OsNPF3.1,a nitrate,abscisic acid and gibberellin transporter gene,is essential for rice tillering and nitrogen utilization efficiency

Low-affinity nitrate transporter genes have been identified in subfamilies 4-8 of the rice nitrate transporter 1(NRT1)/peptide transporter family(NPF),but the OsNPF3 subfamily responsible for nitrate and phytohormone transport and rice growth and development remains unknown.In this study,we described OsNPF3.1 as an essential nitrate and phytohormone transporter gene for rice tillering and nitrogen utilization efficiency(NUtE).OsNPF3.1 possesses four major haplotypes of its promoter sequence in 517 cultivars,and its expression is positively associated with tiller number.Its expression was higher in the basal part,culm,and leaf blade than in other parts of the plant,and was strongly induced by nitrate,abscisic acid(ABA)and gibberellin 3(GA_3)in the root and shoot of rice.Electrophysiological experiments demonstrated that OsNPF3.1 is a pH-dependent low-affinity nitrate transporter,with rice protoplast uptake assays showing it to be an ABA and GA_3 transporter.OsNPF3.1 overexpression significantly promoted ABA accumulation in the roots and GA accumulation in the basal part of the plant which inhibited axillary bud outgrowth and rice tillering,especially at high nitrate concentrations.The NUtE of OsNPF3.1-overexpressing plants was enhanced under low and medium nitrate concentrations,whereas the NUtE of OsNPF3.1 clustered regularly interspaced short palindromic repeats(CRISPR)plants was increased under high nitrate concentrations.The results indicate that OsNPF3.1 transports nitrate and phytohormones in different rice tissues under different nitrate concentrations.The altered OsNPF3.1 expression improves NUtE in the OsNPF3.1-overexpressing and CRISPR lines at low and high nitrate concentrations,respectively.

OsNPF5.16, a nitrate transporter gene with natural variation, is essential for rice growth and yield

Rice has a large number of nitrate or peptide transporter family(NPF) genes, but the effects of most members on rice growth and development are unknown. We report that Os NPF5.16, a nitrate transporter gene with natural variation in its promoter sequence, is essential for rice growth and yield. The promoter sequence showed various differences between indica and japonica cultivars, and higher expression of Os NPF5.16 was found in indica cultivars with higher plant weight and more tillers than japonica cultivars.Os NPF5.16 was highly expressed in roots, tiller basal parts, and leaf sheaths, and its protein was localized on the plasma membrane. In c RNA-injected Xenopus laevis oocytes, Os NPF5.16 transport of nitrate at high nitrate concentration depended on p H. Overexpression of Os NPF5.16 increased nitrate content and total nitrogen content in leaf sheath as well as biomass and tiller bud length in rice. Elevated expression of Os NPF5.16 increased rice tiller number and grain yield by regulating cytokinin levels. Inhibition of Os NPF5.16 expression showed the opposite effects. Regulating Os NPF5.16 expression has potential for improving rice grain yield.

Influences of external nutrient conditions on the transcript levels of a nitrate transporter gene in Skeletonema costatum

To verify the feasibility of high-affinity nitrate transporter gene （Nrt2） as an indicator of nitrogen status, changes in the transcript levels of transcripts associated with phosphate starvation and different nitrate concentrations were studied using real-time quantitative reverse-transcription PCR （QRT-PCR） technology in batch cultures of Skeletonema costatum. The results show that compared with P-replete condition, P starvation could reduce the Nrt2 transcript levels apparently. Nrt2 transcript levels had a significant negative linear correlation with nitrate concentrations below 40 pmol/L. The results of 48 h short-term incubation experiment under different nitrate concentrations confirmed this correlation, and the following regression equation is built： y = -3.305x ＋ 98.95, R2 = 0.988, where x represents nitrate concentrations （〈40 btmol/L） and y represents the Nrt2 transcript levels.

Exogenous addition of nitrate nitrogen regulates the uptake and translocation of lead (Pb) by Iris lacteal Pall. var. chinensis (Fisch.) Koidz.

