杉木和米槠凋落叶DOM对土壤碳矿化的影响

DOM(Dissolved organic matter)是土壤微生物呼吸的重要底物,凋落物淋溶的DOM对土壤碳矿化具有重要影响。选择中亚热带地区具有代表性的杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)凋落叶作为研究对象,通过两个月的短期室内培养,把不同凋落叶浸提出的DOM添加到培养瓶中,定期测定土壤碳矿化速率,计算土壤碳累积矿化量,探讨两种等浓度等量DOM添加对土壤碳矿化的影响,并分析DOM化学性质在土壤碳矿化过程中的重要性。结果表明:米槠凋落叶浸提得到的DOC(Dissolved organic carbon)和DON(Dissolved organic nitrogen)浓度均显著高于杉木凋落叶的(P0.05),而杉木凋落叶浸提得到的DOM的UV吸收值(SUVA_(254))和HIX(Humification index)均显著低于米槠凋落叶的(P0.01)。添加等浓度等量杉木和米槠凋落叶DOM到土壤中均显著增加了土壤碳矿化速率,在第1天内分别比对照高198%和168%,3d后下降到61.8%和44.1%,14d后基本处于平稳状态,表明外源有机物添加对土壤碳矿化的前期影响较大。培养过程中,添加杉木和米槠凋落叶DOM的土壤碳矿化累积量均能采用双因素指数模型进行拟合(r~2=0.99),但添加两者凋落叶DOM后土壤碳矿化累积量没有显著差异。     

不同来源可溶性有机物对亚热带森林土壤CO2排放的影响

采用室内培养法, 比较分析了亚热带地区杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)鲜叶及凋落叶浸提得到的可溶性有机物(dissolved organic matter, DOM)组成和化学性质差异对土壤CO₂排放的影响。结果表明: 添加不同来源的DOM后, 土壤CO₂瞬时排放速率在培养第1天内均显著高于对照(添加去离子水) (p < 0.05), 分别比对照增加了91.5% (添加杉木鲜叶DOM)、12.8% (添加米槠鲜叶DOM)、61.0% (添加杉木凋落叶DOM)和113.3% (添加米槠凋落叶DOM), 但培养5天后, 分别下降到对照的24.1%、8.3%、14.6%和13.2%, 随后逐渐趋于平稳。单次添加外源DOM到土壤中, 引起土壤CO₂排放速率增加的强度较大, 但持续时间短暂。培养31天时, 添加不同来源的DOM均对土壤CO₂累积排放量具有显著影响(p < 0.05), 而在培养59天时, 添加杉木鲜叶和凋落叶DOM的土壤CO₂累积排放量均显著高于添加米槠鲜叶和凋落叶DOM的土壤CO₂累积排放量, 但添加相同树种鲜叶与凋落叶DOM的土壤CO₂累积排放量之间差异不显著。培养结束后, 添加杉木鲜叶DOM和杉木凋落叶DOM后增加的土壤碳排放量, 分别是外源添加可溶性有机碳量的1.76倍和2.56倍, 而添加米槠鲜叶DOM和米槠凋落叶DOM后增加的土壤碳排放量只占外源添加可溶性有机碳量的22.5%和50.0%, 表明单次添加不同来源的DOM对土壤总有机碳库的影响是不一致的。     

不同化学性质叶凋落物添加对土壤有机碳矿化及激发效应的影响

凋落物输入可显著影响土壤有机碳(SOC)矿化速率,但添加不同化学性质叶凋落物对土壤有机碳矿化释放CO₂及激发效应的影响及其机理仍不清楚。本研究将亚热带6种树种¹³C标记的叶凋落物添加至天然次生林0～10 cm原位土柱中,比较不同树种叶凋落物添加对土壤总CO₂、外源凋落物和土壤来源CO₂释放速率和累积量以及激发效应的影响,并量化叶凋落物化学性质与土壤CO₂释放累积量、激发效应的相关关系。结果表明: 添加叶凋落物能够显著提高土壤总CO₂和土壤来源CO₂释放量,存在显著正激发效应,激发效应值为68%～128%。不同树种叶凋落物添加对土壤有机碳矿化和激发效应的影响存在显著差异。Pearson相关分析和逐步多元线性回归分析发现,凋落物来源CO₂释放累积量与叶凋落物C、P和纤维素含量呈显著负相关,而土壤来源CO₂释放量与叶凋落物C:N和木质素:N呈显著正相关。综上,不同化学性质的叶凋落物对土壤有机碳矿化和激发效应的影响存在异质性,在亚热带地区森林类型转变过程中营造具有高质量叶凋落物的人工林将有助于减少森林土壤碳损失。     

