小麦（Triticum aestivum L.）是全世界范围内广泛种植的粮食作物，在三大粮食作物中种植面积位居第一，产量位居第二，全世界有超过40%的人口以小麦为主食[1⇓-3]。穗是小麦籽粒产量形成的重要器官，其形态建成过程关系着穗上小花的发育及穗粒数和穗粒重的形成，同时该过程也易受外界环境因素影响。前人[4]研究普遍聚焦于小麦旗叶对小麦籽粒产量的贡献程度，认为旗叶的光合作用为籽粒干物质积累提供了最主要的同化物[5]。然而，随着对小麦光合器官研究的深入，有人[6]发现小麦非叶的绿色器官或组织同样具有光合能力，其中与逐渐衰老的旗叶相比，穗部的颖壳、芒等同样能在花后对籽粒表现出重要的光合贡献。同时，越来越多的研究挖掘出穗部具有应对干旱、高温等胁迫的能力。水分亏缺时，穗部器官对籽粒灌浆的贡献高于旗叶[7]，可能与颖壳和芒保持较高相对含水量的能力有关[8]。并且适度的水分亏缺能够促进灌浆中后期穗部颖壳中碳同化物的向外转运，推测是维持旱作小麦稳产的生理基础[9]。高温胁迫下，非叶器官持续抗氧化能力和耐热性强于旗叶[10]，并且穗的净光合速率下降幅度小于旗叶[11]。
光合作用是决定小麦产量的关键因素之一，特别是抽穗及灌浆期的光合作用[12]。而光合作用依赖于叶绿体为主要场所和一定的光化学步骤来进行物质的转变，这也恰恰反映了生物体结构与功能相适应的关系，了解小麦穗部各器官与组织的结构及其生理特性是揭示麦穗对籽粒产量贡献的关键。有关研究[10,13-14]集中于对小麦旗叶和穗部器官各功能的比较，近年来，也有研究[15-16]对非叶器官或组织在逆境下的生理特性差异进行分析，但对小麦穗部结构与功能对应的生长发育过程少有系统性梳理。本文在前人研究基础上，以小麦穗的形态建成和生理功能为切入点，在分析形态的基础上对穗光合贡献进行分析总结，以深化小麦穗器官发育机制的探究，同时为挖掘小麦穗的光合潜力、促进籽粒产量提高提供可能的调控途径。
1 小麦穗器官的形态结构
1.1 穗器官的构成
1.2 小麦的穗型
图1
图1
小麦属不同穗型模式图（作者绘制）
Fig.1
Pattern diagram of different spike types of Triticum (the author drew)
1.3 穗器官的发育过程
图2
图2
穗部分化发育过程中各器官进程形态（作者绘制）
(a) 不同分化时期幼穗外部形态；(b~c) 幼穗中部分化原基形态。
Fig.2
Morphology of various organ processes during the differentiation and development of spikes (the author drew)
(a) External morphology of young spikes at different differentiation stages; (b-c) Morphology of differentiation primordia in the middle of young spikes.
在穗部分化过程中可以通过不同的外部形态特征来判断小麦穗发育时期。随着生长锥的生长，小麦幼穗在分化出第1个苞叶原基后进入伸长期[29]。伸长期也被称为幼穗原基分化期，象征着小麦生殖生长的开始。单棱期苞叶原基开始分化，整个幼穗呈环状突起，生长锥分化出更多的苞叶原基[17]。二棱期苞叶原基腋处分化出小穗原基[30]，小穗原基不断生长直到明显大于苞叶原基（图2b）。护颖原基分化期小穗基部出现护颖原基突起，按照分化顺序分为下位护颖和上位护颖，并可从幼穗侧面观察到三角形突起[17]。小花原基分化期分化出外颖原基，在每个小穗上，自下而上分化互生形的小花，小穗中部形成小穗轴，小花着生在穗轴节片上[17]。进入雌雄蕊分化期后中部小穗第4朵小花原基突起出现时，其下部第1朵小花生长锥分化出3个雄蕊原基和1个雌蕊原基，雄蕊原基包围着中心圆形的雌蕊原基[30]（图2c）。药隔形成期雌雄蕊原基变化明显，逐渐趋于长圆形的雄蕊中部出现1个纵沟，雌蕊顶部出现1个凹陷[29]。四分体时期花药颜色由深绿变为淡绿，可在花药纵切面看到4个排在同一平面雄蕊的小孢子体，此时正是雌蕊柱头羽毛开始进入伸长期[17]。
1.4 影响穗器官发育的环境因素
1.4.1 温度
温度对于小麦而言是一个非常重要的生态因子，影响着其幼穗分化发育过程。根据播种时间（季节）的差异，可将小麦划分为春小麦和冬小麦2种不同类型。前人[33]认为，冬小麦幼穗在早期生长阶段需要一定时间的低温才能通过春化阶段，低温环境与小麦的春化过程密切相关，决定着幼穗是否能正常分化。国外也有报道[34]，冬性品种在穗分化过程中对温度的变化比春性品种反应更为敏感。冬性品种在没有低温的条件下也能抽穗开花，认为低温春化对开花都是量的效应，而对开花不是必要的，国内外学者[35-36]相继通过试验证实了这一结论。随着对小麦幼穗分化与温光反应关系研究的深入，有学者[37]将高温促进生长锥伸长的现象解释为积温效应，高温能促进生长锥的伸长，相反低温会抑制幼穗早期生长发育，造成茎生长锥分化进程的推迟[38]。研究[39]表明，受晚播影响而积温不足的小麦幼苗，后期退化的小穗数会更多。大部分研究[40]认为幼穗分化至二棱期是小麦通过春化阶段的标志，在此期间的单棱期和二棱期则是对低温反应最敏感的时期[32]，而当幼穗进入小花原基分化期后便不再受有无低温春化的影响[35]。
