植物吸收硝态氮的分子生物学进展

植物吸收NO3-分为高亲和力(HATS,high.affinitynitratetransportsystem)和低亲和力(LATS,low.affinitynitratetransportsystem)转运系统。这两个系统的编码基因均已被克隆,其中HATS由NRT2基因家族和NAR2基因家族共同编码,LATS由NRT1基因家族编码。本文比较详细地介绍了这些转运蛋白的结构和功能以及在这方面的最新进展,概要性地介绍了这些基因的表达调控;同时摘要点评了该研究领域中还没有解决的一些问题。     

作物硝态氮转运利用与氮素利用效率的关系

【目的】 铵态氮（NH₄+）和硝态氮（NO₃-）是作物氮素吸收利用的主要形态,旱作作物NO₃-的累积与利用是氮素营养研究的主要组成部分,关系到理解作物NO₃-的转运和利用关系及作物体内NO₃-含量和氮素利用效率（nitrogen utilization efficiency,NUE）高低的问题。主要进展 作物吸收的NO₃-分为被作物直接利用、分泌到根外、储存在液泡和向地上部分运输四种途径。其中NO₃-短途分配（液泡NO₃-分配）和长途转运（地上、地下部NO₃-的转运）共同调控着NO₃-的利用效率,进而影响作物的NUE。液泡NO₃-不能被作物直接利用,只有分配到液泡外细胞质中的NO₃-才能被作物迅速代谢和利用;同时有更大比例的NO₃-分配到地上部分,使得作物可以充分利用太阳光能进行NO₃-代谢和能量转换,从而提高了作物的NUE。此外,液泡对NO₃-起到分隔作用,储存在液泡中的NO₃-并不能对NO₃-转运相关基因（如NR、NO₃-长途转运基因NRT1.5和NRT1.8）起到诱导效果;只有分配在液泡外原生质体中的NO₃-才能对NO₃-诱导基因产生强烈的诱导。因此,作物细胞原生质体中液泡内、外NO₃-的分配不仅影响了NO₃-的同化利用,而且直接影响了NO₃-的长途转运。展望 本文对植物原生质体中液泡内、外NO₃-的短途分配和地上、地下部间NO₃-的长途转运机制进行了总结,为进一步深入研究作物地上、地下部NO₃-长途转运和液泡NO₃-短途分配的关系,以及更好地揭示作物NUE对NO₃-转运和利用的响应机理提供参考。     

植物吸收转运硝态氮及其信号调控研究进展

硝态氮是植物吸收利用的主要氮源,其吸收利用是一个高度协调复杂的调控过程。植物为了在各种变化的环境中生存,进化出了适宜不同环境的硝态氮吸收利用机制。植物根系中存在不同类型的硝态氮受体,可以感受外界硝态氮浓度变化,并启用高亲和力或低亲和力硝态氮吸收系统,从而吸收硝态氮;硝态氮进入根系后,大部分被运输到地上部进行同化作用,合成大分子物质,以促进植物生长;如果地上部硝态氮含量过多,植物可把多余的硝态氮运送到液泡内储存,待需要时再从液泡转运至细胞质中利用。植物生长发育过程中,老叶和成熟叶片中的硝态氮可被转运到新生组织中,促进新生组织生长。硝态氮吸收利用过程中大量硝态氮吸收、转运、储存、同化和信号调控基因被有序激活并协调工作,促进植物高效吸收利用硝态氮。本文主要针对NRT1和NRT2硝态氮吸收转运相关基因及其功能,以及参与初级硝态氮反应的相关转录因子和小信号多肽在硝态氮信号传导和组织间的信号交流进行综述,以便深入理解植物吸收利用硝态氮的机理,为高效利用氮素的作物育种和栽培技术的创建提供新的思路。     

营养液pH对小麦生长及吸收铵、硝态氮的影响

采用３种起始ｐＨ不同的营养液进行水培，研究介质ｐＨ对小麦吸收铵、硝态氮及生长量的影响。结果表明，小麦生长期间营养液的ｐＨ因起始值和生育期而变化；这种变化与铵、硝态氮的相对吸收量密切相关。在铵、硝态氮等量共存条件下，介质ｐＨ低有利吸收硝态氮；高、有利吸收铵态氮。起始ｐＨ为５．０、６．５和８．０的营养液，铵，硝态氮的平均吸收比例分别为０．６１、０．９４和１．８５，累积吸收的铵态氮分别占吸氮总量的３３．     

