紧凑大穗型玉米品种陕单902群体源库性状与产量形成的研究

通过对紧凑大穗型玉米品种陕单902的研究发现,保证适宜种植密度,增加群体总粒数是陕单902高产的基础;建立合理的群全结构和干物质生产体系,提高吐丝至成熟期的干物质生产能力是陕单902高产的关键;协调群体库源关系,提高成粒率是陕单902高产的根本。采用合理密植（不超过60000株／hm^2),宽窄行和双株栽培,保证足量氮肥和适宜氮,磷,钾配比等主要配套技术可改善大穗型玉米品种陕单902的群体库源性状,提高产量潜和。     

不同株型玉米物质生产和群体库源特征的研究

玉米产量与吐丝期至成热期干物质积累量和这一阶段群体库源特征密切相关。紧凑型玉米比平展型玉米，吐丝至成熟期的于物质积累量高３０８７．６－４５２５．５ｋｇ／ｈｍ￣２，群体库容量大（１３２２．６－１５１６．８ｇ／ｍ￣２），源供应能力强（１０７３．０－１１６８．８ｇ／ｍ￣２），库源比值适宜（１．４５左右），因而籽粒产量相戍提高了２２１４．０－２７１６．５ｋｇ／ｈｍ￣２。玉米品种改良的关键是提高吐丝后群体物质生产效率和光合生产效率，同时使群体库源关系协调发展，相对平衡.     

种植密度对夏玉米产量和源库特性的影响

以高产玉米品种郑单958(ZD958)和登海661(DH661)为试验材料,在4个不同区域(山东农业大学、汶口、兖州和莱州)设置22500、45000、67500、90000和112500株.hm-25个种植密度,研究了种植密度对夏玉米产量及源库特性的影响.结果表明:两品种在112500株.hm-2密度条件下玉米籽粒产量和生物产量最高,分别为19132和36965kg.hm-2,与22500和67500株.hm-2密度相比,籽粒产量分别增加了72%和48%,生物产量分别增加了152%和112%.两品种单株叶面积、最大花丝数、穗粒数和千粒重随密度增大而减小,但叶面积指数随密度增大而显著提高.收获指数与粒叶比随密度增大而显著减小,当密度超过67500株.hm-2时差异不显著,表明高密度条件下玉米通过增加群体库来提高产量.     

玉米不同株型耐密性的群体生理指标研究

以紧凑型和平展型玉米不同株型的玉米品种为主要研究对象,利用作物生长分析法,系统研究了不同株型玉米品种群体内光分布,物质生产诸因素（LAI、NAR和CGR）和群体库源特征等群体生理指标与品种耐密性的关系,结果表明,群体内光分布合理与否是衡量品种耐密性的重要指标,叶面积系数（LAI）、净同化率（NAR）和作物生长率（CGR）的动态发展规律是反映耐密性的重要指标,叶面积系数（LAI）、净同化率（NAR）和作物生长率（CGR）的动态发展规律是反映耐密性的本质特征,群体库源关系协调与否是鉴定品种耐密性的一个综合指标。     

低氮胁迫对不同基因型夏玉米源库性状和灌浆特性的影响

2007和2008年连续2年在低氮（105 kg·hm^-2）和正常施氮（337.5 kg·hm^-2）两种施肥水平下,分析了6个不同基因型玉米品种的群体源库关系及籽粒灌浆特性间的差异.结果表明：低氮胁迫对不同基因型玉米品种的群体产量、叶面积指数（LAI）、群体源库性状和籽粒灌浆特性影响明显,在低氮胁迫下,先玉335、郑单958等耐低氮能力较好品种的籽粒活跃灌浆期较长、最大灌浆速率高、最大叶面积指数持续期较长,群体库源关系比较协调;陕单902和豫玉22等耐低氮能力较差品种吐丝后的籽粒活跃灌浆时数、最大灌浆速率、灌浆速率最大时的生长量及LAI较低,源的供应能力显著下降;低氮胁迫明显加剧了不同基因型玉米品种间的产量差异.     

