中华绒螯蟹在不同pH下氨氮排泄和血淋巴含氮成分的变化

为研究不同环境pH对中华绒螯蟹(Eriocheir sinensis)氮排泄的影响,将性成熟的中华绒螯蟹置于pH 4.5、6.0、7.5、9.0和10.5的环境中,24h后测定血淋巴中不同含氮成分的变化.结果表明,环境pH从4.5到9.0,中华绒螯蟹的氨氮排泄无显著变化,当pH升高到10.5时,氨氮排泄受到显著抑制;同时环境pH的升高还导致血淋巴pH上升,在pH 10.5时,血淋巴氨氮、尿素氮和尿酸的含量也显著上升分别达到(5.90±0.61) μg/mL、(2.47±0.14)μg/mL和(0.096±0.002)μmol/mL.实验结果还显示,高pH环境影响中华绒螯蟹的蛋白质和氨基酸的代谢水平,降低血淋巴总蛋白和血蓝蛋白的含量,而游离氨基酸含量显著增加,它们的变化可能同机体的氨中毒解毒机制有关.     

Efficient docosahexaenoic acid production by Schizochytrium sp. via a two-phase pH control strategy using ammonia and citric acid as pH regulators

The cell growth and docosahexaenoic acid (DHA) synthesis of Schizochytrium sp. are closely related to the culture pH. A two-phase pH control strategy based on nitrogen consumption was developed in which pH 7.0 was used for biomass accumulation and pH 5.0 for DHA synthesis. Using this strategy, the cell dry weight and DHA content reached 98.07 and 25.85 g/L, respectively. Furthermore, ammonia and citric acid were used as pH regulators. Application of citric acid further resulted in 7.88 and 4.87% improvements of total lipids and the ratio of DHA to total fatty acids, respectively. Ammonia, as a suitable nitrogen source, promoted non-lipid biomass accumulation. Using this method, a maximum DHA yield of 32.75 g/L was obtained with non-lipid biomass (58.01 g/L) and the ratio of DHA to total fatty acids (52.36%). This study provides an easy strategy for large-scale industrial production of DHA via high-cell-density fermentation of Schizochytrium sp.     

大型真菌中SSR分子标记的开发与应用进展

SSR分子标记是近年来普遍应用的分子标记之一。大型真菌中常用的SSR分子标记开发策略有三类,包括传统基因文库筛选法、富集文库筛选法和数据库筛选法,其中富集文库筛选法因其分离效率高而被采用较多。本文综述大型真菌中SSR分子标记的应用现状,发现相关研究多数集中于种系鉴定和遗传多样性分析,有关遗传图谱构建和辅助育种虽有涉及但研究较少。讨论了SSR分子标记在大型真菌研究中存在的问题与发展前景。     

不同盐度、pH条件下氨氮对管角螺稚贝毒性影响

在水温28.5℃,采用实验生态学方法研究了不同盐度、pH条件下氨氮对管角螺(Hemifusus tuba)稚贝[壳高(11.3±0.11)mm,n=30]毒性的影响。结果表明,(1)盐度对氨氮的毒性有较大影响,随着盐度的降低,氨氮在水体中的毒性增强;盐度为16、19、23和28,总氨氮对稚贝的96h半数致死浓度(96hLC50)分别为36.5、43.7、52.6和58.8mg/L,安全浓度(SC)为3.7、4.4、5.3和5.9mg/L。(2)氨氮在水体中的毒性随pH的升高而增强,pH为7.6、8.0、8.4和8.8时,总氨氮对稚贝的96hLC50依次为58.3、54.5、50.6和20.2mg/L,对应的SC依次为5.8、5.5、5.1和2.0mg/L。氨氮在pH8.8时对稚贝的96hLC50急剧下降,其毒性是在pH7.6时的2.9倍。     

pH值对厚颌鲂幼鱼的耗氧率及窒息点的影响

在密封式流水呼吸室内,对厚颌鲂Megalobrama pellegrini幼鱼在pH值分别为5.5、6.0、6.5、7.0、7.5、8.0和8.5试验用水条件下的耗氧率进行了测定.结果 显示:厚颌鲂幼鱼耗氧率存在明显的昼夜变化,白天高于晚上,下午高于上午,夜间变化不大.不同pH值的平均耗氧率为0.7135 mg/g · h,平均耗氧率最高是在pH7.5时,为0.8665 mg/g · h,平均耗氧率最低是在pH5.5时,为0.5397 mg/g · h.在密封式呼吸室内测定pH值在5.5、6.0、6.5、7.0、7.5、8.0和8.5试验用水条件下的厚颌鲂幼鱼的窒息点,分别为1.3920、1.3067、1.1547、1.0683、1.0933、1.1733和1.2331 mg/L,平均窒息点为1.2008 mg/L.     