菠菜叶片硝态氮还原对叶柄硝态氮含量的影响

选用3个菠菜品种,设置N.0.1和0.3.g/kg2个施氮水平进行盆栽试验。在不同时期采样测定叶片内、外源硝酸还原酶活性、硝态氮代谢/贮存库大小,以及加入外源硝态氮培养后叶片硝酸还原酶活性的变化,探讨菠菜叶片的硝态氮还原与叶柄硝态氮含量的关系。结果表明,叶片内源硝酸还原酶活性、内源/外源硝酸还原酶活性比值、叶片的硝态氮代谢库大小及代谢/贮存库比值与叶柄硝态氮含量呈相反趋势。加入外源硝态氮培养后叶片硝酸还原酶活性的增加程度与叶柄硝态氮含量相一致。叶片内源硝酸还原酶活性高低及其发挥程度,叶片硝态氮代谢库大小及硝态氮在代谢、贮存库中的分配是造成品种间叶柄硝态氮含量高低差异的重要原因。     

磷的吸收转运机制研究进展

磷对动物来说具有重要的生理功能。它主要以无机磷的形式在小肠和肾脏近端小管上皮细胞的刷状缘膜被吸收和重吸收,它的吸收转运过程是一个借助于钠磷协同转运蛋白与钠离子一起的主动转运过程,并且磷的吸收受很多因素的调节。在充分了解磷的吸收转运机制以后既可以保证动物以最佳状态生长,又可以使由于磷造成的环境污染降到最低。本文就磷的吸收转运机制最新研究进展进行了概述。     

铜绿微囊藻对亚硝态氮的利用

通过室内培养,研究了不同亚硝态氮浓度对铜绿微囊藻（Microcystis aeruginosa）生长的影响和藻对亚硝态氮的利用,实验分析了水体中亚硝态氮、硝态氮和铵态氮浓度的变化,测定了铜绿微囊藻的生长曲线、藻细胞内亚硝态氮含量和藻亚硝酸氧化酶（NOR）。结果显示,在10mgNO^-2-N·L^-1的处理组中,培养基中亚硝态氮和硝态氮浓度同时减少,说明铜绿微囊藻可以同时利用亚硝态氮和硝态氮;在20和30mgNO^-2-N·L^-1的处理组中,随着藻的生长培养基中亚硝态氮的浓度减少,硝态氮浓度增加,而且电泳实验显示此培养条件下铜绿微囊藻能产生亚硝酸氧化酶,表明培养基中的亚硝态氮被亚硝酸氧化酶氧化为硝态氮。本实验也表明高浓度的亚硝态氮（大于10mgNO^-2-N·L^-1）能够抑制藻的生长。     

