开花结实期小麦氮素损失的初步研究

在气候箱试验条件下,用密闭箱法研究了开花结实期小麦植株NH3、N2O、NO和NO2挥发特征及规律.结果表明:(1)只保留小麦根系处理有明显挥发NH3的作用,但在气候箱控制、白昼有相对良好的光照条件下,小麦地上部没有显著净挥发NH3作用效果;(2)开花结实期小麦植株有明显从空气吸收NO和NO2的效应,NO净吸收速率在0.5～2.7 ug·pot-1·h-1之间,NO2净吸收速率约0.4～1.6 ug·pot-1·h-1;(3)小麦根系是产生N2O的重要部位,只保留小麦根系和保留完整小麦植株处理均有显著净挥发N2O的作用效果.研究发现,开花结实期小麦植株氮素挥发损失是以N2O为主而不足NH3;这一时期小麦植株有净吸收NO、NO2明显效应,但其吸收速率远低于小麦植株N2O排放速率;开花结实期小麦N2O排放速率基本可以表征其氮素挥发损失数量.     

设施菜田不同碳氮管理对反硝化菌结构和功能的影响

【目的】通过6年长期定位试验,比较设施菜田不同碳氮管理下反硝化菌结构和功能的差异。【方法】采用末端限制性片段多态性(T-RFLP)和变性梯度凝胶电泳(DGGE)方法分别分析nir K/nir S和nos Z型反硝化菌群结构特征,利用自动连续在线培养监测体系(Robot系统)测定分析NO/(NO3-+NO2-)和N2O/(N2O+N2)产物比,并通过乙炔抑制法测定反硝化酶活性。【结果】传统施肥处理(CN)显著改变了nir K和nos Z型反硝化菌的结构,增加了NO/(NO3-+NO2-)和N2O/(N2O+N2)产物比。nir S型菌受碳氮管理影响较小。减氮(RN)和添加秸秆处理(RN+S)的nir K和nos Z型反硝化菌结构与CN处理的差异性显著,且会显著降低NO/(NO3-+NO2-)和N2O/(N2O+N2)产物比;与CN和RN相比,RN+S显著增加反硝化酶活性。【结论】设施菜田长期传统施肥措施改变了反硝化菌的结构和功能,增加土壤自身的NO产生能力并减弱了N2O还原N2的能力。减氮和添加秸秆管理能形成自身的反硝化菌群结构,并降低NO和N2O排放风险;秸秆的添加会促进反硝化潜在速率,降低菜田NO3-淋洗风险。     

一株高耐氧反硝化细菌的筛选及其反硝化产物确定

利用浅层振荡培养和连续通气培养方法,获得一株高耐氧反硝化细菌H1.分别利用NO报告克隆nnrS-gfp和乙炔抑制-气相色谱测得菌株H1能够在反硝化条件下产生NO和N2O,不能产生N2,因此其反硝化途径为NO3-→NO2-→NO→N2O.在初始O2浓度为0%～21%范围内,该菌株能将98%以上的NO3-还原为气态氮化物.在150 mL的培养液中,连续以2 L/min的速率通气,H1依然能够反硝化,但是更高的通气速率则反硝化停止.16S rDNA序列分析表明,菌株H1与Ralstonia taiwanensis相似性达98%.     

一氧化氮间接作用机制的研究进展

NO本身并无直接的毒性作用,相反,它在体内常发挥生理或保护作用。而“NO的毒性作用”,主要是由于大量诱生的NO与体内同时大量生产的O2^-等活性氧类反应,生成ONOO^-或N2O3等一系列物质,由二者分别介导氧化损伤或亚硝基化损伤,因而是NO的间接作用。而NO的间接作用到底是通过ONOO^-还是N2O3途径来介导,取决于NO与O2^-的局部相对浓度。若NO与O2^-的局部浓度几乎相等,则生成ONOO^-,由ONOO^-来介导;而若NO的浓度高出O2^-浓度较多,则主要生成N2O3,由N2O3来介导。     

交叉培养法研究养分对作物幼苗释放N2O的影响

为验证土壤中N2 O能否通过植物的输导组织由叶片释放从而干扰植物直接释放N2 O的定量测定 ,实验采用分室隔离法确证了土壤N2 O对测定某些作物 (如玉米、高粱 )直接释放N2 O的干扰 ;采用交叉培养法消除了这种干扰 ,准确地测定了大豆、玉米幼苗直接释放N2 O的强度 ;并研究了N、P营养与植物释放N2 O及体内NO 3 N浓度之间的相关性 .     

