Source : sink ratio and leaf senescence in maize:: I. Dry matter accumulation and partitioning during grain filling

Whether the stay-green characteristic of recent maize hybrids is related to a larger source : sink ratio and/or a more efficient use of N during reproductive development was studied in a 3-year field experiment. The experiment was conducted with two short-season maize hybrids, Pride 5 (old) and Pioneer 3902 (recent), grown at two soil-N levels and with source : sink treatments during grain filling ranging from partial defoliation to no grain. Results confirmed that greater dry matter accumulation of Pioneer 3902, relative to Pride 5, was associated with greater leaf longevity. Change in stover weight from silking to maturity an indicator of the difference in supply and demand of assimilates during grain filling, varied from −30% with defoliation to +25% for the no sink treatment. The change was always greater in the new hybrid, indicating that the old hybrid was more source limited. Number of green leaves, an indicator of leaf longevity, was greatest when supply and demand of assimilates during grain filling were approximately equal. Leaf longevity was enhanced by an increase in soil N and the effect was larger in the high source : sink treatments, but differences in leaf longevity between the two hybrids were not influenced by soil-N level. In conclusion, increased leaf longevity of a new relative to an old hybrid was associated with a larger source : sink ratio during grain filling.     

Note on relationship between leaf soluble carbohydrate and chlorophyll concentrations in maize during leaf senescence

Leaf senescence is typically associated with loss of chlorophyll and decline in photosynthetic capacity. The objectives of this study were: (i) to quantify the relationship between chlorophyll (SPAD) and soluble-carbohydrate concentrations in maize (Zea mays L.) leaves during leaf senescence and (ii) to examine whether this relationship differed between an old and a recent maize hybrid. Field experiments were conducted in 1995 at two locations. A range of leaf soluble-carbohydrate concentrations and SPAD values was obtained through various source-manipulation of source activity by defoliation and thinning. Defoliation treatments were imposed at 3, 4, and 5 weeks after silking. The thinning treatment was imposed at 3 weeks after silking. Two maize hybrids were composed: Pride 5 (old) and Pioneer 3902 (recent). Leaves at three leaf positions, near the topmost ear and the ear internode were sampled at weekly intervals, from 3 weeks after silking until visual completion of leaf senescence. Leaf and internode soluble-carbohydrate concentration declined following defoliation, although the response in leaves was delayed compared to that in the stem. SPAD readings and soluble-carbohydrate concentrations were positively correlated below a plateau value of 55 mg glucose equivalents g⁻¹ leaf. The correlation between SPAD and soluble-carbohydrate concentration was similar for the old and recent maize hybrid.     

玉米氮高效组合杂种优势分析

在氮高效自交系筛选工作的基础上,利用NC-Ⅱ设计的材料进行杂种优势分析,同时探讨氮高效育种中亲本选配等问题。研究结果表明:氮高效类型中氮高效的生理机制各有特点,试验结果可以分为以吸收效率为主和以利用效率为主的两种杂交组合。总结亲本组成规律,氮高效组合的组配可分两大类型:①主要决定于母本的吸收和利用效率;②父母本的吸收效率和利用效率互补。所以,在氮高效育种中,要注重对母本氮效率性状的选择,尤其是氮吸收效率的选择以及亲本间氮效率性状的优势互补。在低氮条件下,注重选择母本穗粒重、行粒数、出籽率,父本的穗粒重、百粒重、穗粒数、株高、棒三叶叶面积等性状,同时考虑亲本的综合农艺性状,使氮高效组合的稳定性和适应性更强。     

不同氮效率玉米杂交种的营养生长及光合特征

以氮效率不同的4个玉米杂交种(组合)为材料,在两个氮水平下分析了营养生长及光合特征。结果表明,施氮条件下玉米营养体的含氮量平均在2.0%左右,低氮处理下降到1.5%左右;氮高效品种的穗位叶光合效率并没有降低,氮低效品种的叶片光合效率则显著降低。氮高效品种在叶片保绿性方面明显具有优势,在低氮条件下保持了较大的绿叶面积和较高的叶绿素含量。这些特征保证了氮高效品种后期光合产物供应能力强,并用于子粒灌浆。     

A comprehensive study of plant density consequences on nitrogen uptake dynamics of maize plants from vegetative to reproductive stages

