土壤渍水对孕穗期冬小麦氮磷钾营养的影响

采用盆栽和池栽试验,研究了孕穗期土壤渍水逆境对不同小麦品种N、P、K素吸收、运输和分配影响。结果表明,孕穗期土壤渍水逆境显著影响小麦根系对N、P、K素的吸收,降低根系、茎鞘、功能叶片和全株N、P、K素相对含量和绝对含量,而对N、P、K素在地上部各器官中的分配比例影响较小。由于土壤渍水逆境影响了小麦根系正常吸收N、P、K素营养,严重影响小麦功能叶片正常光合性能,最终使小麦单穗结实粒数、粒重和产量下降。     

孕穗期渍水逆境对冬小麦氮素营养及产量的影响

采用池栽试验,研究了孕穗期渍水逆境对小麦氮素营养和产量的影响。研究结果表明:孕穗期渍水逆境显著影响小麦氮素的吸收量,降低茎鞘、功能叶片和全株含氮量和全氮积累量,而对氮素在地上不同器官的分配比例影响较小。由于渍水逆境影响了小麦根系正常吸收氮素,使叶片含氮量急剧下降,从而导致旗叶叶绿素含量和净光合速率降低,影响小麦功能叶片正常光合性能,最终使小麦粒重和产量下降。     

孕穗至灌浆期土壤渍水对冬小麦N、P、K素含量和积累量的影响

运用盆栽模拟土壤渍水逆境试验,研究孕穗期和灌浆期土壤渍水对不同小麦品种根系和地上部分N、P 、K素吸收和运转影响.结果表明,土壤渍水逆境对不同小麦品种N、P 、K素吸收的影响有异.孕穗期土壤渍水逆境显著影响根系对N、P素的吸收与运转 ,而对K素吸收与运转影响较小;灌浆期渍水逆境不仅影响根系对N、P、K素的吸收,同时也影响N、P素在地下与地上部器官的运转,但对K素在小麦体内的运转和分配影响较小.     

不同生育时期渍水对冬小麦K素吸收和分配的影响

选用 6个耐湿性不同的冬小麦品种 ,运用人工模拟不同生育时期根际渍水的试验方法 ,研究渍水对不同冬小麦品种K素吸收和分配的影响。结果表明 ,根际渍水对小麦K素吸收的影响与渍害发生时期关系不密切 ,自小麦苗期开始的渍水就影响根系对K素的吸收 ,而对K素在小麦体内的运输和分配影响较小。故基肥中施足K肥对于培育壮秆大穗 ,减轻小麦渍害 ,促进干物质运输、积累和提高小麦籽粒粒重具有非常重要的实际意义。     

不同生育时期渍水对冬小麦P素吸收和分配的影响

研究了不同生育时期根际土壤渍水对不同小麦品种P素吸收和分配的影响。结果表明 ,不同生育时期根际土壤渍水显著影响根系对P素的吸收 ,其影响大小依次为 :孕穗期 >拔节期 >灌浆期 >苗期 >返青期。孕穗期以前渍害主要影响小麦根系对P的吸收 ;灌浆期渍害不仅影响根系对P素的吸收 ,同时也影响P素在地上部各器官中的分配。因此 ,基肥中施足P肥和灌浆期喷施KH2 PO4 对提高受渍小麦粒重具有重要的实际意义     

孕穗期渍水逆境对冬小麦干物质积累与分配的影响

于1997～1999年在安徽农业大学试验总场进行试验,采用柱载试验,研究了孕穗期渍水逆境对小责中后期干物质积累与分配的影响。研究结果表明：孕穗期渍水逆境促使单茎绿叶衰亡加快,单茎绿叶干重、单茎茎鞘干重和穗干重下降;同时严重影响小麦中后期各器官干物质的积累、运转和分配,最终导致粒重和产量下降。     

孕穗期渍水逆境对冬小麦氮素代谢和产量的影响

采用池栽试验,研究孕穗期渍水逆境对冬小麦氮素营养和产量的影响.结果表明:孕穗期渍水显著地影响冬小麦氮素的吸收量,降低茎鞘、叶片和全株的相对含氮量和绝对含氮量,对氮素在不同器官的分配影响较小,从而导致旗叶叶绿素含量和净光合速率降低,最终使粒重和产量下降.     