1.4.2 光照
1.4.3 水分
1.4.4 养分
前人[55]研究表明，合理搭配施用氮、磷、钾能提高光合效率，促使穗粒重的增加，从而达到高产目标。适宜的钾肥有利于小麦生育期内总穗数的增加，并优化籽粒品质[56-57]。适宜的氮肥同样能促进小麦幼穗发育，增加其分蘖数和可孕小花数[58]。然而过多的氮肥易造成无效分蘖，会阻碍籽粒对营养器官中碳水化合物和氮素的吸收[59]。当氮肥过量施用时，小麦穗粒数和千粒重下降，即使单位面积穗数有所增加，但最终产量仍会下降[60]。研究[61]认为在土壤含磷不足或大量施用氮肥的条件下，施用磷肥能帮助小麦显著增产，同时改善小麦品质。在严重缺磷条件下，小麦的小穗数和小花数出现大幅度减少，即最终穗粒数显著降低[62]。前人[63]通过在轻盐土上施加磷肥发现，施磷能促进小麦分蘖，提高小麦成穗率。
1.4.5 植物激素
1.5 影响穗器官发育的调控基因
2 小麦穗器官的生理功能
2.1 光合作用的功能
位于小麦旗叶上层的主要非叶光合器官包括旗叶鞘、穗下节间、颖壳和芒等[91]，已有相关研究[92]证实，花后除叶片作为籽粒形成的光合源外，这些非叶器官同样参与着光合同化物的合成，是经济产量形成的重要光合源部分。前人[93]认为穗部处于光照更为充足的冠层，利于光合作用时间的延长，进而积累更多干物质，因此在逆境下穗部的光合贡献更为明显。Wardlaw[94]在此基础上发现，小麦的非叶绿色器官在干旱、高温等条件下拥有比叶片更强的光合性能，这依赖于其与玉米相仿的C4型高效光合机制，改善了逆境下叶片光合不足的状况。魏爱丽等[95]研究也证明叶片以外的非叶绿色器官（穗、茎、鞘）具有比叶片更高的C4代谢酶活性，而且适度高温和干旱胁迫会诱导增强非叶器官C4酶活性。
尽管前人[96-97]研究已证实小麦不同光合器官在灌浆期所发挥的重要光合作用，但针对小麦开花后不同光合器官对籽粒形成的贡献程度中，究竟是作为非叶器官的穗部更大，还是叶片更大，争议众多。施生锦等[98]对小麦灌浆期不同光合器官在一天中最大光合速率的差异进行研究，发现旗叶>穗下节间>芒>叶鞘>去芒穗。而有研究[99]通过遮光处理小麦不同光合器官，发现其对籽粒粒重形成的相对贡献率依次为穗部>旗叶>节鞘。同样，在小麦节水栽培的条件下，不同器官遮光后引起穗粒重显著降低，顺序为穗部>旗叶>倒二叶[100]。张永平等[101]研究发现与旗叶相比，非叶器官光合功能期较长，在灌浆后期能保持较高的光合活性。综上进一步证明了穗光合对产量形成的突出作用。
2.2 影响籽粒灌浆与物质充实的功能
源、库、流的形成及其功能的发挥相互联系、相互促进。源是小麦生长过程中所需营养物质的提供器官，库是利用或积累这些营养物质的贮藏器官，而流则是源与库之间的桥梁。从源与库的关系看，刘凤霞[102]对源与库的定义是互相制约而取得平衡的关系。一方面，库的消耗跟不上源的供应，源的光合产物得不到合理的运输分配；另一方面，源的供应跟不上库的积累，库内物质无法形成的同时源也会损伤。因此，源与库都影响着小麦的最终产量。从源、库对流的影响看，源、库的大小及其活性都明显影响流的方向、速率及数量，起着“推力”和“拉力”的作用。在保证源库动态平衡的基础上，尽可能帮助小麦生育期内穗粒数与可育小花数的增多，是对源、流条件的最合理利用[103]。
前人[104]在研究源库调节对小麦产量的影响时，发现一定量的去穗能够帮助籽粒产量的增加。Rook等[105]采用对穗部喷施激素的方式研究发现，外部增源后旗叶中光合固定的14C加速向穗部输送，增加了籽粒中光合产物含量。而当对小麦进行穗部遮光时，籽粒粒重受到的影响最大，有明显降低趋势，蛋白质含量则略有增加[106]。因此，源、库、流之间的动态变化与小麦的籽粒形成和最终产量都密不可分。有学者[107]通过同位素标记法证明了小麦中不同源器官对其光合产物的分配方式也存在不同，与旗叶相比，穗部合成的光合同化物能更平均地运输到小穗中。旗叶与穗部的区别在于其合成的光合产物在输送给籽粒基础上，还需要分配至其他源器官中[108]。这也证明了穗部作为非叶源器官对籽粒形成的贡献。
3 展望
3.1 如何挖掘穗光合作用的潜力