Since Pb is a non-biodegradable inorganic pollutant and a non-essential metal,its long-term presence in soil poses a great threat to the environment.Iris lactea Pall.var.chinensis(Fisch.)Koidz.,a perennial dense bush herb with high resistance of Pb and wide adaptability,was used in pot experiments to study the effects of exogenous nitrate N(NO_(3)^(–)-N)on the absorption and transportation of Pb and plant growth under different Pb concentrations.Then,the mechanism of NO_(3)^(-)-N affecting Pb and nutrient uptake and transport was explored.The concentration of Pb in the experiment ranged from 0 to 1600 mg/kg,and the added concentration of NO_(3)^(-)-N was 0.0–0.3 g/kg.The results showed that I.lactea was highly tolerant to Pb,and the shoot fraction was more sensitive to varied Pb concentrations in the soil than the root fraction.This protective function became more pronounced under the condition of raised Pb concentration in the soil.When the concentration of Pb in the soil reached 800 mg/kg,the highest Pb content of I.lactea was found under the condition of 0.1 g/kg of NO–3-N addition.When Pb concentration in the soil increased to 1600 mg/kg,the increase in NO_(3)^(-)-N addition promoted Pb uptake by the root.To ensure the well growth of I.lactea and the effect of remediation of Pb-contaminated soil,the recommended concentration of NO–3-N in the soil is 0.1 g/kg.This result provides a theoretical basis for exogenous N regulation of phytoremediation of Pb-contaminated soil.

红壤区旱作花生地剖面氮素迁移转化模拟研究

为探究红壤区花生种植地氮素的垂向迁移影响因素及其损失特征,本研究利用HYDRUS-1D模型构建适用于红壤地区的水氮耦合模型。该模型结合实地监测数据和室内淋溶实验结果,对模型参数进行率定和验证,并利用校验过的模型模拟研究区不同环境条件下土壤剖面氮素的动态迁移与转化过程。结果表明:HYDRUS-1D模型模拟值与实测值之间吻合度较高,模型可用于模拟花生地不同深度土壤水氮运移过程。土壤铵态氮和硝态氮在降雨施肥后迅速升高,随后下降。施肥量变化主要影响0~40 cm土层内氮素浓度变化,而改变降雨量影响0~80 cm土层内氮素的迁移转化。此外,氮素浓度随土层深度的增加而减小。模拟结果显示,施氮量为225.0 kg·hm^(-2)时,雨季发生总降雨量大于173 mm且降雨强度大于11 mm·d^(-1)降雨事件时,或旱季发生强降雨事件,即总降雨量大于135 mm且降雨强度大于135 mm·d^(-1)时,80 cm土层硝态氮浓度至少上升到1 mg·L^(-1)。受红壤质地黏重的影响,深层土壤氮素对降雨响应具有一定的滞后效应。随着施肥量的增加,作物根系对氮素的吸收通量增大,但氮素吸收量与氮肥施用量的比例却有所下降;降雨量对根系吸收氮素的影响相对较小。在花生生长季,土壤中的主要氮损失形式为硝态氮的淋失。模拟分析表明,降雨和施肥均会影响硝态氮的淋失量,其中降雨量的增加显著提高了硝态氮的浸出量,硝态氮累积淋失量变化范围在5.23~42.97 kg·hm^(-2)之间,证明了花生地对红壤区地下水硝酸盐潜在污染不可忽视。

