,1, 张慧1, 单晶1, 薛艳芳1, 钱欣1, 代红翠2, 刘开昌,2, 李宗新,1Effects of Pre-Silking High Temperature Stress on Yield and Ear Development Characteristics of Different Heat-Resistant Summer Maize Cultivars
GAO YingBo,1, ZHANG Hui1, SHAN Jing1, XUE YanFang1, QIAN Xin1, DAI HongCui2, LIU KaiChang,2, LI ZongXin,1通讯作者:
责任编辑: 杨鑫浩
收稿日期:2020-05-12接受日期:2020-08-24网络出版日期:2020-10-01
| 基金资助: |
Received:2020-05-12Accepted:2020-08-24Online:2020-10-01
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高英波,E-mail：
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高英波, 张慧, 单晶, 薛艳芳, 钱欣, 代红翠, 刘开昌, 李宗新. 吐丝前高温胁迫对不同耐热型夏玉米产量及穗发育特征的影响[J]. 中国农业科学, 2020, 53(19): 3954-3963 doi:10.3864/j.issn.0578-1752.2020.19.009
GAO YingBo, ZHANG Hui, SHAN Jing, XUE YanFang, QIAN Xin, DAI HongCui, LIU KaiChang, LI ZongXin.
0 引言
【研究意义】玉米作为我国第一大粮食作物,对保障国家粮食安全至关重要。近年来,极端高温天气的频发对玉米产量造成了显著的负面影响[1],尽管玉米为喜温作物,但日最高温超过32℃时,玉米产量会显著降低[2],全球平均温度每升高1℃将造成玉米减产7.4%[3]。据估计,到21世纪末,全球表面平均温度变化有可能超过1.5℃,甚至会超过2℃[4],未来玉米生产遭受高温危害的现象将会日趋加重。玉米雌雄穗的发育对产量形成起着关键性作用,研究穗期高温逆境对玉米穗发育及产量形成的影响,对选用适宜品种实现夏玉米高产稳产具有重要指导意义。【前人研究进展】黄淮海夏播玉米区是我国优势玉米种植区之一,在夏玉米生长季内极易遭遇高温热害天气[5]。玉米穗期（拔节—抽雄期）阶段最适温度为24℃—26℃,开花期前后遭遇高温逆境通常会使玉米植株发育进程加快,雌雄穗发育不协调,中、后期分化能力严重降低,易导致雄穗变短、分枝数量和小花数减少,有效花粉数量降低[6,7],散粉时间缩短[8,9],雌穗变细变短,养分不能正常运输形成香蕉穗现象[10,11]。严重时还会导致花药开裂[12,13]、花粉形态结构及表面超微结构改变、花粉花丝活力降低、开花吐丝期间隔拉长[14]、授粉结实能力降低[15,16],严重影响玉米的高产稳产。高温逆境亦会引起玉米叶片光合物质生产能力下降[17,18]、营养器官早衰,同时伴随着呼吸消耗增加,导致净同化物减少[19]、同化物供应不足[20],穗粒数和粒重降低,进而导致玉米的产量降低[21]。【本研究切入点】尽管前人就高温胁迫对玉米生长发育及籽粒建成进行了较多研究,但多数将关注点聚焦于开花吐丝期高温对受精结实及籽粒建成的影响等方面[14,15,16],关于开花期以前高温逆境对雌雄穗发育进程的影响研究相对较少且不系统。已有相关报道大多是在使用聚乙烯薄膜加热的田间简易设施[7,17-18]进行的,难以精确控制温度,受外界环境影响较大,难以准确评估高温逆境对玉米生长发育的影响。【拟解决的关键问题】本研究在人工智能温室控温条件下,系统研究吐丝前高温胁迫对不同耐热型玉米雌雄穗发育特征的影响,从产量形成、雌雄穗生长发育进程、微观形态结构特征角度揭示不同耐热型玉米对高温逆境的响应及品种间差异性,为耐高温玉米品种选育及耐高温栽培技术提供理论依据。1 材料与方法
1.1 试验材料与设计
试验在山东省农业科学院玉米研究所章丘龙山试验基地（117°32′E,36°43′N）人工智能气候温室进行,试验基地位于华北平原冬小麦、夏玉米一年两熟种植区,该区年均降雨量为693.4 mm,年均气温为13.6℃,年均日照时数2 558.3 h,无霜期209.0 d,土壤为棕壤土。人工气候温室采用超白钢化玻璃,内置补光灯,循环风机,保证光照与外界光照无显著差异,CO2浓度基本与室外保持一致。在前期试验[7]及相关研究基础上[17-18,22],选用花粒期耐热型玉米品种郑单958（ZD958）和热敏感型玉米品种联创808（LC808：2017年和2018年在山东淄博等地花期遭遇高温热害,出现较大面积减产或绝收）为供试材料,采用盆栽试验法,盆内径40 cm,高45 cm,侧壁有通气管,也可用于补水。取大田0—20 cm表土,风干过筛,每盆装土+基质共计20 kg。每个品种每个处理各80盆,每盆播种3—4粒,播种深度为3—4 cm,于两叶一心定苗,每盆留苗2株,4叶展期定苗至1株。于第9片叶展开时,选取长势一致的植株,移入人工智能气候温室进行高温处理,直至吐丝期,每天9：00—18：00进行40/30℃（最高温度/最低温度）高温处理,以相对应时间段35/25℃（最高温度/最低温度）处理为对照,处理结束后移出温室于自然条件下生长。高温处理期间平均温度、相对湿度,CO2浓度日变化详见图1,统计分析表明温室内相对湿度和CO2浓度变化趋势无显著差异。试验于2019年6月17日播种,7月23日进行高温胁迫处理,8月18日处理结束,共计25 d。图1
新窗口打开|下载原图ZIP|生成PPT图1高温胁迫期间平均温度、相对湿度和CO2浓度日变化趋势
Fig. 1Diurnal variation of average temperature, relative humidity and CO2 concentration changes on one day during the high temperature stress
1.2 测定项目及分析方法
1.2.1 环境指标测定 高温处理期间,每间温室内温湿度记录仪和CO2采集器自动记录温室温度、相对湿度和CO2浓度日变化。1.2.2 玉米雌雄穗发育进程及形态结构观察 于9叶期开始,每4 d选取2株长势一致的植株,称取雄穗干重,在吐丝期调查雄穗分枝数;观察雌穗（叶腋处最上面雌穗）发育形态变化,轻轻剥去包围在雌穗外部的苞叶,测量穗长,吐丝期称取雌穗干重。
1.2.3 雄丝间隔（ASI）的记录 抽雄前,选取各处理生长均匀一致的10株玉米植株进行标记,每天记录各株的抽雄、吐丝和散粉的时间,单株吐丝的时间与散粉的时间间隔即开花吐丝间隔期,10株的平均值即该处理的开花吐丝间隔期。
1.2.4 花粉花丝超微结构观察 各处理均取散粉后3 d的新鲜花粉和吐丝后3 d的新鲜花丝,用0.1 mol·L-1磷酸缓冲液洗3次,2.5 %戊二醛固定液预固定2 h,磷酸缓冲液冲洗多余的戊二醛,1 %锇酸固定,清洗3次,30%-40%-50%-70%-80%-90%-100%乙醇梯度脱水,样品移入无水乙醇后再转入醋酸戊酯中,放置15 min,取出样品放入临界点干燥仪（Quorum-K850）中干燥,干燥后将样本紧贴于导电碳膜双面胶上放入离子溅射仪（Hitachi-MC1000）样品台上进行喷金30 s左右,在电子扫描显微镜（Hitachi-SU8100）下观察花粉及花丝的超微结构[14]。
