温度、渗透度和pH对反刍动物饲料总可溶氮组成及含量的影响

本研究通过两个试验来评估不同饲料原料氮溶解度。试验1评估了豆科植物、油类植物、谷物、黑麦草和青贮类等14个原料。溶解温度为18和38℃,缓冲液pH为6.8和5.0。试验2在38℃添加下采用4个pH(5.0、5.6、6.2和6.8)以及2个渗透度(300和400 mol/L)评估豆饼、豆粕、豌豆、蚕豆和羽扇豆氮溶解度。结果显示:水溶温度由18℃升高至38℃显著提高了大多数原料氮溶解度(P<0.05),显著影响羽扇豆氮溶解度,使可溶性氮占总氮比例由0.53降低至0.17(P<0.05)。pH由6.8降低至5.0,青贮黑麦草和青贮玉米氮溶解度显著升高(P<0.05)。渗透度由300升高至400 mol/L时,豆粕和豆饼氮溶解度显著升高(P<0.05),同时渗透度和pH对其他原料氮溶解度的影响具有显著交互作用(P<0.05)。溶解pH对豆饼、豌豆、蚕豆和羽扇豆蛋白结构具有显著影响(P<0.05),其中pH=6.2~6.8时,7S和11S蛋白比例最高,而11S可溶氮含量降低。结论:溶解pH由6.8将至5.0时降低了大多数饲料原料氮溶解度。这个pH范围显著提高了羽扇豆、蚕豆、豌豆和豆饼非蛋白氮比例,降低了11S蛋白的比例。

沉积物氮形态与测定方法研究进展

长期以来,国内外学者对沉积物中氮进行了大量的研究,在氮生物地球化学循环和生态学效应方面取得了重要进展。然而,现有关于氮赋存形态的研究主要集中在总氮和无机氮方面,还不能深入阐明沉积物氮的生物和生态学机制。分析了沉积物和土壤氮赋存形态划分和测定方法的研究进展,研究表明:沉积物氮的形态划分与测定方法基本上还是借鉴了土壤氮的研究方法;无机态氮的研究多集中在可交换态氮方面,对固定铵的研究相对较少;在可交换态氮提取方法上并没有针对沉积物与土壤的差异进行必要的论证和改进,沉积物中可溶态氮对可交换态氮测定的影响还不明确;有机氮的测定方法基本上是经验方法,目前还无针对有机氮生态学效应的分类及测定方法;连续分级浸提方法从生态学效应的角度对沉积物氮的研究进行了有益的探索,为深入揭示氮的生态学机制提供了新的思路,但是此类方法目前还集中在国内学者的相关研究中。

长江口沉积物-水界面无机氮交换通量的模拟测定

通过对长江口水下沉积物-水界面可溶态无机氮(DIN=NO3-+NO2-+NH4+)的交换行为研究发现,低潮时近口点(A)沉积物是水体DIN的汇(-2006.99μmol/(m2·h)),而靠近口外点(B)沉积物是水体DIN的源(1848.27μmol/(m2·h))。但高潮时,A点沉积物转变为水体DIN的源(1880.97μmol/(m2·h)),而B点的沉积物转变成为DIN的汇(-956.64μmol/(m2·h))。在距河口较远高低潮盐度变化微弱的地点(P),沉积物始终是水体DIN的源(1872.41μmol/(m2·h))。高低潮海水盐度的变化对沉积物中微生物活动的影响是导致这一变化的主要原因。

应用MODIS影像监测海州湾无机氮浓度的研究

利用连云港海州湾2004年至2006年的水质监测资料,选取时间上完全同步的空间分辨率为500m的 MODIS Terra 1B 数据,对反射率的单波段因子和波段组合因子与可溶无机氮(DIN)质量浓度之间进行相关分析。从总体上看,单波段因子与 DIN 质量浓度的相关性较低,但在含氮基团倍频和合频吸收带附近的波段(波段2、7)反射率与 DIN 质量浓度呈负相关,显示了含氮基团对水体光谱特征的影响;在波段组合因子中,因子 F_(11(3,4))和 F_(13(3,4))与 DIN 质量浓度呈显著正相关,用这两个因子建立 DIN 质量浓度的回归模型,R^2达到0.7以上,相对精度达70%左右,最终选择因子 F_(11(3,4))的线性模型反演该海域的 DIN质量浓度,其结果与实际情况非常吻合。