提高小麦产量的育种方式有2种，一是直接控制小麦自身性状提升产量；二是借助外界小麦生长环境提升产量[57]。针对江苏淮北麦区种植的硬粒小麦品种，不同品种间籽粒品质存在一定差异，体现在产量、农艺性状及品质特性等方面[109]。因此，筛选出适宜地区及气候环境的优异小麦种质资源非常重要。从小麦生长的外界环境角度看，适当的人为干预与处理可帮助小麦穗部加强光合作用，从而积累更多干物质，达到增产效果。前人[110]研究发现，施肥能够影响非叶器官尤其是穗对产量的光合效应，且氮磷钾配合施用后小麦各光合器官之间增产效果差异显著。有研究[111]表明，小麦非叶光合器官在灌浆期有较强的光合能力。在小麦生育后期，与开始逐渐衰老的叶片相比，非叶光合器官中叶绿素的含量下降更少，维持了非叶器官较长的功能期。生育后期当叶片的光合速率明显下降时，非叶光合器官的光合速率才会达到最大值。因此，在小麦花后关注小麦穗部非光合器官的光合作用尤为重要，通过外界手段延缓穗部器官衰老进程，帮助其发挥最大光合作用，有助于挖掘穗光合作用的潜力，促进小麦的优质高产。
3.2 如何合理调控穗器官分化以获得高产
小麦幼穗分化过程是决定小麦小穗数、穗粒数及结实性的关键时期[112]。因此，为了达到高产目标，就需要采取一定人为措施调控穗器官分化，而光照、温度、水分、养分等外在环境条件的变化都能够影响幼穗的分化。
小麦不同播期影响其冬前的积温，而冬前积温对单棱期和二棱期的影响最大。当幼穗进入护颖原基分化期后，积温对其穗分化影响的程度则将减弱。在幼穗分化时期，穗分化速率受温度影响，温度上升会加速小麦穗分化进程，导致分化总天数缩短，即需延长幼穗分化时间，利于小麦大穗的形成[113-114]。因此要确保小麦的适期播种，保证其前期分化的持续时间。同样还需要满足穗器官分化时对水分和养分等的需求。幼穗分化期间急剧分化的细胞对水十分敏感。前人[115]发现在单棱期和二棱期水分供应不足会缩短相应的穗分化时间，同时降低分化的小穗数。氮肥能够促进小麦的生长与代谢，增加其对养分吸收的能力。而在幼穗生长发育时期，植株体内氮素的积累与幼穗分化呈正相关关系[116]。适宜的氮肥水平有利于大穗形成和小花死亡率的下降[117]。相反，缺乏氮肥会导致小花原基分化总量的减少[115]。有学者[118]研究表明，当玉米严重缺氮时，不仅会影响其小花的可育性，还会在较大程度上影响可孕小花数量。
如何进一步提升产量和优化籽粒品质是高效农业关注的重点，而光合作用是小麦籽粒干物质积累的基础，作物光合面积、叶绿素含量和碳氮比等都会影响光合作用的进程，进而影响作物的产量。综上所述，目前有关小麦穗分化的过程前人已进行了一系列形态学的研究，并总结出各项环境因素对穗分化的影响，而在小麦穗的生理功能尤其是光合作用方面，国内外学者已利用增源、减源、缩库等手段证明穗通过生理代谢对籽粒形成的一定贡献。因此，深入研究麦穗结构发育及其生理功能，建立起小麦发育中各阶段穗部结构与功能的对应联系，能够为小麦生长中的穗光合选择提供参考，为小麦高产和优化栽培提供理论依据，提升小麦产量潜力及品质。
参考文献
The accumulation and properties of starch are associated with the development of nutrient transport tissues at grain positions in the spikelet of wheat
施氮量对花后高温胁迫后小麦同化物积累、转运及产量的影响
DOI:10.3864/j.issn.0578-1752.2020.21.006
[本文引用: 1]
【目的】明确不同施氮量对高温胁迫后小麦同化物积累和转运的影响及其生理基础,以期为小麦抗逆稳产栽培提供技术和理论依据。【方法】于2018—2019年在济南和济阳两地进行,以济麦44为材料,田间搭建高温棚进行高温胁迫处理,设置2个温度处理（CK：未胁迫,H：花后高温胁迫）,3个氮肥水平（低氮N1：180 kg·hm<sup>-2</sup>,常规氮N2：240 kg·hm<sup>-2</sup>,高氮N3：300 kg·hm<sup>-2</sup>）。通过分析小麦花前同化物质的转运、成熟期同化物质的积累与分配、叶片与籽粒中蔗糖合成酶在同化物转运中的作用,阐明了不同施氮量对花后高温胁迫后小麦籽粒产量形成的影响机制。【结果】不同施氮量对高温胁迫后小麦的减产率影响不同,N1处理减产率为54.78%（济南）和50.19%（济阳）,N2处理为24.05%（济南）和25.29%（济阳）,N3处理为54.49%（济南）和44.13%（济阳）。高温胁迫后,与N1和N3处理相比,N2处理成熟期同化物积累量、花前营养器官同化物向籽粒中转运量和转运率、花后同化物积累量和积累率、同化物向籽粒中的分配比例均显著增加;N2处理旗叶SPAD值、蔗糖合成酶SS-Ⅱ合成方向活性和籽粒蔗糖合成酶SS-Ⅰ分解方向活性增加。【结论】本试验条件下,施氮量为240 kg·hm<sup>-2</sup>可以显著减缓高温胁迫后旗叶衰老,维持旗叶中SS-Ⅱ和籽粒中SS-Ⅰ较高的酶活性,保持较高的同化物合成能力和向籽粒中的转运能力,提高同化物向籽粒中的积累量和分配比例,降低高温胁迫后小麦籽粒产量的损失率。
小麦穗部光合速率和颖壳抗氧化酶活性对光辐射强度变化的响应
DOI:10.7668/hbnxb.20190982
[本文引用: 1]