缓释尿素减施对冬小麦产量和氮素利用效率的影响

为优化旱地小麦高效施氮管理,实现高效生产目标,通过2 a(2019—2020年度和2020—2021年度)田间试验,设不施肥(CK)、不施氮(T1)、300 kg·hm^(-2)尿素N(T2,常规施氮处理)、300 kg·hm^(-2)缓释尿素N(T3)、195 kg·hm^(-2)缓释尿素N(T4)和90 kg·hm^(-2)缓释尿素N(T5)6个处理,分析不同缓释尿素减施量对农田土壤硝态氮分布及累积、氮素吸收与转运、冬小麦产量和氮素利用效率的影响。结果表明,缓释尿素减施处理(T4和T5)显著降低收获期0~200 cm土层的土壤NO-3-N累积量,同时提高0~40 cm土层NO-3-N占比。施用缓释尿素显著提高冬小麦氮素转运量和花后氮素吸收量,T3处理较当地常规施氮处理分别提高12.9%和13.6%。氮素转运对籽粒的贡献率随缓释尿素减施比例的增加呈先增后降的变化趋势,T4处理最大,较其他施氮处理提高0.2%~50.0%。施用缓释尿素可不同程度地改善冬小麦产量构成因素和提高产量;T4处理两年产量分别为8 434、9 060 kg·hm^(-2),2019—2020年度较T2和T3处理分别提高19.7%和13.9%,2020—2021年度分别提高17.3%和10.4%,其经济效益2019—2020年度较T2和T3处理分别提高33.3%和34.0%,2020—2021年度分别提高26.8%和23.2%。缓释尿素减施显著降低氮素表观损失,提高了氮素利用效率和氮肥偏生产力。通过拟合分析发现,缓释尿素施用量为208.7 kg·hm^(-2)时,两年产量分别为8 054、8 806 kg·hm^(-2),净效益分别为6 890、8 475 CNY·hm^(-2),NHI分别为78.2%和78.9%,可实现西北旱区冬小麦高产高效。

辣椒NRT基因家族的系统鉴定、进化与表达分析

[目的]本研究旨在鉴定辣椒硝酸盐转运蛋白(NRT)基因家族成员,分析其基本性质、染色体定位、进化关系以及在不同组织、不同果实发育阶段和不同非生物胁迫下的表达特征。[方法]利用生物信息学方法在辣椒‘遵辣1号’基因组中鉴定NRT基因家族并分析其理化性质、基因结构、染色体定位、共线性、顺式作用元件分布和进化关系等;利用转录组数据分析辣椒NRT(CaNRT)基因在不同组织和不同果实发育阶段中的表达特征,并利用RT-qPCR技术分析在不同非生物胁迫下的表达模式。[结果]辣椒中共包含73个CaNRT基因,不均匀分布在10条染色体上。系统进化分析表明,CaNRT基因可分为3个亚家族,同一亚家族具有相似基因结构和保守基序。顺式作用元件分析结果表明CaNRT可能受光、激素、逆境胁迫等多种因素调控。CaNRT1亚家族成员主要在根、茎、叶中表达量较高,CaNRT2亚家族在任何时期表达量都较低,CaNRT3亚家族存在组织表达差异性,主要在根中高表达。逆境胁迫数据表明,CaNRT1.18、CaNRT3.3、CaNRT3.1、CaNRT2.1、CaNRT1.23在低温、高温、干旱、盐和氧化处理下明显响应,所有CaNRT基因在低温处理时均有不同程度的正向响应。[结论]在辣椒基因组中共鉴定获得73个CaNRT基因,筛选出多个在辣椒生长发育和逆境胁迫中具有重要作用的关键基因。