亚热带森林不同植物及器官来源的可溶性有机质输入对土壤激发效应的影响及其作用机理

外源有机物的输入可以通过正负激发效应影响土壤有机碳(SOC)的矿化。然而, 当前的研究较少考虑不同植物及器官来源可溶性有机质(DOM)输入对土壤激发效应的影响及其作用机理。该研究以武夷山森林土壤为研究对象, 以室内培养的方式向土壤中添加¹³C标记青冈(Cyclobalanopsis glauca)、杉木(Cunninghamia lanceolata)、木莲(Manglietia fordiana)和相思(Acacia confusa)这4种植物的根和叶来源DOM, 研究不同植物及器官来源DOM输入对土壤激发效应的影响及其作用机理。主要结果: 不同植物及器官来源DOM添加初期加快了SOC的矿化, 呈现正激发效应, 随后转为负激发效应。从整个培养期(90天)的累积激发效应来看, DOM的输入均抑制了SOC的矿化, 使其矿化量减少22%-49%, 其中青冈根DOM输入使SOC的矿化量减少最多, 而由木莲叶DOM输入减少的SOC矿化量最少。DOM输入引起的土壤激发效应强度受不同植物器官影响明显, 具体表现在植物根来源DOM输入所引起的土壤激发效应强度显著高于植物叶来源DOM输入所引起的激发效应强度(相思除外)。DOM的输入总体上提高了土壤微生物生物量碳(MBC)含量、土壤β-葡萄糖苷酶活性、纤维素酶活性以及土壤有效氮含量, 而对微生物群落组成无明显影响。从结构方程模型来看, DOM输入所引起的土壤激发效应主要受土壤微生物对外源碳的利用(¹³C-MBC)、纤维素酶活性以及土壤有效氮含量的影响, 这些因子的变化可解释植物叶来源DOM和根来源DOM添加处理下土壤激发效应变化的68%和86%。该研究结果表明在土壤氮充足的条件下, DOM的输入可以通过提高微生物生物量、土壤酶活性来加快分解所添加的外源有机物, 从而减少了对SOC的分解。因此, 在该研究中“底物优先利用”是土壤激发效应的主要作用机理。     

DOM对米槠次生林不同土层土壤微生物呼吸及其熵值的影响

可溶性有机质(Dissolved organic matter,DOM)作为土壤可溶性有机碳的重要来源,进入土壤之后通过改变土壤微生物数量和活性影响土壤矿化。DOM输入对土壤微生物呼吸和熵值的研究多集中在表层土壤,但对深层土壤微生物呼吸和熵值的影响关注较少。通过室内培养实验(120 d)研究米槠(Castanopsis carlesii)鲜叶DOM添加对表层土壤(0—10 cm)和深层土壤(40—60 cm)微生物呼吸及其土壤代谢熵和微生物熵的影响,为揭示DOM输入对亚热带森林土壤碳过程的影响提供理论依据。结果表明,在培养第1天,添加DOM的表层和深层土壤CO_2瞬时排放速率均显著高于对照(P0.001),分别是对照(不添加DOM)的3.58倍和6.93倍,之后显著下降。就累积排放量而言,无论是DOM添加处理还是对照,表层土壤显著大于深层土壤;在米槠鲜叶DOM添加后,表层土壤累积排放量显著大于对照的表层土壤(P0.001),但DOM添加处理深层土壤累积排放量与对照的深层土壤无明显差异。就微生物生物量碳而言,表层土壤微生物生物量碳含量在培养期间显著大于深层土壤。在整个添加DOM培养期间,表层土壤微生物生物量碳含量显著大于表层对照土壤,深层土壤微生物生物量碳含量显著大于深层对照土壤(第3天除外)。培养结束时(120 d),米槠鲜叶DOM添加处理下,表层土壤和深层土壤有机碳含量与第3天相比分别减少26%和19%。米槠鲜叶DOM添加处理后的深层土壤代谢熵(qCO_2)显著低于对照的深层土壤和DOM添加处理的表层土壤qCO_2(P0.001),说明外源DOM进入深层土壤后提高了土壤微生物对碳的利用效率。米槠鲜叶DOM添加处理后的深层土壤微生物熵是培养第3天的1.58倍,显著大于培养初期(P0.05),而DOM添加处理的表层土壤、对照的表层土壤与深层土壤的微生物熵分别是培养第3天的68%、79%和21%,说明DOM添加提高了深层土壤质量。     