微生物发酵法生产大豆肽工艺条件的研究

以脱脂豆粕为原料,采用地衣芽孢杆菌发酵生产大豆肽。研究菌株种龄、种子液接种量和床速度对多肽产量的影响,结果表明,种龄12h,接种量5%,床速度180r/min最佳。同时,对影响多肽产量的发酵温度、发酵时间及豆粕粉加水量3个主要因素用正交试验方法进行优化,正交试验结果发现,该菌株发酵产多肽的最佳条件为温度37℃,发酵时间48h,加水量94%。优化后该菌株发酵豆粕后的多肽溶液酸性可溶氮含量达到1384.65μg/mL,水解度DH为23.89%。

冻融对温带土壤可溶性氮库、氮转化过程及细菌群落多样性的影响

土壤冻融会影响土壤氮的有效性。氮的转化与土壤微生物密不可分,而土壤冻融对温带土壤细菌群落的影响并不十分清楚。假设:冻融影响细菌群落结构多样性及其组成,从而改变土壤可溶氮含量和氮转化过程。为了验证这一假设,本研究设计了不同冻融循环次数(分别为6次和15次循环)的培养试验,并以2℃恒温培养作为对照。结果表明:随着冻融循环次数的增加,可溶性全氮、可溶性无机氮、微生物生物量氮和净氮矿化率均显著降低。冻融循环次数对细菌α多样性(包括Chao1和Shannon指数)无显著影响,恒温培养的培养周期数与细菌的α多样性呈显著正相关。冻融处理显著影响细菌群落功能和组成,但冻融循环次数对细菌群落结构的影响较小。偏冗余分析表明,冻融处理下细菌群落结构和功能多样性与土壤可溶氮含量和氮转化过程密切相关。

Effect of Different Fertilization Patterns on Carbon and Nitrogen Components of Tobacco Topsoil

In order to explore the fertilizing ways and dynamic changes of soil carbon and nitrogen in the main producing areas of tobacco in Guizhou,research was conducted to study the variations of dissolved organic carbon and nitrogen,total organic carbon and nitrogen and their ratio of tobacco-topsoil in organic fertilization pattern and conventional cultivation pattern （No fertilizer as control） by pot experiment.The results were as follows：（1） The effects of different fertilization patterns on soil dissolved organic carbon and nitrogen and total organic carbon and nitrogen were significantly different.The content of DOC,DON,TOC and TON in tobaccotopsoil was decreased with the advancing of growth period in conventional fertilization pattern.In the conventional fertilization pattern,the accumulation of DOC and TOC was increased first and then decreased,and the accumulation of DON and TON was decreased first and then increased.（2） The TOC content at the different growing stage and DOC content at the middle and later stage of tobacco were significantly improved in organic fertilization patterns.The accumulation of DON and TON in the conventional fertilization pattern was significantly higher than those in the organic fertilizer pattern and control at the rosette stage and vigorous stage.In the harvest period,the content of DOC,DON,TOC and TON of tobacco-topsoil in the conventional fertilization and organic fertilization pattern was significantly higher than those in the control.（3）The DOC/DON ratio and the TOC/TiON ratio was increased gradually with the advancing of growth period in conventional fertilization pattern,but they were increased first and then decreased in the organic fertilization pattern and CK.The DOC/DON and TOC/TON ratio of tobacco-topsoil in different fertilization patterns was showed as Y J＞ CK＞ CG at the different growing stage.The experiment results revealed that：The organic fertilization pattern may improve significantly the accumulation of DOC,DON,TOC and TON of tobacco-topsoil at the middle and later stage and the DOC/DON and TOC/TON ratio at the different growth stage.It contributed to the continuous and balanced supply of nutrients at the middle and later stage of tobacco and the soil fertility.