降雨、施肥对补水河流周边土壤硝态氮迁移分布的影响

补水河流周边土壤硝态氮迁移过程受到河流水文条件、降雨、施肥等多因素的影响,研究多种因素共同作用下土壤硝态氮分布及淋失特征,可以为深入理解土壤氮素循环过程奠定基础。本研究以华北平原白洋淀入淀河流周边农田和农林复合区(AF)为研究对象,其中农田区设置不施肥(CK)、优化施肥(YH)、习惯施肥(XG)3个施肥处理,综合分析在不同降雨类型、生态补水等因素作用下土壤硝态氮剖面分布、淋溶等迁移特征。研究结果表明:施氮量、降雨类型、生态补水等均是影响补水河流周边硝态氮迁移淋失的关键因子。其中,施氮量决定土壤硝态氮淋失总量(P<0.01)。随着施氮量的增加,土壤剖面的硝态氮含量和硝态氮淋失量均显著增加,与XG处理相比,YH处理和AF处理的硝态氮淋失总量分别减少40.6%和40.1%。降雨和生态补水改变了硝态氮在土壤剖面的迁移过程。其中,降雨主要影响表层土壤硝态氮向中下层迁移,生态补水主要影响中下层土壤硝态氮向更深层土壤的迁移。另外,不同降雨类型对土壤硝态氮迁移的影响有所差异,即两种降雨类型下硝态氮向下层土壤迁移速率和迁移量不同。常规降雨(3 d累积降雨65.2 mm)和强降雨(5 h累积降雨49.2 mm)两种情况下硝态氮累积峰均在40~60 cm土层。常规降雨导致XG处理40~60 cm比0~40 cm土层硝态氮储量增加9.7%;强降雨导致XG处理40~60 cm比0~40 cm土层硝态氮储量增加16.7%。生态补水导致YH处理和XG处理在100~140 cm土层硝态氮储量分别减少42.7 kg·hm^(-2)和39.6 kg·hm^(-2)。以上研究结果对于生态补水和极端降雨背景下土壤氮素污染管理具有重要意义。

根际微生态环境中氮源转化及循环研究进展

氮是植物生长所需的三大主要营养元素之一,而硝态氮和铵态氮是植物吸收的2种主要氮素形态。硝态氮与铵态氮在植物生长过程中发挥着不同的作用。植物主要通过根系吸收硝态氮来满足生长过程中氮的需求,并转化为氨基酸、蛋白质等生物活性物质的合成原料,同时硝态氮参与叶绿素的合成,促进光合作用的进行;铵态氮也可被植物根系吸收,并用于植物体内蛋白质和氨基酸的合成,而且铵态氮的吸收速度较快,能够满足植物对氮素的迅速需求。由于植物生长特性不同,植物对硝态氮和铵态氮的利用效率有所差异。植物的基因型和环境因素都会影响其对不同氮素形态的利用能力,形成一些植物对硝态氮偏爱,而另一些植物则对铵态氮更为偏爱。本文从土壤氮素形态与转化影响因子、植物对氮素吸收机制以及高效氮素循环转化展望3个层面综述相关的研究进展,为作物生产中氮肥调控、土壤生态修复等科学研究提供技术理论参考依据。

硝酸盐转运蛋白Sialin在人血管内皮细胞缺氧复氧损伤中的表达

目的研究硝酸盐转运蛋白Sialin及编码基因SLC17A5在血管内皮细胞(HUVECs)上的表达和定位及其在血管内皮细胞缺氧复氧损伤后的表达变化。方法应用免疫荧光激光共聚焦成像实验验证Sialin在人脐静脉血管内皮细胞的表达及定位。以SCC-15及人成纤维细胞为参照,通过Western Blot及RT-PCR实验检测Sialin蛋白及编码基因SLC17A5在HUVECs上的表达。HUVECs随机分组,建立不同缺氧损伤时间的血管内皮细胞缺氧复氧损伤模型,通过Real-time PCR实验验证各组SLC17A5基因的表达变化,通过免疫印迹验证各组Sialin蛋白的表达变化。结果 Sialin蛋白的表达位于HUVECs的细胞质与细胞膜,且具有较高的表达水平。血管内皮细胞缺氧复氧损伤后,SLC17A5及Sialin蛋白与对照组相比表达水平均有明显下降(P<0.05),随缺氧时间增加,表达水平继续降低(P<0.05)。结论硝酸盐转运蛋白Sialin在血管内皮细胞的细胞膜及细胞质有明显表达。在血管内皮细胞缺氧复氧损伤中其表达水平与缺氧时间相关。

Nitrate leaching of winter wheat grown in lysimeters as affected by fertilizers and irrigation on the North China Plain