南京市郊区集约化大棚蔬菜地N2O的排放

采用静态暗箱-气相色谱法,研究了南京市郊区集约化生产管理下,芹菜-空心菜-小白菜-苋菜轮作菜地与休闲裸地的N2O排放通量的动态变化,及其与土壤温度、湿度以及NO3--N和NH4+-N含量的关系.结果表明:轮作菜地的N2O累积排放量达137.2kg N·hm-2,显著大于休闲裸地(29.2 kgN-hm-2);轮作菜地生态系统N2O-N的排放系数高达4.6％.4种蔬菜地中,空心菜地对轮作菜地的周年累积排放量贡献最大,为53.5％,小白菜地次之,为31.9％,芹菜地和苋菜地最小,分别为4.5％和4.8％.轮作菜地的N2O排放通量与土壤温度呈显著正相关,Q10为2.80;土壤湿度以及NO3--N和NH4+-N含量与轮作菜地的N2O排放通量之间的相关性不显著.     

长效碳酸氢铵对土壤硝化-反硝化过程和NO与N2O排放的影响

室内实验(25℃和50%WFPS)比较研究了碳酸氢铵(普碳)和长效碳酸氢铵(长碳)对粘质土壤(粘土)和壤质土壤(壤土)硝化反硝化过程和NO与N2O排放的影响.长碳中的DCD在粘土中的硝化抑制作用很弱,在壤土中显著,与普碳处理相比,NH 4持续时间分别延长7d和33d.15d内,施普碳(100μgN·g-1)情况下,粘土和壤土NO排放量分别占施N量的060%和106%,分别是相应土壤N2O排放量的30和12倍.施长碳后,粘土和壤土NO排放量分别减少67%和95%,N2O排放量分别减少64%和55%.有氧培养39d后,外加硝酸盐(200μgKNO3N·g-1),接着淹水厌氧培养7d,壤土长碳处理较普碳处理反硝化总损失减少50%,但N2O排放量增加113%.     

延安市日光温室蔬菜施肥现状与环境效应

调查分析延安市日光温室蔬菜目前的施肥现状和存在问题,结果表明蔬菜主要施肥问题是偏施氮磷肥,而且用量超过蔬菜的需肥量,忽视钾肥和微量元素的施用。过量施肥造成土壤NO3^-—N累积和地下水NO3^-—N含量超标,地下水NO3^-—N含量达142mg／L。根据西红柿和黄瓜的需肥要求,提出了黄瓜和西红柿合理的N、P、K肥和有机肥用量。日光温室黄瓜产量150000kg／hm^2的施用量为N750—840kg／hm^2,P2O5 450—540kg／hm^2,K2O 450—750kg/hm^2,有机肥60-80t/hm^2较为合理。日光温室西红柿180 000kg/hm^2产量的施用量为N810-960kg/hm^2,P2O5 420-510kg／hm^2,K2O 540-690kg／hm^2,有机肥50-80t/hm^2较为合理。分析了施肥对土壤环境和地下水NO3^-—N含量的影响,并提出了日光温室蔬菜施肥的改进措施。     

NO和H_2O_2在介导热激诱发金丝桃细胞合成金丝桃素中的信号互作

热激处理(40℃,10min)可以诱发金丝桃细胞中金丝桃素的生物合成并诱导细胞产生一氧化氮(NO)和过氧化氢(H2O2).过氧化氢酶(CAT)和NO专一性淬灭剂(cPTIO)不仅可以分别抑制由热激诱发的H2O2积累和NO合成,而且还可以阻断热激处理对金丝桃素生物合成的促进作用.H2O2单独处理虽然不能提高细胞的金丝桃素产量,但是H2O2和NO共同处理对金丝桃素产量的促进作用显著高于NO单独处理,表明NO和H2O2对金丝桃素的生物合成具有协同诱导效应.NO处理可以提高细胞的H2O2水平,而外源H2O2对金丝桃细胞的NO合成积累也具有促进作用,说明NO和H2O2对彼此的合成反应具有促进作用.CAT在抑制热激诱发H2O2合成的同时还能够部分抑制热激细胞中NO的合成,而cPITO也可以同时降低热激细胞的H2O2水平.上述实验结果提示,在热激处理下金丝桃细胞中的NO和H2O2可能通过互作反应提高各自的信号水平.质膜NAD(P)H氧化酶抑制剂DPI和NO合酶抑制剂PBITU可以抑制NO和H2O2之间的互作反应,并且解除NO和H2O2对金丝桃素合成的协同诱导作用,说明NO和H2O2对金丝桃素合成积累的协同效应依赖于两种信号分子之间的互作反应.本文实验结果不仅证实了NO和H2O2是参与热激诱发金丝桃细胞中金丝桃素合成所必需的两种信号分子,而且揭示了NO和H2O2在介导热激诱发金丝桃素生物合成过程中特殊的信号互作现象.     