Extraction Efficiency of Soil Soluble Nitrogen under Different Conditions

[Objective] The extraction efficiency of soluble nitrogen in common moun- tain red soil under different conditions was analyzed to provide experimental refer- ences for the extraction of soil soluble nitrogen. [Method] The fresh soil and air-dried soil, which were the common mountain red soil under evergreen broad-leaved forest vegetation, were used as the experimental materials. The 2 mol/L KCI and 0.5 mol/L K2SO4 were used as the extractants to extract the soil soluble nitrogen with the extractant-to-soil volume ratio at 4：1, 6：1 and 10：1, respectively, to examine the extrac- tion efficiency of soluble nitrogen in the experimental soil with different extraction conditions. [Result] Compared with K2SO4, the NH4＋-N extracted by KCI was better in quantity and stability; while only at high extractant-to-soil volume ratio could K2SO4 fully extract the soil NH4＋-N. The 2 extractants showed small difference in extracting NO3--N, but at low extractant-to-soil volume ratio, the stability of NO3--N extracted by KCI was higher than that extracted by K2SO4. The properties of NO2- -N extracted by the 2 extractants were very similar. As for soil SON extraction, there was small dif- ference between the 2 extractants. However, the SON extracted by KCI was fewer in quantity than that by K2SO4, but had higher stability, and the extracted SON amount of the 2 extractants showed significant correlation. The extractant-to-soil ratio had little effect on MBN extraction using K2SO4, but the effect was significant when using KCI to extract MBN. The difference between the extraction efficiency of KCI and K^SO4 in extracting fresh soils was greater than that in extracting air-dried soil; therefore, the extractants should be carefully selected in soluble nitrogen extraction from fresh soil. [Conclusion] The results lay the experimental foundation for improving the extraction efficiency of soil soluble nitrogen and increasing the comparability of measurement results.

Effects of Different Nitrogen Fertilizer Rates on Soluble Sugar,Starch and Root Tissue Structure of the Peach Trees

[Objective] The research aimed to provide theoretical basis for the cultivation and production of peach.[Method] The three-year-old seedling peach tree was used as the materials,and NH4NO3 was used as the experimental nitrogen fertilizer.Three nitrogen levels,0,3,6 g per pot respectively were set to study the effects of different nitrogen fertilizer on the contents of soluble sugar,starch and internal structure of the root of the peaches.[Result] The contents of soluble sugar of roots and leaves increased with the increase of nitrogen fertilizer level,and the level of 6 g per pot was the highest,which showed extreme differences between the level of 3 g per pot and the control.However,starch contents showed opposite results,which decreased as the level of nitrogen fertilizer increased.Compared with the 3 g per pot level of nitrogen fertilizer and the control,the internal structure of root applied with nitrogen fertilizer of 6 g per pot level had larger fibrovascularcylinder,advanced vascular bundle,small-spaced thin-walled cells,smooth and full cells with smooth cell wall.[Conclusion]Appropriate nitrogen levels can accelerate the accumulation of soluble sugar and the growth of root tissue structure.

Soluble organic nitrogen in forest soils of northeast China

Soluble organic nitrogen （SON） is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by high organic matter and high organic nitrogen content, and soil sampling was made in early spring just after the freeze-thaw period. The water extracted SON pools in the organic layer of forest soils were measured within the range from 156.0 mg·kg^-1 to 292.6 mg·kg^-1, a similar magnitude of salt solution extracted SON pools reported in literatures. However, the water soluble SON pools in 0-15 cm mineral soils in present study were much higher （3-10 times） than any other reports, ranging from 58.6 mg·kg^-1 to 125.2 mg·kg^-1. Water soluble SON varied markedly among the soils under different forests and at different sites. The SON in water extracts were positively and significantly correlated to soil organic matter and total nitrogen contents, but negatively correlated to microbial biomass nitrogen （MBN）. The reasons of the abnormally large SON pools and the negative correlations between SON and MBN in the 0-15cm mineral soils in this study were specially discussed.

Availability of Nonhydrolyzable Soil Nitrogen

ＡｖａｉｌａｂｉｌｉｔｙｏｆＮｏｎｈｙｄｒｏｌｙｚａｂｌｅＳｏｉｌＮｉｔｒｏｇｅｎＺＨＵＯＳＵ－ＮＥＮＧ￣１；ＷＥＮＱＩ－ＸＩＡＯ￣１ａｎｄＣＨＥＮＧＬＩ－ＬＩ￣２（ＬＭＣＰ，ＩｎｓｔｉｔｕｔｅｏｆＳｏｉｌＳｃｉｅｎｃｅ，Ｐ．Ｏ．Ｂｏｘ８２１，Ｎａｎ...