冬小麦节水栽培群体“穗叶比”及其与产量和水分利用的关系

建立高光效低耗水的群体结构是小麦节水高产栽培的核心内容。为此,需要明确节水高产群体的适宜调控指标。以穗叶比(单位面积穗数与上三叶总面积之比,穗/m2)为指标,在不同品种、不同灌水和种植密度条件下研究了小麦群体穗叶比的变化,并分析了穗叶比与群体光合性能、水分利用的关系。结果表明,在相同密度下,随着灌水减少,孕穗、开花和灌浆期的穗叶比均相应增大;在限水灌溉下,随密度增加穗叶比也相应增加。不同品种的穗叶比也存在明显差异。在适宜叶面积基础上,随穗叶比增加,群体中非叶面积指数(NAI)增加,冠层内光照状况明显改善,群体光合效率提高;非叶器官贮藏物质转移率增加,收获指数提高。在一定范围内,随穗叶比增加产量明显增加,而耗水量显著减少,从而使水分利用效率得到提高。研究认为,群体穗/叶比是衡量小麦节水栽培库源关系是否协调的适宜指标。试验中小麦节水省肥高产栽培适宜的穗叶比值为230—270穗/m2。     

黄土塬区不同品种玉米间作群体生长特征的动态变化

不同玉米品种间作,品种间的竞争对群体结构和产量可能有促进作用.为了明确不同密度下品种间作对不同生育期群体生长特征的影响,以及在不同生育期的变化规律,选用郑单958和沈单16两个不同株型的玉米品种在中、高两种密度条件下进行隔行间作田间试验.研究结果表明:不同密度间作群体叶面积指数(Leaf Area Index,LAI)显著增加,同密度不同品种间作LAI在生育后期显著增加,有利于形成合理的冠层结构以获得更多的光照;中等密度下品种间作单株叶面积较单作显著增加,而高密度间作显著降低了单株叶面积;中等密度下,品种间作地上部干物质积累量显著增加,郑单958尤为突出,但高密度间作时的增加幅度较小,这与高密度下株高、茎粗相对减小有关.品种株高、茎粗随间作密度的增加而有所增加,对间作竞争的响应与品种特性密切相关;在不同生育期,郑单958和沈单16号表现不同的生长规律,前者在整个营养生长过程中对间作竞争的响应明显、持续和稳定,而进入生殖期后,间作的生长优势逐渐消失;后者在营养生长期干物质积累量大,但持续时间较短,表现出较弱的竞争性.品种间作可有效改善群体冠层结构,增加群体物质生产力,更好的为增产鉴定基础.     

林火干扰对广东木荷林生态系统碳库的影响

森林碳库在调节CO₂浓度及减缓温室效应中发挥重要作用。选择广东木荷林为研究对象,通过相邻样地法,进行植被生物量、凋落物生物量和土壤样品的采样与分析,研究不同林火干扰强度对生态系统各碳库(植被、凋落物和土壤有机碳)及生态系统碳库产生的变化规律和空间分布格局及其影响因素。结果表明:(1)植被碳密度随着林火干扰强度增强而减少,但不同组分的植被碳密度表现不同,乔木碳密度在不同林火干扰强度下变化与植被碳密度变化一致,而草本碳密度则呈现相反的变化趋势。相同林火干扰强度下,植被各组分碳密度均以乔木层降低幅度最大。林火干扰均显著降低了凋落物碳密度(P<0.05),并随林火干扰强度的增加其降低幅度增大,但不同林火干扰强度对凋落物碳密度的影响有所差异。林火干扰降低了土壤有机碳密度,且降低幅度随土层深度增加而逐渐变小。(2)林火干扰有效改变了生态系统碳库的空间分布格局。对照样地木荷林土壤有机碳库占比为61.59%,重度林火干扰后,土壤有机碳库占比为70.96%呈上升趋势,占生态系统碳库的优势地位,而植被和凋落物碳库占比呈下降趋势,处于生态系统碳库的次要地位。(3)双因素方差分析表明,林火干扰强度和土层深度及其交互作用均对土壤有机碳密度有显著影响。林火干扰强度解释了土壤有机碳密度变异的8.78%,土层深度解释了土壤有机碳密度变异的70.29%,林火干扰强度和土层深度之间的交互作用解释了土壤有机碳密度变异的8.16%。研究发现:林火干扰降低了生态系统碳库,且随林火干扰强度增加,生态系统碳库减少幅度增大。轻度林火干扰对森林生态系统碳库的影响差异不显著,而中度和重度林火干扰对森林生态系统碳库的影响差异显著。研究结果对深化亚热带森林固碳效应的影响机制提供理论支撑。     