添加混合凋落物对沙丘草地土壤有机碳矿化的影响

土壤有机碳矿化是调节温室气体排放、土壤有机质形成以及土壤生物和植物营养供应的重要过程,植物残体分解释放CO_2对土壤有机碳矿化有着重要影响。通过对科尔沁沙地沙丘草地4种优势植物叶凋落物的混合培养试验,测定了凋落物培养过程中CO_2释放速率及其累积释放量,比较了混合凋落物CO_2释放量实测值与预测值的差异,分析了凋落物化学成分和物种多样性(包括物种丰富度和物种组成)与土壤有机碳矿化的相关关系,以期解释添加混合凋落物对土壤有机碳矿化的影响。结果表明,混合凋落物物种丰富度对土壤有机碳矿化的影响不显著,而凋落物一些化学性质与土壤有机碳矿化紧密相关;所有混合组合处理中,80%的凋落物组合处理对土壤有机碳矿化产生显著(P0.05)的非加和效应;氮含量较高的豆科植物达乌里胡枝子凋落物与禾本科植物凋落物混合后土壤有机碳矿化表现极显著(P0.001)的协同非加和效应,而禾本科植物凋落物交互混合后土壤有机碳矿化产生显著拮抗非加和效应,这可能是凋落物化学成分相似或凋落物叶片的空间异质性引起的。     

米槠常绿阔叶次生林和杉木人工林穿透雨和树干径流可溶性有机质浓度和质量的比较

以中亚热带米槠常绿阔叶次生林和杉木人工林为研究对象,定位观测了穿透雨和树干径流中可溶性有机质(DOM)浓度的变化,分析了DOM腐殖化程度和芳香性特征.结果表明: 研究区米槠次生林穿透雨可溶性有机碳(DOC)浓度的变化幅度明显高于杉木人工林,且前者DOC浓度显著高于后者,相比大气降水DOC浓度,分别增加了7.2和3.2倍.杉木人工林树干径流DOC浓度约为米槠次生林的2.5倍,且两种林分树干径流DOC浓度均呈现旱季高于雨季的趋势.相关分析结果显示:米槠次生林和杉木人工林树干径流DOC浓度均与其相应的水量呈极显著负相关.米槠次生林穿透雨DOM腐殖化程度和芳香性均显著高于杉木人工林;相反,杉木人工林树干径流DOM腐殖化程度和芳香性均显著高于米槠次生林.说明米槠次生林穿透雨中DOM结构较复杂且具有较多的芳香族化合物,而杉木人工林树干径流中DOM结构复杂于米槠次生林.米槠次生林和杉木人工林穿透雨和树干径流的DOM数量和质量具有明显差异,对土壤有机碳的积累可能产生重要影响.     

