茶树氮吸收效率的早期鉴定技术研究

氮是植物生长的重要营养元素,在茶树栽培过程中常需施用大量氮肥,不仅消耗大量的资源,施用不当还会造成一系列环境问题。培育氮肥高效利用的茶树品种是解决这一问题的重要途径,而建立快速筛选高效株系的早期鉴定方法对于缩短育种茶树育种年限具有重要意义。本研究分析龙井43（LJ43）和中茶108（ZC108）两个茶树品种在不同氮素水平下对氨态氮和硝态氮的吸收与利用数据,通过与¹⁵N同位素标记技术的比对,验证非损伤微测技术（NMT）和实时荧光定量（qRT-PCR）技术在早期鉴定茶树株系氮素吸收利用能力方面的可行性与实用性,以期建立茶树氮吸收效率的室内早期鉴定技术。试验结果表明,¹⁵N同位素标记技术的稳定性和可重复性分别为89.51%、99.26%,而NMT的稳定性、可重复性分别为95.22%、96.76%;两种方法测定结果均显示茶树具有明显的喜铵特性;硝酸根转运蛋白基因CsNRT3.2和CsNRT2.4在两个品种中均表现出诱导上调表达效应,相比中茶108,龙井43中CsNRT2.4和CsNRT3.2具有更高的表达量,表明LJ43对外界氮源的响应高于ZC108。综上所述,认为NMT技术可在短时间内处理并测得茶树的瞬时吸收速率,且试验材料损耗少,可以用于茶树氮瞬时吸收速率的早期鉴定;CsNRT2.4和CsNRT3.2的表达量一定程度上反映了茶树对硝态氮吸收的能力。本研究可为氮高效茶树品种的早期鉴定技术建立提供依据。     

烤烟烟碱合成及其氮素来源与移栽期和氮肥的关系研究

采用田间试验与15N同位素示踪微区试验,在湖北襄樊植烟生态区老湾村(N 31°27,′E 111°14′,海拔1130 m)研究了3个不同移栽期和施用氮肥对烤烟烟碱含量和烟碱氮素来源的影响。研究结果表明,与5月5日移栽相比,推迟移栽期至5月15日2~5日,烟碱含量、烟碱氮占总氮比例以及烟碱肥料氮比例分别平均增加10%8~5%、5%1~10%和21%5~6%;与不施氮相比,施用氮肥提高烟碱含量12%5~9%,提高烟碱氮占总氮比例5%~127%。烤烟烟碱氮占总氮的比例随生育进程逐渐增加,而各部位烟叶烟碱肥料氮比例随生育进程和叶位上升逐渐下降。土壤氮是烟碱氮的主要来源,对烟叶烟碱含量有决定性影响。结果说明在当地条件下,控施氮肥和适当提前移栽期更有利于降低烟叶(尤其是中、上部叶)中的烟碱含量。     

可变电荷与恒电荷稻田土壤硝态氮和铵态氮淋失规律

A variable-charge (VC) and a permanent-charge paddy soil (PC) were selected to study nitrate (NO3--N) and ammonium (NH4+-N) leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls (CK), 15N-labeled (NH4)2SO4 (NS) and milk vetch (NV) applied at a rate equivalent to 238 kg N ha–1 to unplanted lysimeters, totaling six treatments replicated in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added 15N respectively; and > 85% of leached NO3--N came from native N in the soil. In the case of VC, NH4+-N made up to 92% of the total inorganic N in leachate. Moreover, NH4+-N leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3--N leaching during the drained season in permanent-charge paddy soils and NH4+-N leaching in variable-charge soils deserve more attention for regional environmental control.     

Evidence for acclimation of N cycling to episodic N inputs in anthropogenically-affected intertidal salt marsh sediments

Nitrate removal was compared in anthropogenically-impacted and unimpacted salt marsh sediments in microcosms using the acetylene block technique and ¹⁵N natural abundance measurements. Potential denitrification rates were greater at the impacted site than the unimpacted site at all added NO₃⁻ concentrations (233, 467, or 700 μg N g dw⁻¹). Although the change in concentration of NH₄⁺ over time was small (69-104 μg N g dw⁻¹), the δ¹⁵N of accumulated NH₄⁺ increased significantly (0.26-13.22‰), and was more enriched for all NO₃⁻ treatments in the impacted sediments than the unimpacted site. The impacted site may be acclimated to episodic N inputs, and based on concentrations and ¹⁵N natural abundance had greater denitrification and N cycling than the unimpacted site.     