春灌模式对晚播冬小麦水分利用及产量形成的影响

为了明确华北严重缺水区晚播冬小麦耗水规律及高产高效灌溉制度,在大田条件下设置不灌水(W0)、1水(W1,拔节水)、2水(W2,拔节水+开花水)、3水(W3,起身水+孕穗水+开花水)和4水(W4,起身水+孕穗水+开花水+灌浆水)等五种春季灌溉模式,研究了不同灌溉模式下晚播冬小麦水分利用特征及产量形成特点.结果表明,在晚播且免浇冬水条件下,春季每增加750m3/hm2的灌溉水量则减少土壤水消耗量约440 m3/hm2,增加小麦总耗水量约230m3/hm2;从播种到拔节,小麦阶段耗水强度低,此生育阶段控制灌溉可显著降低总耗水量;春季第一水推迟至拔节期可提高土壤水消耗量占总耗水量比例至50%,土壤水利用率增加;开花前仅灌一次拔节水可基本满足拔节-开花期耗水需要,其群体库容量与开花前灌起身水+孕穗水模式无显著差异,且由于相对降低了开花期群体叶面积,显著增加了群体粒叶比; 晚播密植条件下,单位面积穗数是群体库容形成的主要贡献因素,在保证大库容建成条件下,灌浆期灌水会降低开花前贮藏物质向籽粒再转运比例,而后期控水可显著提高开花前贮藏物质再转运比例和对库容填充的贡献率,且较高的群体库源比增强了库对源的反馈促进作用,使花后单位叶面积的物质生产能力提高,这可补偿后期水分亏缺对叶片光合生产的不利影响.连续两年试验结果显示,晚播密植条件下,春季灌拔节水和开花水可以实现高产与水分高效利用的统一.     

外源乙烯利施用时期对花生源库形成的调控效应

为了解决源库关系不协调而限制花生产量提高的问题,在大田栽培条件下,以‘山花9号’花生为试验材料,设置花后10、20、30 d 3个喷施时期,以不喷施处理为对照,探讨不同时期喷施乙烯利对花生源库形成的调控效应。结果表明: 花后10和20 d喷施乙烯利可显著减少花生的开花数量、果针数、幼果数,提高秕果数和饱果数,而花后30 d喷施处理对开花数量、果针数和幼果数无抑制作用。喷施乙烯利可以增加花生单株叶面积,开花后10 d喷施处理的单株叶面积增幅最大,随着喷施时期的推迟增幅减小。花后10和20 d喷施乙烯利显著提高了花生叶片的光合速率,但花后30 d喷施处理只能在短期内提高光合速率,对生育后期的叶片光合速率无显著影响。从源库综合性状来看,花后20 d喷施乙烯利的源库关系最协调,有利于促进同化物向荚果的运输,提高有效果比例和荚果充实度,从而提高产量。因此,喷施乙烯利是解决花生“花多不实、果多不饱”源库失衡现象的有效措施,生产中使用乙烯利控花应选择在开花后20 d喷施。     

下层土壤容重对玉米生育后期光合特性和产量的影响

在耕层（0～20 cm）土壤容重不变情况下,采用池栽方法研究了下层（20～40 cm,40～60 cm）土壤容重变化对玉米生育后期光合特性和产量的影响.结果表明：当下层土壤容重不同时,玉米的光合速率（P_n）和产量都存在显著差异,随着下层土壤容重的增加,叶片P_n和产量降低,下层土壤容重越大,降幅越大.不同处理玉米叶片的P_n和细胞间隙CO₂浓度（C_i）的变化趋势不同,P_n早晨和傍晚较低,中午较高,且随着下层土壤容重的增加而降低, C_i的变化趋势则相反.气孔限制值（L_s）和气孔导度（G_s）也随着下层土壤容重的增加而降低. 随着玉米生育进程,P_n、L_s和G_s不断下降,而C_i不断升高.     