川西亚高山针叶林树种云杉和冷杉土壤酸碱性差异及其机制

比较了川西亚高山针叶林主要树种粗枝云杉(Picea asperata)和岷江冷杉(Abies faxoniana)样地各土层(0—5 cm、5—10cm、10—20 cm)土壤pH值差异,并从两树种养分吸收和养分归还相关累积H~+输入方面探究其差异原因。研究结果表明:云杉样地各土层土壤pH值均显著高于冷杉样地(P0.05);云杉样地地被物累积H~+输入显著低于冷杉样地(P0.05);云杉样地凋落物中P、Mg、N、C平均浓度显著低于冷杉(P0.05),而Ca、C/N、木质素/N、C/P显著高于冷杉样地(P0.05),两树种凋落物中木质素、K平均浓度无显著差异。云杉和冷杉凋落物化学特性主成分分析PC_1、PC_2方差贡献率分别为73.7%和15.6%,累积方差贡献率为89.4%,其中PC_1主要综合Ca、C/P、C/N、木质素/N、P、N、Mg的信息;PC_2主要综合木质素、K、C的信息。各土层土壤pH值均与地被物累积H~+输入显著负相关,与PC_1样本分数显著正相关。研究结论:云杉和冷杉样地土壤pH值存在显著树种差异,且云杉使土壤pH值变大,冷杉使土壤pH值变小,这主要与地被物形成以及凋落物化学特性有关,即与凋落物的量和凋落物分解速率、凋落物养分归还率密切相关。     

The influence of pH on sulphite formation by yeasts

The influence of the initial pH of the substrate on the sulphite formation of three low-sulphite-and five high-sulphite-forming yeasts is described. Four distinctly different groups become apparent. The need for better evaluation of pure culture wine yeasts is stressed.     

用氨气敏电极测定L—天门冬酰胺酶的活力

本文建立了用氨气敏电极测定发酵液和细胞悬浮液中Ｌ－天门冬酰胺酶的方法,发现样品加入的一些化学试剂对测定结果有影响,而将样品稀释到一定程度可以消除这些影响。实验结果表明,用氨电极测定的精密度优于用奈斯勒试剂测定的精密度。     

Models for relating pH measurements in water and calcium chloride for a wide range of pH,soil types and depths

Soil pH is commonly measured in water (pHw) or 0.01 M CaCl₂ (pH_Ca). The need to convert between these methods has led to the publication of linear, quadratic and cubic polynomial relationships for limited suites of soils. Concerns over the applicability of such relationships when mapping a wide range of soils and pH led to the establishment of a database of pH_W and pH_Ca values on each of 7894 samples from soil survey and field experimental sites in Queensland. The relationship between pH_W and pH_Ca across all soils was investigated and preliminary results examining the effect of soil depth and soil type on the relationship are presented.For all soils and depths, a linear regression accounted for 93.2% of the variation but did not predict pH_Ca well at very high or low pH_W values. The inclusion of second and third powers of pH_W accounted for significantly more of the variation (R²=0.94) in pH_Ca and the resultant curve matched the data better at high and low pH.Analysis of surface, sub-surface and subsoil groupings did not reveal any appreciable differences in the relationship between pH_W and pH_Ca attributable to depth. In contrast, differences in the relationship were evident between soil types. Generally, the mildly leached soils had linear relationships, while the weathered soils were distinctly curvilinear at low pH.     