为了给小麦高光效和高抗逆相结合的高产品种选育提供理论依据，在大田条件下，以黄淮地区3个小麦主栽品种为研究对象，探究了不同小麦品种穗部光合速率和颖壳抗氧化酶活性对一天中光辐射强度变化的响应。结果表明，在不同生育时期，百农4199、矮抗58和周麦18的穗部光合速率（Pn）以及颖壳超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）的活性均随着一天中光辐射强度由弱到强再到弱的变化而呈现先升后降的趋势，颖壳丙二醛（MDA）的含量随着光辐射强度变化呈现先降后升的趋势。从品种比较来看，在抽穗期、开花期、花后10 d、花后20 d的7：30、11：30、13：30和17：30，百农4199的穗部光合速率分别比矮抗58高出15.72%，27.99%，28.01%和62.46%、33.49%，15.09%，20.94%和17.97%、37.90%，21.41%，6.30%和40.11%、9.34%，10.70%，17.27%和19.32%；分别比周麦18高出12.45%，19.74%，25.36%和58.58%、14.89%，3.13%，22.52%和13.48%、40.64%，25.93%，9.70%和10.89%、13.13%，21.47%，28.34%和22.53%。究其原因，百农4199的颖壳在不同时期不同光照条件下其SOD、CAT和APX等抗氧化酶活性高于矮抗58和周麦18，较高的抗氧化酶活性降低了百农4199颖壳的MDA含量，使穗部能充分利用少量的弱光或耗散多余的光能，从而使自己适应不同的光照辐射水平。
Response of wheat ear photosynthesis and photosynthate carbon distribution to water deficit
Effects of low-temperature stress during the anther differentiation period on winter wheat photosynthetic performance and spike-setting characteristics
System to uniquely name wheat plant structures
New avenues for increasing yield and stability in C3 cereals: exploring ear photosynthesis
DOI:S1369-5266(20)30002-9
PMID:32088154
[本文引用: 1]
Small grain cereals such as wheat, rice and barley are among the most important crops worldwide. Any attempt to increase crop productivity and stability through breeding implies developing new strategies for plant phenotyping, including defining ideotype attributes for selection. Recently, the role of non-foliar photosynthetic organs, particularly the inflorescences, has received increasing attention. For example, ear photosynthesis has been reported to be a major contributor to grain filling in wheat and barley under stress and good agronomic conditions. This review provides an overview of the particular characteristics of the ear that makes this photosynthetic organ better adapted to grain filling than the flag leaf and revises potential metabolic and molecular traits that merit further research as targets for cereal improvement. Currently, the absence of high-throughput phenotyping methods limits the inclusion of ear photosynthesis in the breeding agenda. In this regard, a number of different approaches are presented.Copyright © 2020 Elsevier Ltd. All rights reserved.
