结果表明,3个黄河鲤群体可分为2个亚群［抗病群体（SP）和易感群体（FP和LP）］。可见,通过黄河鲤死亡时间划分的群体与通过聚类分析及遗传结构分析得出的群体基本一致。【结论】黄河鲤抗嗜水气单胞菌的能力随着群体遗传多样性的增大而增强。因此,在黄河鲤抗病品种（系）选育过程中应保证足够的群体数量,在提高生长、营养等经济性状的同时保证一定的基因杂合度。  相似文献   

Versatile physiological functions of the Nudix hydrolase family in berry development and stress response in grapevine          下载免费PDF全文

WANG Pei-pei  WANG Zhao-ke  GUAN Le  Muhammad Salman HAIDER  Maazullah NASIM  YUAN Yong-bing  LIU Geng-sen  LENG Xiang-peng 《农业科学学报》2022,21(1):91-112

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