密度与氮肥对关中灌区夏玉米(Zea mays L.)群体光合生理指标的影响

合理的密度是玉米构建良好群体结构、优化群体光合生理功能的基础,适宜的氮肥施用量是玉米进行光合生产的营养物质保障.运用作物群体生理学的方法,采用二次饱和D试验设计,研究了关中灌区夏玉米密度与氮肥耦合和群体光合生理指标的关系及其效应,明确了在关中灌区夏播条件下,在45000～75000株/hm2的密度范围内,密度与玉米籽粒产量、总干物质积累量(DMA)、吐丝期叶面积指数(MLAI)、总光合势(LAD)、平均作物生长率(CGR)为正相关,在45000～60000株/hm2的密度范围内,密度与玉米叶片平均净同化率(NAR)为正相关,而在60000～75000株/hm2的密度范围内,密度与玉米NAR为负相关;在氮素施用量≤600.0 kg/hm2的范围内,氮素施用量与玉米籽粒产量、DMA、CGR为正相关,在氮素施用量≤260.55 kg/hm2的范围内,氮素施用量与玉米MLAI、LAD为正相关,与玉米NAR为负相关,而在氮素施用量260.55～600.0kg/hm2的范围内,氮素施用量与玉米MLAI、LAD为负相关,与玉米NAR为正相关.密度对其影响较大的指标为:籽粒产量、DMA、LAD、CGR和MLAI , 影响较小的指标为:NAR;氮肥对其影响较大的指标为:DMA、CGR、籽粒产量、NAR,影响较小的指标为:LAD和MLAI .对籽粒产量和群体生理指标的综合影响效应,密度显著大于氮肥,玉米生产中,尤其要重视合理密植.通过对回归模型的解析,筛选确定了陕单8806玉米在关中灌区夏播中,实现高产的密度与氮肥耦合优化技术方案:合理密度为61713～66177株/hm2,适宜纯氮施用量为309.88～569.02kg/hm2.     

Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

Grain yield and kernel weight of two maize genotypes differing in nitrogen use efficiency at various levels of nitrogen and carbohydrate availability during flowering and grain filling

Grain yield per plant (GYP) and mean kernel weight (KW) of maize (Zea mays L.) are sensitive to changes in the environment during the lag phase of kernel growth (the time after pollination in which the potential kernel size is determined), and during the phase of linear kernel growth. The aim of this study was to assess genotypic differences in the response to environmental stresses associated with N and/or carbohydrate shortage at different phases during plant development. The rate and timing of N and carbohydrate supply were modified by application of fertilizer, shading, and varying the plant density at sowing, at silking or at 14 d after silking. The effects of these treatments on the photosynthetic capacity, grain yield and mean kernel weight were investigated in two hybrids differing in N use efficiency. The total above-ground biomass and grain yield per plant of the efficient hybrid responded little to altered environmental conditions such as suboptimal N supply, enhanced inter-plant competition, and shading for 14 d during flowering, when compared to the less efficient genotype. We conclude that grain yields in the efficient genotype are less sensitive not only to N stress, but also to carbohydrate shortage before grain filling. Shading of N deficient plants from 14 d after silking to maturity did not significantly reduce grain yield in the non-efficient genotype, indicating complete sink limitation of grain yield during grain filling. In the efficient genotype, in contrast, grain yield of N-deficient plants was significantly reduced by shading during grain filling. The rate of photosynthesis declined with decreasing foliar N content. No genotypic differences in photosynthesis were observed at high or low foliar N contents. However, at high plant density and low N supply, the leaf chlorophyll content after flowering in the efficient genotype was higher than that in the non-efficient genotype. Obviously, the higher source capacity of the efficient genotype was not due to higher photosynthetic N use efficiency but due to maintenance of high chlorophyll contents under stressful conditions. In the efficient genotype, the harvest index was not significantly affected by N fertilization, plant density, or shading before the grain filling period. In contrast, in the non-efficient genotype the harvest index was diminished by N deficiency and shading during flowering. We conclude that the high yielding ability of the efficient genotype under stressful conditions was associated with formation of a high sink capacity of the grains under conditions of low carbohydrate and N availability during flowering and with maintenance of high source strength during grain filling under conditions of high plant density and low N availability.     

