Effect of Planting Date on Time and Rate of Nitrogen Accumulation by Maize (Zea mays L.)1

Effects of environment on time and rate of nutrient accumulation by crops affects fertilizer nutrient use efficiency. The effect of planting date on rate, time and amount of nitrogen (N) accumulated by maize from a Hamerly cl soil (Aeric Calciaquoll) was examined with and without supplemental irrigation. Maize was planted on three dates spaced at 2-to 3-week, intervals; the earliest planting date was 1 May in 1984 and 1985. N accumulation was examined as uni- and diphasic tanh[k(time)] functions and solved for total N accumulation at harvest, time of maximum N accumulation rate and the time coefficient of N accumulation. A diphasic function, which indicates two periods of intense N accumulation, provided the closest agreement with observed N accumulation. As planting was delayed, time required to reach maximum N accumulation rates, τ (uniphasic) or τ₁ and τ₂ (diphasic), decreased from an average of nearly 75 to 42 days (uniphasic) and from nearly 65 to 35 days and 100 to 75 days after planting for τ₁ and τ₂, respectively. Maximum N accumulation rates increase from about 59 to 75 mg N plant^?1 day^?1 (uniphasic) or 35 to 65 mg N plant^?1 day^?1 and 20 to 70 mg N plant^?1 day^?1 for the first and second maxima in the diphasic model, respectively. Average maximum total N accumulation ranged from 2.85 g N plant^?1 for early plantings to 1.5 g N plant^?1 for plantings made on 25 June. The time coefficient, k (uniphasic) or k₁ (diphasic), tended to increase from average values of about 0.04 to > 0.09 day^?1 for k and from about 0.04 to > 0.105 day^?1 for k₁. The second time coefficient, k₂, of the diphasic function varied widely between about 0.075 to > 0.12 day^?1 and showed complex relationships with planting date. Periods of N accumulation shortened and intensity of N accumulation increased as the time coefficient increased.     

Effect of Thermal Energy Intensity on Time and Rate of Nitrogen Accumulation by Maize (Zea mays L.)1

The effect of thermal energy intensity (TEI) on the rate of nitrogen (N) accumulation by maize from a Hamerly clay loam soil (Aerie Calciaquoll) was examined with and without supplemental irrigation. Soil- and air-TEI expressed as cumulative growing degree days (GDD) was determined from hourly temperature measurements taken within each plot at soil depths of 0.05-, 0.15-, and 0.3-m and at a height of 1.2-m above ground surface. A daily mean TEI (GDD per day) was calculated for each growth period. Estimates of time coefficient(s), k, in uni- and diphasic tanh[k(time)] functions, plotted against mean TEI for the periods; 1) planting to emergence, 2) emergence to eighth leaf, 3) eighth leaf to time(s) of maximum N accumulation rate, (t₀), 4) planting to t₀, 5) emergence to t₀, 6) first diphasic maximum accumulation rate (t₀₁) to 50 % silking, and 7) silking to second diphasic maximum accumulation rate t₀₂ showed several linear relationships. Uniphasic time coefficients were modelled as functions of air-TEI. The first diphasic time coefficient, k₁ was modelled as a function of pre- and post-emergent soil-TEI. Attempts to model k₂, the second time coefficient of the diphasic model were unsuccessful; however, this time coefficient was linearly related to TEI for the growth period ‘t₀₁, to 50 % silking’ and curvilinearly related to k₁.     

An Analysis of Seasonal Effects on Leaf Nitrate Reductase Activity and Nitrogen Accumulation in Maize (Zea mays L.)

