【作者】 薛艳芳；

【导师】 邹春琴； 赵方杰；

【作者基本信息】 中国农业大学 ， 植物营养学， 2014， 博士

【摘要】 人体锌和铁营养缺乏是世界范围内普遍存在的营养问题,饮食中锌铁的摄取量不足和饮食结构的单一化是引起人体锌铁缺乏的主要原因,尤其是以谷类作物为主要饮食来源的低收入国家。研究表明氮素供应可以提高小麦和玉米籽粒锌和铁浓度。锌从土壤进入作物籽粒是一个复杂的过程,需要经过根系吸收、运输和分配等生理过程最终在籽粒累积。目前关于氮素供应如何影响这些生理过程的报道很少。本论文基于田间试验系统研究了不同氮肥供应水平对冬小麦和夏玉米根系锌吸收、锌从根系向地上部运输、锌的再转移以及锌在籽粒累积等生理过程的影响,进一步定量化不同产量水平下冬小麦和夏玉米籽粒微量元素需求量,主要结果如下：1.4年田间试验结果表明,与不施氮肥相比,施用不同用量的氮肥后,小麦籽粒锌、铁和铜浓度平均分别增加了1.1-10.2mg kg-1,1.6-5.8mg kg-1(?)(?)0.5-1.1mg kg-1,相应的增加幅度分别为4.341.4%,6.1-22.6%和16.7-34.3%；玉米籽粒锌、铁和锰浓度平均分别增加了0.2-3.1mg kg-1,1.3-3.6mg kg-1和0.0-0.6mg kg-1,增加幅度分别为1.3-20.8%,9.3-25.8%和0.4-19.7%；玉米籽粒铜浓度增加了约0.5mg kg-1,增加幅度为44.7%。相反施用氮肥后小麦和玉米籽粒磷浓度均分别下降了0.22-0.73g kg-1和0.18-0.20g kg-1,相应的降低幅度分别为5.9-19.7%和8.4-9.2%；小麦籽粒锰浓度下降了2.6-4.9mg kg-1,下降幅度为7.9-14.7%。小麦和玉米籽粒钾、镁和钙浓度几乎不受氮素供应水平的影响。2.氮素供应提高了小麦和玉米根长、根表面积和根系干重,从而增加了根系锌吸收能力。在小麦拔节、开花和成熟期,高达80-92%的根系干重、88-96%的根长、85-94%的根表面积和85-96%的根系锌累积量均分布在0-30cm的土层,并且0-20cm或0-30cm土层根系锌浓度显著高于30-60cm土层,这些结果表明小麦根系生长与根系锌吸收在0-30cm耕作层有很好的空间耦合。3.在拔节期、开花期和成熟期,小麦地上部植株锌累积量占总锌累积量(地上部和根系锌累积量之和)的比例分别为55-79%,61-87%和83-90%。在玉米生长的各个时期,地上部植株锌累积量占总锌累积量比例均高达89-98%,表明锌从根系向地上部的转移能力很强,不是籽粒锌累积的限制因子。而且,小麦和玉米总锌累积量、地上部植株锌累积量和冠根锌浓度比均随氮素供应增加而增加,表明氮素供应能有效促进根系锌吸收以及锌从根系向地上部的转移。4.67-100%的小麦籽粒锌累积来自于花前锌从营养器官向籽粒的再转移,而且灌浆期内锌从营养器官向籽粒的转移量与氮从营养器官向籽粒的转移量显著相关(R2=0.59***),表明氮素供应显著提高锌从营养器官向籽粒的再转移能力。与小麦相反,74-99%的玉米籽粒锌累积来自于花后根系锌吸收,而且根系锌吸收对籽粒锌累积的绝对贡献量(0.95-2.32mg plant-1)和相对贡献率均随氮素供应增加而增加。5.氮素供应显著增加小麦籽粒不同组分(种皮、糊粉层、胚乳)锌铁浓度,但增加的部分主要以难溶性锌铁存在,而可溶性锌铁浓度(用三羟甲基氨基甲烷缓存溶液提取,pH7.5)却没有增加,反而有所下降。进一步用高效液相色谱联用电感耦合等离子体质谱(SEC-ICP-MS)分析发现,籽粒不同组分中可溶性提取液中尼克酰胺螯合态锌和尼克酰胺-麦根酸螯合态铁的含量均随氮素供应增加而显著降低,分别降低了4-37%和5-12%；而一些可溶性高分子化合物和可溶性植酸几乎不受氮素供应影响。这些研究结果表明尼克酰胺或麦根酸可能仅在锌铁向籽粒的韧皮部运输中起着重要的作用,而不是籽粒锌铁存在的主要形态。6.通过对104个冬小麦数据分析发现,随着产量水平的增加(<6,6-7.5和>7.5Mg ha-1),生产1Mg冬小麦籽粒的需锌量从36.5g降低到28.9g,需铁量从130.2g增加到151.2g,需锰量从49.6g增加到55.0g,铜的需求量先增加后下降,分别为5.0,6.3和5.0g。产量增加后秸秆锌浓度从12.5mg kg-1降低至(?)10.5mg kg-1,籽粒锌浓度从28.1mg kg-1降低至(?)22.9mg kg-1,可能是籽粒需锌量下降的主要原因。7.通过对149个夏玉米数据分析发现,随着产量水平的增加(<7.5,7.5-9,9-10.5和>10.5Mgha-1),生产1Mg夏玉米籽粒的需锌量从36.3g降低到18.0g,需铁量从68.6g降低到57.4g,需铜量从5.6g降低到4.9g,需锰量从17.8g增加到19.0g。单位籽粒需锌量随产量增加显著下降的主要原因是锌收获系数(41-60%)增加和籽粒锌浓度(从17.4mg kg-1降低到12.2mgkg-1)和秸秆锌浓度的下降(从24.4mg kg-1降低至(?)10.7mg kg-1)。更多还原

【Abstract】 Zinc (Zn) and iron (Fe) deficiencies are widespread nutritional disorders. Insufficient dietary intakes of Zn and Fe and limited dietary diversity are thought to be responsible for human micronutrient deficiencies, especially in developing countries where cereals constitute the major part of the diet.Nitrogen (N) supply is an important factor for improving grain Zn and Fe concentrations of wheat (Triticum aestivum L.) and maize (Zea mays L.). There are various physiological steps involved in the route of Zn from soil to grain, including root uptake, root-to-shoot