氮肥水平对不同基因型水稻氮素利用率、产量和品质的影响

以不同基因型的水稻品种日本晴、N70、N178和OM052为供试品种,氮肥采用尿素,按基肥(70%)和蘖肥(30%)两次施用,设置3个施氮水平(N用量设0、120、270 kg·hm^-2)的田间小区试验,研究氮素水平对水稻产量、氮素利用效率和稻米品质的影响,以期为氮肥合理施用和氮高效水稻品种创制提供科学依据.结果表明:施氮能增加水稻品种产量的原因是提高了有效穗数和每穗实粒数;与对照(0 kg·hm^-2)相比,当施氮量为120和270 kg·hm^-2时,OM052籽粒产量在4个品种中增幅最大,分别为41.1%和76.8%;品种产量增幅不同是由于氮素利用效率的差异,在120、270 kg·hm^-2氮处理下,4个供试品种中,日本晴籽粒产量和氮素农学利用率(40.90 g·g^-1、18.56 g·g^-1)都最低,为氮低效品种,OM052籽粒产量和氮素农学利用率(145.9 g·g^-1、81.24 g·g^-1)都最高,为氮高效品种.施N能够增加各品种的直链淀粉和蛋白质含量,使胶稠度变长,降低垩白率、垩白度和碱消值;随施氮量增加,热浆黏度、峰值黏度、回复值和崩解值递减,而消碱值递增.相关性分析表明,低N水平下,供试品种产量及产量构成因子与外观品质、蒸煮食味的相关性更显著.综上,OM052是一个籽粒产量和氮素利用效率“双高”基因型品种,合理施用氮肥可以显著增加水稻的有效穗数和每穗粒数,改善稻米籽粒品质,实现高产和优质的协同.     

施氮水平对2种穗型冬小麦品种产量及氮素吸收利用的影响

在大田高产栽培条件下,以大穗型小麦品种‘兰考矮早八’和多穗型品种‘豫麦49-198’为材料,研究了4个施氮水平下2种穗型冬小麦品种的籽粒产量、氮素吸收和氮肥利用效率。结果显示:随着施氮水平的提高,2种穗型小麦植株地上部生物量(返青期、拔节期除外)、籽粒产量和籽粒蛋白质产量均呈先增加后降低的趋势并都显著高于对照(不施氮),且均以180 kg.hm-2施氮处理最高,而2品种小麦各生育期植株氮素积累量和成熟期籽粒蛋白质含量却逐渐增加,且大都显著高于对照;2品种小麦的氮肥利用率、土壤氮贡献率以及氮收获指数均表现出180 kg.hm-2>90 kg.hm-2>360 kg.hm-2的趋势,且不同氮肥处理间均存在极显著差异(P<0.01)。研究表明,2种穗型冬小麦品种在试验条件下施用纯氮180 kg.hm-2可获得较高籽粒产量、蛋白质产量和氮收获指数。     

不同氮磷钾施肥方式对水稻碳、氮累积与分配的影响

基于我国南方双季稻区20年长期田间定位施肥试验,研究了不同氮磷钾施肥方式对水稻碳、氮积累与分配的影响.结果表明:偏施氮肥处理水稻籽实的碳、氮含量最高,分别达到433和18.9 g·kg-1.水稻植株的碳、氮储量以氮磷钾平衡施肥(NPK)及氮磷钾基础上有机物料循环施肥处理(NPKC)最高,其中NPKC和NPK处理籽实碳储量分别为2015和1960kg hm-2,茎叶碳储量分别为2048和2002 kg·hm-2;籽实氮储量分别为80.6和80.5kg·hm-2,茎叶氮储量则以NPK处理最高,为59.3 kg·hm-2.有机无机肥的配合施用显著增加了水稻植株体内碳和氮的累积;与偏施氮肥处理相比,氮磷钾的综合施用更利于水稻生长过程中碳、氮的累积与分配.     

湖南烟区土壤交换性钙、镁含量及对烤烟品质的影响

分析了湖南烟区主要土壤类型交换性钙、镁元素含量状况及其对烟叶品质的影响,结果表明:(1)土壤交换性钙、镁含量在不同土壤类型间存在显著性差异,交换性钙含量平均为8.87cmol/kg,以红壤含量最高;交换性镁含量平均为1.16cmol/kg,以黄棕壤含量最高;交换性钙镁比值大小依次为:红壤(11.74)>水稻土(10.25)>黄壤(6.84)>黄棕壤(6.14),在烟叶实际生产中,应重视镁肥在红壤和水稻土中的施用;(2)烟叶钙含量偏高(21.93g/kg±4.37g/kg),烟叶镁含量偏低(2.52g/kg±1.26g/kg),两者均存在广泛的变异性;(3)整体来看,烟叶钙含量随土壤中交换性钙含量的升高和镁含量的降低而显著升高;烟叶镁含量随土壤交换性镁含量的升高而升高,与土壤交换性钙含量的相关性不显著;(4)典型相关分析表明,土壤中交换性镁含量的降低可能引起烟叶钾含量的提高,从而使得烟叶钾素和镁素含量达到较好的平衡;(5)土壤交换性钙、镁含量与烟叶其它化学成分指标的相关分析表明,土壤交换性钙有利于烟株对硼和氯素的吸收,对氮、锌和锰素的吸收则有显著的抑制作用;而土壤交换性镁有利于烟叶总糖、硼素和锰素的积累,对氮、磷、铁和锌素的吸收具有显著的抑制作用。     

