Lateral root elongation in maize is related to auxin synthesis and transportation mediated by N metabolism under a mixed NO_(3)^(–) and NH_(4)^(+) supply

A mixed nitrate (NO_(3)^(–)) and ammonium (NH_(4)^(+)) supply can promote root growth in maize (Zea mays),however,the changes in root morphology and the related physiological mechanism under different N forms are still unclear.Here,maize seedlings were grown hydroponically with three N supplied in three different forms (NO_(3)^(–)only,75/25 NO_(3)^(–)/NH_(4)^(+)and NH_(4)^(+)only).Compared with sole NO_(3)^(–)or NH_(4)^(+),the mixed N supply increased the total root length of maize but did not affect the number of axial roots.The main reason was the increased total lateral root length,while the average lateral root (LR) length in each axle was only slightly increased.In addition,the average LR density of 2nd whorl crown root under mixed N was also increased.Compared with sole nitrate,mixed N could improve the N metabolism of roots (such as the N influx rate,nitrate reductase (NR) and glutamine synthase (GS)enzyme activities and total amino content of the roots).Experiments with exogenously added NR and GS inhibitors suggested that the increase in the average LR length under mixed N was related to the process of N assimilation,and whether the NR mediated NO synthesis participates in this process needs further exploration.Meanwhile,an investigation of the changes in root-shoot ratio and carbon (C) concentration showed that C transportation from shoots to roots may not be the key factor in mediating lateral root elongation,and the changes in the sugar concentration in roots further proved this conclusion.Furthermore,the synthesis and transportation of auxin in axial roots may play a key role in lateral root elongation,in which the expression of ZmPIN1B and ZmPIN9 may be involved in this pathway.This study preliminarily clarified the changes in root morphology and explored the possible physiological mechanism under a mixed N supply in maize,which may provide some theoretical basis for the cultivation of crop varieties with high N efficiency.

Increasing nitrogen absorption and assimilation ability under mixed NO_(3)^(–)and NH_(4)^(+) supply is a driver to promote growth of maize seedlings

Compared with sole nitrate (NO_(3)^(-)) or sole ammonium (NH_(4)^(+)) supply,mixed nitrogen (N) supply may promote growth of maize seedlings.Previous study suggested that mixed N supply not only increased photosynthesis rate,but also enhanced leaf growth by increasing auxin synthesis to build a large sink for C and N utilization.However,whether this process depends on N absorption is unknown.Here,maize seedlings were grown hydroponically with three N forms (NO_(3)^(-)only,75/25 NO_(3)^(-)/NH_(4)^(+) and NH_(4)^(+) only).The study results suggested that maize growth rate and N content of shoots under mixed N supply was little different to that under sole NO_(3)^(-)supply at 0–3 d,but was higher than under sole NO_(3)^(-)supply at 6–9 d.^(15)N influx rate under mixed N supply was greater than under sole NO_(3)^(-) or NH_(4)^(+) supply at 6–9 d,although NO_(3)^(-) and NH_(4)^(+) influx under mixed N supply were reduced compared to sole NO_(3)^(-) and NH_(4)^(+) supply,respectively.qRT-PCR determination suggested that the increased N absorption under mixed N supply may be related to the higher expression of NO_(3)^(-) transporters in roots,such as ZmNRT1.1A,ZmNRT1.1B,ZmNRT1.1C,ZmNRT1.2 and ZmNRT1.3,or NH_(4)^(+) absorption transporters,such as Zm AMT1.1A,especially the latter.Furthermore,plants had higher nitrate reductase (NR)glutamine synthase (GS) activity and amino acid content under mixed N supply than when under sole NO_(3)^(-) supply.The experiments with inhibitors of NR reductase and GS synthase further confirmed that N assimilation ability under mixed N supply was necessary to promote maize growth,especially for the reduction of NO_(3)^(-) by NR reductase.This research suggested that the increased processes of NO_(3)^(-)and NH_(4)^(+) assimilation by improving N-absorption ability of roots under mixed N supply may be the main driving force to increase maize growth.

