利用15N示踪研究烤烟对氮素的吸收和分配规律

为了解河南烟区烤烟对氮素的吸收分配情况,试验采用15N分别标记基肥中的铵态氮（15NH4+）、基肥中的硝态氮（15NO3-）以及追肥氮的方法研究了烤烟大田生育期内各器官中氮素的吸收分配规律。结果显示:（1）在整个大田生育期烟株体内氮素积累量不断增加,其中旺长期增幅最大;烟株对土壤氮的积累量显著大于肥料氮,且吸收的氮素50%以上分布在叶片中;烟株根系对氮素的积累在整个生育期都呈现持续增加的趋势。（2）随生育期推进烟株各器官中积累肥料氮量占总氮比例不断降低;不同叶位间,叶片积累肥料氮占总氮的比例一直是:下部叶＞中部叶＞上部叶。（3）烟株在大田移栽后40d～60d期间为氮素积累强度最大时期,随后逐渐减弱,且生育后期烟株对肥料氮的积累表现为负值,而对土壤氮的吸收则表现出滞后性;烟株对基肥中硝态氮的吸收能力强于铵态氮,对追肥中氮素的吸收能力强于基肥氮。      

冬油菜叶片SPAD的时空分布和氮素诊断的叶位选择

在大田试验条件下测定分析不同施氮水平冬油菜关键生育期SPAD值的时空分布特征,并对不同叶位及叶片不同部位SPAD值与叶绿素含量、叶片含氮量、植株全氮含量及籽粒产量之间的相关性进行分析,探求应用SPAD仪诊断油菜氮素营养状况的最佳测试叶位及位点。结果表明,油菜主茎顶部4片完全展开叶SPAD值存在显著空间差异,增加施氮量能显著提高各叶位叶SPAD值,同时减少叶位间的差异;六叶期、蕾薹期以顶4叶（TIA）SPAD值对氮素的敏感性最大,初花期和盛花期则最低。不同部位间,六叶期和初花期以中部SPAD值对施氮量增加的响应最敏感,盛花期则最迟钝,蕾薹期介于顶部和基部之间。综合分析认为,应用SPAD仪监测油菜氮素营养状况的最佳测试叶位和位点为主茎顶4片完全展开叶中部,该部位SPAD值与叶绿素含量、叶片含氮量和植株全氮含量之间的相关性均达到显著或极显著水平,满足氮素营养快速诊断的要求。     

钾对烟草根际氮细菌、氮古菌群落及氮代谢的影响

为提高烟草栽培品质,采用高通量测序技术和分光光度法探讨了不同施钾水平对根际氮细菌、氮古菌和氮代谢的影响。结果表明:旺长期,烟草根际反硝化作用菌和硝酸还原菌与施钾水平呈负相关,且当N:K₂O=1:2.1时,氮素有效性较高,相比对照提高了20.9%,利于烟草生长。晚成熟的上部叶总氮、烟碱含量升高,糖含量降低,烟叶质量受到影响,但在N:K₂O=1:3.5~4.2时总氮含量显著降低,此时根际脲酶活性同样显著降低。揭示出施钾水平不仅会直接影响烟草根际氮细菌、氮古菌的群落结构,还会影响土壤氮素有效性、土壤酶活,进而影响氮营养的供应和烟草品质。建议前期适量施肥,并在打顶后追施钾肥,改变根际钾环境,提高烟草品质。      

基于~(15)N同位素示踪技术的烤烟品种上部叶氮积累和氨挥发量差异分析

为明确贵州黔东南烟区不同烤烟品种上部叶对土壤氮源和肥料氮源的利用差异,以当地主栽品种云烟87和K326为试验材料,通过施用~(15)N同位素标记的~(15)NH_4~(15)NO_3肥(基肥,70%)和K~(15)NO_3肥(追肥,30%)研究了两个品种上部叶的氮素积累和氨挥发的差异性。两个品种烤烟上部叶氮素含量(质量分数)随生育期的推进呈先升高后降低的趋势,两个品种烤烟吸收土壤氮素含量占烟株全氮含量的比例随生育期的推进而逐渐升高,对上部叶的氮素营养贡献率较大;云烟87上部叶氨挥发量大于K326,两个品种烤烟上部叶氨挥发的氮源主要来自肥料氮。黔东南烟区土壤氮对上部叶的氮素营养起主导作用,不同烤烟品种上部叶对土壤氮和肥料氮的利用存在差异。     