中亚热带杉木人工林和米槠次生林凋落物添加与去除对土壤呼吸的影响

在未来大气CO₂浓度升高的背景下, 植被净初级生产力的增加将促使森林土壤碳输入增多。凋落物是土壤碳库的重要来源, 对土壤呼吸会产生重要影响。为了模拟植物净初级生产力提高、凋落物产量增加情景下凋落物对土壤呼吸和土壤碳库的影响, 2013年1月到2014年12月, 在福建省三明市陈大镇国有林场, 在杉木(Cunninghamia lanceolata)人工林和米槠(Castanopsis carlesii)次生林, 通过设置去除凋落物、添加凋落物和对照(保留凋落物, 不做任何处理)处理, 研究了土壤呼吸和土壤碳库的动态变化。研究发现: 土壤含水量在10%-25%范围内, 土壤呼吸温度敏感性指数(Q₁₀)随着土壤含水量的增加呈递增趋势, 当含水量<10%时, 由于干旱胁迫打破了土壤呼吸与温度之间的耦合, 改变了Q₁₀值, 使得Q₁₀值小于1。土壤呼吸与凋落物输入量呈显著的线性正相关关系, 杉木人工林对照和添加凋落物处理及米槠次生林对照处理, 土壤呼吸与2个月前的凋落物输入量相关性最好。而米槠次生林添加凋落物处理, 土壤呼吸与当月的凋落物输入量相关性最好, 不同林分凋落物呼吸对土壤呼吸的贡献率不同, 米槠次生林凋落物层呼吸年通量明显大于杉木人工林, 分别占各林分土壤总呼吸的34.4%和15.1%, 添加凋落物后, 杉木人工林和米槠次生林的土壤呼吸速率增加, 但添加凋落物处理的土壤呼吸年通量与对照的差值小于年凋落物输入量。因此, 在未来全球CO₂升高背景下, 植被碳储量的增加、凋落物增加并没有引起土壤呼吸成倍增加, 更有利于中亚热带地区土壤碳吸存。     

三个亚热带森林优势种凋落物非结构性碳水化合物含量的季节动态

非结构性碳水化合物(NSC)是凋落物中的易分解组分,在凋落物分解早期快速释放进入土壤并被微生物利用,参与森林土壤生物地球化学循环,因此新鲜凋落物中NSC变化规律是认识森林土壤碳和养分循环的关键之一。选取亚热带常绿阔叶林优势树种米槠(Castanopsis carlesii)和主要造林树种杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)为研究对象,分析其新鲜凋落叶和凋落枝中NSC(可溶性糖和淀粉)含量的动态变化规律。结果表明：凋落物中NSC含量在不同月份表现出明显的时间动态,米槠、杉木和马尾松凋落叶和凋落枝中NSC含量总体上在11—12月呈上升趋势,而在2—6月呈缓慢下降趋势。不同类型的凋落物NSC含量存在显著差异,米槠、杉木和马尾松凋落叶中NSC含量分别为3.03%—3.56%、2.18%—4.37%、3.38%—4.89%,凋落枝中NSC含量分别为1.87%—4.22%、2.88%—4.28%、2.75%—5.27%,米槠和马尾松凋落叶中NSC含量高于凋落枝,而杉木凋落枝中NSC含量高于凋落叶。不同树种凋落物NSC含量差异显著,米槠和...     

亚热带不同树种凋落叶分解对氮添加的响应

为探究不同质量凋落物对氮(N)沉降的响应,该研究采用尼龙网袋分解法,在亚热带福建三明格氏栲(Castanopsis kawakamii)自然保护区的米槠(Castanopsiscarlesii)天然林,选取4种本区常见的具有不同初始化学性质的树种凋落叶进行模拟N沉降(N添加)分解实验(施N水平为对照0和50 kg·hm~(–2)·a~(–1))。研究结果表明:在2年的分解期内,对照处理的各树种凋落叶的分解速率依次为观光木(Michelia odora, 0.557 a~(–1))、米槠(0.440 a~(–1))、台湾相思(Acacia confusa, 0.357 a~(–1))、杉木(Cunninghamia lanceolata, 0.354 a~(–1)); N添加处理凋落叶分解速率依次为观光木(0.447 a~(–1))、米槠(0.354 a~(–1))、杉木(0.291 a~(–1))、台湾相思(0.230a~(–1)),除杉木凋落叶外, N添加显著降低了其他3种凋落叶分解速率。N添加不仅使4种树木凋落叶分解过程中的N释放减慢,同时还抑制凋落叶化学组成中木质素和纤维素的降解;N添加在凋落叶分解过程中总体上提高β-葡萄糖苷酶(βG)和酸性磷酸酶活性,对纤维素水解酶的活性影响不一致,而降低β-N-乙酰氨基葡萄糖苷酶活性和酚氧化酶活性。凋落叶分解速率与凋落叶中的碳获取酶(βG)活性以及其化学组分中的可萃取物含量极显著正相关,与初始碳浓度、纤维素和木质素含量极显著负相关,与初始N含量没有显著相关性。凋落物类型和N添加的交互作用虽未影响干质量损失速率,但对木质素和纤维素的降解具有显著效应。综上所述,化学组分比初始N含量能更好地预测凋落叶分解速率,而N添加主要通过抑制分解木质素的氧化酶(如PHO)来降低凋落叶分解速率。     