1.2.5 光合特性测定 高温胁迫处理结束前,采用美国产LI-6400型便携式光合作用测定系统在上午9：00—11：00之间测定夏玉米穗位叶净光合速率（Pn）、气孔导度（Gs）、胞间二氧化碳浓度（Ci）和蒸腾速率（Tr）。
1.2.6 测产及考种 籽粒成熟期进行测产取样,考察果穗长、秃尖长、穗粗、穗行数、行粒数,并称量千粒重,同时测定籽粒含水率,计算单株籽粒产量（按14%安全含水量进行折算）。
1.3 数据处理与分析
采用Microsoft Excel 2016录入与整理数据,软件SAS 9.0进行方差分析,软件Sigma Plot 12.0作图。2 结果
2.1 吐丝前高温胁迫对籽粒产量及穗部性状的影响
由表1可见,吐丝前高温胁迫显著降低了夏玉米单株籽粒产量、穗长、行粒数和穗粒数,秃尖长显著增加,穗粒数降低主要是行粒数减少引起,ZD958的产量、穗粒数和粒重下降幅度高于LC808。与35/25℃相比,40/30℃处理下ZD958和LC808产量分别降低44.98%和40.88%,千粒重分别降低24.04%和17.47%,穗粒数分别降低29.85%和27.80%,穗长分别降低15.63%和25.93%,秃尖长分别增加93.00%和67.76%,行粒数分别降低22.21%和24.59%。LC808的产量在35/25℃和40/30℃处理下分别比ZD958高12.28%和20.65%,千粒重分别高6.04%和15.21%,穗粒数分别高7.40%和4.35%。方差分析表明,夏玉米籽粒产量、千粒重、穗长、秃尖长和行粒数在品种和高温处理之间差异均达到显著或极显著水平,品种及高温胁迫交互作用不显著。Table 1
表1
表1吐丝前高温胁迫对夏玉米产量、产量构成及穗部性状的影响
Table 1
| 品种 Variety | 处理 Treatment | 籽粒产量 Grain yield (g/plant) | 千粒重 1000-kernel weight (g) | 穗粒数 Grains per ear | 穗长 Ear length (cm) | 秃顶长 Barren tip length (cm) | 穗行数 Rows of ear | 行粒数 Grains per row |
|---|---|---|---|---|---|---|---|---|
| LC808 | 35/25℃ | 80.53a | 245.18a | 319.33a | 16.00a | 1.83b | 13.33a | 24.00a |
| 40/30℃ | 47.61b | 202.34b | 224.00b | 13.50b | 3.07a | 12.00a | 18.67b | |
| ZD958 | 35/25℃ | 71.72a | 231.21a | 297.33a | 14.00a | 1.00b | 14.67a | 20.33a |
| 40/30℃ | 39.46b | 175.62b | 214.67b | 10.37b | 1.93a | 14.00a | 15.33b | |
| 品种 Variety (V) | ** | ** | ns | *** | ** | ** | *** | |
| 高温High temperature (T) | *** | *** | *** | *** | ** | ns | *** | |
| 品种×高温V×T | ns | ns | ns | ns | ns | ns | ns | |
新窗口打开|下载CSV
2.2 吐丝前高温胁迫对雌雄穗干重、雌穗长度和雄穗分枝的影响
随着高温处理时间增长,40/30℃处理下2个品种玉米雄穗干重相比35/25℃处理降低趋势显著,ZD958雄穗干重降低幅度高于LC808（图2）。与35/25℃相比,40/30℃处理下ZD958的雄穗干重分别降低33.33%（5 d）、32.79%（10 d）、22.42%（15 d）、29.16%（20 d）和39.42%（25 d）;LC808的雄穗干重分别降低13.48%（5 d）、16.61%（10 d）、8.32%（15 d）、13.37%（20 d）和15.60%（25 d）。高温胁迫结束后（25 d）,40/30℃处理下,ZD958雄穗分枝数比35/25℃处理显著降低40.43%,LC808雄穗分枝数比35/25℃处理降低14.29%,但无显著差异。图2
新窗口打开|下载原图ZIP|生成PPT图2吐丝前高温胁迫对夏玉米穗发育的影响
柱上不同小写字母表示同一品种在不同处理下差异显著（P<0.05）。下同
Fig. 2Effects of pre-silking high temperature stress on ear development of summer maize
Different small letters above the bars represent significant differences of the same variety among different treatments (P<0.05). The same as below
高温胁迫导致夏玉米雌穗长度和雌穗干重降低。与35/25℃处理相比,40/30℃处理下ZD958的雌穗长度分别降低70.21%（10 d）、24.44%（15 d）、23.25%（20 d）和19.77%（25 d）;LC808的雌穗长度分别降低36.54%（10 d）、4.94%（15 d）、9.80%（20 d）和11.67%（25 d）。高温胁迫结束后（25 d）,40/30℃处理下,ZD958和LC808雌穗干重分别比35/25℃处理显著降低22.50%和15.56%。
2.3 吐丝前高温胁迫对开花吐丝间隔期（ASI）的影响
高温胁迫延长了玉米雌雄穗的生长发育,抽雄吐丝期延迟,开花吐丝间隔期（ASI）延长（表2）。与35/25℃处理相比,40/30℃处理下ZD958的抽雄和吐丝时间分别延迟2 d和5 d,LC808的抽雄时间无变化,吐丝时间延迟2 d。35/25℃处理下ZD958和LC808的ASI均为4 d,40/30℃处理下ZD958和LC808的ASI分别为7 d和6 d,40/30℃处理下ZD958和LC808的ASI分别比35/25℃处理增加3 d和2 d,高温胁迫对ZD958抽雄吐丝影响高于LC808。Table 2
表2
表2吐丝前高温胁迫对夏玉米开花吐丝间隔期（ASI）的影响
Table 2
| 品种Variety | 处理Treatment | 抽雄日期Tassel(M-D) | 吐丝日期Silking (M-D) | 雄丝间隔ASI (d) |
|---|---|---|---|---|
| ZD958 | 35-25℃ | 8-10 | 8-14 | 4 |
| 40-30℃ | 8-12 | 8-19 | 7 | |
| LC808 | 35-25℃ | 8-12 | 8-16 | 4 |
| 40-30℃ | 8-12 | 8-18 | 6 |
新窗口打开|下载CSV