拔节孕穗期渍水及补肥措施对小麦淮麦28产量和干物质积累的影响

研究拔节孕穗期不同渍水时间及渍后不同补肥措施对小麦产量及干物质积累等性状的影响。结果表明,拔节孕穗期小麦渍水时间越长则减产越多,渍水5 d处理较对照减产20.1%;渍水后补肥有补救效果,且补肥量越大效果越好,渍水1 d不补肥的667 m²产量为520 kg,与对照无差异。小麦拔节孕穗期渍水对花前干物质积累影响较小,但降低了花后干物质的积累,补肥有利于干物质的积累;渍水时间延长,干物质积累会减少。     

不同基因型冬小麦穗粒数与粒重生理差异分析

为分析不同穗型冬小麦籽粒建成的生理差异,以大穗基因型(JS)、小穗基因型(XS)和中穗基因型(JM22)冬小麦品种为材料,测定籽粒形成期和灌浆期器官干物质积累、蔗糖含量和蔗糖相关代谢酶活性、籽粒灌浆特性以及成熟期穗粒数和粒重等指标。结果表明:1)冬小麦穗粒数和粒重基因型间差异显著;2)大穗基因型冬小麦从四分体时期到成熟期单株干物质积累量、开花期穗部干物质分配比例和强、弱势粒灌浆速率都高于中、小穗基因型;3)大穗基因型冬小麦开花期茎鞘的蔗糖积累量显著高于中、小穗基因型,开花后叶片和茎鞘的蔗糖积累高峰晚于中、小穗基因型;4)大穗基因型冬小麦四分体时期到开花期茎鞘的蔗糖转化酶活性以及花后茎鞘和籽粒的蔗糖合酶和转化酶活性显著高于中、小穗基因型。5)相关分析显示,不同时期各器官干物质、开花期上二茎的蔗糖合酶活性和蔗糖含量、四分体时期穗茎的蔗糖合酶和转化酶活性与穗粒数和粒重都呈正相关,花后上二茎转化酶活性以及各器官的蔗糖合酶活性与粒重都呈显著正相关。总之,大穗基因型冬小麦穗粒数较多主要由于开花期穗部干物质分配比例、茎鞘蔗糖合酶活性和转化酶活性均较高;而籽粒灌浆速率和粒重较高则是由于花后茎鞘和穗的蔗糖代谢旺盛,且茎叶同化物向籽粒的转运率和贡献率较高。     

花后喷肥对不同穗型小麦旗叶光合速率及籽粒产量的影响

为了探讨不同穗型小麦品种对花后喷肥的反应,选用大穗型和多穗型小麦品种为试验材料,研究了花后混喷多种肥料对2种穗型小麦品种旗叶光合速率、干物质积累及籽粒产量的影响。结果表明:花后喷肥可提高旗叶净光合速率,增加单茎地上干物质积累,多穗型品种豫麦49旗叶净光合速率和地上干物质积累增幅均大于大穗型品种宿2001。喷肥后茎节单位长度干重增加,茎节贮存物质有所增加,以宿2001较为明显。混喷多种肥料后2种穗型小麦品种的籽粒产量均显著高于对照,其中,豫麦49增产7.41%,宿2001增产6.35%,品种间差异不明显。     

穴盘规格和苗龄对塑料大棚菜豆性状及产量的影响

本试验以菜豆品种先行者为试材,采用32孔、50孔两种规格穴盘,设置10、15、20、25 d等4个苗龄段,通过研究不同穴盘规格和苗龄对菜豆性状及产量的影响,筛选出适合菜豆育苗的穴盘规格和适宜的苗龄。结果表明：穴盘育苗的营养面积增大,菜豆产量随之增加,25 d苗龄条件下,32孔穴盘的前期产量和总产量均显著高于50孔穴盘;随着苗龄的增长,菜豆的前期产量和总产量呈增加趋势,其中25 d苗龄的产量显著高于其他苗龄。综合上述各项指标,菜豆育苗阶段,10 d苗龄可选用32孔、50孔穴盘,15 d以上秧苗选用32孔穴盘为宜。     