translocation and remobilization of Zn. However, there was little information regarding how different N levels affected these physiological processes. In this study, a series of field experiments were conducted on winter wheat and summer maize to1) examine the effects of different N supplies on root uptake, root-to-shoot translocation, and remobilization of Zn from vegetative tissues into developing grain tissues,2) to quantify Zn, Fe, manganese (Mn) and copper (Cu) requirements (g of nutrient requirement in plant dry matter per Mg grain yield) in response to increased grain yields. The main results were summarized as follows:1. Results from a4-year experiment of winter wheat and summer maize, respectively showed that compared with no N application (the control), grain Zn, Fe and Cu concentrations of wheat increased1.1-10.2,1.6-5.8and0.5-1.1mg kg-1, respectively and their corresponding increasing percentages were4.3-41.4%,6.1-22.6and16.7-34.3%with N supplies. Compared with the control, grain Zn, Fe, Mn and Cu concentrations of maize increased0.2-3.1,1.3-3.6,0.0-0.6and about0.5mg kg-1, respectively and their corresponding increasing percentages were1.3-20.8%,9.3-25.8%,0.4-19.7%and about44.7%, respectively with N supplies. However, compared with the control, grain phosphorus (P) concentration of wheat and maize decreased0.22-0.73and0.18-0.20g kg-1respectively and their corresponding decreasing percentages were5.9-19.7%and8.4-9.2%with N supplies. Grain Mn concentration of wheat decreased2.6-4.9mg kg-1with its decreasing percentage being7.9-14.7%with N supplies. Grain potassium (K), magnesium (Mg) and calcium (Ca) concentrations of wheat and maize were less affected by different N supplies.2. Increasing N supply improved root length (RL), root surface area (RSA) and root dry weight (RDW) of wheat and maize, thus resulting in an improved ability to take up Zn from the soil. During the growing period of wheat,88-96%of RL,85-94%of RSA,80-92%of RDW and85-96%of root Zn uptake were recovered from the upper30cm soil layer. Additionally, root Zn concentration in the upper0-20cm or0-30cm depth of soil was significantly higher than in the30-60cm layer of soil. These results suggest a good spatial matching between root spatial distribution and root Zn uptake, especially in the upper30cm plough layer.3. For wheat, the percentages of shoot Zn content to total Zn content (the sum of shoot Zn content and root content) were55-79%,61-87%and83-90%at joining, anthesis and maturity, respectively. During the growing period of maize, the percentage of shoot Zn content to total Zn content was up to89-98%. These results indicate a strong Zn transport from root to shoot in wheat, especially in maize, which