2.4 吐丝前高温胁迫花粉、花丝微观形态结构的影响
35/25℃处理下,ZD958（图3-a,3-b）和LC808（图3-c,3-d）花粉粒表面光滑,略有褶皱,萌发孔突出;玉米花丝毛较多,大部分花丝毛均立于花丝表面（图3-I,3-k）,花丝表面轻微褶皱（图3-j,3-l）。40/30℃处理下,2个玉米品种花粉粒表面均出现干缩褶皱,形态受损、萌发孔内陷,ZD958（图3-e,3-f）花粉粒形态受损程度明显重于LC808（图3-g,3-h）;玉米花丝毛数明显降低,存在的花丝毛几乎全部倒伏于花丝表面上（图3-m,3-o）,玉米花丝表面褶皱,横向收缩剧烈（图3-n,3-p）,易导致花丝接受花粉的表面积减少,造成授粉障碍。图3
新窗口打开|下载原图ZIP|生成PPT图3高温胁迫对夏玉米花粉花丝微观形态结构的影响
花期35/25℃和40/30℃处理的花粉、花丝的电子显微镜扫描图像。a、c分别表示35/25℃处理下ZD958和LC808单个花粉粒扫描图像,e、g分别表示40/30℃处理下ZD958和LC808单个花粉粒扫描图像,标尺=50 μm;b、d分别表示35/25℃处理下ZD958和LC808花粉萌发孔扫描图像,f、h分别表示40/30℃处理下ZD958和LC808花粉萌发孔扫描图像,标尺=10 μm;i、k分别表示35/25℃处理下ZD958和LC808花丝扫描图像,m、o分别表示40/30℃处理下ZD958和LC808花丝扫描图像,标尺=500 μm;j、l分别表示35/25℃处理下ZD958和LC808花丝表面扫描图像,n、p分别表示40/30℃处理下ZD958和LC808花丝表面扫描图像,标尺=100 μm
Fig. 3Effects of pre-silking high temperature stress on ultrastructure of pollen and filament of summer maize
Scanning electron microscope images of pollen grains and silks under 35/25℃ and 40/30℃ treatments. a and c represent the single pollen grains of ZD958 and LC808 at 35/25℃treatment, e and g represent the single pollen grains of ZD958 and LC808 at 40/30℃ treatment, respectively (scale bar = 50 μm). b and d represent the germinal aperture of ZD958 and LC808 at 35/25℃ treatment, f and h represent the germinal aperture of ZD958 and LC808 at 40/30℃treatment, respectively (scale bar = 10 μm). i and k represent the filament of ZD958 and LC808 at 35/25℃ treatment, m and o represent the filament of ZD958 and LC808 at 40/30℃ treatment, respectively (scale bar = 500 μm). j and l represent the filaments surface of ZD958 and LC808 at 35/25℃ treatment, n and p represent the filaments surface of ZD958 and LC808 at 40/30℃ treatment, respectively (scale bar = 100 μm)
2.5 吐丝前高温胁迫对夏玉米穗位叶光合特性的影响
由图4可见,高温胁迫处理下玉米叶片净光合速率、气孔导度、蒸腾速率显著降低,胞间CO2浓度显著增加。与35/25℃相比,40/30℃处理下ZD958和LC808穗位叶净光合速率分别降低48.70%和56.48%,气孔导度分别降低35.99%和43.22%,蒸腾速率分别下降27.17%和32.24%,胞间二氧化碳浓度分别增加111.70%和224.11%。在同一温度处理下,2个品种玉米叶片净光合速率、气孔导度、蒸腾速率和胞间CO2浓度无显著差异。图4
新窗口打开|下载原图ZIP|生成PPT图4高温胁迫对夏玉米吐丝期穗位叶光合特性的影响
Fig. 4Effects of high temperature stress on photosynthetic characteristics of summer maize ear leaves during silking stage
3 讨论
玉米产量的高低与单位面积穗数、穗粒数和粒重密切相关,三者之间的相互协调是获得高产的基础。高温作为导致玉米减产最主要的非生物胁迫因子之一,几乎在玉米的整个生育时期都有发生,均会对玉米生长发育造成不同程度的影响,最终影响产量形成[21, 23]。前人研究表明,高温胁迫会导致玉米果穗变短,粒重和穗粒数降低[21,24],玉米吐丝开花期高温胁迫下玉米籽粒产量降低主要是由穗粒数减少所致[14,17],籽粒建成期高温胁迫则会使穗粒数和粒重均显著降低[25]。本研究结果表明,9叶展至开花吐丝期高温胁迫下2个夏玉米品种的穗长、行粒数、穗粒数、千粒重和籽粒产量显著降低,秃尖长显著增加,穗粒数降低主要是行粒数的减少引起,产量降低则是穗粒数和粒重共同作用的结果。玉米产量实质上是通过光合作用直接或间接形成的,并取决于光合产物的积累与分配[26,27,28],穗期阶段是玉米营养器官生长与生殖器官分化发育同时并进阶段,地上器官干物质积累始终以叶、茎为主[29],该阶段遭遇逆境胁迫会导致干物质向茎和叶片中的分配比例增加,向穗中的转运积累减少[30,31]。本研究表明,高温胁迫会导致玉米穗位叶净光合速率、气孔导度、蒸腾速率显著降低,胞间CO2浓度显著增加。穗期高温逆境使玉米功能叶片光合能力降低,导致同化物供应不足,以上是否是雌穗变短、小花退化和花粉粒发育不健全、穗粒数降低的主要因素?有待于进一步深入研究。雌雄穗的发育对玉米产量的形成起着关键性作用。拔节至开花期是玉米营养生长与生殖生长并进阶段,是决定穗数、穗的大小、可孕小花数的关键阶段,该阶段遭遇高温逆境会导致雄穗发育持续时间缩短,雌雄穗分化能力降低,雄穗分枝减少,雌穗变短变细,结实性差[7,8,9]。本试验条件下,高温胁迫处理的2个品种玉米雄穗干重、雌穗干重和雌穗长度均显著降低,ZD958雄穗分枝数显著降低,LC808雄穗分枝数有所降低但不显著。高温胁迫严重时不仅会影响玉米雄穗的外部形态结构及发育进程,还会引起花粉花药发育异常[32]、花药开裂[13],花粉形态结构及表面超微结构改变,花粉功能部分丧失[14];相比花丝,花粉对高温胁迫更敏感[9]。本研究表明,高温胁迫处理下2个玉米品种花粉粒表面均出现干缩褶皱,形态受损、萌发孔内陷;玉米花丝表面褶皱,横向收缩剧烈,玉米花丝毛数明显降低,存在的花丝毛几乎全部倒伏于花丝表面,ZD958花粉花丝形态受损程度明显重于LC808。玉米的成功受精结实需要雄穗散粉和雌穗吐丝的同步,高温胁迫不仅可以单独影响玉米雌、雄穗的生长,同时也会影响二者之间的协调生长[33]。雄丝间隔（ASI）是玉米对逆境胁迫反应较为敏感的一个指标,也是逆境胁迫条件下限制玉米产量的主要因素之一[34,35]。本研究表明,第9片叶展开期至吐丝期高温胁迫对夏玉米抽雄时间影响较小,主要延缓夏玉米的雌穗发育,进而拉长了雄丝间隔（ASI）,高温胁迫对ZD958抽雄吐丝影响重于LC808。