Internal radiotherapy of painful bone metastases

Internal radiotherapy is effective in the treatment of metastatic bone pain and can improve quality of life. A number of controlled studies using various agents have shown a mean response rate in pain relief of 70–80% of treated patients. Some investigators prefer radionuclides which emit low beta particles for the treatment of bone pain, because the assumption of lower bone marrow toxicity of this agents. However, neither dosimetric data for radiation absorbed dose to the bone marrow nor clinical blood count depression have shown any significant differences between these agents. Other researchers suggest enhanced antitumoral effects using high-energy beta emitters and propose aggressive first-line treatment in the early disease stage instead of using these radiopharmaceuticals only in end-stage patients suffering intractable bone pain. Another approach consists of including other treatment modalities such as autologous stem cell rescue or in combination with chemo or bisphosphonate therapy to a radionuclide treatment scheme. Future research should focus more on the curative effects of combination with radiosensitizer, for example, chemotherapy, or repeated treatments with bone seeking agents.     

Retention of radionuclides by some aquatic fresh water plants

The uptake of radionuclides ⁶⁰Co, ³²P and ¹³⁴Cs by some aquatic plants (Lemna gibba, Ceratophyllum demersum and Potamogeton crispus) present in the Ismailia Canal at different pH values and for different contamination periods was studied. The experimental results showed that the uptake generally decreases as the water pH increased. The tested macrophytes proved to be reliable biological indicators.     

13C-31P Couplings in the Study of Conformational Properties of Some Diastereomeric Nucleoside-3′-Thiophosphate Derivatives

Synthesis and stereochemical characterization of enantiomerically pure nucleoside-3′-phosphorothioate esters and salts are reported. Vicinal carbon–phosphorus couplings reflect different predominance of the ? conformation in the isomeric (Rp and Sp) esters, while for the salts the ?^t conformation prevails in both stereoisomers. The influence of solvent and temperature on the conformational preferences is also described.     

血清IL-6、IL-8、IgM抗体及T细胞亚群水平对新生儿先天性梅毒的诊断价值

目的:探讨血清白介素-6(IL-6)、白介素-8(IL-8)、IgM抗体及T细胞亚群对先天性梅毒新生儿的诊断价值。方法:选择2015年5月至2017年5月在我院进行临床治疗的先天性梅毒新生儿81例为观察组,另选同期来我院进行健康体检81例新生儿为对照组。比较两组患者血清IL-6、IL-8、T细胞亚群中CD~(3+)、CD~(4+)、CD~(8+)、CD~(4+)/CD~(8+)细胞及IgM抗体的阳性率。结果:治疗后,观察组血清IL-6、IL-8水平均明显高于对照组(P0.05),T细胞亚群中CD~(3+)、CD~(4+)、CD~(4+)/CD~(8+)明显低于对照组,而CD~(8+)T细胞比例高于对照组(P0.05)。19S-IgM-TP ELISA法检测出IgM的阳性率92.59%,明显高于TRUST法(74.07%)及TP-ELSA法(70.37%)(P0.05)。ROC曲线中,血清IL-8特异度为88.34%明显高于血清IL-6特异度81.48%、IgM抗体特异度60.13%、T细胞亚群特异度65.34%;IgM抗体的曲线面积88.91 cm~2明显大于IL-6的曲线面积45.09 cm~2、IL-8的曲线面积76.19 cm~2、T细胞亚群的曲线面积77.35 cm~2;T细胞亚群准备性67.89%明显高于IL-6准确性60.39%、IL-8准确性51.09%、IgM抗体准确性50.12;IgM抗体的灵敏度60.13%高于IL-6灵敏度59.19%、IL-8灵敏度42.35%、T细胞亚群灵敏度59.37%。具有比较意义(P0.05)。结论:血清IL-6、IL-8水平、T细胞亚群中CD~(3+)、CD~(4+)、CD~(8+)、CD~(4+)/CD~(8+)及IgM抗体阳性率是诊断先天性梅毒新生儿的重要指标。     