不同基因型小麦苗期耐低氮性评价及筛选

氮素作为重要的营养元素,限制着小麦的生长发育和经济产量,筛选和培育耐低氮小麦品种是提高氮素利用率、降低生产成本的有效途径。以118份不同基因型小麦为材料,在低氮(0.1 mmol·L^-1)和正常氮(5 mmol·L^-1)条件下苗期水培,测定根干重、茎叶干重、根冠比、植株干重、最大根长、初生根数和二级初生根数等相关指标,采用模糊隶属函数法、主成分分析以及聚类分析法综合评价小麦品种的耐低氮性。结果表明,在低氮胁迫下小麦幼苗的根干重、根冠比和初生根数目显著提高,茎叶干重、植株干重和最大根长不同程度的降低,7个苗期性状指标在两个氮水平下均存在显著性差异。主成分分析提取3个主成分,贡献率分别为 43.575%、22.904%和17.873%,累积贡献率达 84.351%。以耐低氮性综合评价D值进行聚类分析,将118份小麦品种划分为强耐低氮型、耐低氮型、中间型、较敏感型和敏感型5类。筛选出3份耐低氮型小麦（齐大195、金丰7183和天民198）和2份强耐低氮型小麦（山农0917和鲁麦8号）。不同小麦品种的耐低氮机制不同,研究结果为小麦耐低氮品种的选育提供理论依据和材料基础。     

一串红N、P、K、Ca、Mg、Fe缺素症状研究

以‘展望红’为材料,研究N、P、K、Ca、Mg、Fe缺乏对其生长发育的影响,并总结缺素症状,研究结果表明:N缺乏时植株矮小,叶发黄;P缺乏时叶色暗绿,且影响开花;K缺乏时基部叶枯黄,并易落叶;缺Fe症状较为明显,但能正常开花;Ca、Mg未表现出缺素症状,且各项指标要优于全素处理;N、P显著影响一串红的生长发育,K对开花品质的影响较大。     

Segregation of form, color, movement, and depth: anatomy, physiology, and perception

Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.     

ICP-OES法同时测定果蔬中铅、砷、镉、铬、铜、锡含量

果蔬样品经混酸消化后,控制一定的酸度,定容后应用等离子体发射光谱法(ICP-OES)对果蔬中铅、砷、镉、铬、铜、锡六种有害重金属进行测定,研究了分析测定条件,方法简单快速。测定结果表明,五种元素的加标平均回收率在91.0%~107%之间。其RSD均小于3.5%。按该方法进行处理及测定铅、砷、镉、铬、铜、锡,在选择的测定条件下最低检出限分别为0.0006 mg/kg、0.0003 mg/kg、0.00003 mg/kg、0.00005 mg/kg、0.00003 mg/kg、0.0006 mg/kg。     

Space, stars, c60, and soot

Although carbon has been subjected to far more study than all other elements put together, the buckminsterfullerene hollow-cage structure, recently proposed to account for the exceptional stability of the C(60) cluster, has shed a totally new and revealing light on several important aspects of carbon's chemical and physical properties that were quite unsuspected and others that were not previously well understood. Most significant is the discovery that C(60) appears to form spontaneously, and this has particularly important implications for particle formation in combustion and in space as well as for the chemistry of polyaromatic compounds. The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot. Although the novel structural proposal has still to be unequivocally confirmed, this article pays particular attention to the way in which it provides convincing explanations of puzzling observations in several fields, so lending credence to the structure proposed for C(60).     

Strategic command, control, communications, and intelligence

Command, control, communications, and intelligence (C(3)l) for nuclear forces are essential elements in the deterrence of nuclear war. The present C(3)l) system has vulnerabilities associated with its reliability, survivability, and endurance under attack, thereby weakening deterrence by increasing the ambiguity in our capabilities. Development of a reliable and enduring C(3)l) system would reduce this ambiguity. Its reliable, positive control of nuclear forces would give the national leadership more time to assess situations, ensure discriminate retaliation, and improve our ability to manage crises in general. These capabilities could help to stop a war rapidly should one start. A reliable and enduring C(3)1) system will be needed for a long time to come, even if a freeze on strategic nuclear forces is accomplished or other arms control successes achieved. Indeed, C(3)l) may be the best source today of confidence-building measures to reduce tensions and the threat of nuclear catastrophe.