Nitrogen (N) use efficiency (NUE), defined as grain produced per unit of fertilizer N applied, is difficult to predict for specific maize (Zea mays L.) genotypes and environments because of possible significant interactions between different management practices (e.g., plant density and N fertilization rate or timing). The main research objective of this study was to utilize a quantitative framework to better understand the physiological mechanisms that govern N dynamics in maize plants at varying plant densities and N rates. Paired near-isogenic hybrids [i.e., with/without transgenic corn rootworm (Diabrotica sp.) resistance] were grown at two locations to investigate the individual and interacting effects of plant density (low—54,000; medium—79,000; and high—104,000 pl ha⁻¹) and sidedress N fertilization rate (low—0; medium—165; and high—330 kg N ha⁻¹) on maize NUE and associated physiological responses. Total aboveground biomass (per unit area basis) was fractionated and both dry matter and N uptake were measured at four developmental stages (V14, R1, R3 and R6). Both plant density and N rate affected growth parameters and grain yield in this study, but hybrid effects were negligible. As expected, total aboveground biomass and N content were highly correlated at the V14 stage. However, biomass gain was not the only factor driving vegetative N uptake, for although N-fertilized maize exhibited higher shoot N concentrations than N-unfertilized maize, the former and latter had similar total aboveground biomass at V14. At the R1 stage, both plant density and N rate strongly impacted the ratio of total aboveground N content to green leaf area index (LAI), with the ratio declining with increases in plant density and decreases in N rate. Higher plant densities substantially increased pre-silking N uptake, but had relatively minor impact on post-silking N uptake for hybrids at both locations. Treatment differences for grain yield were more strongly associated with differences in R6 total biomass than in harvest index (HI) (for which values never exceeded 0.54). Total aboveground biomass accumulated between R1 and R6 rose with increasing plant density and N rate, a phenomenon that was positively associated with greater crop growth rate (CGR) and nitrogen uptake rate (NUR) during the critical period bracketing silking. Average NUE was similar at both locations. Higher plant densities increased NUE for both medium and high N rates, but only when plant density positively influenced both the N recovery efficiency (NRE) and N internal efficiency (NIE) of maize plants. Thus plant density-driven increases in N uptake by shoot and/or ear components were not enough, by themselves, to increase NUE.     

山西高产氮高效玉米品种的筛选及其干物质氮素累积与分配

通过分析16个玉米品种在施氮(225 kg/hm2)和不施氮条件下的产量及其节氮潜力等筛选高产氮高效品种.结果表明,两年中晋玉18、登海605、先玉335增产潜力在5％以上,节氮潜力为15.48％～18.39％(2018年)和14.26％～29.47％(2019年).根据供试品种在施氮和不施氮条件下的产量平均值作为分界...     

Functional dynamics of the nitrogen balance of sorghum. II. Grain filling period

Maintenance of green leaf area during grain filling can increase grain yield of sorghum grown under terminal water limitation. This ‘stay-green’ trait has been related to the nitrogen (N) supply–demand balance during grain filling. This study quantifies the N demand of grain and N translocation rates from leaves and stem and explores effects of genotype and N stress on onset and rate of leaf senescence during the grain filling period. Three hybrids differing in potential height were grown at three levels of N supply under well-watered conditions. Vertical profiles of biomass, leaf area, and N% of leaves, stem and grain were measured at regular intervals. Weekly SPAD chlorophyll readings on main shoot leaves were correlated with observed specific leaf nitrogen (SLN) to derive seasonal patterns of leaf N content. For all hybrids, individual grain N demand was sink determined and was initially met through N translocation from the stem and rachis. Only if this was insufficient did leaf N translocation occur. Maximum N translocation rates from leaves and stem were dependent on their N status. However, the supply of N at canopy scale was also related to the amount of leaf area senescing at any one time. This supply–demand framework for N dynamics explained effects of N stress and genotype on the onset and rate of leaf senescence.     