Proper application of nitrogen（N） fertilizers and irrigation management are important production practices that can reduce nitrate leaching into groundwater and improve the N use efficiency（NUE）. A lysimeter/rain shelter facility was used to study effects of the rate of N fertilization, type of N fertilizer, and irrigation level on key aspects of winter wheat production over three growing seasons（response variables were nitrate transport, N leaching, and NUE）. Results indicated that nitrate concentration in the soil profile and N leaching increased with the rate of N fertilization. At the end of the third season, nitrate concentration in the top 0–75 cm layer of soil was higher with manure treatment while urea treatments resulted in higher concentrations in the 100–200 cm layer. With normal irrigation, 3.4 to 15.3% of N from applied fertilizer was leached from the soil, yet no leaching occurred under a stress irrigation treatment. The manure treatment experienced less N leaching than the urea treatment in all cases except for the 180 kg N ha^-1 rate in 2011–2012（season 3）. In terms of grain yield（GY）, dry matter（DM） or NUE parameters, values for the manure treatment were lower than for the urea treatment in 2009–2010（season 1）, yet were otherwise higher for urea treatment in season 3. GY and crop nitrogen uptake（NU） were elevated when the rate of N fertilizer increased, while the NUE decreased; GY, DM, and NU increased with the amount of irrigation. Data indicated that reduced rates of N fertilization combined with increased manure application and proper irrigation management can lower nitrate levels in the subsoil and reduce potential N leaching into groundwater.

Evaluation of the Impact of the Ongoing Water Resource Management Plans on Nitrate Concentration in Gaza Coastal Aquifer Using Modeling Approach

Groundwater crisis in Gaza includes two major folds: shortage of water supply and contamination. The groundwater pollution by nitrates increased rapidly as a result of wastewater leakage, sewage sludge, animal manure and N-fertilizers. The aims of this study are to obtain the impacts of implementing the Gaza Emergency Technical Assistance Programme (GETAP) on the nitrate concentration in groundwater in Gaza Strip using modeling approach. A flow and transport model using a three dimensional, finite difference simulation model (VMODFLOW Pro.) was applied to simulate the Gaza coastal aquifer (GCA). The approach for selecting the management scenarios was carried out depending on the GETAP projects and focuses into the aquifer system during the next 24 years. It was estimated that work as usual scenario will raise the average nitrate concentration by 8.15 mg/l annually, while upgrade and maintain pipe work scenario will reduce the rising of average nitrate concentration by 4.51 mg/l annually. This means that the average nitrate concentration will increase by only 3.63 mg/l annually. Also, it was estimated that scenarios imported water from Israel, construction of short term low volume desalination plant (STLV), Construction of two regional desalination plant and Reuse of treated wastewater in addition to decrease N-fertilizer will annually increase the average nitrate concentration by only (4.67, 2.78, 3.87, 2.15) mg/l, respectively. The results show that applying all the scenarios together will decrease the average nitrate concentration by 2.44 mg/l annually. Regionally, the best scenario to solve the increasing of nitrate concentration problem is a combination of those scenarios. In domestic areas, the best scenarios is STLV and upgrading and maintaining pipe work. In Agriculture areas, the best scenario and the only one that has significant effect is the reuse of treated wastewater in addition to decrease N-fertilizer.

硝酸盐转运蛋白(Sialin)与口腔鳞状细胞癌预后的相关性研究

目的:探究硝酸盐转运蛋白(Sialin)与口腔鳞状细胞癌预后的相关性。方法:收集2018年1月—2018年9月我院收治口腔鳞状细胞癌患者80例,取其癌组织,进行免疫组织化学检测法,检测Sialin和Ki-67表达情况,分析Sialin表达与口腔癌临床病理因素的相关性,以及Sialin和Ki-67的相关性。结果:Sialin的表达与肿瘤的分期、浸润程度以及分化程度有关(P<0.05);Sialin与Ki-67之间呈较强的正相关(Pearson相关系数为0.48,P<0.05)。结论:Sialin的表达和口腔鳞状细胞癌的发生发展相关,同时和Ki-67呈较强的正相关,是一个较好的预后因子。