温度、水分和施氮量对温室土壤pH及电导率的耦合作用

选取5年棚龄温室土壤样品进行培养试验,研究温度(T)、水分(W)、施氮量(N)及其耦合效应对温室土壤pH及电导率（EC）的影响.结果表明：随着培养时间延长,温室土壤pH逐渐下降,下降速率可用一级反应模型进行定量描述,其速率常数受各因素的影响表现为N>W>W×N>T×W. EC在培养的第1周内快速上升到最大值后略有下降,并在培养后期逐渐趋于稳态值（EC_sty）,EC_sty受N、W、T×W、T及W×N的影响,其中N、W、T×W和T的影响达到极显著水平,W×N的影响达到显著水平;通过减小施氮量及适当亏水灌溉可有效延缓温室土壤酸化和EC升高.建立了pH下降速率常数及EC_sty回归模型,可对不同环境及水肥条件下土壤酸化及EC变化进行预测.     

The effect of soil pH on the ability of ectomycorrhizal fungi to increase the growth of Eucalyptus globulus Labill.

We examined the effect of two levels of soil pH (5 and 6) on the ability (effectiveness) of ectomycorrhizal fungi to increase the growth of Eucalyptus globulus Labill. at a deficient supply of P. Plants were inoculated with one of six fungal isolates [Laccaria laccata (Scop. ex Fr.) Berk. and Br. (isolates A and B), Pisolithus tinctorius (Pers.) Coker and Couch (isolates A and B), Descolea maculata Bough. and Mal. and Setchelliogaster sp. nov.] and were grown in a P-deficient sand, in pots, in a temperature-controlled glasshouse. Seedlings were harvested 89 days after planting and were assessed for dry matter production, tissue P concentrations, ectomycorrhizal colonization of roots and hyphal development in soil.Uninoculated plants had less than 5% of their fine root length colonized by ectomycorrhizal fungi. In contrast, inoculated plants had 30% or greater of their fine root length ectomycorrhizal. Inoculation increased the uptake of P and growth of plants for all isolates and at both levels of soil pH, although growth responses to inoculation were greater at pH 6, particularly for the two L. laccata isolates. Isolates which colonized roots most extensively increased plant growth to the greatest extent. D. maculata was the most effective fungal isolate at pH 5, and both D. maculata and L. laccata A were most effective at pH 6. The effects of soil pH on plant growth were also related to some extent to the effects of soil pH on colonized root length. Growth responses to inoculation were related less well to hyphal development in soil. The L. laccata isolates formed more hyphae in soil (on a per pot, per m of fine root, and per m of colonized fine root basis) than other fungal isolates, but were not always more effective in increasing plant grown.     

土壤pH对玉米与微生物竞争吸收氨基酸的影响

化学合成肥料的大量使用导致土壤pH发生显著变化,但其对植物与根际微生物竞争吸收氨基酸的影响机制尚不明确.本试验通过电解法调节杭州红壤和铁岭棕壤两种土壤pH, 采用外源添加¹⁵N标记甘氨酸短期吸收4 h的方法,研究了pH对玉米及根际微生物竞争吸收氨基酸的影响.结果表明:土壤pH对玉米根和地上部生物量有显著影响,对于红壤,pH为6.48最适宜玉米生长,且玉米地上部¹⁵N丰度和¹⁵N-甘氨酸吸收量也显著高于其他处理;对于棕壤,pH为7.65最适宜玉米生长,其玉米地上部和根系¹⁵N丰度显著低于pH为5.78处理,但¹⁵N-甘氨酸吸收量显著高于其他处理.红壤pH为6.48条件下,其微生物生物量碳相对较高,而棕壤pH为7.65条件下,其微生物生物量碳相对较低.综合根系吸收、转运及微生物竞争吸收的结果,推断红壤在pH为6.48条件下虽然面临着微生物的竞争吸收,但生长于其上的玉米通过提高吸收速率和转移比率提高了氨基酸的吸收量;在pH为7.65的棕壤中,微生物活性较低,降低了与玉米竞争吸收氨基酸的能力,从而增加了玉米对氨基酸的吸收量.     