施氮模式对番茄氮素吸收利用及土壤硝态氮累积的影响

采用田间小区试验,以番茄为指示植物,研究不同施氮模式：农民习惯施肥（N—hmxer）、减施化肥氮26％（74％N-farmer）、减施化肥氮26％结合调节土壤C／N（74％N—farmer＋S）、减施化肥氮26％结合调节土壤C／N和采用滴灌（74％N-farmer＋S＋D）、减施化肥氮45％结合调节土壤C／N和采用滴灌（55％N-farmer＋S＋D）的集成模式对设施番茄氮素吸收利用及土壤硝态氮累积的影响。结果表明。55％N-farmer＋S＋D模式下番茄产量最高为108349kg·hm^-2,产投比最高为26．1;与N—farmer模式相比,74％N-farmer、74％N—farmer＋S、74％N-farmer＋S＋D和55％N—farmer＋S＋D模式的氮素利用率和氮素农学利用效率均有增加,其中55％N—farmer＋S＋D模式的氮素当季利用率为9．56％,氮素农学效率为43．67kg·kg^-1,均显著高于N—farmer模式（P〈0．05）;氮肥生理利用效率在各施氮模式间没有显著差异,55％N-farmer＋S＋D模式的效率最高为598．06kg·kg^-1;55％N-farmer＋S＋D模式的氮素果实生产效率和收获指数分别为493．81kg·kg^-1和53．84％,均高于N—farmer模式。氮平衡结果表明,N—farmer模式的表观损失最高,55％N-farmer＋S＋D模式显著低于N—farmer模式;相同土壤剖面中不同模式硝态氮含量随番茄生育进程均呈先增高后降低的趋势;番茄盛果期和拉秧期,74％N—farmer＋S、74％N—farmer＋S＋D和55％N-farmer＋S＋D模式在0～100cm剖面累积的硝态氮含量均低于N—farmer模式,拉秧期N—farmer模式累积的硝态氮含量最高达705．24kg·hm^-2,74％N-farmer＋S＋D模式累积的硝态氮含量最低为453．75kg·hm^-2;番茄在3个不同生育期,土壤硝态氮多累积在0—40cm土层,硝态氮的相对累积量约为50％。综合以上分析结果,集成模式55％N—farmer＋S＋D具有明显优势,能够提高氮肥的吸收和利用效率,减少土壤硝态氮的残留。     

冬小麦对铵态氮和硝态氮的响应

在陕西省永寿县和河南省洛阳市分别设置了11和7处大田试验,分5层采集0~100 cm土壤样品并测定其起始硝态氮含量。永寿试验设7个处理,分别为不施氮,硝态氮、铵态氮品种、硝态氮与铵态氮2∶1组合各2个处理;洛阳试验设6个处理(硝态氮肥只有1个品种),施氮处理均施N 150 kg hm-2,研究小麦对铵态氮和硝态氮肥响应的差异及其与不同深度土层硝态氮累积量的关系。试验表明,同一形态不同氮肥品种之间的增产差异显著低于不同形态之间的差异。比较不同形态氮肥的小麦产量、增产量和增产率的平均值,硝态氮肥最高,硝态氮、铵态氮组合次之,铵态氮最低。氮肥增产量和增产率随土壤累积硝态氮量增加而显著下降;累积量越低,氮肥增产效果越突出,硝态氮的效果也越显著。由此可见,土壤累积的硝态氮量是决定氮肥肥效的主要因子,也是决定不同形态氮素效果的主要因子。只有在硝态氮累积量低的土壤上,氮肥才能充分发挥作用,硝态氮也才能表现出明显的优势。     

Diurnal uptake of nitrate and potassium during the vegetative growth of tomato plants

Tomato plants (Lycopersicon esculentum Mill.) of the F₁ hybrid variety Turbo were grown in a NFT system for 22 days. On days 16 and 20–22 inclusive of the experiment, the diurnal variation in nitrate (NO₃), potassium (K), and water uptake rates were measured. Nitrate and K uptake rates were subject to large diurnal variation with maximum uptake rates occurring during the day period. Two peaks of diurnal uptake rates were identified, one large peak during the day period and a second much smaller one during the first 2–4 hours of the night. Under the conditions of the experiment, night nutrition made up 35 to 40% of the total daily uptake of K and NO₃. Water uptake rates followed a diurnal oscillation with a single peak pattern. Highest rates occurred at the middle of the photoperiod and lowest rates were measured at night. Over the entire day and night cycle there was no correlation between the rates of water and nutrient uptake. This may be of importance in the fertilization of hydroponically grown plants since in horticultural practice nutrients and water are supplied together in quantities large enough to meet plant water demand but not nutrient requirements.     

酚类物质对土壤和植物的作用机制研究进展

酚类物质是重要的植物次生代谢物质之一,它对植物的生长、养分吸收、生理特性、酶活性以及生长环境中的土壤、微生物等都存在影响。本研究对酚类物质对土壤和植物的作用机制、植物生态系统中酚类物质的含量分布、酚类物质对植物生理生化特性的影响以及对土壤理化特性的影响进行探讨,展望农林生产实践中酚类物质的研究趋势,为解决农业和林业生产中因酚类物质的影响引起生产力下降问题提供依据。     

Nitrogen and water uptake patterns and growth of plants at various minimum solution nitrate concentrations