稻米镉积累的铁肥调控

以FeSO4和EDTA二钠亚铁（EDTA·Na2Fe,也称EDTA二钠铁）为铁肥,通过土施和叶片喷施研究不同形态铁肥及施肥方式对水稻（Oryza Sativa L．）镉积累的影响．结果显示不论施用何种形态铁肥或何种施用方式对水稻生长和产量性状均没有不利影响．土施EDTA·Na2Fe显著降低了水稻根系、地上部以及稻米（糙米和精米）中的镉含量,并且两基因型水稻精米中的镉含量远低于0．2mg／kg,达到国家限制标准．但土施FeSO4、叶面喷施FeSO4及叶面喷施EDTA·Na2Fe处理均显著增加了根系、地上部及稻米（糙米和精米）中的镉含量．结果还显示施用铁肥可显著提高稻米的铁、铜、锰含量,同时对锌含量也有影响．研究结果认为土施EDTA·Na2Fe等络合态亚铁肥,维持土壤中较高的有效态铁含量以及亚铁含量是控制稻米镉积累的一条新型可行途径．     

磷肥施用对冬小麦产量及土壤氮素利用的影响

为确定河北保定地区磷肥投入阈值,提高肥料利用效率,以冬小麦为研究对象进行大田试验,研究了磷肥施用对小麦产量、土壤硝态氮含量及氮素利用的影响.结果表明:与不施磷肥(P0)相比,优化施磷(P1,120 kg·hm-2)、200%优化施磷(P2,240 kg·hm-2)和400%优化施磷(P3,480 kg·hm-2)处理均能增加小麦株高、旗叶面积和单株叶面积,有利于光合产物的积累.施用磷肥显著提高了冬小麦的穗数、穗粒数和籽粒产量,但千粒重有所下降.其中,以P2处理小麦产量最高,为6102 kg·hm-2,显著高于P0和P3处理,但与P1处理差异不显著.施用磷肥可有效降低耕层土壤硝态氮的积累量,但0~100 cm土体总积累量仍然偏高,可通过降低氮肥施入等方法减少土壤硝态氮含量.P1和P2处理冬小麦的氮素生产效率、氮素吸收效率均较高,但两者间并无显著差异.P1处理的磷肥利用率、磷肥农学效率、磷肥偏生产力显著高于P2和P3处理.本试验条件下,施磷量为120 kg·hm-2(P1)是兼顾小麦产量、氮磷利用效率和较低土壤硝态氮累积的适宜施磷量.     

夏闲期地表覆盖对旱地土壤水分、小麦氮素吸收运转及产量的影响与施氮调控

为提高旱作麦区土壤水分贮备能力,并探明此基础上提高产量的适宜施氮水平,本文采用大田试验在山西农业大学闻喜试验基地研究了夏闲期覆盖与不覆盖条件下75、150、225 kg·hm-23个施氮量对旱地土壤水分、小麦氮素吸收运转及产量的影响。结果表明:夏闲期深翻覆盖后,播种前0~300 cm土层土壤蓄水量提高约70~80 mm,尤其是80cm以下土层;成熟期0~300 cm各土层土壤蓄水量均低于播种前,尤其是0~160 cm各土层低20~30 mm;各生育期群体茎数、穗数提高,且低、高氮条件下处理间差异显著,小麦总耗水量提高5.68~31.30 mm,产量提高1.43%~7.16%,水分利用效率提高1.27%~4.23%;各生育时期植株氮素积累量、花前氮素运转量和花后氮素积累量提高,且各生育时期植株氮素积累量处理间差异显著,氮肥农学效率提高0.47~1.24 kg·kg-1,氮肥当季回收率显著提高3.01%~4.96%;覆盖配施氮肥后,成熟期0~160 cm土层土壤蓄水量、总耗水量以施氮量150 kg·hm-2最低;各生育期群体茎数、产量构成因素、产量和水分利用效率以施氮量150 kg·hm-2显著最高,75 kg·hm-2最低,且中氮较低氮与高氮处理产量分别提高574.75和341.14 kg·hm-2,水分利用效率提高12.89%和7.77%;各生育时期植株氮素积累量、花前氮素运转量及其对籽粒的贡献率、氮肥农学效率和氮肥当季回收率均以施氮量150 kg·hm-2显著最高,75 kg·hm-2最低,且中氮较低氮与高氮处理氮肥农学效率分别提高1.91 kg·kg-1、3.12 kg·kg-1,氮肥当季回收率提高1.74%和5.32%;此外,产量与穗数的相关性最大(r=0.906),穗粒数居中,千粒重最小;总之,旱地小麦休闲期深翻覆盖有利于蓄水保水,提高底墒,且配施氮量为150 kg·hm-2更有利于水氮互作,促进氮素吸收、运转,达到增产、高效的目的。     