不同NO_(3)^(-)-N/NH_(4)^(+)-N配比对丹江口水库脆杆藻生长和叶绿素荧光的影响

通过模拟丹江口水库总氮浓度1.5 mg/L,以硝酸钠和氯化铵作为氮源,研究了硝铵配比为0∶100、25∶75、50∶50、75∶25、100∶0条件下脆杆藻细胞密度和叶绿素荧光参数的变化。结果表明:随着硝氮比例的增加,脆杆藻的藻细胞密度呈逐渐增高的趋势,且100∶0组的比生长速率(0.174)明显大于其他各组(p<0.05)。F_(v)/F_(m)、α、ETR_(max)值均表现出高比例硝氮组大于低比例硝氮组,与其生长趋势较为一致。研究表明,在1.5 mg/L总氮浓度下提高硝氮比例可促进脆杆藻的生长以及提高其对光能利用效率。

酸性环境下作物幼苗对NO_3^--N和NH_4^+-N的吸收特征

以水稻、小麦、玉米3种作物的不同品种为试验材料,采用溶液培养方法研究介质pH对幼苗根系铵态氮(NH_4^+- N)和硝态氮(NO_3^--N)吸收速率的影响。结果表明:植物幼苗根系对2种无机氮素的吸收速率受介质pH的影响大,影响程度与作物的种类、品种和苗龄有关。多数作物品种在pH 4.0条件下对NO_3^--N的吸收速率高于pH 6.0,而介质pH对NH_4^+-N吸收速率的影响与此相反。水稻幼苗对NO_3^--N的吸收速率随苗龄的增大而减慢,但对NH_4^+-N的吸收速率则逐渐加快。小麦和玉米对NO_3^--N和NH_4^+-N的吸收速率均随苗龄的增大而加快。

小白菜硝酸盐含量与NO_3^-/NH_4^+及氮代谢关键酶的相关性

采用液体培养实验研究了不同NO_3^-与NH_4^+浓度比(分别为50:50、75:25和100:0)对10个品种小白菜(Brassica chinensis L.)的硝酸盐含量、光合系统参数及氮代谢关键酶活性的影响。结果表明,随着硝铵比的增加,小白菜总干质量逐渐增加(除品种天津小白菜和大头清江白菜的总干质量随硝铵比的增加先降低后升高,品种香港春秀甜白菜(236)和正旺达88的总干质量先升高后降低外),与c(NO_3^-):c(NH_4^+)为50:50比较,增幅分别为12.66%~76.88%(c(NO_3^-):c(NH_4^+)为75:25)和17.98%~95.07%(c(NO_3^-):c(NH_4^+)为100:0);小白菜叶和根中的硝酸盐含量增加,而叶柄硝酸盐含量则表现出先增加后下降的趋势,小白菜硝酸盐的含量叶柄(3 882.62~5 448.81 mg/kg)>叶(2 004.86~4 146.50 mg/kg)>根(505.39~2 188.68 mg/kg)。小白菜叶片中硝酸盐含量与硝酸还原酶活性成显著负相关,而与亚硝酸还原酶和谷氨酰胺合成酶活性成显著正相关。小白菜叶片中硝酸盐的含量随着净光合速率(Pn)和胞间二氧化碳浓度(Ci)的增加而下降,随蒸腾速率(Tr)的增强而增加。

Tomato Growth and Organic Acid Changes in Response to Partial Replacement of NO_3^--N by NH_4^+-N

A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.

平原区承压水上部弱透水层对NH_(4)^(+)、NO_(3)^(-)的阻滞能力分析研究——以北京市通州区为例

由于工农业经济快速发展引起的广大平原区浅部地下水不同程度污染已经成为比较普遍的问题。平原区深部的承压水因水质较好,往往成为当地供水的主要水源,因此其地下水保护至关重要。承压含水层上部的弱透水层在阻滞浅部污染物进入承压含水层的过程中起到极其关键的作用。本次研究,以华北平原典型区域通州区为例,以研究区水文地质单元为基础,结合钻孔资料获取的地层结构特征、岩性特征等,开展了潜水与承压水之间弱透水层对污染物阻滞能力的探索模拟研究,评价结果显示研究区弱透水层污染物阻滞能力西北部最差,自西北向东南呈现出先增强后减弱的态势。本次研究的思路和方法可为同类平原区弱透水层对污染物阻滞作用研究提供借鉴。