was not a limiting factor for grain Zn accumulation. Total Zn content, shoot Zn content and the ratios of shoot to root Zn concentrations were improved with increasing N supply, indicating that N supply improved both root uptake and root-to-shoot translocation of Zn.4.67-100of wheat grain Zn accumulation was provided by Zn remobilization from pre-anthesis vegetative tissues with N supplies. There was significant positive correlation between straw Zn and N remobilization from vegetative tissues to grains during grain filling stage (R2=0.59***). These results suggest N supplies improved Zn remobilization from vegetative tissues to grain. However,74-99%of maize grain Zn accumulation was provided by post-silking root Zn uptake (0.95-2.32mg plant-1). Moreover, the post-silking root Zn uptake and its contribution to grain Zn accumulation were increased with increasing N supply.5. Nitrogen supply increased the concentrations of total and the portions of Zn and Fe unextractable with a Tris-HCl buffer (pH7.5), but decreased the concentrations of Tris-HCl-extractable Zn and Fe of wheat grain tissues. Size-exclusion chromatography coupled with inductively-coupled plasma mass spectrometry (SEC-ICP-MS) was used to determine Zn and Fe speciation in the soluble extracts of grain tissues. Within the soluble fraction, Zn and Fe bound to low molecular weight compounds, likely to be Zn-nicotianamine (NA) or Fe-NA and Fe-deoxymugineic acid (Fe-DMA) were decreased by4-37%and5-12%, respectively, by high N treatment. Zn and Fe bound to soluble high molecular weight or soluble phytate fractions were less affected. These results suggest that NA and/or DMA are only responsible for Zn and Fe transport into grain where Zn and Fe are then sequestered in other forms.6. Based on a four-year experiment of winter wheat(n=104), with increasing grain yield (<6,6-7.5,>7.5Mg ha-1), the Zn requirement per Mg grain yield decreased from36.5to28.9g, while Fe and Mn increased from130.2to151.2g and49.6to55.0g, respectively. Cu requirements per Mg grain yield were5.0,6.3and5.0g, respectively. The decrease in Zn requirement was attributed to a decrease in Zn concentrations of grain (from28.1to22.9mg kg-1) and straw (from12.5to10.5mg kg-1).7. Based on a four-year experiment of summer maize (n-149), with increasing grain yield (<7.5,7.5-9,9-10.5and>10.5Mg ha-1), the requirements per Mg grain yield for Zn, Fe and Cu decreased from36.3to18.0g,68.6to57.4g and5.6to4.9g, respectively, while Mn increased from17.8to19.0g. The decrease in Zn requirement was attributed to the increase in Zn harvest index (from41to60%) and the decrease in Zn concentrations of grain (from17.4to12.2mg kg-1) and especially straw (from24.4to10.7mg kg-1更多还原