硝酸盐转运蛋白（Sialin）与口腔癌的相关性研究

目的探究硝酸盐转运蛋白与口腔癌的相关性。方法收集2018年1月至2018年8月我院收治口腔癌患者50例,取其口腔癌组织和癌旁组织,同时取50例健康人的正常口腔组织作为对照,进行免疫组织化学染色,并进行阳性评定,比较三者阳性表达率,统计Sialin表达与口腔癌临床因素的相关性。结果口腔癌组织中阳性表达率为94.00%,癌旁组织为62.00%,显著高于正常组织(P<0.05);Sialin的表达与口腔癌的分期和分化程度有关(P<0.05)。结论 Sialin表达在口腔癌的发生发展中具有重要作用,对口腔癌的诊断分期具有一定的临床意义。

洱海西侧潜流带水交换作用及溶质迁移研究

随着云南大理洱海西侧冲积扇和湖相沉积层平原区域旅游业和农业快速发展,扇缘农业种植活动和扇中人类活动产生大量三氮污染物,由苍山18溪入渗补给使得受氮素污染地下水不断向洱海排泄,使得高原湖泊水体富营养化风险进一步增大。河床潜流带对于入渗的地表水具有净化作用,为了深入研究冲积扇河床潜流带对氮素迁移及转化机制,通过模拟河床潜流带渗滤系统,结合扇中城镇生活污水下渗污染、扇缘农田施肥垂直下渗污染以及扇顶基流地表水和地下水交替补给迁移污染,为河床潜流带地下水氮素污染防治奠定基础。试验结果表明河床潜流带对氮素迁移转化影响明显,扇中NH4+-N和NO3--N在垂向入渗时主要是通过反硝化作用进行脱氮达到水质净化的目的,总体划分为正面效应和负面效应两类,正效应包括阴阳离子交替吸附作用、硝化与反硝化作用的脱氮行为,导致污染物浓度降低使水净化的过程,主要以反硝化作用为主硝化反应为辅进行脱氮;负面效应则是硝化作用和阴阳离子吸附作用使总硬度随着水体析出的Ca2+、Mg2+浓度的升高而升高。扇顶交替流作用下,NO3--N的迁移转化通过以反硝化作用为主,DNRA为辅去氮达到水质净化的过程。

小麦硝酸盐转运蛋白基因TaNRT1.1的鉴定及其等位变异分析

为解析小麦硝酸盐转运蛋白基因TaNRT1.1的生物学功能,本研究通过同源克隆的方法从普通小麦中克隆了小麦硝酸盐转运蛋白基因TaNRT1.1(TaNRT1.1-1A、TaNRT1.1-1B和TaNRT1.1-1D)。生物信息学分析表明,这三个同源基因编码的蛋白均为疏水蛋白,含有丰富的α-螺旋和无未见则卷曲,主要定位于质膜上。小麦不同组织qRT-PCR分析表明,TaNRT1.1-1A和TaNRT1.1-1B基因在根中表达量最高,其次是叶和茎,TaNRT1.1-1D基因在茎中表达量最高,其次是叶和根。因此,推测TaNRT1.1-1A和TaNRT1.1-1B基因在硝酸盐吸收过程中发挥了重要作用,TaNRT1.1-1D基因在硝酸盐转运过程中发挥了重要作用。通过对小麦TaNRT1.1基因多态性筛选发现,在TaNRT1.1-1A基因启动子上游1120 bp的位置有一个8 bp(TGCATGCA)的插入位点,该位点可能与小麦氮利用效率相关。不同氮利用效率小麦品种qRT-PCR分析结果表明,氮高效小麦品种(基因型为TaNRT1.1-1A-b)苗期根中TaNRT1.1-1A基因的相对表达量显著高于氮低效小麦品种(基因型为TaNRT1.1-1A-a)。