应用~（36）Cl、~（15）N示踪研究烟草对氯化铵养分的吸收与分布

通过３６Ｃｌ示踪研究表明：烟草对氯素的吸收很快，至成熟期利用率为２６．１９％；烟草吸收的氯素大部分分布在叶和茎等营养器官，占全株总含氯量的９５％以上，其中又以叶部最多，根和果实中含量很少。在土壤施氯１００～４００ｍｇ／ｋｇ范围内，氯素对烟草生长发育和产量有一定的促进和提高作用。由１５Ｎ测定结果看出，烟草对氯化铵中氮素的利用率为３０．３１％，烟草吸自肥料的氮素占全株总氮量的１６％，绝大部分氮吸自土壤；烟草吸收的氮素大部分分配在叶部，占全株总含氮量的７０％左右。     

不同基因型烟草对氮素营养响应的差异研究

采用水培盆栽试验,研究了氮素营养对不同基因型烟草幼苗生长的影响.结果表明,不同基因型烟草对氮素营养的响应有明显差异,其硝酸盐还原酶活性、叶绿素含量、根系总吸收面积、氮含量均与氮浓度呈显著或极显著相关.不同基因型间硝酸盐还原酶活性差异显著,其中不耐氮肥基因型8136、红花大金元的硝酸盐还原酶活性明显高于其它品种,其叶绿素含量、根系活力及氮含量也高于其它品种,但其生物量随氮浓度的升高而降低;而较耐氮肥的基因型中烟90、KY17则与之相反.     

稳定氮同位素示踪技术在烟草研究中的应用

综述了稳定氮同位素示踪技术在烟草氮素营养吸收转化、烟草肥料利用、烟草生物碱合成与代谢等方面的应用,指出了目前研究中存在的缺憾,并对今后稳定氮同位素示踪技术在烟草研究中的应用进行了展望。      

烟草氮素营养的基因型差异初探

以36个烟草品种为供试材料,利用低氮下的相对生物产量作为耐低氮能力评价指标,分析了不同烟草品种的耐低氮能力,同时对烟草在低、中、高3种氮水平下的氮素利用效率(NUE)、吸收效率(NAE)和氮素利用效率响应度(NUER)的基因型差异进行比较。结果表明:(1)烟草种质资源在低氮下生物产量的形成能力具有明显的基因型差异;(2)烟草种质的NUE和NAE存在显著的基因型差异,且差异水平随着氮素水平的升高而降低。而对某一确定的烟草品种,NUE表现为NUE_低 >NUE_中 >NUE_高,NAE表现为中、高氮显著高于低氮,NUER表现为NUER_低-高 >NUER_低-中 >NUER_中-高;(3)烟草种质资源的NUE、NAE、NUER的变异系数的大小存在极大的差别,表现为NUER >NAE >NUE。对以上结果分析表明:烟草是对氮肥极为敏感的作物,且不同氮素水平下烟草对氮素的吸收利用的内在机制表现不同,缺氮下较强的氮素吸收能力是烟草品种在氮胁迫条件下耐低氮能力形成的主要原因,而中、高氮水平下的氮素利用效率的不同是形成氮效率基因型差异的主要原因。      

低氮胁迫对烟草生物学性状、生长素及NtPINs基因家族的影响

为了探究低氮胁迫下烟株体内生长素的分布对烟草根系发育和腺毛发生的影响,以DR5::GUS转基因烟草为材料,通过沙培试验研究低氮胁迫对烟株生物量、全氮含量、叶片及根系发育、生长素浓度、叶片腺毛密度以及生长素极性运输蛋白NtPINs家族基因表达的影响。结果表明:与对照处理（NH₄NO₃:2.5 mmol/L）相比,低氮胁迫下（NH₄NO₃:0.25 mmol/L）烟草上部叶、茎及根部生物量显著下降,地上部全氮含量降低30%,根系全氮含量降低40.2%,上部叶腺毛密度增加13.9%,中部叶和下部叶腺毛密度分别降低40%和31.9%,上部叶生长素含量增加26%,中部叶和根系生长素分别下降7.1%和13.1%;qRT-PCR结果表明,低氮胁迫下烟草根系中NtPIN1、NtPIN4、NtPIN9的基因表达水平分别降低了40%,55%,65%,与对照相比差异均有统计学意义（P < 0.05）。结论:低氮胁迫下烟草叶片腺毛的发生及根系的构型发生改变与体内生长素从地上部（上部叶、中部叶、下部叶）到根系极性运输减少密切相关。      