Increasing fertilizer and energy costs, as well as awareness of environmental quality, require greater fertilizer use efficiency. Providing plant nutrients in the quantity and at the time needed, possibly through fertigation, should lead to more efficient fertilizer use. Knowledge on crop nutrient requirements and minimum nutrient concentrations in the root zone at different stages of growth is important. Hydroponic greenhouse experiments were conducted using tomato and lettuce plants to determine minimum solution nitrogen concentrations which would allow maximum plant growth for a system of frequent nitrogen application and to quantitatively measure nitrogen uptake rates as a function of time. Minimum N levels for the tomato experiment were 2, 10, and 20 mg/1. Solutions were analyzed three times a week to determine N uptake and sufficient KNO₃ was added each time to supply the plant N demand so that the targeted minimum N concentration would be achieved at the next sampling time. The minimum N concentrations in the lettuce trial were 5, 10, 20 and 50 mg/1. A control consisting of 105 mg/1 N was used for both crops. There was no significant effect of N concentration on N uptake throughout the experiment for lettuce and during the early stages of tomato growth. Higher N uptake during the latter stages of tomato growth occurred for the control as compared to the other treatments. The latter observation was probably caused by N diffusion gradient development because of the dense root system and inadequate solution stirring. Plant growth results were comparable to N uptake results. The ratio of N to water uptake was fairly constant throughout the growth period with a trend toward decrease in the ratio with time for tomatoes. Low N concentrations can occur at the root surface without limiting plant growth.     

Influence of photosynthetic irradiance on nitrate reductase activity,nutrient uptake and partitioning in tomato plants

The objective of the present work was to study the nutritional behavior of tomato plants (Lvcopersicon esculentum Mill.) subjected to high pressure sodium (HPS) supplementary lighting in relation to nitrate reductase activity (NRA). Tomato plants were grown with or without HPS supplementary lighting at 2 different root‐zone temperatures (RZT). Supplementary lighting combined with low RZT promoted NRA and cation uptake. Magnesium uptake appeared particularly related to the NRA daily pattern. Effects of photosynthetic irradiance (PI) at two growth stages on partitioning of 45Ca and 86Rb were also investigated. Low light level stimulated 45Ca uptake in fruiting plants but depressed 86Rb uptake. A hypothetical mechanism involving the influence of NRA and K cycling on HCO₃‐ excretion by root is proposed to explain the effects of treatments on mineral uptake.     

An experimental set-up to study carbon, water, and nitrate uptake rates by hydroponically grown plants

The experimental system described allows concomitant hourly measurements of CO2, H2O, and NO3 uptake rates by plants grown hydroponically in a greenhouse. Plants are enclosed in an airtight chamber through which air flows at a controlled speed. Carbon dioxide exchange and transpiration rates are determined from respective differences of concentrations of CO2 and water vapor of the air at the system inlet and outlet. This set-up is based on the "open-system" principle with improvements made on existing systems. For instance, propeller anemometers are used to monitor air flow rates in the chamber. From their signal it is possible to continuously adjust air speed to changing environmental conditions and plant activity. The air temperature inside the system therefore never rises above that outside. Water and NO3 uptake rates are calculated at time intervals from changes in the volume and the NO3 concentration of the nutrient solution in contact with the roots. The precise measurement of the volume of solution is achieved using a balance which has a higher precision than any liquid level sensors. Nitrate concentration is determined in the laboratory from aliquots of solution sampled at time intervals. A number of test runs are reported which validate the measurements and confirm undisturbed conditions within the system. Results of typical diurnal changes in CO2, H2O, and NO3 uptake rates by fruiting tomato plants are also presented.     