水热法合成的LaVO4/WO3复合纳米片的可见光光催化还原工业废水中Cr（Ⅵ）效果分析

针对工业废水中Cr(Ⅵ)毒性大,迁移性强的问题,采用水热法制备了不同复合比例的LaVO4/WO3复合纳米片光催化剂,通过XRD、SEM、XPS和DRS测试手段进行了表征。结果表明:LaVO4能进入WO3晶格之中,使其产生晶格缺陷;晶格缺陷可作为活性位点,促进光生载流子的分离,提高WO3的光催化活性。可见光下光催化还原工业废水中Cr(Ⅵ)测试表明:LaVO4/WO3复合纳米片的光催化还原效率比WO3更高,当LaVO4以质量比为3%负载WO3时,复合纳米片光催化还原性最高,可达92%,是纯WO3还原效率的8.3倍。分析结果表明,LaVO4能使WO3的氧空位得到扩散,提高界面光生电子的迁移速率,促进光生电子还原Cr(Ⅵ),提高复合纳米片的光催化还原性能。本研究为重金属工业废水,特别是难降解重金属污染物高效治理技术的研发提供了理论参考。

合成3,4-二甲氧基苯乙胺的工艺改进

3,4-二甲氧基苯乙胺是合成许多异喹啉生物碱的重要中间体,如罂粟啶(Papaveraldine)、海罂粟碱(Gdauciue)、维尼碱(wilsonirine)等,因此其合成方法有大量的文献报道,其中应用最多的是以3,4-二甲氧基苯甲醛为原料与硝基甲烷缩合生成β-硝基-3,4-二甲氧基苯乙烯,再用氢化铝锂还原的方法。此方法中的还原剂氢化铝锂价格昂贵,应用于大规模的工业化生产成本很高。因此我们对工艺中从3,4-二甲氧基苯甲醛至3,4-二甲氧基苯乙胺的合成工艺进行了研究,改用价格低廉锌汞齐加盐酸为还原剂取得了较好的结果。

7-苯乙酰氨基-3-吡啶甲基-3-头孢菌素-4-羧酸对甲氧苄酯的合成

对7-苯乙酰氨基3-吡啶甲基-3-头孢菌素4-羧酸对甲氧苄酯的合成工艺进行优化，结果改进工艺后可缩短生产周期4～6h，收率达88．3％，含量97．1％。该工艺简化了操作过程，降低了生产成本，提高了生产效率，为工业化生产提供了更有利的保障。

SrAl_2O_4∶Eu^(2+),Dy^(3+)磷光粉低成本制备工艺及发光性能研究

以工业铝酸钠溶液制备的氢氧化铝为铝基原料,采用高温固相反应法合成了SrAl2O4∶Eu2+,Dy3+磷光粉,考察了稀土掺杂量、烧结温度及硼酸加入量对其发光性能、激发光谱及发射光谱的影响,并通过XRD谱及余辉衰减曲线对最佳工艺条件下制备的样品进行表征。结果表明,当稀土掺杂量x(Eu)=3%、x(Dy)=3%,烧结温度为1 300℃,烧结时间为4h,硼酸加入量w(H3BO3)=9%时,所制备磷光粉样品仍保持SrAl2O4的晶体结构,其发光性能最好,发光强度最大,主激发波长在360nm左右,主发射波长在510nm左右;余辉为黄绿色,衰减时间长。

功率对空气分级NH_(3)、NH_(3)/CH_(4)火焰排放的影响

NH_(3)作为氢能载体,可实现氢能远距离输运。针对NH_(3)燃烧的反应性低、稳定性差、高燃料型NO_(x)排放问题,设计旋流燃烧器和空气分级燃烧室,实验研究功率为5~23 k W的NH_(3)、NH_(3)/CH_(4)扩散火焰NO_(x)排放特性。并采用化学反应器网络(CRN)进行化学动力学模拟,分析排放变化的原因。结果表明:5 kW、Ф_(pri)=1.05的条件下,NH_(3)火焰NO_(x)测量排放最低为114.4×10^(-6)@15%O_(2);随着功率升高,NO_(x)排放增加,且导致燃烧不充分、火焰延长,此时最佳Ф_(pri)提前、燃烧范围减少、NO_(x)进一步增加;本文的CRN更适合模拟预混燃烧的NO_(x)排放,而不是扩散燃烧;功率升高不会改变反应路径,但生成NO的基元反应速率的升高幅度略大于消耗NO的基元反应速率,从而导致NO排放升高.

