Impact of foliar nickel application on urease activity,antioxidant metabolism and control of powdery mildew (Microsphaera diffusa) in soybean plants

Nickel (Ni) is a cofactor for urease, an enzyme that breaks down urea into ammonia and carbon dioxide. This study aimed to evaluate the physiological impact of Ni on urea, antioxidant metabolism and powdery mildew severity in soybean plants. Seven levels of Ni (0, 10, 20, 40, 60, 80 and 100 g ha^?1) alone or combined with the fungicides fluxapyroxad and pyraclostrobin were applied to soybean plants. The total Ni concentration ranged from 3.8 to 38.0 mg kg^?1 in leaves and 3.0 to 18.0 mg kg^?1 in seeds. A strong correlation was observed between Ni concentration in the leaves and seeds, indicating translocation of Ni from leaves to seeds. Application of Ni above 60 g ha^?1 increased lipid peroxidation in the leaf tissues, indicative of oxidative stress. Application of 40 g ha^?1 Ni combined with 300 mL ha^?1 of fungicide reduced powdery mildew severity by up to 99%. Superoxide dismutase, catalase, peroxidase and urease enzyme activity were greatest under these conditions. Urea concentration decreased in response to Ni application. Urease activity in soybean leaves showed a negative correlation with powdery mildew severity. The leaf Ni concentration showed a positive correlation with the urease and a negative correlation with powdery mildew severity. The results of this study suggest that urease is a key enzyme regulated by Ni and has a role in host defence against powdery mildew by stimulating antioxidant metabolism in soybean plants.     

在骨架镍上松香催化加氢反应的研究

测定在不同类型搅拌器下高压釜的持气量和反应效果，认识到骨架镍上松香催化加氢是外扩张控制的反应。采用溶剂法、双层组合式搅拌器及改变搅拌转速达到了消除外扩散影响的目的，从而使骨架镍显示出与贵钨Pb/C催化剂相似的活性。在反应过程中，在线跟踪了反应物和产物的浓度随时间的变化关系，结果表明在170℃、5．0MPa的反应条件下，枞酸加氢生成二氢枞酸和四氢枞酸是并行反应。     

化学镀镍单板的导电性和电磁屏蔽效能

为了实现单板的导电性和电磁屏蔽效能,对单板进行了化学镀镍研究,通过表面电阻率和电磁波网络分析仪测量方法对化学镀镍单板的导电性和电磁屏蔽效能进行了分析。结果表明：化学镀镍单板的导电性随着金属镍沉积量的增加而增加,但单板的导电性具有各向异性,平行于纤维方向的导电性要好于垂直于纤维方向的导电性。此外,这种各向异性在金属镍沉积量较少的情况下表现得更加明显,化学镀镍单板的电磁波屏蔽效能随着由于金属镍沉积量的增加而引起导电性的增加而增大,在本研究中化学镀镍单板的电磁波屏蔽效能可以达到30～60dB。     

改性橘子皮对废水中钴镍离子的吸附性能

采用冰醋酸-Ca(OH)2制备了新型活化橘子皮生物吸附剂HCOP,借助扫描电镜从微观组织形态上对比了未改性橘子皮(OP)、冰醋酸-Ca(OH)2活化橘子皮(HCOP)2种不同的生物吸附剂;研究了HCOP用量、p H、吸附时间和温度对HCOP吸附Co2+、Ni2+的影响,并讨论了吸附动力学和热力学模式。结果表明,当HCOP用量为5 g/L、p H 6.0的条件下,HCOP对2种离子的吸附速率均较快,符合准二级动力学方程。HCOP对Co2+、Ni2+的最大吸附量分别为44.58、52.47 mg/g,均符合Langmuir模型。在钴、镍二元混合体系中,HCOP对Ni2+的吸附选择性大于Co2+,HCOP可通过用HCl洗涤再生后循环使用6次。     

长株潭地区5种母质发育水稻土锌和铜及镍元素剖面分布特征

以长株潭地区5种母质发育的水稻土,即河沙泥、红黄泥、黄泥田、麻沙泥和紫泥田为研究对象,按土壤系统分类原则挖掘典型剖面24个及剖面土样137个,分析测定了土壤全量和有效态铜、锌、镍含量以及土壤pH值、颗粒分级组成、有机质、游离氧化铁含量,研究水稻土铜、锌、镍元素的剖面分布特征以及与土壤理化性质之间的关系。结果表明:剖面各层土壤全铜、全锌含量平均值随剖面加深逐渐降低,耕作层、犁底层、底土层全铜含量分别为26.82、21.54、18.54 mg/kg,全锌含量分别为75.84、66.00、63.19 mg/kg,全镍含量分别为18.40、17.50、18.23 mg/kg;土壤铜、锌、镍有效态含量平均值随剖面加深均逐渐降低,耕作层、犁底层、底土层有效铜含量分别为4.04、2.99、1.29 mg/kg,有效锌含量分别为4.77、2.76、1.14 mg/kg,有效镍含量分别为0.54、0.44、0.23mg/kg;黄泥田的全量和有效态铜、锌、镍含量均较高,麻沙泥的较低;土壤有机质含量是决定土壤有效态铜、锌、镍含量的主要因子,土壤游离氧化铁含量是决定土壤全铜、全镍含量的主要因子,全锌含量与土壤pH值、颗粒分级组成、有机质、游离氧化铁含量均无显著相关性。总体上,长株潭地区水稻土0～25 cm土体以及部分剖面土壤全层有效态铜和锌含量高于临界值(铜1.5 mg/kg、锌0.5 mg/kg),呈盈余状态,可满足浅根或中根作物对铜、锌的需求。     