Screening of soil fungi for in vitro degradation of endosulfan

Intensive use of endosulfan has resulted in contamination of soil and water environments at various sites in Pakistan. This study was conducted to isolate efficient endosulfan-degrading fungal strains from contaminated soils. Sixteen fungal strains were isolated from fifteen specific sites by employing enrichment techniques while using endosulfan as a sole sulfur source, and tested for their potential to degrade endosulfan. Among these fungal strains, Chaetosartorya stromatoides, Aspergillus terricola, and Aspergillus terreus degraded both α- and β-endosulfan upto 75% in addition to ∼20% abiotic degradation of the spiked amount (100 mg l⁻¹) in the broth within 12 days of incubation. Biodegradation of endosulfan by soil fungi was accompanied by a substantial decrease in pH of the broth from 7.0 to 3.2. The major metabolic product was endosulfan diol along with very low concentrations of endosulfan ether. Maximum biodegradation of endosulfan by these selected fungal strains was found at an initial broth pH of 6, incubation temperature of 30°C and under agitation conditions. This study indicates that the isolated strains carried efficient enzyme systems required for bioremediation of endosulfan-contaminated soil and water environments.     

Bulk soil pH and rhizosphere pH of peach trees in calcareous and alkaline soils as affected by the form of nitrogen fertilizers

One-year old nectarine trees [Prunus persica, Batsch var. nectarina (Ait.) Maxim.], cv Nectaross grafted on P.S.B2 peach seedlings [Prunus persica (L.) Batsch] were grown for five months in 4-litre pots filled with two alkaline soils, one of which was also calcareous. Soils were regularly subjected to fertigation with either ammonium sulphate or calcium nitrate providing a total of 550 mg N/tree. Trees were also grown in such soils receiving only deionized water, as controls. Rhizosphere pH, measured by the use of a microelectrode inserted in agar sheet containing a bromocresol purple as pH indicator and placed on selected roots, was decreased by about 2–3 units compared to the bulk soil pH in all treatments. This decrease was slightly less marked when plants were supplied with calcium nitrate rather than ammonium sulphate or control. Measurements conducted during the course of the experiment indicated that ammonium concentration was similar in the solution of soils receiving the two N fertilizers. During the experiment, soil solution nitrate-N averaged 115 mg L^–1 in soil fertilized with calcium nitrate, 68 mg L^–1 in those receiving ammonium sulphate and 1 mg L^–1 in control soils. At the end of the experiment nitrate concentrations were similar in soils receiving the two N sources and bulk soil pH was decreased by about 0.4 units by ammonium sulphate fertigation: these evidences suggest a rapid soil nitriflcation activity of added ammonium. Symptoms of interveinal chlorosis in apical leaves appeared during the course of the experiment in trees planted in the alkaline-calcareous soil when calcium nitrate was added. The slightly higher rhizosphere pH for calcium nitrate-fed plants may have contributed to this. The findings suggest that using ammonium sulphate in a liquid form (e.g. by fertigation) in high-pH soils leads to their acidification and the micronutrient availability may be improved.     

Effect of annual variation in soil pH on available soil nutrients in pear orchards

Soil pH is an important factor affecting the availability of soil nutrients that impact plant growth. Given the susceptibility of soil pH to excessive fertilization and the widespread use of manures, it is essential to examine the influence of soil pH on the distribution and availability of soil nutrients. We sampled and analyzed brown soils from pear orchards in thirteen towns in Wendeng county. Samples were obtained from areas along or between rows of trees at specified distances and depths. The results showed that the soil pH fluctuated from 4.06 to 6.59 in October 2008 and from 4.24 to 7.57 in April 2009. The quantity of soil samples with pH below 5.50 increased by 34.6%. Analysis of the soil pH for samples obtained along the rows of trees showed that the pH decreased as the depth increased (except for the range 5.5 to 6.0); soil pH in the samples obtained between the rows of trees demonstrated different trends. The average organic matter (O.M.) content as well as the N (NH₄⁺) and available P, K, Cu, Zn, Fe, and Mn contents in the samples collected in October 2008 were higher than those observed in April 2009. Conversely, the values for other available nutrients were lower than those in the samples collected in April 2009. The available nutrients and organic matter (O.M.) content in different pH ranges varied. The soil pH was significantly or very significantly correlated with N (NH₄⁺ and NO₃^-), available K, Cu, Fe, and exchangeable Ca for the October 2008 samples, while a significant or very significant correlation existed between N (NH₄⁺), available P, Zn, exchangeable Ca, and exchangeable Mg for the April 2009 samples. The correlations between soil pH and the amounts of available nutrients and organic matter (O.M.) along the rows of trees in September 2009 were nearly consistent with those between the rows.     