Convergence and synchrony-a review of the coordination of development in wheat
Effects of temperature on spikelet number of wheat
1987-2012年黄淮海地区冬小麦生育期气候适宜指数时空分布特征
DOI:10.11924/j.issn.1000-6850.2014-1717
[本文引用: 1]
为了研究气候资源对黄淮海地区冬小麦生产的气候适宜度，以冬小麦气候适宜度模型为基础，选取5省63站1987—2012年逐旬气象数据分析了该区域冬小麦气候适宜指数时空分布特征。结果表明，黄淮海地区冬小麦生长季内温度适宜度、日照适宜度、降水适宜度的空间分布差异较大，温度适宜指数由北向南、日照适宜指数由东向西，降水适宜指数由南向北总体呈现递减的地域分布特征。黄淮海地区冬小麦气候适宜程度较高，总体能满足冬小麦不同阶段生长发育的需要。光温资源总体较好，相应的气候适宜指数较高，各个发育期日照适宜指数均高于0.8，温度适宜指数除分蘖期受气温起伏影响值偏小以外，其余发育阶段均高于0.7；但降水适宜指数明显较低，均小于0.6，是制约该区域冬小麦生产的关键因素。
水分和钾肥对冬小麦群体物质生产和产量形成的影响
为明确灌水次数和施钾量对高产冬小麦群体物质生产特性和产量形成的影响, 分别于2006 -2007 、2007 -2008 年度在保定市和藁城市选用当地冬小麦推广品种(` 河农822' 、` 石新616' )进行了灌水次数(0 、1、2 和3水)和施钾量(K2O 0、112.5 和225 kg/hm2)的两因素裂区试验。结果表明:2 年中越冬期和起身期的总茎数、越冬期的干物质积累量的方差不同质, 其它各生育时期的总茎数、干物质积累量、籽粒产量及3 个产量构成因素均方差同质。2 年综合分析, 4 个灌水水平中以W2 中后期的总茎数最多, 而W3 的总茎数下降;干物质积累量也随灌溉次数增加而增大, 但不同时期不同灌水水平间干物质积累的差异显著性不同, 总的趋势是不灌水的W0处理最低,W3 处理最高;随着灌溉次数的增加, 产量及3 个产量构成因素的值均有所增加, 但各个参数增加的幅度不同。由于3 个产量构成因素相互作用, 总的看来, W2 产量最高, W0 最低。生育中后期的群体总茎数、干物质积累量、产量及各产量构成因素均随施钾量增加而增加。不同施钾量水平比较, 仅K0 与K1 的穗粒数差异不显著, 而3 个施钾量水平之间的其他产量构成因素及籽粒产量都是两两之间差异显著。由此可见, 增施钾肥可以全面改善小麦的群体物质生产和产量构成因素, 从而提高产量。综合本研究结果, 在保证底墒基础上全生育期灌拔节期和抽穗开花期2 次水, 在氮磷配合适宜条件下施用K2O 225 kg/hm2, 可以基本满足目前高产、超高产对水分和钾肥的需求, 实现高产节水的双重效果。
播期、密度和氮肥运筹对高产品种‘淮麦33’产量和品质的调控
DOI:10.11924/j.issn.1000-6850.casb18020039
[本文引用: 1]
为了明确高产小麦品种淮麦33优质、高产、高效栽培的群体调控和氮肥管理策略，以淮麦33为材料，研究了播期、密度、施氮水平和基追比对其籽粒产量和品质的影响。结果表明，播期和密度对淮麦33的籽粒产量均有显著影响。5个播期中，10月11日播种的籽粒产量最高，10月1日、10月21日亦可以取得较高产量，10月31日播种产量明显下降，11月10日播种产量下降最多。密度为225万?hm-2时产量最高。蛋白质含量也随着密度的增加和播期的推迟呈上升趋势。同时，增加氮肥用量和后期施肥比例不仅可以提高淮麦33产量，亦可以增加蛋白质含量、湿面筋含量和沉淀值。综合分析，在本试验条件下，10月11日播种、225万?hm-2基本苗、施氮量300 kg?hm-2，氮肥运筹5:3:2时淮麦33产量最高，品质最好。
Auxin-cytokinin interaction regulates meristem development
Exogenous gibberellins induce wheat spike development under short days only in the presence of VERNALIZATION11[C][W][OPEN]
Plant Physiology,
Interplay between sugar and hormone signaling pathways modulate floral signal transduction
DOI:10.3389/fgene.2014.00218
PMID:25165468
[本文引用: 1]
NOMENCLATURE The following nomenclature will be used in this article: Names of genes are written in italicized upper-case letters, e.g., ABI4. Names of proteins are written in non-italicized upper-case letters, e.g., ABI4. Names of mutants are written in italicized lower-case letters, e.g., abi4. The juvenile-to-adult and vegetative-to-reproductive phase transitions are major determinants of plant reproductive success and adaptation to the local environment. Understanding the intricate molecular genetic and physiological machinery by which environment regulates juvenility and floral signal transduction has significant scientific and economic implications. Sugars are recognized as important regulatory molecules that regulate cellular activity at multiple levels, from transcription and translation to protein stability and activity. Molecular genetic and physiological approaches have demonstrated