Synthesis, characterisation and solution behaviour of fluoroalkyl phosphoryl complexes of tin tetrachloride

The synthesis, characterisation and solution behaviour of a series of octahedral complexes SnCl₄·2L (L = R₂NP(O)(OCH₂CF₃)₂; R = Me (1); Et (2) or L = P(O)(OCH₂R_f)₃; R_f = CF₃ (3); C₂F₅ (4)) are described. Complexes 1-4 were prepared from SnCl₄ and 2 equiv. of the ligand, L, in anhydrous CH₂Cl₂ solution. The adducts have been characterised by multinuclear (¹H, ³¹P and ¹¹⁹Sn) NMR, IR spectroscopy and elemental analysis. In dichloromethane solution, the NMR data showed the presence of a mixture of cis and trans isomers for 1 and 2 and only the cis isomer for 3 and 4. The difference could be interpreted in terms of the electronic effects of the substituents on the phosphorus atom of the ligand. In addition, the solution structure of the complexes studied by variable temperature ³¹P-{¹H} and ¹H NMR in the presence of excess ligand indicated that the ligand exchange on the cis isomer dominates the chemistry. The metal-ligand exchange barriers were estimated to be 13.38 and 11.39 kcal/mol for 1 and 3, respectively. The results are discussed and compared with those previously reported for the related hexamethylphosphoramide adduct, SnCl₄·2HMPA.     

Microsampling of Fish Otoliths: A Comparison Between DM 2800 and Dremel in Stable Isotope Analysis

This paper describes and compares two microsampling methods, DM 2800 and Dremel, which were used in taking aragonite samples from otolith zones of cod, Gadus morhua, for stable isotope analysis. There were no significant differences between the two sampling methods both in carbon and oxygen isotope ratios (¹³C/¹²C, ¹⁸O/¹⁶O) and in annual and seasonal otolith zones. The possible finite effect with Dremel could be minimized or negligible by selecting otoliths of younger fishes. Thus, Dremel may be accepted as a convenient microsampling method in stable isotope analysis of otoliths.     

Ischemic changes in myocardial ionic contents of the isolated perfused rat hearts as studied by NMR

Using³¹P-,²³Na- and³⁹K-NMR, we assessed ischemic changes in high energy phosphates and ion contents of isolated perfused rat hearts continuously and systematically. To discriminate intra- and extracellular Na⁺, a shift reagent (Dy(TTHA)^3–) was used in²³Na-NMR study. In³⁹K-NMR study, the extracellular K⁺ signal was suppressed by inversion recovery pulse sequence in order to obtain intracellular K⁺ signal without using shift reagnets. During the early period of ischemia, increases in intracellular Na⁺ and inorganic phosphate (Pi) were observed in addition to the well-documented decreases in creatine phosphate and ATP and a fall of intracellular pH, suggesting an augmented operation of Na⁺–H⁺ exchange triggered by a fall of the intracellular pH resulted from breakdown of ATP. At around 15 min of ischemia, a second larger increase in intracellular Na⁺ and a decrease in intracellular K⁺ were observed in association with a second increase in Pi. This was accompnanied by an abrupt rise of the ventricular end-diastolic pressure. As there was a depletion of ATP at this time, the increase in intracellular Na⁺ and associated decrease in intracellular K⁺ may be explained by inhibition of the Na⁺–K⁺ ATPase due to the depletion of ATP. A longer observation with³¹P-NMR revealed a second phosphate peak (at lower magnetic field to ordinary Pi peak) which increased its intensity as ischemic time lengthened. The pH of this 2nd peak changed in parallel with the changes in pH of the bathing solution, indicating the appearance of a compartment whose hydrogen concentration is in equilibrium with that of the external compartment. Thus, the peak could be used as an index of irreversible membrane damage of the myocardium.     