不同烟草基因型氮素吸收效率与利用效率差异

为探究不同烟草基因型氮素吸收与利用的差异,采用营养液培养方法对74个不同基因型烟草苗期进行低氮(0.5mmol/L)和高氮(5.0 mmol/L)处理,分析了其氮素营养指标和氮效率。结果表明,不同烟草基因型之间的氮效率差异显著,且基因型与氮水平之间互作显著。依据地上部生物量可以将不同烟草基因型的氮效率分为双高效型、低氮高效型、高氮高效型和双低效型4类。不同供氮水平下,氮素吸收效率对氮效率的直接作用均大于氮素利用效率,氮高效基因型的地上部生物量、植株氮累积量、氮素吸收效率、氮效率均显著高于氮低效基因型,氮素利用效率则差异不显著。由此,氮素吸收能力在氮高效烟草基因型的选育和栽培上更加重要。     

THE GROWTH OF TOP-FERMENTATION YEASTS IN BINARY MIXTURES OF VARIOUS NITROGEN NUTRIENTS

The growth of English top-fermentation yeasts in various nitrogen sources, used singly—including ammonium phosphate and a number of amino acids—has previously been investigated and reported upon. But malt wort, the natural medium for yeast growth, contains, not a single nitrogen source, but a mixture of many derived from the breakdown of barley proteins. It is therefore important to know whether growth in such mixtures is simply the average of growth in the individual nitrogen sources or whether the different nitrogen sources interact with each other in such a way as to produce enhanced or diminished growth. The object of the work described in this paper was to ascertain whether the admixture of two different nitrogen sources introduces any new effects unpredictable from the known behaviour of the same nitrogen sources used singly. Nutrient media were prepared containing graded proportions of various selected pairs of nitrogen sources. Four different top-fermentation brewery yeasts were cultured in these media, measurements being made of fermentation, nitrogen assimilation and rate and extent of yeast growth. It was thus possible to observe the influence of the percentage composition of any particular binary mixture of nitrogen nutrients upon the growth and fermentation of a variety of yeasts. Among the mixtures investigated there was generally found a slight enhancement of growth and fermentation over what would be expected from the individual behaviour of the nitrogen sources. In a few cases, however, the observed enhancement was very large and was practically independent of the particular variety of yeast used. No important depressive effects were found in any of the mixtures. It may therefore be concluded that the mere admixture of different nitrogen sources can make a special contribution to yeast growth and fermentation; this contribution is generally relatively small but may in some circumstances becomes very significant. A chemical interpretation of some of the phenomena of yeast growth in mixed nutrients has been put forward.     

Atmospheric emission of reactive nitrogen during biofuel ethanol production

This paper evaluates emissions to the atmosphere of biologically available nitrogen compounds in a region characterized by intensive sugar cane biofuel ethanol production. Large emissions of NH3 and NOx, as well as particulate nitrate and ammonium, occur at the harvest when the crop is burned, with the amount of nitrogen released equivalent to approximately 35% of annual fertilizer-N application. Nitrogen oxides concentrations show a positive association with fire frequency, indicating that biomass burning is a major emission source, with mean concentrations of NOx doubling in the dry season relative to the wetseason. During the dry season biomass burning is a source of NH3, with other sources (wastes, soil, biogenic) predominant during the wet season. Estimated NO2-N, NH3-N, NO3- -N and NH4+ -N emission fluxes from sugar cane burning in a planted area of ca. 2.2 x 10(6) ha are 11.0, 1.1, 0.2, and 1.2 Gg N yr(-1), respectively.     

The influence of different nitrogen and carbon sources on mycotoxin production in Alternaria alternata

The aim of this study was to determine the influence of different carbon and nitrogen sources on the production of the mycotoxins alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) by Alternaria alternata at 28 °C using a semi-synthetic medium (modified Czapek-Dox broth) supplemented with nitrogen and carbon sources. Additionally the effect of shaken and static cultivation on mycotoxin production was tested. Initial experiments showed a clear dependency between nitrogen depletion and mycotoxin production. To assess whether nitrogen limitation in general or the type of nitrogen source triggers the production, various nitrogen sources including several ammonium/nitrate salts and amino acids were tested. In static culture the production of AOH/AME can be enhanced greatly with phenylalanine whereas some nitrogen sources seem to inhibit the AOH/AME production completely. TA was not significantly affected by the choice of nitrogen source. In shaken culture the overall production of all mycotoxins was lower compared to static cultivation. Furthermore tests with a wide variety of carbon sources including monosaccharides, disaccharides, complex saccharides such as starch as well as glycerol and acetate were performed. In shaken culture AOH was produced when glucose, fructose, sucrose, acetate or mixtures of glucose/sucrose and glucose/acetate were used as carbon sources. AME production was not detected. The use of sodium acetate resulted in the highest AOH production. In static culture AOH production was also stimulated by acetate and the amount is comparable to shaken conditions. Under static conditions production of AOH was lower except when cultivated with acetate. In static cultivation 9 of 14 tested carbon sources induced mycotoxin production compared to 4 in shaken culture. This is the first study which analyses the influence of carbon and nitrogen sources in a semi-synthetic medium and assesses the effects of culture conditions on mycotoxin production by A. alternata.     