不同土壤肥力条件下麦秆还田与氮肥运筹对杂交稻氮素利用、产量及米质的影响

以杂交稻F优498为材料,研究了高、低土壤肥力下麦秆覆盖与氮肥运筹对杂交稻主要生育期氮素吸收利用特征、产量及米质的影响,并探讨了不同土壤肥力下麦秆覆盖和氮肥运筹对结实期剑叶SPAD值与稻米品质的形成的影响。结果表明,不同土壤肥力下,麦秆覆盖均有效促进杂交稻各生育时期氮素积累,提高了氮素利用效率以及稻谷产量,增加了稻米蛋白质含量、稻米胶稠度,显著降低了稻米垩白度以及垩白粒率,且高土壤肥力下麦秆覆盖优于低土壤肥力下麦秆覆盖处理。同时,不同土壤肥力下麦秆覆盖处理,均以m基肥∶m蘖肥∶m穗肥为3∶3∶4的氮肥运筹模式最优,均能有效调节水稻灌浆结实期叶片SPAD值,提高水稻氮素吸收利用效率及稻谷产量;但稻米品质方面,高土壤肥力以m基肥∶m蘖肥∶m穗肥为5∶3∶2时最佳;而低土壤肥力可适当提高氮肥后移比例,以m基肥∶m蘖肥∶m穗肥=3∶3∶4最佳。相关分析表明,水稻灌浆期剑叶SPAD值与稻米出糙率、整精米率以及蛋白质含量显著或极显著正相关(r=0.47*~0.90**);与垩百度、垩白粒率负相关,但相关未达显著水平;而高土壤肥力下稻米品质各项指标分别与齐穗后19~27d剑叶SPAD值,低土壤肥力下麦秆覆盖与齐穗后13~19d剑叶SPAD值相关系数最大。     

Effects of spraying exogenous cytokinin or spermine on the starch physicochemical properties of waxy maize exposed to post-silking high temperature

Plant growth regulators (PGR) can be used to alleviate heat injury on the starch quality of crops. In this study, two waxy maize hybrids with exogenous cytokinin or spermine at silking stage were exposed to post-silking ambient temperature (AT; 28/20 °C) and high temperature (HT; 35/27 °C) during grain filling. Results indicated that spraying exogenous cytokinin or spermine increased the grain weight and starch content at both temperature regimes. The starch granule size, amylopectin chain length, and relative crystallinity differed between two hybrids and were affected by PGRs and temperatures. Peak viscosity decreased at HT, unaffected by cytokinin, and increased by spermine at both temperature regimes. The retrogradation percentage at HT with PGR was lower than that without PGR in both hybrids. In conclusion, spraying exogenous cytokinin or spermine at silking stage can increase peak viscosity and reduce retrogradation percentage at HT, thereby alleviating the detrimental effects of post-silking heat injury.     

通过剪叶改变源库关系对玉米子粒营养组分含量的影响

2004～2005年在吉林省梨树县大田条件下以吉单209(普通玉米品种)、吉油199(高油玉米品种)、郑单958(高淀粉玉米品种)为试材,在授粉后25d和35d将植株全部绿叶剪掉1/2,玉米成熟后对子粒淀粉、蛋白质、油分等营养组分含量的变化进行了测定分析。结果表明:各类玉米品种的源库关系在线性灌浆期改变为源小库大后,单粒淀粉积累量均显著减少,但淀粉百分含量除供试高油品种外则有明显提高;单粒蛋白质积累量均显著减少,同时蛋白质百分含量显著下降;单粒油分积累量显著减少,但油分百分含量变化不大;赖氨酸/蛋白质显著提高,与蛋白质百分含量的变化趋势相反。改变源库关系对子粒淀粉、蛋白质和油分百分含量的效应不同,各类玉米品种均表现为子粒蛋白质百分含量变化受到的影响最大,对源库关系改变的反应最敏感;淀粉百分含量次之;油分百分含量一般不易受源库关系改变的影响,表现稳定。     

1970s～2000s玉米主栽品种灌浆与脱水速率研究

1970s推广玉米单交种,标志着我国利用玉米杂种优势育种从选育双交种转向选育单交种为主的阶段。不同年代玉米单交种的灌浆与脱水速率随着年代的更替所呈现的变化规律尚未引起关注。试验于2013年在中国农业科学院试验基地进行,以1970s~2000s大面积推广的14份单交种为试验材料,对不同年代玉米单交种各个时期的子粒、苞叶、穗轴含水量进行分析,计算和分析子粒、穗轴和苞叶的脱水速率及子粒灌浆速率。结果表明,2000年以后审定的新品种子粒灌浆速率快于以前的老品种;新品种的子粒百粒干重高于老品种;新品种的穗轴、苞叶和子粒的含水量均高于老品种。穗轴脱水速率则老品种明显快于新品种;子粒、苞叶脱水速率在不同年代品种之间并无明显差异。     

N-use efficiency of single, double and synthetic maize lines grown at four N levels in three ecological zones of West Africa