Effect of annual variation in soil pH on available soil nutrients in pear orchards

Soil pH is an important factor affecting the availability of soil nutrients that impact plant growth. Given the susceptibility of soil pH to excessive fertilization and the widespread use of manures, it is essential to examine the influence of soil pH on the distribution and availability of soil nutrients. We sampled and analyzed brown soils from pear orchards in thirteen towns in Wendeng county. Samples were obtained from areas along or between rows of trees at specified distances and depths. The results showed that the soil pH fluctuated from 4.06 to 6.59 in October 2008 and from 4.24 to 7.57 in April 2009. The quantity of soil samples with pH below 5.50 increased by 34.6%. Analysis of the soil pH for samples obtained along the rows of trees showed that the pH decreased as the depth increased (except for the range 5.5 to 6.0); soil pH in the samples obtained between the rows of trees demonstrated different trends. The average organic matter (O.M.) content as well as the N (NH₄⁺) and available P, K, Cu, Zn, Fe, and Mn contents in the samples collected in October 2008 were higher than those observed in April 2009. Conversely, the values for other available nutrients were lower than those in the samples collected in April 2009. The available nutrients and organic matter (O.M.) content in different pH ranges varied. The soil pH was significantly or very significantly correlated with N (NH₄⁺ and NO₃^-), available K, Cu, Fe, and exchangeable Ca for the October 2008 samples, while a significant or very significant correlation existed between N (NH₄⁺), available P, Zn, exchangeable Ca, and exchangeable Mg for the April 2009 samples. The correlations between soil pH and the amounts of available nutrients and organic matter (O.M.) along the rows of trees in September 2009 were nearly consistent with those between the rows.     

Ammonia excretion byAzotobacter chroococcum in liquid culture and soil in the presence of manganese and clay minerals

Summary Ammonia excretion was studied in the presence of Mn⁺⁺ in liquid culture and soil with amendments of the minerals using two ammonia excreting strains ofAzotobacter chroococcum (AC2 and AC50) and a non-excreting strain (AC45) under sterilized as well as unsterilized conditions. Ammonia excretion increased in the presence of 1×10⁻⁷M Mn⁺⁺ in liquid culture as well as in soil. But there was a decrease in ammonia excretion with increasing clay content.     

Intracellular pH and the increase in protein synthesis accompanying activation of Xenopus eggs

Metabolic activation following egg fertilization corresponds to an increase in protein synthesis and the initiation of DNA synthesis, which lead to cell division and development of the embryo. Since in several biological systems protein synthesis is regulated by intracellular pH (pHi), we have decided to investigate the situation during Xenopus egg activation. We confirmed that egg activation is accompanied by a pHi rise of 0.3 pH unit. Measurements of the rates of protein synthesis is unactivated and activated eggs, after microinjection of 3H-leucine, demonstrated that activation was followed by a 2.5-fold increase. Treatment of unactivated eggs with weak bases also increased pHi, but did not result in an increase in the rate of protein synthesis. Moreover, in vitro translation in cytoplasmic extracts was found to be pH-independent, at least between 6.8 and 8.2.     

Effects of soil pH and associated cations on growth of apple trees planted in old orchard soil

Summary Trunk circumferences were measured on apple trees which had been grown for 5 to 10 years on land previously in apple orchard. Soil beneath each tree was analysed for soil acidity characteristics and basic cations. Tree growth (trunk circumference), was generally retarded but highly variable, but correlated well with the soil measurements in four of the six orchards investigated. Size of Delicious, Tydeman and Rome Beauty cultivars correlated positively with soil pH and negatively with 0.02M CaCl₂-soluble Al and Mn, while that of McIntosh grown adjacent to the Delicious and Tydeman trees in two of those orchards correlated little or not at all with these soil acidity characteristics. However, in the three orchards where McIntosh trees were grown, their size correlated (r=0.72^**, 0.71^**, 0.54^**) well with exchangeable soil Mg. The effects of soil acidity and associated nutrient deficiencies on growth of young apple trees is discussed.Contribution No. 602.