用优质素材创设有价值的教学情境--以“工业合成NH_(4)NO_(3)”为例

情境是“素养为本”课堂教学的基本要素,创设真实且富有价值的教学情境,有利于促进学生学习方式的转变和化学学科核心素养的发展。基于对“情境素材”和“教学情境”的分析,提出精选优质情境素材,创设真实且富有价值的教学情境的实施路径;以“工业合成NH_(4)NO_(3)”情境素材为例开展教学实践,为高三主题式复习的情境化教学提供借鉴。

NO_(3)^(-)缓解小麦NH_(4)^(+)胁迫的生理机制研究

本实验研究了NO3-对单一NH4+胁迫下小麦(Triticum aestivum)根系生理特性的响应机制。结果表明:单一NH4+处理下,与对照相比,根系鲜重显著降低;吲哚乙酸(IAA)和茉莉酸含量显著降低,水杨酸含量显著升高;抗氧化酶活性显著降低,活性氧与丙二醛含量显著升高;氮代谢酶活性显著降低,谷氨酰胺含量显著增加。傅里叶转换红外光谱检测表明,纤维素、木质素等峰值增大,其含量也显著升高。非损伤微测结果表明,NH4+、H+外排速率以及IAA内流速率增加。NH4++NO3-处理能提高小麦根系IAA、茉莉酸等激素含量,降低水杨酸含量,提高抗氧化酶与氮代谢关键酶活性,降低NH4+、H+外排速率以及细胞壁结构性成分的含量,从而缓解NH4+抑制作用。综上所述,NH4++NO3-处理有效缓解了单一NH4+处理对小麦根系的抑制作用。

Fe-doped Co_(3)O_(4) nanowire strutted 3D pinewood-derived carbon: A highly selective electrocatalyst for ammonia production via nitrate reduction

Nitrate(NO_(3)^(-)),a nitrogen-containing pollutant,is prevalent in aqueous solutions,contributing to a range of environmental and health-related issues.The electrocatalytic reduction of NO_(3)^(-)holds promise as a sustainable approach to both eliminating NO_(3)^(-)and generating valuable ammonia(NH_(3)).Nevertheless,the reduction reaction of NO_(3)^(-)(NO_(3)^(-)RR),involving 8-electron transfer process,is intricate,necessitating highly efficient electrocatalysts to facilitate the conversion of NO_(3)^(-)to NH_(3).In this study,Fe-doped Co_(3)O_(4) nanowire strutted three-dimensional(3D)pinewood-derived carbon(Fe-Co_(3)O_(4)/PC)is proposed as a high-efficiency NO_(3)^(-)RR electrocatalyst for NH_(3) production.Operating within 0.1 M NaOH containing NO_(3)^(-),Fe-Co_(3)O_(4)/PC demonstrates exceptional performance,obtain an impressively large NH_(3) yield of 0.55 mmol·h^(-1)·cm^(-2) and an exceptionally high Faradaic efficiency of 96.5%at-0.5 V,superior to its Co_(3)O_(4)/PC counterpart(0.2 mmol·h^(-1)·cm^(-2),73.3%).Furthermore,the study delves into the reaction mechanism of Fe-Co_(3)O_(4) for NO_(3)^(-)RR through theoretical calculations.

不同铵硝配比对茶树生长及生长素含量的影响

【目的】明确不同茶树品种最适生长铵硝比,为实现“因种施肥”、茶园氮肥营养管理提供借鉴与参考。【方法】采用营养液水培试验分析5种铵硝配比(NH_(4)^(+)∶NO_(3)-=4∶0、3∶1、2∶2、1∶3、0∶4)条件下1 a生茶树扦插苗‘信阳10号’和‘中茶108’的生长表型及游离生长素IAA和IBA含量。【结果】5种铵硝配比条件下,信阳10号在铵硝比3∶1时长势最好,表现为叶片数和单株芽头数最多,根系和芽叶干重最高,平均不定根最长,根系游离生长素IAA和IBA含量均最高;中茶108则在铵硝比4∶0时长势最好,具有较高的株高、茎粗、单株芽头数和发芽率,根、茎、芽叶干重最高,氮素积累量最多,侧根数目和侧根密度最高,根系IAA以及IAA、IBA的总量最高。相关性分析结果表明,信阳10号根系参数与生长素含量相关性较强,而中茶108根系参数则与氮含量相关性较强。【结论】信阳10号和中茶108最适生长铵硝比分别为3∶1和4∶0,前者耐硝,后者对硝敏感。