Efficiencies in uptake and use of N by maize cultivars have been widely studied, but little has been done on this subject in West Africa. Six single-cross hybrids, three double-cross hybrids and a synthetic line were grown at different N levels (0–210 kg N ha⁻¹) in three ecological zones of West Africa. The maize cultivars differed widely in grain yield and N-accumulation parameters. Most cultivars absorbed similar amounts of N ranging from 2.04 g plant⁻¹ to 2.60 g plant⁻¹, but produced different grain yields, with those that accumulated more N after silking tending to have higher grain yield. Grain yields in the forest zone were lower than those in two Savanna regions. Differences were also observed for N-uptake (total N-uptake per unit N supplied to the soil), N-utilization (grain produced per unit N absorbed from the soil) and N-use efficiency (NUE) (grain produced per unit N supplied to the soil). Cultivars varied in their response to change in available soil N. The hybrids were more efficient in N-use and its component traits than the synthetic cultivar. Hybrid 1368 × KU1414-SR yielded the most grain as well as exhibiting superior traits for N-uptake and N-use efficiency.     

Crop management affects dry-milling quality of flint maize kernels

Dry-milling performance of maize (Zea mays, L.) kernels primarily depends on their hardness. The flint type is harder than the dent and semi-dent maize, yielding a higher proportion of big endosperm pieces in the mill. Nevertheless, crop growing conditions could modify milling properties. The objective of this work was to analyze the effect of different crop environments and management practices on dry-milling quality of flint maize kernels. Two orange-flint hybrids from different eras of breeding differing in flint type expression and grain yield potential were evaluated. They were grown at three different locations of the Argentina's main maize-production area under different sowing dates, plant densities, and fertilization rates during two growing seasons. Crop post-silking growth, grain yield and its components (kernel number and weight), kernel size and hardness-associated properties (test weight, percent floaters and milling ratio), and flaking-grit yield were analyzed. Most of observed differences in physical properties of kernels, particularly for the high-yielding new hybrid with unstable flint expression, were associated with the source-sink ratio established during the post-silking period (explored range from 154 to 617 mg kernel⁻¹). This variable mainly results from changes in crop growth during that period. Increases in weight per kernel improved hardness-associated properties. High crop grain yields together with top dry-milling quality were achieved when the new high-yielding hybrid was cropped with an appropriated crop management.     

杂种小麦干物质积累及其杂种优势的研究

对6个澳大利亚杂种小麦在不同生育期植株及各器官的干物质积累、分配及干物质积累的杂种优势进行了研究。结果表明,植株总干物质积累在籽粒灌浆末期达到最大值,茎秆和叶片干物质积累均在开花期达到最大值。挑旗期茎秆、叶片各占植株总干物质的50％;从孕穗王灌浆末期,茎秆为干物质的主要贮存器官,占植株总干物质的 39.87％～66.67％;在成熟期,籽粒成为干物质贮存的最主要部位,占37.65％,茎秆占35.23％。从6个杂交种平均值来看,干物质积累多表现为正向杂种优势,尤其在营养生长期优势最明显。相关分析表明,营养生长期植株总干物质积累量较大且主要分配在茎秆部位的杂交品种,一般具有较高的籽粒产量和较强的产量优势。     

美国先锋玉米杂优模式利用对中国玉米育种的影响

近年来,美国先锋种子公司在国内审定了许多品种,其利用主要杂优模式是A×B;母本来源主要是Reid血缘的选系,父本是Lancaster血缘选系。先锋玉米杂交种以其脱水快、出籽率高、品质好、生育期适中等优点,深受农民青睐,种植面积迅速扩大,在辽宁北部、吉林、黑龙江南部成为主栽品种。国内玉米品种利用主要模式是Reid×旅系、Reid×唐四平头改良系,其杂交种存在着后期脱水慢,出籽率不高,熟期偏长,商品性一般等缺点,逐渐被先锋杂交种所取代。先锋玉米对中国育种有着很重要的影响,育种者普遍认为：熟期适中,出籽率高,品质好,脱水快,抗多种病害,抗倒,适应区域广,是今后玉米育种主攻目标,改变了中国育种者的育种观念。     

4个玉米品种氮素利用效率的比较研究

以郑单958、农大108、京单28、京科308为试验材料,研究了不同玉米品种产量、干物重、氮含量、氮利用效率的差异.结果表明:4个玉米品种产量、总吸氮量存在一定程度的差异,氮利用效率差异均不显著.植株干重、子粒氮含量、总吸氮量与产量显著相关,子粒氮含量对产量的直接影响最大.植株干重与子粒氮含量显著相关,植株干重越大子粒氮含量越高;子粒氮含量与植株干重对产量的影响不同品种之间存在差异;氮收获指数与产量呈负相关.     