不同种类镁肥对烤烟中微量元素含量和产质量的影响

针对福建武平烟区土壤酸化严重,土壤有效镁含量偏低导致烟叶镁含量低的问题,研究了3 种不同镁肥对土壤和烤后烟叶中微量元素含量以及烤烟产质量的影响。结果表明,施用不同镁肥后均能显著提高土壤交换镁的含量,但不同镁肥对提高土壤交换镁含量的时效不同。各处理土壤其它中微量元素含量以施用硫酸镁的土壤较高,施用氢氧化镁的土壤偏低。烤后烟叶的镁含量以氧化镁处理最高,其次为氢氧化镁。施用镁肥会影响烟叶其它中微量元素的含量,其中施用氢氧化镁会导致中上部烟叶钙铁含量轻度缺乏,而施用硫酸镁会导致烟叶中锌锰含量过高。各处理中以氧化镁处理烟叶化学成分含量最适宜,且经济性状最优。因此,在福建武平烟区建议施用氧化镁,既可以防止烤烟生育前期有效镁的淋失,又可以提高烟叶的产量和质量。     

氮、磷、钾肥不同用量对花生生理特性及产量品质的影响

在田间条件下研究了氮、磷、钾肥不同用量对花生叶片生理特性及产量品质的影响.结果表明:与不施肥处理相比,花生分别单独施用氮、磷、钾肥可提高叶片叶绿素、可溶性蛋白质含量和光合速率,增加SOD、POD和CAT活性,降低MDA积累量,以施N300～450kg.hm-2、施P5O2150～225kg.hm-2、施K2O300～450kg.hm-2的效果最显著;对叶片光合性能的改善,氮肥的作用主要在前期,磷在中后期,钾肥前后期比较一致.施肥可显著提高花生荚果产量,随施氮量的增加花生产量显著提高,施磷、钾肥以中等施肥量(P5O2150kg.hm-2、K2O300kg.hm-2)花生产量最高,钾肥的增产作用大于氮、磷肥.少量施用磷、钾肥(P2O575kg.hm-2、K2O150kg.hm-2)可显著增加花生籽仁蛋白质和脂肪含量,少量施用氮肥(N150kg.hm-2)可显著增加蛋白质含量,大量施用氮肥(N450kg.hm-2)才可显著增加脂肪含量;磷肥对提高籽仁蛋白质和脂肪含量效果明显,氮肥对增加蛋白质含量作用较大,钾肥主要提高了可溶性糖含量.施用氮、磷、钾肥可增加花生籽仁的赖氨酸、蛋氨酸和油酸、亚油酸含量,提高油酸/亚油酸比值,从而改善花生营养品质,延长花生制品的货价寿命.     

施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响

在苏南太湖地区开展田间试验,研究了施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响.结果表明:施氮对水稻产量、各生育时期植株累积吸氮量、阶段氮累积量和花后氮素转运量具有显著的促进作用(P＜0.01),当施氮量高于200 kg·hm-2时,增施氮肥的增产效应不显著(P＞0.05);花后氮素转运率和氮肥利用率均随施氮量的增加而降低.施用肥料添加剂可进一步提高水稻产量、累积吸氮量、花后氮素转运量和氮肥利用率,且该效应在高施氮量( ≥200 kg·hm-2)条件下表现更明显.本试验条件下不施用肥料添加剂时,施氮150kg·hm-2可同时获得较高的产量和氮肥利用率.     

Quantification of Mg2+ extrusion and cytosolic Mg2+-buffering in Xenopus oocytes

Intracellular Mg(2+) buffering and Mg(2+) extrusion were investigated in Xenopus laevis oocytes. Mg(2+) or EDTA were pressure injected and the resulting changes in the intracellular Mg(2+) concentration were measured simultaneously with Mg(2+)-selective microelectrodes. In the presence of extracellular Na(+), injected Mg(2+) was extruded from the oocytes with an estimated v(max) and K(M) of 74 pmol cm(-2)s(-1) and 1.28 mM, respectively. To investigate genuine cytosolic Mg(2+) buffering, measurements were carried out in the nominal absence of extracellular Na(+) to block Mg(2+) extrusion, and during the application of CCCP (inhibiting mitochondrial uptake). Under these conditions, Mg(2+) buffering calculated after both MgCl(2) and EDTA injections could be described by a buffer equivalent with a concentration of 9.8mM and an apparent dissociation constant, K(d-app), of 0.6mM together with an [ATP](i) of 0.9 mM with a K(d-app) 0.12 mM. Xenopus oocytes thus possess highly efficient mechanisms to maintain their intracellular Mg(2+) concentration.     