高等植物氨基酸吸收与转运及生物学功能的研究进展

氨基酸不仅是细胞中蛋白质生物合成的必需底物,而且也参与植物体内的氮代谢途径以及碳氮平衡的调节。近年来,氨基酸的转运与吸收机制及其生物学功能已成为植物分子生物学特别关注和研究的热点之一。最近,学术界亦发现某些氨基酸可能作为信号分子对植物生长发育具有特殊的生物学意义。本文就氨基酸吸收与转运的分子生理机理及其在植物生长发育中的重要功能（如调控生长、 适应各种环境胁迫等）的研究进展进行了较详细地综述。     

Aluminum effects on nitrate uptake and reduction in sorghum

The effects of Al on nitrate uptake and on the activity of the nitrate reductase (NR) in two hybrid cultivars of sorghum (Sorghum bicolor (L.) Moench) differing in Al tolerance were studied. The nitrate uptake by intact root system was strongly reduced by Al in both cultivars, but mainly in the Al‐sensitive cultivar. The kinetic constants also changed in the presence of Al: Vmax decreased 98% and 71% and Km increased 267% and 42% in the Al‐sensitive and Al‐tolerant cultivar, respectively. Aluminum reduced the in vitro NR activity on the roots and shoots of both cultivars, especially of the Al‐sensitive cultivar. Aluminum added to the nutrient solution or to the reaction mixture, however, inhibited differentially the NR of the roots and shoots, indicating marked differences between the enzymes from these two tissues. Aluminum reduced the Vmax but did not affect the Km of nitrate activation of the shoot NR. Therefore, Al inhibition of the NR was non‐competitive and could not be reversed by increasing nitrate concentration. Aluminum not only reduced the nitrate uptake but also had a direct effect on the NR and consequently on nitrate reduction. A correlation between NR tolerance to Al and plant tolerance to Al was observed.     

植物氮素吸收利用相关NPF基因家族研究进展

氮(N)是植物生长发育需要量最大的矿质营养元素,也是作物产量的限制因子。硝态氮(NO₃^--N)是植物吸收利用氮素的主要形态之一。目前,植物中已报道4个基因家族(NPF、NRT2、CLC和SLAC1/SLAH)参与硝态氮的吸收和利用,其中NPF基因家族成员数量众多且功能多样化,近年来获得较多关注和深入研究。模式植物拟南芥和主要粮食作物水稻、玉米和小麦中,分别含有53、93、79和331个NPF基因。拟南芥NPF家族中已有超过一半成员(31/53)的生物学功能被解析,粮食作物水稻中NPF基因功能亦有较多报道。研究表明,NPF基因广泛参与了植物对氮素的吸收及其调控、转运、分配/再分配等过程,一些成员对于改良和提高作物氮素利用率(nitrogen use efficiency, NUE)具有重要作用。因此,从氮素进入植物体及其在植物体内流动的层面出发,发掘具有重要功能的候选NPF基因,对于解析植物利用氮素的分子机制及其遗传改良具有重要意义。本文综述了模式植物拟南芥以及粮食作物中已报道的NPF基因在氮素吸收和利用中的生物学功能。目前粮食作物玉米中仅有4...     

Role of Azospirillum brasilense nitrate reductase in nitrate assimilation by wheat plants

Summary The nitrogen metabolism of wheat plants inoculated with various Azospirillum brasilense strains and nitrate reductase negative (NR^–) mutants was studied in two monoxenic test tube experiments. The spontaneous mutants selected with chlorate under anaerobic conditions with nitrite as terminal electron acceptor fixed N₂ in the presence of 10 mM NO₃ ^– and were stable after the plant passage. One strain (Sp 245) isolated from surface-sterilized wheat roots produced significant increases in plant weight at both NO₃ levels (1 and 10 mM) which were not observed with the NR^– mutants or with the two other strains. Similar effects were observed in a pot experiment with soil on dry weight and total N incorporation but only at the higher N fertilizer level. In the monoxenic test tube experiments plants inoculated with the mutants showed lower nitrogenase activities than NR⁺ strains at the low NO₃ ^– level (1 = mM) but maintained the same level of activity with 10 mM NO₃ ^– where the activity of all NR⁺ strains was completely repressed. The nitrate reductase activity of roots increased with the inoculation of the homologous strains and with the mutants at both NO₃ ^– levels. At the low NO₃ ^– level this also resulted in increased activity in the shoots, but at the high NO₃ ^– level the two homologous strains produced significantly lower nitrate reductase activity in shoots while the mutants more than doubled it. The possible role of the bacterial nitrate reductase in NO₃ ^– assimilation by the wheat plant is discussed.