南京市郊区集约化大棚蔬菜地N2O的排放

采用静态暗箱-气相色谱法,研究了南京市郊区集约化生产管理下,芹菜-空心菜-小白菜-苋菜轮作菜地与休闲裸地的N2O排放通量的动态变化,及其与土壤温度、湿度以及NO3--N和NH4+-N含量的关系.结果表明： 轮作菜地的N2O累积排放量达1372 kg N·hm-2,显著大于休闲裸地(29.2 kg N·hm-2);轮作菜地生态系统N2O-N的排放系数高达46%.4种蔬菜地中,空心菜地对轮作菜地的周年累积排放量贡献最大,为53.5%,小白菜地次之,为31.9%,芹菜地和苋菜地最小,分别为4.5%和4.8%.轮作菜地的N2O排放通量与土壤温度呈显著正相关,Q10为2.80;土壤湿度以及NO3--N和NH4+-N含量与轮作菜地的N2O排放通量之间的相关性不显著.     

Production of Nitric Oxide and Nitrous Oxide During Denitrification by Corynebacterium nephridii

Resting cells of Corynebacterium nephridii reduce nitrate, nitrite, and nitric oxide to nitrous oxide under anaerobic conditions. Nitrous oxide production from nitrite was optimal from pH 7.0 to 7.4. The stoichiometry of nitrous oxide production from nitrite was 99% of the theoretical-two moles of nitrite was used for each mole of nitrous oxide detected. Hydroxylamine increases gas evolution from nitrite but inhibits the reduction of nitric oxide to nitrous oxide. Hydroxylamine is converted to nitrogenous gas(es) by resting cells only in the presence of nitrite. Under certain conditions nitric oxide, as well as nitrous oxide, was detected.     

Separate Nitrite, Nitric Oxide, and Nitrous Oxide Reducing Fractions from Pseudomonas perfectomarinus

Pseudomonas perfectomarinus was found to grow anaerobically at the expense of nitrate, nitrite, or nitrous oxide but not chlorate or nitric oxide. In several repetitive experiments, anaerobic incubation in culture media containing nitrate revealed that an average of 82% of the cells in aerobically grown populations were converted to the capacity for respiration of nitrate. Although they did not form colonies under these conditions, the bacteria synthesized the denitrifying enzymes within 3 hr in the absence of oxygen or another acceptable inorganic oxidant. This was demonstrated by the ability, after anaerobic incubation, of cells and of extracts to reduce nitrite, nitric oxide, and nitrous oxide to nitrogen. From crude extracts of cells grown on nitrate, nitrite, or nitrous oxide, separate complex fractions were obtained that utilized reduced nicotinamide adenine dinucleotide as the source of electrons for the reduction of (i) nitrite to nitric oxide, (ii) nitric oxide to nitrous oxide, and (iii) nitrous oxide to nitrogen. Gas chromatographic analyses revealed that each of these fractions reduced only one of the nitrogenous oxides.     

Distribution of Graphene Oxide and TiO2-Graphene Oxide Composite in A549 Cells

Graphene and its derivatives are increasingly applied in nanoelectronics, biosensing, drug delivery, and biomedical applications. However, the information about its cytotoxicity remains limited. Herein, the distribution and cytotoxicity of graphene oxide (GO) and TiO₂-graphene oxide composite (TiO₂-GO composite) were evaluated in A549 cells. Cell viability and cell ultrastructure were measured. Our results indicated that GO could enter A549 cells and located in the cytoplasm and nucleus without causing any cell damage. TiO₂ nanoparticles and GO would be separated after TiO₂-GO composite entered A549 cells. TiO₂-GO composite could induce cytotoxicity similar to TiO₂ nanoparticles, which was probably attributed to oxidative stress. These results should be considered in the development of biological applications of GO and TiO₂-GO composite.     

一氧化氮与植物耐盐性

盐胁迫是制约植物生长发育的主要环境因子之一,信号分子一氧化氮（NO）参与调节植物的耐盐性,本文介绍近年来NO合成及其与植物耐盐性关系的研究进展,并讨论了NO可能的作用机制。     

Nitric Oxide and Low-Density Lipoprotein Oxidation

Nitric oxide can have both pro-oxidant and antioxidant effects on low-density lipoprotein. Nitric oxide does not appear to react directly with components of LDL. However, in the presence of oxygen (through NO₂ and N₂O₃ formation) or superoxide (through peroxynitrite formation) nitric oxide may cause oxidation of the lipid, protein and antioxidant components of LDL. Conversely, nitric oxide is a potent inhibitor of LDL oxidation when initiated by copper ions or by azo-initiators. The possible implications of these observations to vascular pathology are discussed.