Multielement Isotope Ratios of Vegetables from Integrated and Organic Production

In this paper we discuss the use of isotope ratios as indicators of organic production. Few studies have investigated the influence of plant nutrition on the isotopic signatures of plants. As plant nutrition is often significantly different between integrated and organic production systems the isotope ratios in the plants may reflect this. Plant samples from a 2-year field-experiment were analyzed for ¹⁵N, ¹³C and ³⁴S content of the bulk-material and ¹⁸O-content of the leaf water. In this experiment cabbages (Brassica oleracea v. capitata f. alba cv. Rolly), onions (Allium cepa cv. Alisa Craig), lettuces (Lactuca sativa v. capitata cv. Ponchito) and Chinese cabbage (Brassica pekinesis cv. Parkin) were cultivated according to good agricultural practices for integrated and organic production. No differences in the δ ³⁴S and δ ¹⁸O values of the plants grown under the two production systems were observed. The organically produced vegetables were significantly enriched in ¹⁵N and depleted in ¹³C compared to those grown under the integrated system.     

The sodium cycle: A novel type of bacterial energetics

The progress of bioenergetic studies on the role of Na⁺ in bacteria is reviewed. Experiments performed over the past decade on several bacterial species of quite different taxonomic positions show that Na⁺ can, under certain conditions, substitute for H⁺ as the coupling ion. Various primary Na⁺ pumps ( generators) are described, i.e., Na⁺-motive decarboxylases, NADH-quinone reductase, terminal oxidase, and ATPase. The formed is shown to be consumed by Na⁺ driven ATP-synthase, Na⁺ flagellar motor, numerous Na⁺, solute symporters, and the methanogenesis-linked reverse electron transfer system. InVibrio alginolyticus, it was found that , generated by NADH-quinone reductase, can be utilized to support all three types of membrane-linked work, i.e., chemical (ATP synthesis), osmotic (Na⁺, solute symports), and mechanical (rotation of the flagellum). InPropionigenum modestum, circulation of Na⁺ proved to be the only mechanism of energy coupling. In other species studied, the Na⁺ cycle seems to coexist with the H⁺ cycle. For instance, inV. alginolyticus the initial and terminal steps of the respiratory chain are Na⁺ - and H⁺-motive, respectively, whereas ATP hydrolysis is competent in the uphill transfer of Na⁺ as well as of H⁺. In the alkalo- and halotolerantBacillus FTU, there are H⁺ - and Na⁺-motive terminal oxidases. Sometimes, the Na⁺-translocating enzyme strongly differs from its H⁺-translocating homolog. So, the Na⁺-motive and H⁺-motive NADH-quinone reductases are composed of different subunits and prosthetic groups. The H⁺-motive and Na⁺-motive terminal oxidases differ in that the former is ofaa ₃-type and sensitive to micromolar cyanide whereas the latter is of another type and sensitive to millimolar cyanide. At the same time, both Na⁺ and H⁺ can be translocated by one and the sameP. modestum ATPase which is of the F₀F₁-type and sensitive to DCCD. The sodium cycle, i.e., a system composed of primary generator(s) and consumer(s), is already described in many species of marine aerobic and anaerobic eubacteria and archaebacteria belonging to the following genera:Vibrio, Bacillus, Alcaligenes, Alteromonas, Salmonella, Klebsiella, Propionigenum, Clostridium, Veilonella, Acidaminococcus, Streptococcus, Peptococcus, Exiguobacterium, Fusobacterium, Methanobacterium, Methanococcus, Methanosarcin, etc. Thus, the sodium world seems to occupy a rather extensive area in the biosphere.