The important enzyme in nitrogen (N) assimilation, nitrate reductase (NR), is an inducible enzyme influenced by many external (light, temperature, etc.) and internal (genotype) factors. The efficiency of the N assimilation system may vary with genotype and season. In the present study, the effects of season on NR activity in relation to N accumulation in maize plants were investigated. Six different cultivars of maize, namely Ganga-11, Deccan-103, Hi-starch (hybrids), Arun, Manjari and Vijay (composites), were sown during the monsoon (88-day crop duration) and in winter (150-day crop duration). In vivo NR activity in the last fully expanded leaf (LFEL), and the N contents of the whole plant and the LFEL were estimated at seven phenological growth stages. Three different states of N metabolism in maize, namely (i) low NR activity per unit leaf area per unit time coinciding with high accumulation of N, (ii) high NR activity coinciding with low N accumulation, and (iii) low NR activity coinciding with low N accumulation, were noted. These results clearly demonstrate that the relationships between N uptake and accumulation parameters change with the season and crop growth stage and are subject to a genotypic influence. Thus it is necessary to evaluate genotypes under similar environments to select a genotype with high N use efficiency. As these relationships are growth dependent, care must be taken to evaluate them at a particular phenological stage rather than on the basis of days after sowing.     

氮素对玉米淀粉累积及相关酶活性的影响

氮素在提高玉米籽粒产量和改善品质方面起着重要的调节作用,淀粉是玉米籽粒的主要成分,其数量多寡直接影响玉米的产量.正在发育的玉米籽粒中,合成淀粉的原料来自叶片中合成的或淀粉降解产生的蔗糖,通过韧皮部长距离运输至籽粒[1].     

施氮对夏玉米顶部籽粒早期发育及产量的影响

以夏玉米杂交种郑单958为材料,对不同施氮水平下顶部籽粒的早期发育状况及产量进行了研究。结果表明,施氮明显促进关键酶活性的增强,促进顶部籽粒的早期发育。当施氮量为180 kg/hm²时,顶部籽粒的酸性蔗糖转化酶（AI）、中性蔗糖转化酶（NI）、蔗糖合成酶（SS）、腺苷二磷酸葡萄糖焦磷酸化酶（ADPGase）、淀粉     

不同氮肥管理对春玉米干物质生产、分配及转运的影响

为探索华北地区春玉米高产可持续栽培技术,研究了不同氮素管理(不施氮、推荐施氮、经验施氮)对春玉米的干物质积累、分配及转运的影响。结果表明,在高肥力土壤条件下,第一年推荐和经验施氮同不施氮相比在干物质积累、叶面积指数、籽粒产量、穗位叶光合速率等方面都没有起到明显的促进作用,但在第二年不施氮处理产量比推荐施氮和经验施氮分别下降了12.0%和11.6%。推荐施氮的优势不仅体现在减少氮肥投入的前提下保持产量的稳定,同时也明显促进了生育后期植株营养体干物质向籽粒的转运,各器官干物质转运总量占籽粒总干质量的22.1%,比经验施氮高6.1%。     

玉米生育期和生育阶段的纬度效应研究

为玉米品种合理引种提供参考,采用不同玉米品种在南北纬度不同试点进行生态试验,探讨玉米生育时期与纬度的关系。结果表明,在海拔基本一致的前提下,低纬度种植的玉米成熟期明显提前,播种～成熟、出苗～成熟时间均缩短;纬度对玉米营养生长的影响大于生殖生长;玉米全生育期、营养生长时间、生殖生长时间与纬度存在正的线性关系,同一年份的回归系数相近,不同年份间差异较大。     

夏玉米铜的吸收与器官间的分配研究

以两种不同株型夏玉米品种为材料，就不同生育时期玉米植株对铜的吸收、积累及其在不同器官之间的分配情况进行了研究。结果表明，玉米植株铜的含量在苗期较高，随生长发育的进程而逐渐降低；穗期吸收量最大，子粒灌浆期间对铜的吸收量也较多，两品种吸收铜的差异主要在花粒期，紧凑型品种在乳熟期吸收量较大，而平展型品种在子粒形成期吸收量较大。成熟期不同器官铜的积累量依次为叶片、子粒、茎秆（雌穗）、叶鞘（苞叶）、雄穗、穗柄、花丝。两品种间单株吸铜量差异不明显，单位面积吸收量的差异主要是由于密度造成的。     