Response of ammonia oxidizing archaea and bacteria to changing water filled pore space

This study examined the effect of water filled pore space (WFPS) on gross N fluxes and community structure and abundance of ammonia oxidizing archaea and bacteria in a semi-arid soil. Different WFPS altered the community structure of both AOA and AOB. Ammonia oxidizer communities (for both archaea and bacteria) from ‘wet’ soils (95, 85 and 75% WFPS) and ‘dry’ soils (25, 45 and 55% WFPS) were distinctly different from one another. Additionally there was a significant relationship between community structure and gross rates of nitrification. There was also a significant relationship between WFPS and bacterial amoA abundance but not archaeal amoA abundance suggesting that bacterial ammonia oxidizers are more responsive to changes in soil water availability. These results are in agreement with other studies suggesting that both groups of ammonia oxidizers have distinct physiological characteristics and ecological niches with consequences for nitrification in response to WFPS. Overall findings from this study indicate that nitrification, both in terms of process rates and populations responsible for nitrification activity, is highly responsive to soil water availability.     

Plant uptake of dual-labeled organic N biased by inorganic C uptake: Results of a triple labeling study

Direct plant uptake of organic nitrogen (N) is often studied using the dual-labeling approach (¹⁵N + ¹³C or ¹⁵N + ¹⁴C). However, the method might be hampered by uptake of labeled inorganic carbon (C) produced by mineralization of labeled organic compounds. Here we report the results from a triple labeling experiment (¹⁵N + ¹³C + ¹⁴C) investigating whether root uptake of labeled inorganic C can bias the results obtained in studies of organic N uptake using dual-labeled amino acids (¹⁵N, ¹³C). In a rhizosphere tube experiment we investigated ¹³C and ¹⁴C uptake by maize either supplied with labeled glycine or , but found no differences in uptake rates between these C-sources. The uptake of inorganic C to the shoot tissue was higher for maize grown in full light compared to shading, which indicates a passive uptake of inorganic C with water. We conclude that uptake of inorganic C produced by mineralization of amino acids can significantly bias the interpretations of organic N uptake studies using dual-labeling.     

15N同位素稀释法研究固氮菌接种对甘蔗生物固氮的影响

利用15N同位素稀释法,研究接种固氮菌klebsiella L03对甘蔗品种B8和ROC22的生物固氮的影响。结果表明： B8的固氮百分率最高为3128%Ndfa,从苗期开始就显著高于ROC22,分蘖期和伸长初期的固氮量和固氮百分率与ROC22相比差异达到极显著水平。B8和ROC22的根、茎、叶都可发生固氮,以伸长初期（60d）叶片中的固氮能力最强。接种L03能显著提高B8和ROC22各器官的含氮量,其中对ROC22叶片和B8茎的含氮量提高作用最明显。不同甘蔗品种、相同品种的不同器官甚至相同器官的不同生长时期固氮作用有很大差异。     

基肥(~(15)N)施用时间对烤烟产量、产值及氮素利用率的影响

采用15N同位素示踪微区试验与田间试验,在湖北襄樊2个不同海拔的植烟生态区(赵家山和老湾)研究了不同基肥施用时间(提前0、15和30d)条件下,施用氮肥对烤烟产量、产值及氮素吸收、利用和分配的影响。结果表明,施用氮肥显著增加烤烟产量和产值,增幅分别为13%～40%(低海拔赵家山地点)和14%～35%(高海拔老湾地点)。与移栽当天施用基肥相比,提前施用基肥15～30d有利烤烟产值的提高,其中高海拔试验点增幅为10%～30%,达到显著水平(P0.05)。与移栽当天或者提前15d相比,提前30d施用基肥还提高2个海拔地区烤烟对氮素的吸收累积量8%～26%。提前基肥施用时间对低海拔地区氮肥利用率的影响不显著,但显著提高高海拔地区烤烟生育中后期氮肥利用率3%～6%。结果说明,在光、温条件较差的高海拔地区,适当提前施用基肥(15d),有利于提高肥料利用率,从而提高烤烟产量产值。     

“红灯”甜樱桃对秋季叶施15N-尿素的吸收、分配及利用特性

在田间条件下以7年生"红灯"甜樱桃/大青叶为试材,探讨了甜樱桃不同枝类叶片对晚秋叶施¹⁵N-尿素的吸收和翌年的分配及利用特性,研究了晚秋叶面施氮对果实品质的影响。结果表明:晚秋对甜樱桃叶面施用浓度为1.00%的¹⁵N-尿素,施用总量的16.30%1～7.27%随落叶脱离树体,其余82.73%8～3.70%进入树体。在翌年,叶片回流贮藏的氮素化合物可迅速转移到新生器官中,不同处理间的¹⁵N分配运转特性存在差异。长枝叶片吸收、回流贮藏的氮素化合物在翌年铃铛花期主要供应至新梢,促进营养生长;随着物候期的推移,表现出明显的极性分配特性。短枝叶片吸收、回流的氮素化合物主要运至花、果等生殖器官中,用于甜樱桃开花、结果。验证试验表明:叶施尿素处理甜樱桃果实单果重较对照增加21.84%;总糖含量、糖酸比分别提高11.98%、21.84%,同时叶施尿素促进了己醛、2-己烯醛(、E)-2-己烯-1-醇、苯甲醛4种果实重要香气成分的合成。