玉米是异花授粉作物,雄穗分枝较多能够提供更多的花粉进而提高受精率,但雄穗分枝越多对同化物消耗就越多,与雌穗生长产生竞争[36],尤其在逆境条件下更不利于雌穗生长发育。为减少雄穗对同化物的消耗,近年来培育的玉米品种雄穗分枝越来越少[37]。前人研究表明,玉米对高温胁迫的响应存在显著基因型差异[17-18,23],且大多数研究中筛选或采用的耐热型品种（郑单958,浚单20,等）都表现出雄穗分枝较多[7,17-18]的特点,这可能与这些研究中高温胁迫时期集中在开花吐丝期,雄穗分枝多,花粉量大[6,14],能够弥补高温逆境产生的不利影响有关,开花吐丝期易发生高温逆境区域可选用同类品种。本试验条件下,第9片叶展开期至吐丝期郑单958高温胁迫下表现出更弱的耐高温能力,表明同一品种在不同生育阶段对高温胁迫的耐受性不同,吐丝前高温主要影响了玉米的光合物质生产能力、雌雄穗分化能力及二者之间的协调生长,使玉米雄穗分枝减少、果穗变短、秃尖变长、行粒数减少、雄丝间隔（ASI）拉长,进而导致玉米产量降低;而相关研究表明花粒期高温主要通过影响玉米雄穗小花受精率、结实率[38]、光合物质生产能力和籽粒灌浆持续期[20,25,34]影响产量。生产中应选用在高温胁迫下穗分化能力和根系活力强、叶片光合速率高、抗氧化能力和授粉结实能力强的玉米品种[39],并结合区域高温逆境易发生阶段选择适宜品种。
4 结论
第9片叶展开期至吐丝期高温胁迫对夏玉米籽粒产量、雌雄穗发育进程和花粉花丝微观形态结构有显著影响,该阶段高温胁迫对郑单958雌雄穗发育及产量的影响均高于联创808。高温胁迫下夏玉米光合性能降低、穗粒数和粒重显著下降,进而导致籽粒产量降低。高温胁迫下玉米雌雄穗的分化能力下降、雌穗的发育推迟,雄丝间隔（ASI）拉长、花粉花丝结构发生改变是导致玉米雌穗变短和玉米穗粒数降低的主要原因。同一品种在不同生育阶段对高温胁迫的耐受性不同,生产中应根据种植区域高温热害易发生阶段来选择玉米品种。参考文献 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子
DOI:10.1111/pbr.2014.133.issue-6URL [本文引用: 1]
DOI:10.1111/gcb.12069URLPMID:23504849 [本文引用: 1]
Improved crop yield forecasts could enable more effective adaptation to climate variability and change. Here, we explore how to combine historical observations of crop yields and weather with climate model simulations to produce crop yield projections for decision relevant timescales. Firstly, the effects on historical crop yields of improved technology, precipitation and daily maximum temperatures are modelled empirically, accounting for a nonlinear technology trend and interactions between temperature and precipitation, and applied specifically for a case study of maize in France. The relative importance of precipitation variability for maize yields in France has decreased significantly since the 1960s, likely due to increased irrigation. In addition, heat stress is found to be as important for yield as precipitation since around 2000. A significant reduction in maize yield is found for each day with a maximum temperature above 32 degrees C, in broad agreement with previous estimates. The recent increase in such hot days has likely contributed to the observed yield stagnation. Furthermore, a general method for producing near-term crop yield projections, based on climate model simulations, is developed and utilized. We use projections of future daily maximum temperatures to assess the likely change in yields due to variations in climate. Importantly, we calibrate the climate model projections using observed data to ensure both reliable temperature mean and daily variability characteristics, and demonstrate that these methods work using retrospective predictions. We conclude that, to offset the projected increased daily maximum temperatures over France, improved technology will need to increase base level yields by 12% to be confident about maintaining current levels of yield for the period 2016-2035; the current rate of yield technology increase is not sufficient to meet this target.