Assessment of nickel's sufficiency critical levels in cultivated soils,employing commonly used calibration techniques

Although Ni has been officially recognized as an essential micronutrient for all higher plants since 2004, research on assessing its sufficiency critical levels with different soil tests is missing in the literature. The objective of the study was to determine Ni critical levels in unpolluted cultivated soils utilizing four methods, employing three commonly used calibration techniques. Ten soils with different physical–chemical properties and low Ni content were treated with Ni at rates of 1, 2, 4, and 8 mg kg^?1. After equilibration for one month, the soils were analyzed for extractable Ni by four methods, namely DTPA, AB‐DTPA, AAAc‐EDTA, and Mehlich‐3. Response to soil‐applied Ni was assessed by a greenhouse pot experiment, with the untreated and Ni‐treated soils in three replications, using ryegrass (Lolium perenne L.). The aboveground biomass of ryegrass was harvested two months after sowing, dry weight of biomass was measured and relative biomass yield was calculated. Nickel's critical levels were determined employing the: (a) graphical technique of Brown and co‐workers, (b) Mitscherlich–Bray equation, and (c) Cate and Nelson graphical technique. According to the first technique, Ni critical levels were ≈ 2 mg kg^?1 for the DTPA and AB‐DTPA methods, and 6.0 and 5.3 mg kg^?1 for the AAAc‐EDTA and Mehlich‐3 methods, respectively. Similar levels were obtained by the Mitscherlich–Bray equation. However, the critical levels assessed by the Cate and Nelson technique were lower and ranged from 0.5 to 1.3 mg kg^?1 for all four methods. Conclusively, Ni sufficiency critical levels for all four methods are expected to range at levels of a few mg Ni kg^?1 of soil. As far as the three calibration techniques are concerned, a distinct boundary between Ni response and non‐response was accomplished by none. However, the fact that 60–74% of the soils were correctly separated into responsive and non‐responsive to added Ni by the graphical technique of Brown and co‐workers suggests that this is the most suitable technique.     

外质体H2O2和木质素积累在镍诱导的水稻对白叶枯病系统抗性中的作用

[目的]植物外质体是病原入侵的结构和生理性屏障.本文研究外质体反应在镍诱导的、对白叶枯病系统抗性中的作用,以探讨植物对病原和重金属交叉抗性的生理机制. [方法]以0.5、1.0和2.0mol·L~(-1)硝酸镍喷施三叶期水稻幼苗的第二叶及以下部位,3 d后在未处理的第三叶接种稻白叶枯菌(xanthomonas oryzae pv.oryzae,Xoo),接种后12d调查病情.测定了2.0 mol·L~(-1)镍处理或/和Xoo接种的幼苗第三叶外质体中愈创木酚POD(G-POD)、NADH-POD,二胺氧化酶(DAO)活性、H_2O_2和木质素含量.[结果]镍诱导了幼苗对白叶枯病的系统抗性,其中2.0 mmol·L~(-1)镍的诱导效果最佳.镍处理下,第三叶外质体液(AWF)中和细胞壁结合的G-POD、NADH-POD,以及AWF中DAO的活性和H_2O_2水平快速上升,木质素含量显著提高;镍诱导且接种组中,上述指标均明显高于未诱导但接种组.另外,产生H_2O_2的POD的抑制剂NaN_3降低了镍诱导的H_2O_2积累水平和对白叶枯病的系统诱抗效应,而NADPH氧化酶抑制剂(diphenyleneiodonium chloride)预处理则无明显影响.[结论]本研究结果提示,NADH-POD和DAO活性上升是镍诱导外质体H_2O_2产生的原因;外质体H_2O_2和木质素在细胞壁中的积累可能参与了镍诱导的水稻对白叶枯病系统抗性的建立.     

Pathways of chemical recovery in acidified,metal-contaminated lakes near Sudbury,Ontario, Canada

This paper describes the recovery pathways of two lakes situated near the Coniston nickel-copper smelter. These lakes were exposed to very intense airborne pollution, including SO₂, H₂SO₄, Ni and Cu, during the 60 year operation of the smelter. After the closure of the Coniston smelter in 1972 and the subsequent improvement in air quality, the water quality in both lakes began to improve. Despite their proximity and exposure to similar inputs, the lakes differed both in the rate and magnitude of recovery. This study demonstrates the capacity of lakes to recover from chemical stresses over a very short period. Changes in Cu and Ni concentration could be predicted, while changes in pH, measured as H⁺, could not. The reasons for this discrepancy as well as the processes and lake parameters that control chemical recovery are discussed.