EFFECT IN RATS OF PARTIAL REPLACEMENT OF COW'S MILK PROTEIN BY SUPPLEMENTARY NITROGEN

SUMMARY: A number of experiments studied growth of weanling rats and urinary nitrogen excretion in young adult rats when cow's milk protein was partially replaced by varying levels supplementary nitrogen. A mixture of nonessential L-amino acids (NEAA) or a mixture of diammoniumcitrate and glycine (DAC-Gly) was used as the source of nitrogen. Substitution of the 15% milk protein diet to the extent of 10% slightly reduced growth; significant growth reduction occurred with substitutions of 20% and greater. Fortification of the diets containing 10.5% milk protein and the supplementary nitrogen sources with sulfur amino acids did not restore growth the maximum rate obtained with the 15% milk protein diet. Additional supplementation with tryptophan further improved growth slightly but not to the maximum rate. Several other essential amino acids, alone or in combination, had no apparent effect. Based on urinary nitrogen excretion, comparable results were obtained with young adult rats by substituting nitrogen for milk protein the diets. The reduced performance following substitution of milk protein with supplementary nitrogen may be due partly to decreased utilization of sulfur amino acids and possibly to decreased utilization of all essential amino acids.     

COMPARISON OF THE PROTEIN NUTRITIONAL VALUE OF TVP, METHIONINE ENRICHED TVP AND BEEF AT TWO LEVELS OF INTAKE FOR HUMAN ADULTS

SUMMARY— The objective of the study was to compare the protein nutritive value for adult men of beef, an extruded soybean product resembling beef (TVP) and a 1% DL-methionine-fortified TVP product at two levels of nitrogen intake. Experimental diets were maintained adequate in calories, vitamins and minerals. Mean nitrogen balances of subjects fed 8.0g nitrogen per subject per day from beef, TVP or methionine-fortified TVP were +0.74, +0.78 and +0.72g nitrogen per day, respectively, indicating that at this level of protein intake all three sources equaled or exceeded the protein requirements of adult men. Mean nitrogen balances of subjects fed 4.0g nitrogen per subject per day from beef, TVP or methionine-fortified TVP were -0.30, -0.70 and -0.45g nitrogen per day, respectively. While none of the test protein sources fully met the protein needs of the subjects at this level of nitrogen intake, beef was superior to TVP on the basis of nitrogen balance data. DL-methionine fortification at the 1% level of the TVP was demonstrated to be partially effective in improvement in nitrogen balance.     

福建烟草病毒种群及其发生频率的研究

1984-1991年的调查研究结果表明,福建烟区的烟草病毒有TMV-C,Tom,YM和RS株系,CMV-C,Yel和TN株系,以及TEV,TLCV,TRV,TRSV,TSV,TVBMV,ToAV,ToBRV,PVX,PVY,其中以CMV-C和TMV-C为优势株系,分别占样品总数的27.8%和27.7%。各种病毒(株系)及其发生的频率因地区和年份而有所不同。在田间各种病毒(株系)的株发病率因烟草品种、烟苗来原和前作类型不同而有差异。      

营养条件对绿僵菌生长特性和抑菌活性的影响

研究了不同培养基、碳、氮营养对金龟子绿僵菌菌落直径、菌丝生物量、分生孢子产生量及其次生代谢产物对植物病原真菌的抑菌活性。发现金龟子绿僵菌的菌丝线性生长以PSA、麦芽糖和酵母最好,以Czapek、甘露醇和脲最差;菌丝生物量以PSA、白砂糖和蛋白胨最大,以Czapek、乳糖和脲最小;分生孢子产生量以PSA、麦芽糖和KNO3最多,以Czapek、甘油和硫酸铵最少。代谢液的抑菌活性实验结果表明,在不同培养基培养的代谢液中,Czapek的抑菌效果最好,SDAY的抑菌效果最差。在不同碳营养培养的代谢液中,白砂糖的抑菌效果最好,乳糖的抑菌效果最差。在不同氮营养培养的代谢液中,蛋白胨的抑菌效果最好,脲的抑菌效果最差。     