播种时期与密度对关中灌区夏玉米群体生理指标的影响

采用二次饱和D最优试验设计,运用作物群体生理学方法,研究了关中灌区玉米密度、播期与群体生理指标的关系及其影响效应.结果表明,关中灌区夏播条件下,在6月13日—7月22日,播期与玉米籽粒产量、干物质积累量(DMA)、吐丝期叶面积指数(LAImax)、总光合势(LAD)、群体净同化率(NAR)、作物生长率(CGR)呈负相关,播期对CGR、LAD的影响较大,对LAImax和NAR的影响较小;在45000～65918株·hm-2范围内,密度与玉米籽粒产量、DMA、LAImax、LAD、CGR呈正相关,而与NAR呈负相关,密度对CGR、LAImax和LAD的影响较大,而对NAR的影响较小.播期对玉米群体生理指标的总影响效应显著大于密度,实际生产中应力争早播.对密度和播期与玉米群体生理指标建立的回归模型表明,陕单8806玉米在关中灌区夏播中实现高产的适宜播期为6月10—20日,密度应控制在57767～71706株·hm-2.     

Reduction in seed set upon exposure to high night temperature during flowering in maize

High temperature reduces crop production; however, little is known about the effects of high night temperature (HNT) on the development of male and female reproductive organs, pollination, kernel formation and grain yield in maize (Zea mays L.). Therefore, a temperature-controlled experiment was carried out using heat-sensitive maize hybrid and including three temperature treatments of 32/22°C (day/night; control), 32/26°C and 32/30°C during 14 consecutive days encompassing the flowering stage. When exposed to 30°C night temperature, grain yield and kernel number reduced by 23.8 and 25.1%, respectively, compared with the control. The decrease in grain yield was mainly because of the lower kernel number rather than change in kernel weight under HNT exposure around flowering. No significant differences in grain yield and kernel number were found between 22 and 26°C night temperatures. HNT had no significant effects on the onset of flowering time and anthesis-silking interval but significantly reduced time period of pollen shedding duration and pollen viability, and increased leaf night respiration. Different from high daytime temperature, HNT had no lasting effects on daytime leaf photosynthesis, biomass production and assimilate transportation. From the perspective of source–flow–sink relationship, the unchanged source and flow capacities during daytime are supposed to alleviate the adverse effects on sink strength caused by HNT compared with daytime heat stress. These new findings commendably filled the knowledge gaps concerning heat stress in maize.     

种植密度对玉米-大豆间作群体产量和经济产值的影响

采用二次饱和D最优设计,研究了种植密度对玉米 大豆间作群体产量和经济产值的影响,并建立了以玉米和大豆密度为变量,以间作群体籽粒产量、干物质积累和经济产值为目标函数的二元二次数学模型.模型解析表明： 种植密度对玉米 大豆间作群体籽粒产量、干物质积累和经济产值影响显著,玉米密度对群体各指标的影响大于大豆密度.在低密度水平下,群体籽粒产量、干物质积累和经济产值均随密度的增加而增加.群体籽粒产量达到8101.31 kg·hm^-2,最优措施组合为：玉米密度72023株·hm^-2+大豆密度99924株·hm^-2;群体干物质积累达到15282.45 kg·hm^-2,最优措施组合为：玉米密度75000株·hm^-2+大豆密度93372株·hm^-2;群体经济产值达到23494.50元·hm^-2,最优措施组合为：玉米密度73758株·hm^-2+大豆密度87597株·hm^-2.通过计算机模拟得出,在本试验条件下,玉米-大豆间作群体籽粒产量≥7500kg·hm^-2、干物质积累≥14250 kg·hm^-2、经济产值≥22500元·hm^-2的最佳密度组合为：玉米种植密度58554～71547株·hm^-2,大豆种植密度82217～100303株·hm^-2.