喷施尿素硝酸铵提高夏玉米产量并降低氮肥用量和土壤氮素盈余

【目的】尿素分次追施是黄淮海夏玉米的常规施肥方法,但费事费力,播撒不匀还可能降低肥效,引发氮素损失。我们结合当前推广的微喷灌技术,研究了喷施尿素硝酸铵液体肥(UAN)替代土施尿素的可行性以及适宜的施肥量。【方法】于2019和2020年,在泰安市岱岳区马庄镇开展田间试验,供试夏玉米品种为登海605(DH605)和登海518(DH518)。设沟施尿素-N 210 kg/hm^(2)(Ur),喷施UAN-N 126 kg/hm^(2)(U1,减氮40%)、168 kg/hm^(2)(U2,减氮20%)和210 kg/hm^(2)(U3)处理,以及1个不施氮对照(N0)。在玉米抽雄期(VT)、成熟期(R6),采集植株样品分析不同部位氮素含量和干物质积累量,计算氮素吸收、运转和利用率。于玉米播前、拔节期(V6)、大喇叭口期(V12)、抽雄期(VT)、乳熟期(R3)和成熟期(R6),取0—20、20—40、40—60 cm土层土样,分析硝态氮和铵态氮含量,计算氮素残留和盈余量。【结果】DH605和DH518两个玉米品种的产量均表现为U3处理显著高于U2和Ur处理,而U1处理显著低于U2和Ur处理,U3处理DH605的产量和净收益较Ur处理分别增加了6.71%和11.75%,DH518分别增加了7.57%和13.61%。干物质积累量、氮素积累量、氮素转运量和花后氮素同化量均随UAN用量的增加而增加,U3处理各指标均显著高于其他处理,两品种氮素回收率较Ur处理分别提高了20.78和19.22个百分点,氮素农学利用率分别增加了4.57和4.99 kg/kg。U2处理两品种玉米产量与Ur处理无显著差异,但植株氮素积累量、氮素转运量和花后氮素同化量高于Ur处理,最终提高了氮素回收率和氮素农学利用率。VT时期20—40 cm土层NO_(3)^(−)-N含量随UAN施用量增加而增加。玉米VT至R6时期,各处理0—20 cm土层NO_(3)^(−)-N含量基本呈降低趋势,Ur处理降低幅度最大,且喷施UAN处理与沟施尿素处理相比减少了玉米R6时期40—60 cm土层NO_(3)^(−)-N含量,降低了氮素淋失潜在风险。此外,与Ur相比,喷施UAN处理降低了土壤氮素盈余,U3处理DH605和DH518两年分别平均降低43.63和40.36 kg/hm^(2),U2处理则分别平均降低了48.25和51.91 kg/hm^(2)。【结论】在施氮量较传统用量减少20%的前提下,喷灌施用尿素硝酸铵溶液促进了玉米氮素积累和再分配,在保证产量的同时,可显著增加氮素回收率和氮素农学利用率,降低土壤NO_(3)^(−)-N淋失的潜在风险和土壤氮素盈余,实现夏玉米生产减肥增效的目标。

基于全耦合的地表水土壤水运动与溶质运移数值模拟

为探究降水条件下水分与溶质在地表和土壤中的运动规律,分别采用二维扩散波方程和传统的三维Richards方程描述地面径流和土壤水分运动,选用双层结点法对两者进行耦合,根据达西定律和地表与土壤水中的溶质浓度,计算地面径流和土壤水分的溶质交换量,从而构建地表水土壤水运动与溶质运移全耦合数值模型。选取已发表文献中的物理模型实验进行数值模拟,算例1和算例2中地表径流数值模拟结果和模型实验结果的平均相对误差分别小于14.8%和21.5%,均方根误差分别小于0.147cm^(2)/s和0.833cm^(2)/s;算例2中径流硝态氮浓度的数值模拟结果和模型实验结果的平均相对误差小于24.7%,均方根误差小于1.334mg/L。物理实验和数值模拟所得地表径流量和溶质浓度数据的对比分析验证了模型的合理性和准确度。研究结果可为地表水土壤水水分运动与溶质运移耦合分析提供理论支持。