Characterization of Pseudomonas mendocina LR capable of removing nitrogen from various nitrogen-contaminated water samples when cultivated with Cyperus alternifolius L

A new strain of denitrifying bacterium, Pseudomonas mendocina LR, was isolated from rhizosphere soil of aquatic plants living in a river contaminated with industrial wastewater and domestic sewage. The isolate was found to fully remove as much as 613.2 mg nitrate in 60 h under stationary culture conditions. The effects of carbon sources and nitrogen sources on nitrogen removal were investigated using a modified denitrification medium (DM). Sodium citrate was identified as the most effective source of carbon. The ability of LR to adapt to different nitrogen sources, including nitrite, indicated that LR could be used in the purification of wastewater containing different forms of nitrogen. The optimal C/N ratio was 7 for LR, and it was resistant to antibiotics Amp, Chl, Ery, and Str. Plant-microbe bioaugmentation was performed to remove nitrogen dissolved in Hoagland medium and natural wastewater. An increased rate of nitrogen removal was observed when root exudates of Cyperus alternifolius L. were added simultaneously with LR. LR was not able to survive in the natural wastewater unless root exudates from umbrella grass were added. LR cultured with umbrella grass exhibited a maximal nitrogen reduction rate of 95.9% and 97.3% in Hoagland medium and wastewater, respectively. This shows that bioaugmentation utilizing plant-microbe interactions can be an effective and exhaustive means of removing nitrogen and may be an attractive approach to nitrogen reduction in natural environments and wastewater treatment factories.     

BIOSYNTHETIC FORMATION OF HIGHER ALCOHOLS BY YEAST. DEPENDENCE ON THE NITROGENOUS NUTRIENT LEVEL OF THE MEDIUM

In previous investigations it has been shown that in batch fermentations the yield of higher alcohols formed biosynthetically (in the sense that yeast synthesizes the carbon skeletons needed) is mainly negatively correlated with the intial level of nitrogenous nutrients in the medium. The validity of this relationship has been established with different nitrogen sources and sugars, and at different sugar concentrations. Its causes have been studied in simple systems, using single, rapidly-absorbed nitrogen sources, usually ammonium salts. Under such conditions it is the amount, rather than the concentration, of nitrogen source that is of importance. Yields of higher alcohols per unit weight sugar consumed are practically identical at varying nitrogen levels as long as nitrogen is available in the medium, but they increase sharply after nitrogen exhaustion, by a factor of about 2–3. However, if allowance is made for the production of valine, leucine, and isoleucine during the period when nitrogen is present, there is no rise in the total production of carbon skeletons along these pathways after the nitrogen is exhausted. On the contrary, the yields of valine-isobutanol and isoleucine-2-methylbutanol skeletons per unit weight of sugar are appreciably reduced in the absence of nitrogen, whereas the yields of leucine-3-methylbutanol skeletons are nearly unchanged.     

Effects of intake and postruminal casein infusion on performance and concentrations of hormones in plasma of lactating cows

Four Holstein cows were utilized in a Latin square design with a factorial arrangement of treatments to examine the interaction between effects of dry matter intake (107 vs. 78% of energy requirements) and postruminal infusions (water vs. 395 g/d casein) on lactational performance, utilization of nitrogen and energy, and plasma concentrations of hormones. Yields of milk and milk protein were decreased by feed restriction and increased by casein infusion with no treatment interactions. Restricting feed intake decreased total nitrogen intake by 143 g/d and resulted in smaller quantities of fecal, absorbed, urinary, milk, and retained nitrogen compared with cows fed ad libitum. Casein infusion increased total nitrogen intake (55 g/d), absorbed nitrogen (54 g/d), urinary nitrogen excretion (28 g/d), and milk nitrogen (13 g/d). Casein by dry matter intake interactions were not significant for nitrogen utilization. Restricting feed intake increased plasma growth hormone and decreased concentrations of insulin and triiodothyronine. Glucagon, prolactin, and thyroxine were not affected by intake. Casein infusion did not affect growth hormone, insulin, prolactin, triiodothyronine, or thyroxine. Increased milk and milk protein yields obtained with casein infusion were apparently not mediated through changes in circulating concentrations of these hormones; however, plasma glucagon was increased by casein infusions.