硝态氮与铵态氮配合缓解黄瓜苗期铵毒害作用的研究

为明确硝态氮在缓解黄瓜苗期铵毒害的作用及相关机制,采用盆栽试验的方法,以‘津研4号’黄瓜为试验材料,以蛭石为育苗基质,在总氮浓度为15 mmol/L的条件下,苗期分别供给铵态氮与硝态氮,出苗5周后,测定黄瓜生长及生理相关指标。结果表明,在全NH_(4)^(+)-N处理条件下,极易产生铵毒害。全NO_(3)^(-)-N处理下,幼苗地上部全氮与全磷含量分别为全NH_(4)^(+)-N处理的1.08倍与1.11倍,叶面积、生物量及壮苗指数显著高于全NH_(4)^(+)-N处理;全NH_(4)^(+)-N供给条件下,地上部MDA含量显著高于全NO_(3)^(-)-N处理,而叶绿素含量却显著低于全NO_(3)^(-)-N处理,生长明显受抑;在NH_(4)^(+)-N中混入等量NO_(3)^(-)-N后,抑制作用减弱,幼苗根际pH由6.28上升至6.54,叶绿素含量与叶面积均有不同程度增加,地上部与根系干重较全NH_(4)^(+)-N处理分别增加了26.6%与29.5%,壮苗指数与全NO_(3)^(-)-N处理间无显著差异。研究认为,NO_(3)^(-)-N对铵毒害有一定的缓解作用,且缓解作用依赖于幼苗自身营养与生理代谢的平衡。

Distinct effect of preparation methods on reaction efficiency of Mn-Ce/Al_(2)O_(3) catalysts in low-temperature NH_(3)-SCR

In this study,a series of Mn-Ce/Al_(2)O_(3) catalysts was prepared by different methods of depositionprecipitation(MnCeAl-DP),impregnation(MnCeAl-IM) and citric acid(MnCeAl-CA),and the distinct effect of preparation methods on NO_(x) removal performance at low temperature was explored.Results show that MnCeAl-DP exhibits not only the best activity but also the highest resistance against SO_(2)/H_(2)O.With the assistance of comprehensive characterizations from scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-te mperature programmed deso rption(NH_(3)-TPD),and X-ray photoelectron spectroscopy(XPS),it is revealed that the MnCeAl-DP sample owns admired features of large surface area and pore volume,enriched Mn^(4+) and chemisorbed oxygen species originating from enhanced interaction between MnO_x and CeO_(2),as well as improved adsorption capacity to NH_(3) and NO.All these factors contribute to activity enhancement.Further in-situ DRIFTS studies reveal that the improvement of NH_(3)-SCR performance over MnCeAI-DP is related to the formation of abundant nitrate species,which is beneficial to the "NH_(4)NO_(3)" reaction pathway and thus enhances low-temperature activity.

微筛孔反应器液相沉淀法制备纳米CaCO_(3)

采用微筛孔反应器,以Ca(NO_(3))_(2)·4H_(2)O为钙源连续相、(NH_(4))_(2)CO_(3)为碳源分散相,液相沉淀法制备纳米CaCO_(3)。利用XRD、TEM等表征手段分析研究分散相与连续相流量、浓度和停留时间等制备条件对碳酸钙的粒径、产率和形貌的影响。结果表明,使用微筛孔反应器通过液相沉淀法可制得平均粒径45~92 nm、产率达80%以上的方解石型纳米CaCO_(3)。适宜的制备条件为:连续相进料流量F_(C)=150 mL/min、分散相进料流量F_(D)=150 mL/min、连续相浓度[Ca^(2+)]=0.05 mol/L、分散相浓度[CO^(2-)_(3)]=0.2 mol/L、停留时间τ=5 s。微筛孔反应器特有的孔道结构能够均匀分散液相体系,从而避免了一般微反应器在液相沉淀反应中出现的堵塞问题,微筛孔反应器的分子扩散混合模式可大幅度强化液相体系的扰动程度并提高CaCO_(3)过饱和度,使制得样品粒径较小且分布极窄。同时,通过改变制备条件可灵活调控样品的形貌与粒径。

立方氮化硅的冲击波合成实验

氮化硅在常态下的两种已知物相（α和β相）均为六方结构，最近新发现第3种具有立方尖晶石结构的氮化硅（以下称立方氮化硅或γ-Si3N4）可通过高温高压条件合成得到，是继金刚石、立方氮化硼之后的又一种超硬材料。各国学者在合成立方氮化硅的研究中开展了积极的工作，然而，目前所用的技术手段仅能合成出极少量的γ-Si3N4粉体样品，无法进一步开展其块体材料的研究，并制约了该新材料在工业技术中的应用。