玉米（Zea mays L.）×大刍草（Zea diploperennis L.）远缘杂交选育玉米自交系的研究

为了丰富玉米遗传变异,从1990年起,我们进行了玉米(Zea mays L.)和多年生二倍体大刍草(Zea diploperennis L.)远缘杂交的研究。经过5年8个世代的杂交、回交和自交选择,目前已获得抗逆性、抗病虫能力较强,农艺性状优良的玉米自交系14个。在测配1000个杂交组合中,所选系表现出较高的一般配合力和特殊配合力。实践证明,这是一条导入外缘种质、拓宽玉米遗传基础,进一步提高杂交种增产潜力的途径之一。     

夏玉米光合特性对氮素用量的反应

随氮素用量增加,植株下位叶、穗位叶和上位叶的光合速率（P_n）、叶绿素含量（Chl）、可溶蛋白含量（Pro）、Hill反应活性、Ca²⁺-ATPase活性、Mg²⁺-ATPase活性和PEPCase活性均不断增大。植株不同叶位Pn和Pro随生长进程均不断下降;不同叶位Chl的变化动态表现为下位叶在各测定时期之间差异较小、穗位叶和上位叶为单峰曲线。Hill反应活力、Ca²⁺-ATPase活性和Mg²⁺-ATPase活性的变化规律不同,随生长进程表现不断下降、单峰曲线和双峰曲线等不同形式。各叶位PEPCase活性均表现单峰曲线型变化。随氮素用量增加,叶源量、生物产量和籽粒产量不断增加。适量施氮具有全面改善玉米光合效率和内在生理、生化过程的作用。Ca²⁺-ATPase活性是影响光反应活力的重要因素;在叶片生长前中期,P_n受到PEPCase的影响较小,主要受到光反应活力和暗反应效率的调控。可采用叶源量作为玉米单株生产力的参考诊断指标。     

玉米幼胚培养能力性状QTL分析

以18-599（红）和R15组配的F₂群体,构建了含88对SSR标记的玉米遗传连锁图谱,覆盖基因组1 636.6 cM,标记间平均距离为18.6 cM。结合幼胚组织培养试验将幼胚发生胚性愈伤组织诱导率和胚性愈伤组织绿苗再分化数作为反映玉米培养过程中胚性愈伤组织诱导力和胚性愈伤组织绿苗再分化力的性状指标,以此调查玉米幼胚培养能力。利用复合区间作图法进行QTL分析,共检测到5个与胚性愈伤组织诱导率有关的QTL,位于第1、3、7和8染色体上,可解释5.25%～23.4%的表型变异;检测到1个与胚性愈伤组织绿苗发生数有关的QTL,位于第3染色体上,可解释表型变异率为13.42%。     

玉米种子休眠性的QTL定位

选用两个种子休眠性差异较大的普通玉米自交系R08与A318组配的F2群体共331个单株,构建了包含137个SSR标记的分子遗传连锁图谱,覆盖玉米基因组2 076.7 cM,平均图距15.2 cM。采用复合区间作图法对F_2:3家系种子休眠性数据进行分析,共检测到7个QTL,分别位于玉米第1、3、5和10染色体上。7个QTL的贡献率在2.45%~26.     

Effect of Planting Date and Thermal Energy Intensity on Rate of Phosphorus and Potassium Accumulation by Maize (Zea mays L.)1