DOI:10.1073/pnas.1701762114URLPMID:28811375 [本文引用: 1]
Wheat, rice, maize, and soybean provide two-thirds of human caloric intake. Assessing the impact of global temperature increase on production of these crops is therefore critical to maintaining global food supply, but different studies have yielded different results. Here, we investigated the impacts of temperature on yields of the four crops by compiling extensive published results from four analytical methods: global grid-based and local point-based models, statistical regressions, and field-warming experiments. Results from the different methods consistently showed negative temperature impacts on crop yield at the global scale, generally underpinned by similar impacts at country and site scales. Without CO2 fertilization, effective adaptation, and genetic improvement, each degree-Celsius increase in global mean temperature would, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%. Results are highly heterogeneous across crops and geographical areas, with some positive impact estimates. Multimethod analyses improved the confidence in assessments of future climate impacts on global major crops and suggest crop- and region-specific adaptation strategies to ensure food security for an increasing world population.
DOI:10.1016/j.techfore.2014.12.002URL [本文引用: 1]
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DOI:10.1016/j.wace.2015.08.001URL [本文引用: 2]
DOI:10.1016/j.fcr.2017.11.013URL [本文引用: 3]
DOI:10.1016/S0176-1617(88)80019-1URL [本文引用: 1]
DOI:10.1016/j.fcr.2016.09.024URL [本文引用: 1]
DOI:10.1046/j.1365-3040.2001.00716.xURL [本文引用: 1]
DOI:10.1016/j.envexpbot.2010.08.009URL [本文引用: 2]
In future climates, rice could more frequently be subjected to simultaneous high temperature and water stress during sensitive developmental stages such as flowering. In this study, five rice genotypes were exposed to high temperature, water stress and combined high temperature and water stress during flowering to quantify their response through spikelet fertility. Microscopic analyses revealed significant differences in anther dehiscence between treatments and genotypes, with a moderately high association with the number of germinated pollen grains on the stigma. There was a strong relationship between spikelet fertility and the number of germinated pollen on stigmas. Although, all three stress treatments resulted in spikelet sterility, high-temperature stress caused the highest sterility in all five genotypes. A cumulative linear decline in spikelet fertility with increasing duration of independent high-temperature stress and in combination with water stress was quantified. Better anther dehiscence, higher in vivo pollen germination, and higher spikelet fertility were observed in both the N22 accessions compared with IR64, Apo and Moroberekan under high temperature, water stress and combined stress, indicating its ability to tolerate multiple abiotic stresses. (C) 2010 Elsevier B.V.
DOI:10.1016/j.envexpbot.2018.11.007URL [本文引用: 6]
[本文引用: 2]
DOI:10.1016/j.fcr.2014.06.018URL [本文引用: 2]
Several studies have indicated that maize (Zea mays L.) kernel weight is severely affected by heat stress, but this response was never evaluated under field conditions. Our objective was to assess the effect of brief episodes of above-optimum temperatures on the dynamics of biomass and water accumulation in kernels of maize hybrids with contrasting tolerance to heat stress. Heat effect on assimilate supply from the plant (i.e., current biomass production and water-soluble carbohydrates in stem) to developing grains was also analyzed. Field experiments included a factorial combination of (i) three hybrids (Te: temperate; Tr: tropical; TeTr: Te x Tr), (ii) two temperature regimes, control and heated during daytime hours (ca. 33-40 degrees C at ear level), and (ii) three 15-d periods (GS1: immediately before anthesis; GS2: from silking onwards; GS3: early phase of active grain filling). Heat effects on final kernel weight were larger (i) when they occurred during the first half of effective grain filling (-23.1% for GS3) than around flowering (-4.8% for GS1, -6.3% for GS2), and (ii) for the Te hybrid (-20.4%) than for the TeTr (-8.6%) and the Tr (-6.8%) hybrids. Heating around flowering (i) enhanced the assimilate availability per kernel during the effective grain-filling period, (ii) increased carbohydrates reserves in stem at physiological maturity, (iii) and had no significant effect on the dynamics of biomass and water accumulation in kernels. The opposite trend was detected among plots heated during GS3, which mostly exhibited the interruption of grain filling. Robust associations were established between (i) carbohydrate reserves in stem at physiological maturity and assimilate availability per kernel during effective grain filling (r(2) = 0.49; P < 0.001), and (ii) the rate of water loss from kernels and the duration of effective grain filling (r(2) = 0.71; P < 0.001). These responses underlay the enhanced sensitivity to heat stress of the hybrid with full temperate genetic background. (C) 2014 Elsevier B.V.