Nutritional Aspects of Two Widely Consumed Wild Edible Mushrooms in Jordan

Two wild mushrooms frequently consumed in Jordan were collected form Jordan forests in spring 2012. Each sample was studied in the lab by taking measurements on the morphological structures of the cap, stem, and recording gill＇s color, shape and dimensions. Also smell and taste for each fruiting structure were taken in consideration. Spore print for each sample was also defined. Spores of each mushroom were microscopically tested and measured. These mushrooms were identified as Pleurotus eryngi and Tricholoma terreum. The two mushrooms were evaluated for their physical properties, chemical and mineral composition. Contents of Ca, Na, K, Zn, Mn, Cu, Fe and Mg were determined. For each mushroom species two mixed samples were analyzed. Nitrogen content was detected with Kjeldahl method and protein content （%） was calculated by multiplying nitrogen content with the factor 4.38. The highest protein content calculated on oven dry weight basis was found in Pleurotus eryngi which was around 30.6%, while Tricholoma terreum contained lowest protein content （17.4%）. Pleurotus eryngi accumulated trace elements at high ratios as for P, Ca and Na 0.99%, 0.65% and 0.57% respectively while Tricholoma terreum contained more K （5.1%） than the other wild mushroom. Total soluble carbohydrates （50.8%）, crude fiber （13.4%） and ash （12.2%） percentages were higher in Tricholoma terreum than in Pleurotus eryngi.

Effects of Nitrogen Sources on Nitrate Reductase Activity and Some Physiological Parameters in Psyllium （Plantago ovata F.） under Salinity Stress

The effects of three nitrogen sources （ammonium, nitrate and ammonium＋nitrate） and three salt treatments （0, 100 and 200 mM NaCl） on nitrate reductase activity, proline, soluble protein and carbohydrate contents in psylliom （Plantago ovata） plants were Studied. The nitrate reductase activity tended to increase when NO3- was included in the root-zone solution, but decrease as salinity increased. All N sources stimulated plant growth and nutrient uptake. Shoot and root dry matter tended to decrease as salinity increased, but less so when both NH4＋ and NO3- were present. Shoot biomass accumulated to significantly greater quantities under the mixed-N treatments than when produced using either NH4＋ or NO3- N-form alone. Although not statistically significant, the root biomasses showed a similar tendency. Generally, leaf proline and soluble shoot carbohydrate contents increased with increasing salinity in contrast to soluble protein which decreased regardless of the N source. Under salinity conditions, the concentration of Na＋ in shoot and root tissues was highest in ammonium-N treatment, while that of K＋ was highest in the mixed-N treatment.

Duodenum has the greatest potential to absorb soluble non-ammonia nitrogen in the nonmesenteric gastrointestinal tissues of dairy cows

In cattle, dietary protein is gradually degraded into peptide-bound amino acids（PBAAs）, free amino acids（FAAs）, and ultimately into ammonia by the rumen microbes. Both PBAA and FAA are milk protein precursors, and the rumen and small intestines are the main sites where such precursors are produced and absorbed. This work was designed to investigate the expression of the peptide transporter Pep T1 and the AA transporters ASCT2, y＋LAT1, and ATB0,＋, and the concentrations of PBAA, FAA, and soluble protein in the rumen, omasum, and duodenum of dairy cows. Tissues and digesta were collected from six healthy Chinese Holstein dairy cows immediately after the animals were slaughtered. The expression of transporters was analyzed by real-time quantitative polymerase chain reaction（PCR）. The FAA concentration was assessed using an amino acid（AA） analyzer, PBAA concentration by quantification of AA before and after acid-hydrolysis by 6 mol/L HCl, and soluble protein concentration by quantification of the bicinchoninic acid content. The results showed that the relative abundance of m RNA of the transporters and the soluble non-ammonia nitrogen（SNAN） concentration of each fraction were greater in the duodenum than in the rumen or omasum. These results indicate that the duodenum is the predominant location within the nonmesenteric digestive tract for producing milk protein precursors. In addition, PBAA was the largest component of SNAN in the digesta from the rumen, omasum, and duodenum. In conclusion, the duodenum has the greatest concentrations of SNAN and PBAA, and the greatest potential for absorption of SNAN in the form of PBAA in the nonmesenteric gastrointestinal tissues of dairy cows.