The effect of planting date and thermal energy intensity (TEI) on the rate of phosphorus (P) and potassium (K) accumulation by maize from a Hamerly clay loam soil (Aerie Calciaquoll) was examined with and without supplemental irrigation. Soil- and air-TEI expressed as growing degree days per day (GDD d^?1) were determined from hourly temperature measurements taken within each plot. Net K accumulation occurred during the vegetative growth stage, reached maximal rates of about 62.2 to 91.4 mg plant^?1 day^?1, and attained maximal accumulations ranging from about 1.15 to 2.3 g plant^?1. Accumulation of P occurred during vegetative and reproductive growth stages, reached maximal rates of about 4.6 to 10.3 mg and 6.5 to 12.1 mg plant^?1 day^?1, respectively and maximal accumulations of 0.175 to 0.27 g and 0.11 to 0.26 g plant^?1, respectively. During vegetative growth, K and nitrogen (N) accumulation characteristics were closely correlated with about 2 moles of N accumulated per mole of K. Maximal accumulation of K (and N) consistently preceded that of P by about 5.2 to 8.3 days and that of the plant dry weight by about 15.9 to 20.5 days during the vegetative growth stage. Time required to reach maximal accumulation during the reproductive growth stage, t_r followed the order N < P < dry weight for early plantings and followed the order N < P < dry weight for delayed plantings. Time coefficients for K and P accumulation were correlated closely with soil-TEI, but models of each coefficient relied on unique combinations of TEI. Time coefficients for dry matter accumulation were apparently unrelated to soil- or air-TEI.     

Effect of Low Night Temperatures on Photosynthetic Activity of the Maize Seedlings (Zea mays L.)

Night chilling (5 °C) subsequently lowered photosynthetic intensity in the leaves of maize seedlings at 20 °C through an increase in leaf diffusive resistance brought on by lower tissue water content in morning hours. A more significant increase in leaf diffusion resistance was observed when soil temperature was lowered than in the case of lower air temperature.
The unfavorable effect of soil and air cooling temperature on photosynthesis was limited by air saturated with water vapour. However, as a result of lowering the night temperature from 5 °C to 1 °C, the efficiency of the protective influence of higher atmospheric humidity was decreased. This demonstrates that the participation of factors unrelated to plant water status in inhibiting photosynthesis increases with lower night temperatures.
An additional reason for inhibited photosynthesis following cool nights was a decrease in chlorophyll accumulation, below 50 μg per 1 cm² of leaf area.     

Effect of Mulch from Selected Multipurpose Trees (MPTs) on Growth, Nitrogen Nutrition and Yield of Maize (Zea mays L.)

Leaf extracts and mulch from 14 multipurpose trees were used to test their effects on maize germination, growth and yield. Maize germination was significantly reduced by leaf extracts of all species with increasing extract concentration. The most drastic reductions were caused by Gliricidia sepium , Tetrapleura tetraptera , Lonchocarpus sireceus , Senna siamea and Leucaena leucocephala . Terminalia superba , Tetrapleura tetraptera , Pithecelobium dulce , Gliricidia sepium and Senna siamea significantly reduced maize root growth at the lowest extract concentration, while shoot length was most significantly reduced by Gliricidia sepium , Leucaena leucocephala , Alchornea coordifolia , Pithecelobium dulce , Terminalia superba , and Tetrapleura tetraptera at all concentrations. Growth of maize in pots and yield in the field were controlled by nitrogen supply and uptake. Fast-decomposing leaf material rich in nitrogen promoted growth and yield of maize. Thus Leucaena leucocephala and Gliricidia sepium , both nitrogen-fixing legumes with high nitrogen contents and fast-decomposing leaf materials, significantly increased maize growth and yield. This suggests that the negative effects of leaf extracts observed in the laboratory are ecologically irrelevant in the field.     

玉米种子休眠性的数量遗传分析

运用植物数量性状主基因+多基因混合遗传模型多世代联合分析的方法,对普通玉米自交系R08与A318杂交组合的P₁、P₂、F₁、F_2:3、B_1:2和B_2:26个世代群体的种子休眠性进行了分析。结果表明,它们的遗传符合1对负向完全显性主基因+加性-显性多基因模型。在F_2:3、B_1:2和B_2:2三个家系世代,主基因方差分别为0.9260、1.4176和0.5863;多基因方差分别为0.1184、0.1022和0.4623。主基因加性效应值为1.2172,显性效应值为-1.2172;多基因加性效应值为1.5028,显性效应值为1.4334。主基因遗传率在F_2:3、B_1:2和B_2:2三个分离家系群体中为44.8%~79.65%,多基因遗传率为5.74%~35.33%。其中,主基因遗传率在B_1:2世代中最大,为79.65%。     