DOI:10.3864/j.issn.0578-1752.2012.23.023URL [本文引用: 6]
【Objective】The objective of this study was to identify exogenous spermidine on photosynthesis and chlorophyll fluorescence under high temperature treatments during flowering (0–8 d before silking and 0–8 d after silking).【Method】The heat-tolerant maize genotype XD20 and heat-sensitive maize genotype ZY309 were used in this study. Photosynthetic parameters, chlorophyll fluorescence variation, the activities of ribulose-l,5-bi-sphosphate carboxylase (PEPCase) and phosphoenolpyrovate carboxylase (RuBPCase) were investigated during flowering.【Result】The results showed that the heat-sensitive genotype got a significant reduction in grain yield with a more reduction rate under the treatment after flowering than before flowering. It was less affected for heat-tolerant genotype. SPAD, net photosynthetic rate (Pn), stomatal conductance (Gs), primarily photochemical efficiency (Fv/Fm), actual photochemical efficiency (?PSII), photochemical quenching (qP), PEPCase and RuBPCase activities of ear-leaves were reduced. But intercellular CO2 concentration (Ci), non-photochemical quenching (qN) were increased.【Conclusion】The results showed that there were significant effects of high temperature treatments during flowering on photosynthetic characteristics of summer maize, and the yield were significantly decreased. The heat-tolerant maize genotype has more photosynthesizing capacity and chlorophyll content than the heat-sensitive maize genotype.
DOI:10.3864/j.issn.0578-1752.2012.23.023URL [本文引用: 6]
【Objective】The objective of this study was to identify exogenous spermidine on photosynthesis and chlorophyll fluorescence under high temperature treatments during flowering (0–8 d before silking and 0–8 d after silking).【Method】The heat-tolerant maize genotype XD20 and heat-sensitive maize genotype ZY309 were used in this study. Photosynthetic parameters, chlorophyll fluorescence variation, the activities of ribulose-l,5-bi-sphosphate carboxylase (PEPCase) and phosphoenolpyrovate carboxylase (RuBPCase) were investigated during flowering.【Result】The results showed that the heat-sensitive genotype got a significant reduction in grain yield with a more reduction rate under the treatment after flowering than before flowering. It was less affected for heat-tolerant genotype. SPAD, net photosynthetic rate (Pn), stomatal conductance (Gs), primarily photochemical efficiency (Fv/Fm), actual photochemical efficiency (?PSII), photochemical quenching (qP), PEPCase and RuBPCase activities of ear-leaves were reduced. But intercellular CO2 concentration (Ci), non-photochemical quenching (qN) were increased.【Conclusion】The results showed that there were significant effects of high temperature treatments during flowering on photosynthetic characteristics of summer maize, and the yield were significantly decreased. The heat-tolerant maize genotype has more photosynthesizing capacity and chlorophyll content than the heat-sensitive maize genotype.
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DOI:10.1016/j.fcr.2015.10.009URL [本文引用: 1]
DOI:10.1016/S2095-3119(16)61409-0URL [本文引用: 2]
DOI:10.1016/j.fcr.2012.11.009URL [本文引用: 3]
Temperate and tropical maize differ in their tolerance to heat stress but the ecophysiological bases for genotypic differences are poorly understood. Our objectives were (i) to assess the sources of kernel loss, and (ii) to identify the main differences in these traits among genotypes of contrasting genetic background. We used the classic relationships that associate final kernel number per plant (KNP) with plant (PGR(CP)) and ear (EGR(CP)) growth rates during the critical period for kernel set and developed an alternative approach based on the combined analysis of these relationships for assessing sources of kernel loss in field conditions. We identified three sources of loss associated with (i) PGR(CP) reductions (Delta KNR1), (ii) changes in biomass partitioning to the ear (Delta KNP2), and (iii) constraints not directly related to assimilate allocation to the ear (Delta NP3). A partitioning index was also established (PI = EGR(CP) PGR(CP)(-1)). Field experiments included three contrasting maize hybrids (Te: temperate; Tr: tropical; TeTr: Te x Tr) grown under two temperature regimes (control and heated) during daytime hours. We tested heating (ca. 33-40 degrees C at ear level) along two 15-d periods (GS(1): pre-anthesis; GS(2): from silking onwards). Final KNP was severely reduced by heating, and this negative effect was larger (i) when it occurred during silking (-75% for GS(2)) than before anthesis (-52% for GS(1)), and (ii) for the Te hybrid (-77%) than the TeTr (-69%) and the Tr (-44%) hybrids. The contribution of each source of loss to the decrease in KNP was 47% for Delta KNP1, 27% for Delta KNP2, and 32% for Delta KNP3. Variations in Delta KNP2 were explained by changes in PI (r(2) =0.85, P < 0.001), and a critical PI value (0.25) for avoiding kernel loss due to Delta KNP2 was established. A similar pattern among genotypes was found for the response of KNP to variations in both PGRcp and EGRcp, but the new approach indicated that enhanced tolerance of the tropical genotype was mainly associated with reduced KNP3. (C) 2012 Elsevier B.V.