different aspects of carbohydrate involvement and its interactions with other signal transduction pathways in regulation of the juvenile-to-adult and vegetative-to-reproductive phase transitions. Sugars regulate juvenility and floral signal transduction through their function as energy sources, osmotic regulators and signaling molecules. Interestingly, sugar signaling has been shown to involve extensive connections with phytohormone signaling. This includes interactions with phytohormones that are also important for the orchestration of developmental phase transitions, including gibberellins, abscisic acid, ethylene, and brassinosteroids. This article highlights the potential roles of sugar-hormone interactions in regulation of floral signal transduction, with particular emphasis on Arabidopsis thaliana mutant phenotypes, and suggests possible directions for future research.
Auxin: regulation, action, and interaction
DOI:10.1093/aob/mci083
PMID:15749753
[本文引用: 1]
The phytohormone auxin is critical for plant growth and orchestrates many developmental processes.This review considers the complex array of mechanisms plants use to control auxin levels, the movement of auxin through the plant, the emerging view of auxin-signalling mechanisms, and several interactions between auxin and other phytohormones. Though many natural and synthetic compounds exhibit auxin-like activity in bioassays, indole-3-acetic acid (IAA) is recognized as the key auxin in most plants. IAA is synthesized both from tryptophan (Trp) using Trp-dependent pathways and from an indolic Trp precursor via Trp-independent pathways; none of these pathways is fully elucidated. Plants can also obtain IAA by beta-oxidation of indole-3-butyric acid (IBA), a second endogenous auxin, or by hydrolysing IAA conjugates, in which IAA is linked to amino acids, sugars or peptides. To permanently inactivate IAA, plants can employ conjugation and direct oxidation. Consistent with its definition as a hormone, IAA can be transported the length of the plant from the shoot to the root; this transport is necessary for normal development, and more localized transport is needed for tropic responses. Auxin signalling is mediated, at least in large part, by an SCFTIR1 E3 ubiquitin ligase complex that accelerates Aux/IAA repressor degradation in response to IAA, thereby altering gene expression. Two classes of auxin-induced genes encode negatively acting products (the Aux/IAA transcriptional repressors and GH3 family of IAA conjugating enzymes), suggesting that timely termination of the auxin signal is crucial. Auxin interaction with other hormone signals adds further challenges to understanding auxin response.Nearly six decades after the structural elucidation of IAA, many aspects of auxin metabolism, transport and signalling are well established; however, more than a few fundamental questions and innumerable details remain unresolved.