Dissolved Organic Nitrogen in Mediterranean Ecosystems

Dissolved organic nitrogen （DON） in soils has recently gained increasing interest because it may be both a direct N source for plants and the dominant available N form in nutrient-poor soils, however, its prevalence in Mediterranean ecosystems remains unclear. The aims of this study were to i） estimate soil DON in a wide set of Mediterranean ecosystems and compare this levels with those for other ecosystems; ii） describe temporal changes in DON and dissolved inorganic nitrogen （DIN） forms （NH＋ and NO3）, and characterize spatial heterogeneity within plant communities; and iii） study the relative proportion of soil DON and DIN forms as a test of Schimel and Bennett＇s hypothesis that the prevalence of different N forms follows a gradient of nutrient availability. The study was carried out in eleven plant communities chosen to represent a wide spectrum of Mediterranean vegetation types, ranging from early to late successional status. DON concentrations in the studied Mediterranean plant communities （0-18.2 mg N kg-1） were consistently lower than those found in the literature for other ecosystems. We found high temporal and spatial variability in soil DON for all plant communities. As predicted by the Schimel and Bennett model for nutrient-poor ecosystems, DON dominance over ammonium and nitrate was observed for most plant communities in winter and spring soil samples. However, mineral-N dominated over DON in summer and autumn. Thus, soil water content may have an important effect on DON versus mineral N dominance in Mediterranean ecosystems

Biased activity of soluble guanylyl cyclase:the Janus face of thymoquinone

The natural compound thymoquinone, extracted from Nigella sativa(black cumin), is widely used in humans for its anti-oxidative properties. Thymoquinone is known for its acute endotheliumindependent vasodilator effects in isolated rat aortae and pulmonary arteries, depending in part on activation of adenosine triphosphate-sensitive potassium channels and inhibition of voltage-dependent calcium channels. The compound also improves endothelial dysfunction in mesenteric arteries of ageing rodents and in aortae of rabbits treated with pyrogallol, by inhibiting oxidative stress. Serendipitously,thymoquinone was found to augment contractions in isolated arteries with endothelium of both rats and pigs. The endothelium-dependent augmentation it causes counterintuitively depends on biased activation of soluble guanylyl cyclase(sGC) producing inosine 3',5'-cyclic monophosphate(cyclic IMP) rather than guanosine 3',5'-cyclic monophosphate. This phenomenon shows a striking mechanistic similarity to the hypoxic augmentation previously observed in porcine coronary arteries. The cyclic IMP preferentially produced under thymoquinone exposure causes an increased contractility of arterial smooth muscle by interfering with calcium homeostasis. This brief review summarizes the vascular pharmacology of thymoquinone, focussing in particular on how the compound causes endothelium-dependent contractions by biasing the activity of sGC.

Effect of planting date and nitrogen fertilization on photosynthesis and soluble carbohydrate contents of cotton in relation to silverleaf whitefly （Bemisia tabaci biotype “B”） populations

The impacts of planting date and nitrogen fertilization on cotton （Gossypium hirsutum L.） photosynthesis and soluble carbohydrate contents in relation to silverleaf whitefly, Bemisia tabaci （Gennadius） biotype “B”, populations were examined in field experiments. Cotton planted in late April and early June was treated with 0, 112, 168 and 224 kg/N hectare in soil using urea fertilizer. The mean photosynthetic rate of April-planted cotton was 4%-20% higher than that of June-planted cotton early in the season, but 10%- 18% lower than that of June-planted cotton late in the season. The photosynthetic rates for both planting dates were positively correlated with levels of added nitrogen. While levels of glucose for both planting dates were positively correlated with nitrogen levels, fructose and sucrose levels were not. The mean levels of fructose were up to 40% lower, while that of sucrose were up to 59% higher, in April-planted cotton than in June-planted cotton. Levels of photosynthetic rate or stomatal conductance were not correlated with adult whitefly densities for either planting date. Levels of glucose and fructose were positively correlated with whitefly densities only for June-planted cotton late in the season.