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DOI:10.1016/j.fcr.2007.11.005URL [本文引用: 2]
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DOI:10.3864/j.issn.0578-1752.2017.11.013URL [本文引用: 2]
【Objective】Clarifying the influence of heat stress durations at grain formation stage on grain yield and starch quality of waxy maize, which could afford a theoretical basis for waxy maize starch quality improvement.【Method】The pot trials were conducted at Yangzhou University in 2014 and 2015. After artificial pollination, heat stress treatments (35℃) were introduced by intelligent greenhouse and the heat stress durations were 1-5 d, 1-10 d, and 1-15 d after pollinations (DAP), respectively. The grain yield, grain protein and starch content, starch physicochemical parameters (starch granule size and distribution, chain-length distribution, crystallinity, pasting and thermal properties) were analyzed using Suyunuo 5 and Yunuo 7 as materials.【Result】Heat stress at grain formation stage reduced grain number and weight, which induced yield loss and the loss at 1-5, 1-10 and 1-15 DAP was 39.3%, 47.4%, 50.9%, respectively. Heat stress increased protein content and decreased starch content in grains, respectively. High temperature increased the starch average granule size and the granule size gradually decreased with the prolongation of heat stress durations. The starch maximum absorption wavelength, crystalline structure and setback viscosity present typical waxy character. Heat stress at grain formation stage increased the proportion of long-chains in amylopectin, and the values were the highest and the lowest at 1-10 DAP heat stress conditions for Suyunuo 5 and Yunuo 7, respectively, among different treatments. Relative crystallinity in response to heat stress durations was different between two varieties and two planting years. Generally, 10 d heat stress did not affect the pasting characteristics, while the peak, trough, breakdown, and final viscosities and pasting temperature were increased by 1-5 and 1-15 DAP heat stress and the increase of peak, trough and breakdown viscosities were the highest in 1-15 DAP heat stress. Compared with control, heat stress decreased gelatinization enthalpy and increased the other thermal characteristics. The gelatinization enthalpy was the lowest in 1-15 DAP heat stress, gelatinization temperatures were the highest in 1-5 DAP heat stress, and retrogradation percentage were similar among different heat stress durations.【Conclusion】Heat stress at grain formation reduced the grain yield and the reduction was gradually severe with the prolongation of heat stress durations. High temperature suppressed grain starch accumulation and increased the protein content. Starch pasting and thermal properties were changed as the starch granule size enlarged and proportion of long-chains in amylopectin increased. Among different heat stress durations, the peak and breakdown viscosities were the highest and setback viscosity was the lowest when high temperature was introduced at 1-15 DAP. The gelatinization temperatures were the highest under 1-5 DAP heat stress conditions and no difference was observed for retrogradation percentage among three heat stress treatments.
DOI:10.3864/j.issn.0578-1752.2017.11.013URL [本文引用: 2]
【Objective】Clarifying the influence of heat stress durations at grain formation stage on grain yield and starch quality of waxy maize, which could afford a theoretical basis for waxy maize starch quality improvement.【Method】The pot trials were conducted at Yangzhou University in 2014 and 2015. After artificial pollination, heat stress treatments (35℃) were introduced by intelligent greenhouse and the heat stress durations were 1-5 d, 1-10 d, and 1-15 d after pollinations (DAP), respectively. The grain yield, grain protein and starch content, starch physicochemical parameters (starch granule size and distribution, chain-length distribution, crystallinity, pasting and thermal properties) were analyzed using Suyunuo 5 and Yunuo 7 as materials.【Result】Heat stress at grain formation stage reduced grain number and weight, which induced yield loss and the loss at 1-5, 1-10 and 1-15 DAP was 39.3%, 47.4%, 50.9%, respectively. Heat stress increased protein content and decreased starch content in grains, respectively. High temperature increased the starch average granule size and the granule size gradually decreased with the prolongation of heat stress durations. The starch maximum absorption wavelength, crystalline structure and setback viscosity present typical waxy character. Heat stress at grain formation stage increased the proportion of long-chains in amylopectin, and the values were the highest and the lowest at 1-10 DAP heat stress conditions for Suyunuo 5 and Yunuo 7, respectively, among different treatments. Relative crystallinity in response to heat stress durations was different between two varieties and two planting years. Generally, 10 d heat stress did not affect the pasting characteristics, while the peak, trough, breakdown, and final viscosities and pasting temperature were increased by 1-5 and 1-15 DAP heat stress and the increase of peak, trough and breakdown viscosities were the highest in 1-15 DAP heat stress. Compared with control, heat stress decreased gelatinization enthalpy and increased the other thermal characteristics. The gelatinization enthalpy was the lowest in 1-15 DAP heat stress, gelatinization temperatures were the highest in 1-5 DAP heat stress, and retrogradation percentage were similar among different heat stress durations.【Conclusion】Heat stress at grain formation reduced the grain yield and the reduction was gradually severe with the prolongation of heat stress durations. High temperature suppressed grain starch accumulation and increased the protein content. Starch pasting and thermal properties were changed as the starch granule size enlarged and proportion of long-chains in amylopectin increased. Among different heat stress durations, the peak and breakdown viscosities were the highest and setback viscosity was the lowest when high temperature was introduced at 1-15 DAP. The gelatinization temperatures were the highest under 1-5 DAP heat stress conditions and no difference was observed for retrogradation percentage among three heat stress treatments.
DOI:10.1016/j.jenvman.2017.10.035URLPMID:29149723 [本文引用: 1]
Soil cadmium (Cd) contamination and drought stress are among the main issues hindering global food security. Biochar has been used to reduce metal uptake by plants and water stress mitigation, but long-term residual effects of biochar under Cd stress at different moisture levels needs to be investigated. A following rice (Oryza sativa L.) was grown after wheat on Cd-contaminated soil amended with different levels of biochar (0, 3.0, and 5.0%, w/w). Thirty five days old plants were irrigated with three moisture levels including zero drought as a control (1-2 cm water layer on soil), mild drought (MD, 50% of soil water holding capacity, WHC), and severe drought (SD, 35% of soil WHC) for an accompanying 35 days. Plant height, biomass and photosynthesis were reduced whereas oxidative stress increased under MD and SD than control in un-amended soil while opposite trends were observed in plants grown in biochar amended soil. At the same biochar addition, Cd concentrations in seedlings were lower in continuous flooding than MD and SD treatments. The biochar supply reduced the bioavailable Cd in the soil whereas increased the soil EC and pH than the control treatment. In conclusion, continuous flooding plus residual biochar can be strategized in mitigating Cd-contamination in paddy soils and decreased Cd concentrations in rice which may reduce the potential risks to humans.