陆地棉硝酸盐转运体NRT基因家族鉴定及表达分析

硝酸盐转运体(nitrate transporters,NRTs)在植物氮素吸收、利用和存储等过程中发挥着重要作用。本研究利用HMM软件和Blastp方法,在陆地棉中,鉴定出了106个GhNRT1/PTR(NPF)(Nitrate transporter 1(NRT1)/Peptide Transporter(PTR)family(NPF))和14个GhNRT2(Nitrate transporter 2 family)成员,对它们的保守结构域、系统发育关系、理化性质、亚细胞定位、保守基序、基因结构、启动子区顺式作用元件和表达模式进行了分析。结果表明,GhNPF均具有典型的PTR2(Peptide Transporter 2 family,肽转运蛋白)结构域,个别蛋白(GhNPF2.6bD、GhNPF4.1cA和GhNPF2.14aD)出现了2个PTR2和/或其他结构域,表明棉花NPF进化保守性较低;GhNRT2具有典型的MFS_1(Major Facilitator Superfamily,主要促进子超家族)单域。多数GhNRTs定位于细胞质膜上,为疏水性蛋白。系统发育分析显示GhNRTs可分为10个类群,相同类群具有相似的基因结构及基序分布。顺式作用元件组成表明,大部分GhNRTs的表达可能与植物激素、非生物胁迫和光反应等相关。此外,GhNPF不同亚类间的表达模式存在一定差异,但同一亚类内不同成员的表达模式相对保守;GhNRT2基因则主要在根中高表达。盐胁迫处理后的转录组数据分析发现,近1/5的GhNRTs基因表达量发生了显著上调或下调,表明其可能参与棉花盐胁迫应答。选择6个GhNRTs基因检测其在根系、幼叶、功能叶和老叶中的表达对不同NO_(3)^(-)供应水平的响应发现,GhNPF6.3dA和GhNPF7.3aA可能具有双亲和吸收NO_(3)^(-)的能力,GhNPF6.2bD则可能编码高亲和NO_(3)^(-)转运蛋白;三者在功能叶和老叶中可能参与NO_(3)^(-)卸载。这些结果与拟南芥等植物中的报道不同。上述研究结果为进一步揭示棉花硝酸盐转运蛋白的功能提供了参考,为解析棉花氮素吸收和利用机制提供了初步依据。

Characteristics and sources of peroxyacetyl nitrate(PAN)in the rural North China Plain:Results from1-year continuous observations

Peroxyacetyl nitrate(PAN)is an important photochemical pollutant in the troposphere,whereas long-term measurements are scarce in rural areas in North China Plain(NCP),resulting in unclear seasonal variations and sources of PAN in rural NCP.In this study,we conducted a 1-year observation of PAN during 2021-2022 at the rural NCP site.The average concentrations of PAN were 1.10,0.75,0.65,and 0.88 ppbv in spring,summer,autumn,and winter,respectively,with a 1-year average of 0.81±0.60 ppbv.Calculations indicate that the loss of PAN through thermal decomposition in summer accounts for 43.2% of the total formed PAN,which is an important reason for the low concentration of PAN in summer.We speculate that since the correlation between PAN and O_(3) in winter is significantly lower than that in other seasons,the observed regional transport of PAN cannot be ignored in winter.Through budget analysis,regional transport accounted for 12.8% and 55.9% of the observed PAN on the spring and winter pollution days,respectively,which showed that regional transport played key roles during the photochemical pollution of the rural NCP in winter.The potential source contribution function revealed that the transported PAN mainly comes from southern Hebei in spring.In winter,the transported PAN was mainly from Langfang,Hengshui,and southern Beijing.Our findings may aid in understanding PAN variations in different seasons in rural areas and highlight the impact of regional transport on the PAN budget.