基于玉米重组自交系生育期的相关性状分析

摘要：本试验以K12为母本、黄早四为父本,杂交获得F1,以单粒传法选育单株分别进行自交6代构建重组自交系（Recombinant inbred line,RIL）分离群体为供试材料,通过对抽雄、散粉,吐丝等花期性状的考察,分析RIL群体对两亲本的改良效果。结果表明,RIL群体的抽雄、散粉,吐丝等花期性状均有不同程度的改变,且达到了较好的相关效果。多数性状的表型变异系数在群体内有不同程度的增加,符合RIL群体的特点。频率分布符合正态分布,表明群体具有进一步QTL研究的潜力。     

玉米茎秆弯曲性能与抗倒能力的研究

为探讨不同玉米品种茎秆抗倒伏相关的力学特点, 选用不同抗倒性品种登海3719、京科519和农大108, 设置3.00、5.25、7.50、9.25和12.00万 hm-2 5个密度, 分别于玉米抽雄前和蜡熟期取样, 用WDW3020型电子万能试验机对茎秆第3、5、7节间进行悬臂梁弯曲试验, 同时测定节间形态特征。结果表明, 随密度的增加, 茎秆基部节间直径变细、节间长度增长。品种间有一定的差异, 在3个品种中登海3719的平均直径和长度均低于其他2个品种; 品种间茎秆惯性矩也有较大差异。基部节间弹性模量、最大抗弯应力均随生育进程而增加, 但随群体密度的增加和节位的上升而逐渐降低, 登海3719在两个生育期均为最大, 且随密度增加的下降幅度较小。以京科519最低, 其对密度反应较敏感, 下降幅度大, 易发生倒伏。在玉米抽雄期, 基部节间平均弹性模量为40.0 MPa, 最大抗弯应力为2.8 MPa, 可能是茎秆抗折力学指标的下限。茎秆弹性模量与最大抗弯应力极显著相关, 茎秆直径与弹性模量和最大抗弯应力在抽雄前显著正相关, 而到蜡熟期相关不显著。它们与田间倒伏率呈极显著负相关。茎秆弯曲弹性模量反映茎秆的耐密能力, 茎秆最大抗弯应力反映品种茎秆的抗折能力, 而茎秆直径不能作为评价茎秆抗弯强弱的主要指标。玉米抽雄前期与蜡熟期茎秆抗弯性状的变化规律基本一致, 因此利用抽雄前茎秆基部弯曲力学性能鉴定与评价玉米茎秆抗倒、耐密性是可行的。     

渍涝胁迫对玉米生理生化的影响研究进展

渍涝胁迫是玉米生产中重要的非生物逆境之一,对玉米的生长发育造成危害,严重制约了玉米产量的提升。因此回顾了人们针对渍涝胁迫对玉米生理生化的影响及其适应机制的研究,介绍了人们从栽培耕作和遗传育种两个角度提高玉米抗渍涝能力的研究现状,并展望了未来玉米抗渍涝胁迫的重点研究方向。     

Functional Crop and Cob Growth Models of Maize (Zea mays L.) Cultivars

Various mathematical models were fitted to describe total dry matter production (DMP) and cob weight in two maize cultivars viz., Deccan hybrid and Deccan 101 . The data on periodical crop growth from an agronomic trial conducted at the University of Agricultural Sciences, Bangalore, were used to predict crop and cob growth empirically. In cv. Deccan hybrid , Gompertz followed by Richards models predicted DMP by 99 % nearer to the actual values. Whereas in cv. Deccan 101 , Richards-cum-logistic for vegetative-cum-reproductive stage simulated DMP with R² of 92 to 99 %. Further, cob growth was estimated realistically with high R² of 97 to 98 % using empirical models of logistic followed by Richards in cv. Deccan 101 and Richards followed by Gompertz in cv. Deccan hybrid . Comparing the empirical models in describing DMP and cob growth, the models showing higher predictions in DMP also estimated cob growth meaningfully in both the cultivars, indicating similarity in growth functions.