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DOI:10.3389/fpls.2018.00709URLPMID:29896208 [本文引用: 1]
ZmNF-YB16 is a basic NF-YB superfamily member and a member of a transcription factor complex composed of NF-YA, NF-YB, and NF-YC in maize. ZmNF-YB16 was transformed into the inbred maize line B104 to produce homozygous overexpression lines. ZmNF-YB16 overexpression improves dehydration and drought stress resistance in maize plants during vegetative and reproductive stages by maintaining higher photosynthesis and increases the maize grain yield under normal and drought stress conditions. Based on the examination of differentially expressed genes between the wild-type (WT) and transgenic lines by quantitative real time PCR (qRT-PCR), ZmNF-YB16 overexpression increased the expression of genes encoding antioxidant enzymes, the antioxidant synthase, and molecular chaperones associated with the endoplasmic reticulum (ER) stress response, and improved protection mechanism for photosynthesis system II. Plants that overexpression ZmNF-YB16 showed a higher rate of photosynthesis and antioxidant enzyme activity, better membrane stability and lower electrolyte leakage under control and drought stress conditions. These results suggested that ZmNF-YB16 played an important role in drought resistance in maize by regulating the expression of a number of genes involved in photosynthesis, the cellular antioxidant capacity and the ER stress response.
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DOI:10.3390/w10111561URL [本文引用: 1]
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DOI:10.3390/plants2030489URLPMID:27137389 [本文引用: 1]
Sexual reproduction in flowering plants is very sensitive to environmental stresses, particularly to thermal insults which frequently occur when plants grow in field conditions in the warm season. Although abnormalities in both male and female reproductive organs due to high temperatures have been described in several crops, the failure to set fruits has mainly been attributed to the high sensitivity of developing anthers and pollen grains, particularly at certain developmental stages. A global view of the molecular mechanisms involved in the response to high temperatures in the male reproductive organs will be presented in this review. In addition, transcriptome and proteomic data, currently available, will be discussed in the light of physiological and metabolic changes occurring during anther and pollen development. A deep understanding of the molecular mechanisms involved in the stress response to high temperatures in flowers and, particularly, in the male reproductive organs will be a major step towards development of effective breeding strategies for high and stable production in crop plants.
DOI:10.1016/j.fcr.2007.03.013URL [本文引用: 1]
DOI:10.1016/j.fcr.2011.04.015URL [本文引用: 2]
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DOI:10.1038/s41588-020-0616-3URLPMID:32341525 [本文引用: 1]
Since the development of single-hybrid maize breeding programs in the first half of the twentieth century(1), maize yields have increased over sevenfold, and much of that increase can be attributed to tolerance of increased planting density(2-4). To explore the genomic basis underlying the dramatic yield increase in maize, we conducted a comprehensive analysis of the genomic and phenotypic changes associated with modern maize breeding through chronological sampling of 350 elite inbred lines representing multiple eras of germplasm from both China and the United States. We document several convergent phenotypic changes in both countries. Using genome-wide association and selection scan methods, we identify 160 loci underlying adaptive agronomic phenotypes and more than 1,800 genomic regions representing the targets of selection during modern breeding. This work demonstrates the use of the breeding-era approach for identifying breeding signatures and lays the foundation for future genomics-enabled maize breeding.
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DOI:10.3724/SP.J.1006.2012.00857URL [本文引用: 1]
Lodging is one of the most important factors restricting the wide extension of dry-cultivated rice (DCR). The objective of the study was to investigate the reasons for lodging in DCR using Shanyou 63 (indica hybrid combination) and 9516 (japonica) as materials. The results showed that the lodging percentage in DCR was significantly higher than that in conventional moist-cultivated rice (MCR), leading to significant decrease in seed-setting percentage and grain weight, and grain yield in DCR. The mechanical strength (thickness and weight per centimeter) and carbohydrate (especially starch) content in basal internodes from heading to maturity were much lower in DCR than in MCR, while α-amylase activity in basal internodes was higher in DCR than in MCR. The starch content was very significantly and positively correlated with thickness and weight per centimeter of basal internodes, and significantly or very significantly and negatively correlated with α-amylase activity in basal internodes. The starch exportation was significantly or very significantly and positively correlated with α-amylase activity. The application of silicon and potassium fertilizers could decrease α-amylase activity and increase the starch content in basal internodes, enhance the mechanical strength of basal internodes, decrease the lodging percentage, and increase seed-setting percentage and grain weight, result in the increase of grain yield in DCR. The results were reversed when 1/2 leaves were cut at booting stage. The results above indicated that the higher α-amylase activity in basal internodes in DCR caused more starch degradation, decreasing the mechanical strength of basal internodes, and resulting in the lodging in DCR.
DOI:10.3724/SP.J.1006.2012.00857URL [本文引用: 1]
Lodging is one of the most important factors restricting the wide extension of dry-cultivated rice (DCR). The objective of the study was to investigate the reasons for lodging in DCR using Shanyou 63 (indica hybrid combination) and 9516 (japonica) as materials. The results showed that the lodging percentage in DCR was significantly higher than that in conventional moist-cultivated rice (MCR), leading to significant decrease in seed-setting percentage and grain weight, and grain yield in DCR. The mechanical strength (thickness and weight per centimeter) and carbohydrate (especially starch) content in basal internodes from heading to maturity were much lower in DCR than in MCR, while α-amylase activity in basal internodes was higher in DCR than in MCR. The starch content was very significantly and positively correlated with thickness and weight per centimeter of basal internodes, and significantly or very significantly and negatively correlated with α-amylase activity in basal internodes. The starch exportation was significantly or very significantly and positively correlated with α-amylase activity. The application of silicon and potassium fertilizers could decrease α-amylase activity and increase the starch content in basal internodes, enhance the mechanical strength of basal internodes, decrease the lodging percentage, and increase seed-setting percentage and grain weight, result in the increase of grain yield in DCR. The results were reversed when 1/2 leaves were cut at booting stage. The results above indicated that the higher α-amylase activity in basal internodes in DCR caused more starch degradation, decreasing the mechanical strength of basal internodes, and resulting in the lodging in DCR.