Comparison of dynamic changes of endogenous plant hormones and hormone-related gene expression between near isogenic lines with normal spike and branched spike wheat
Plant hormones and seed germination
Exogenous 6-benzyladenine improved the ear differentiation of waterlogged summer maize by regulating the metabolism of hormone and sugar
Early growth of the developing ear of spring barley
小麦穗粒数的调节:Ⅱ开花前遮光对穗碳水化合物代谢和内源激素水平的影响
DOI:10.3321/j.issn:1000-7091.1997.04.009
[本文引用: 1]
在小麦开花前16～8d和开花前8d至开花期进行遮光处理（遮光率70%～80%）分别使穗粒数减少了37%和23%.在处理期间，遮光穗的还原糖（葡萄糖+果糖）和果聚糖浓度显着低于对照穗，而蔗糖浓度与对照差异较小。遮光处理降低了穗中蔗糖-蔗糖果糖基转移酶（SST）和可溶性酸性转化酶（AI）的活性。分析穗器官吲哚乙酸（IAA）、玉米素/玉米素核苷（Z/ZR）和脱落酸（ABA）含量表明，遮光处理对穗中IAA和Z/ZR水平没有明显影响，但显着提高了穗中ABA水平。这些结果暗示，遮光限制了同化物供给，也限制了穗库对同化物的转化和利用；穗库活性的下降可能与ABA水平的上升有关。
The maize SBP-box transcription factor encoded by tasselsheath4 regulates bract development and the establishment of meristem boundaries
Molecular characterization and expression analysis of Triticum aestivum squamosa-promoter binding protein-box genes involved in ear development
DOI:10.1111/jipb.12153
[本文引用: 1]
<p>Wheat (<em>Triticum aestivum</em> L.) is one of the most important crops in the world. Squamosa-promoter binding protein (SBP)-box genes play a critical role in regulating flower and fruit development. In this study, 10 novel SBP-box genes (<em>TaSPL</em> genes) were isolated from wheat ((<em>Triticum aestivum</em> L.) cultivar Yanzhan 4110). Phylogenetic analysis classified the <em>TaSPL</em> genes into five groups (G1–G5). The motif combinations and expression patterns of the <em>TaSPL</em> genes varied among the five groups with each having own distinctive characteristics: <em>TaSPL20/21</em> in G1 and <em>TaSPL17</em> in G2 mainly expressed in the shoot apical meristem and the young ear, and their expression levels responded to development of the ear; <em>TaSPL6/15</em> belonging to G3 were upregulated and <em>TaSPL1/23</em> in G4 were downregulated during grain development; the gene in G5 (<em>TaSPL3</em>) expressed constitutively. Thus, the consistency of the phylogenetic analysis, motif compositions, and expression patterns of the <em>TaSPL</em> genes revealed specific gene structures and functions. On the other hand, the diverse gene structures and different expression patterns suggested that wheat SBP-box genes have a wide range of functions. The results also suggest a potential role for wheat SBP-box genes in ear development. This study provides a significant beginning of functional analysis of SBP-box genes in wheat.</p><p> </p><p>Zhang B, Liu X, Zhao G, Mao X, Li A, Jing R (2014) Molecular characterization and expression analysis of <em>Triticum aestivum</em> squamosa‐promoter binding protein‐box genes involved in ear development. <strong>J Integr Plant Biol </strong>56: 571–581. doi: 10.1111/jipb.12153</p>
小麦转录因子基因TaPHR1参与调控每穗小穗数
DOI:10.3724/SP.J.1006.2023.31008
[本文引用: 1]
利用水分高效基因资源创制新型小麦品种是应对气候变化和人口高速增长的有效途径。MYB (v-myb avian myeloblastosis viral oncogene homolog)是植物中最大的转录因子家族之一, 参与调控植物生长发育, 生物和非生物胁迫。本研究在TaPHR1-4A和TaPHR1-4B中分别鉴定出19个和15个SNP, 基于这些多态性位点开发了分子标记。关联分析表明, Hap-4B-I是小穗数多的优异单倍型。通过创制两个回交导入系群体, 进一步证实Hap-4B-I有利于改善小麦穗部性状。TaPHR1的转录表达分析发现Hap-4B-I单倍型幼穗中TaPHR1的表达水平均高于Hap-4B-II单倍型。此外, TaPHR1在水稻中的异源表达导致穗分支变多, 也证实TaPHR1参与调控每穗小穗数。小麦育成品种的时空分布分析发现尽管Hap-4B-II在我国现代育成品种中占比最多, 但随小麦育种时间的推进, Hap-4B-I的占比在逐渐增多。总之, TaPHR1是小麦每穗小穗数的正调节因子。因此, 本研究开发的分子标记可作为小麦标记辅助选择和遗传改良的重要来源。
Analysis on photosynthetic productive ability of the green organs for winter wheat by the daily net total photosynthesis
Interaction between drought and chronic high temperature during kernel filling in wheat in a controlled environment
DOI:10.1093/aob/mcf219
PMID:12324270
[本文引用: 1]
Wheat plants (Triticum aestivum L. 'Lyallpur'), limited to a single culm, were grown at day/night temperatures of either 18/13 degrees C (moderate temperature), or 27/22 degrees C (chronic high temperature) from the time of anthesis. Plants were either non-droughted or subjected to two post-anthesis water stresses by withholding water from plants grown in different volumes of potting mix. In selected plants the demand for assimilates by the ear was reduced by removal of all but the five central spikelets. In non-droughted plants, it was confirmed that shading following anthesis (source limitation) reduced kernel dry weight at maturity, with a compensating increase in the dry weight of the remaining kernels when the total number of kernels was reduced (small sink). Reducing kernel number did not alter the effect of high temperature following anthesis on the dry weight of the remaining kernels at maturity, but reducing the number of kernels did result in a greater dry weight of the remaining kernels of droughted plants. However, the relationship between the response to drought and kernel number was confounded by a reduction in the extent of water stress associated with kernel removal. Data on the effect of water stress on kernel dry weight at maturity of plants with either the full complement or reduced numbers of kernels, and subjected to low and high temperatures following anthesis, indicate that the effect of drought on kernel dry weight may be reduced, in both absolute and relative terms, rather than enhanced, at high temperature. It is suggested that where high temperature and drought occur concurrently after anthesis there may be a degree of drought escape associated with chronic high temperature due to the reduction in the duration of kernel filling, even though the rate of water use may be enhanced by high temperature.