Transmembrane Mg2+ Currents and Intracellular Free Mg2+ Concentration in Paramecium tetraurelia

The properties of Mg²⁺ conductances in Paramecium tetraurelia were investigated under two-electrode voltage clamp. When bathed in physiological Mg²⁺ concentrations (0.5 mm), depolarizing steps from rest elicited a prominent Mg²⁺-specific current (I _Mg) that has been noted previously. The dependence of this current on extracellular Mg²⁺ approximated that of Mg²⁺-induced backward swimming, demonstrating that I _Mg contributes to normal membrane excitation and behavior in this ciliate. Closer analysis revealed that the Mg²⁺ current deactivated biphasically. While this might suggest the involvement of two Mg²⁺-specific pathways, both tail-current components were affected similarly by current-specific mutations and they had similar ion selectivities, suggesting a common pathway. In contrast, a Mg²⁺ current activated upon hyperpolarization could be separated into three components. The first, I _Mg, had similar properties to the current activated upon depolarization. The second was a nonspecific divalent cation current (I _NS) that was revealed following suppression of I _Mg by eccentric mutation. The final current was relatively minor and was revealed following suppression of I _Mg and I _NS by obstinate A gene mutation. Reversal-potential analyses suggested that I _Mg and I _NS define two intracellular compartments that contain, respectively, low (0.4 mm) and high (8 mm) concentrations of Mg²⁺. Measurement of intracellular free Mg²⁺ using the fluorescent dye, Mag-fura-2, suggested that bulk [Mg²⁺] _i rests at around 0.4 mm in Paramecium. Received: 12 January 1998/Revised: 16 March 1998     

引进巨胚稻与普通稻的米质和营养成分分析比较

对引进的巨胚稻进行引种栽培并对其米质和营养成分进行全面分析.结果表明,巨胚稻的胚重是普通水稻胚重的3～5倍,多项营养成分如蛋白质、钙、磷、钾、钠、锰、VE、VB6和膳食纤维等的含量比普通稻米要高得多,这个结果表明巨胚稻是加工婴幼儿食品非常好的原料.     

Rice Allergenic Protein and Molecular-genetic Approach for Hypoallergenic Rice

Allergenic proteins with a molecular mass of about 14 to 16 kDa were isolated from a rice salt-soluble fraction based on the reactivity with IgE antibodies from patients allergic to rice. cDNA clones encoding these allergenic proteins were isolated from a cDNA library of maturing rice seeds, and the deduced amino acid sequences showed considerable similarity to wheat and barley α-amylase/trypsin inhibitors, which have recently been identified as major allergens associated with baker’s asthma. An antisense RNA strategy was applied to repress the allergen gene expression in maturing rice seeds. Immunoblotting and ELISA analyses of the seeds using a monoclonal antibody to a 16-kDa allergen showed that allergen content of seeds from several transgenic rice plants was markedly lower than that of the seeds from parental wild type rice.     

Mg2+ homeostasis: the Mg2+nificent TRPM chanzymes

TRPM6 and TRPM7 are distinct from all other ion channels in that they are composed of linked channel and protein kinase domains. Recent studies demonstrate that these 'chanzymes' are essential for Mg(2+) homeostasis, which is critical for human health and cell viability.     

K-Cl cotransport modulation by intracellular Mg in erythrocytes from mice bred for low and high Mg levels

Mg is an importantdeterminant of erythrocyte cation transport system(s) activity. Weinvestigated cation transport in erythrocytes from mice bred for high(MGH) and low (MGL) Mg levels in erythrocytes and plasma. We found thatK-Cl cotransport activity was higher in MGL than in MGH erythrocytes,and this could explain their higher mean corpuscular hemoglobinconcentration, median density, and reduced cell K content. Althoughmouse KCC1 protein abundance was comparable in MGL and MGHerythrocytes, activities of Src family tyrosine kinases were higher inMGH than in MGL erythrocytes. In contrast, protein phosphatase (PP)isoform 1 (PP1) enzymatic activity, which has been suggested toplay a positive regulatory role in K-Cl cotransport, was lower in MGHthan in MGL erythrocytes. Additionally, we found that the Src familykinase c-Fgr tyrosine phosphorylates PP1 in vitro. These findingssuggest that in vivo downregulation of K-Cl cotransport activity by Mgis mediated by enhanced Src family kinase activity, leading toinhibition of the K-Cl cotransport stimulator PP1.