Effect of nitrogen supply on the comparative productivity of maize and sorghum in a semi-arid tropical environment II. Radiation interception and biomass accumulation

Differences in biomass accumulation due to variable nitrogen supply in maize and sorghum grown under irrigation in the semi-arid tropics were associated with differences in both radiation interception and the efficiency with which intercepted radiation was used to produce dry matter. Radiation-use efficiency was more responsive to N supply than was radiation interception. Radiation-use efficiency increased with higher rates of applied N; maximum radiation-use efficiency was greater in maize than in sorghum; and radiation-use efficiency declined during grain filling in maize more than in sorghum. These differences were explained in terms of specific leaf N. A linear relationship, which was similar for both species, was fitted between radiation-use efficiency and specific leaf N. It is concluded that radiation-use efficiency may not be as stable across environments as was previously thought, but rather depends on the balance of leaf growth, N uptake and allocation to leaves, and N mobilization from leaves to grain.     

氮肥减施对夏玉米花后生理特性的影响

以黄淮海地区主栽玉米品种郑单958(ZD958)、先玉335(XY335)、郑单309(ZD309)、奥玉3111(AY3111)、浚单20(XD20)和迪卡653(DK653)等6个杂交种为试材,设0、120(较正常施氮量减少1/2)、160(减氮1/3)、200(减氮1/6)和240 kg/hm2(正常施氮量)共5个施氮水平,在大田条件下研究氮肥减施对夏玉米产量、花后氮素转运、叶片叶绿素荧光和硝酸还原酶NR、谷氨酰胺合成酶GS活性的影响。结果表明,施氮后玉米产量平均提高20.2%,与正常氮处理相比,减氮1/3和1/6的产量、子粒氮浓度、收获指数和氮收获指数(NHI)无显著变化,ZD309和XY335产量和NHI高于其他品种。随施氮量增加,ZD958、XY335和ZD309叶转运量显著增加,茎转运效率无显著变化。减氮1/3和1/6处理穗位叶SPAD值无变化,叶绿素最大荧光Fm、综合性能指数PI、NR活性明显增加,各基因型分别以AY3111叶片SPAD、PI为最高,ZD958、XY335和ZD309的NR和GS活性高于其他品种。     

Changes in chemical and physical quality parameters of maize grain during three decades of yield improvement

Concern exists that the grain quality of maize (Zea mays L.) may decline due to breeding for increased yield. This study quantified chemical- and physical-quality parameters of maize grain for hybrids representing three decades of grain yield improvement in Ontario, Canada. Six hybrids that were commercially important in Ontario from 1959 to 1988 were grown at two locations in southern Ontario during 1986 and 1987 at two plant densities. Grain contents of N, P, K, Ca, Mg, Zn, Cu, Mn, Se, lysine, tryptophan, and lipid were evaluated as chemical-quality parameters. Test weight, kernel density and weight, kernels exhibiting stress cracks, and breakage susceptibility were examined as indications of physical quality. Concentrations of Mg, Cu, Mn, and Se were greater in kernels of old hybrids than in more recent ones. Nitrogen concentration was greater in grain of recent hybrids and levels of N, P, and Mn all were lesser at high than at low plant density. Concentrations of lysine and tryptophan did not differ among hybrids. Differences in nutrient concentration were often greater among hybrids within an era than among means for eras of hybrid release. Among physical-quality traits, test weight, kernel density and kernel weight increased with more recent hybrids. These parameters were also higher with the lower plant density. Breakage susceptibility of kernels, although not affected by era of hybrid release, was less at low plant density.     

华北区部分主栽玉米杂交种的氮效率分析

玉米生产中氮肥的过量施用,不但导致氮肥利用率下降,生产成本提高,而且还会造成地下水污染,因而越来越受到人们的重视.选用氮高效作物品种是解决这些问题的重要途径.本试验利用华北地区主栽的8个杂交种在高、低氮条件下研究了产量、吸氮量、氮效率及其生理基础.两年结果表明,不同玉米杂交种的产量、氮效率和不同生育期吸氮量都存在显著的基因型差异.农大108高、低氮条件下都有较高产量,且吸氮量高,成熟期茎秆氮残留多.中单2996在两个氮水平和两种土壤条件下,吸氮量相对较高,茎秆残留少,氮转移率较高.通径分析表明,吸收效率对