Impaired sucrose-induction mutants reveal the modulation of sugar-induced starch biosynthetic gene expression by abscisic acid signaling
DOI:10.1046/j.1365-313x.2001.2641043.x
PMID:11439129
[本文引用: 1]
Plants both produce and utilize carbohydrates and have developed mechanisms to regulate their sugar status and co-ordinate carbohydrate partitioning. High sugar levels result in a feedback inhibition of photosynthesis and an induction of storage processes. We used a genetic approach to isolate components of the signalling pathway regulating the induction of starch biosynthesis. The regulatory sequences of the sugar inducible ADP-glucose pyrophosphorylase subunit ApL3 were fused to a negative selection marker. Of the four impaired sucrose induction (isi) mutants described here, two (isi1 and isi2) were specific to this screen. The other two mutants (isi3 and isi4) showed additional phenotypes associated with sugar-sensing screens that select for seedling establishment on high-sugar media. The isi3 and isi4 mutants were found to be involved in the abscisic acid signalling pathway. isi3 is allelic to abscisic acid insensitive4 (abi4), a gene encoding an Apetala2-type transcription factor; isi4 was found to be allelic to glucose insensitive1 (gin1) previously reported to reveal cross-talk between ethylene and glucose signalling. Here we present an alternative interpretation of gin1 as an allele of the ABA-deficient mutant aba2. Expression analysis showed that ABA is unable to induce ApL3 gene expression by itself, but greatly enhances ApL3 induction by sugar. Our data suggest a major role for ABA in relation to sugar-signalling pathways, in that it enhances the ability of tissues to respond to subsequent sugar signals.
The pattern of grain growth within the ear of wheat
The supply of photosynthetic assimilates to the grain from the flag leaf and ear of wheat
冬麦春播小麦发育进程中主茎叶片内源激素的变化
DOI:10.11869/j.issn.100-8551.2016.02.0355
[本文引用: 1]
为探讨冬麦春播小麦内源激素在其生育进程中的动态变化规律,以长江中下游地区冬播小麦品种扬麦13、渝麦10为材料,在忻定盆地春播条件下,研究在早播(Ⅰ:3月7日)和适播(Ⅱ:3月14日)2个处理下,不同生育时期小麦主茎叶片内源激素赤霉素(GA)、吲哚乙酸(IAA)、 玉米素核苷(ZR)和脱落酸(ABA)含量变化及其对籽粒产量的影响。结果表明,内源激素在小麦生育进程中呈现不同动态变化,其中拔节期、开花期是内源激素调节的关键时期。多元相关分析、通径分析等表明,冬麦春播条件下,扬麦13、渝麦10在拔节期(GA和ABA)、开花期(ZR和GA)激素与产量的偏相关系数最高,分别为0.88~0.91、0.995~0.997,即GA水平与产量关系较为密切。品种间内源激素含量的差异大于播期间差异,其中扬麦13(Ⅰ)的GA含量较稳定,其拔节期ABA含量明显低于其它处理,且GA/ABA、IAA/ABA、ZR/ABA和(GA+IAA+ZR)/ABA值均为品种间最高;此外,扬麦13的籽粒产量、成穗数及穗粒数均显著高于渝麦10和宁2038(CK),在早播处理下扬麦13的增产幅度较大。本研究为冬麦春播小麦生长发育及产量形成受内源激素调控提供了理论参考。
Rice yield potential is closely related to crop growth rate during late reproductive period
Achieving yield gains in wheat
Aberrant meiotic modulation partially contributes to the lower germination rate of pollen grains in maize (Zea mays L.) under low nitrogen supply
