干旱高温及高浓度CO2复合胁迫对冬小麦生长的影响

研究了不同CO₂浓度、不同温度和水分条件及其组合对冬小麦产量、光合及水分的影响,以阐明气候变化对冬小麦的影响.结果表明: CO₂浓度升高对冬小麦光合速率没有影响,而升温和干旱均使光合速率显著下降.升高CO₂浓度与温度对冬小麦旗叶水分条件没有影响,干旱胁迫下旗叶相对含水量显著降低,而升温与干旱同时发生可降低旗叶水势.气温、CO₂浓度升高以及干旱胁迫共同作用下,冬小麦光合速率和旗叶水分条件显著降低,产量下降41.4%.CO₂浓度升高使冬小麦增产21.2%,温度升高使产量降低12.3%,CO₂浓度和温度同时升高对产量没有影响,干旱胁迫下产量下降程度更大.未来气候变化情景下,保持较高的土壤水分含量是减少气候变暖危害的重要手段.
     

干旱高温及高浓度CO2复合胁迫对冬小麦生长的影响

研究了不同CO₂浓度、不同温度和水分条件及其组合对冬小麦产量、光合及水分的影响,以阐明气候变化对冬小麦的影响.结果表明: CO₂浓度升高对冬小麦光合速率没有影响,而升温和干旱均使光合速率显著下降.升高CO₂浓度与温度对冬小麦旗叶水分条件没有影响,干旱胁迫下旗叶相对含水量显著降低,而升温与干旱同时发生可降低旗叶水势.气温、CO₂浓度升高以及干旱胁迫共同作用下,冬小麦光合速率和旗叶水分条件显著降低,产量下降41.4%.CO₂浓度升高使冬小麦增产21.2%,温度升高使产量降低12.3%,CO₂浓度和温度同时升高对产量没有影响,干旱胁迫下产量下降程度更大.未来气候变化情景下,保持较高的土壤水分含量是减少气候变暖危害的重要手段.
     

Testing the responses of four wheat crop models to heat stress at anthesis and grain filling

Higher temperatures caused by future climate change will bring more frequent heat stress events and pose an increasing risk to global wheat production. Crop models have been widely used to simulate future crop productivity but are rarely tested with observed heat stress experimental datasets. Four wheat models (DSSAT‐CERES‐Wheat, DSSAT‐Nwheat, APSIM‐Wheat, and WheatGrow) were evaluated with 4 years of environment‐controlled phytotron experimental datasets with two wheat cultivars under heat stress at anthesis and grain filling stages. Heat stress at anthesis reduced observed grain numbers per unit area and individual grain size, while heat stress during grain filling mainly decreased the size of the individual grains. The observed impact of heat stress on grain filling duration, total aboveground biomass, grain yield, and grain protein concentration (GPC) varied depending on cultivar and accumulated heat stress. For every unit increase of heat degree days (HDD, degree days over 30 °C), grain filling duration was reduced by 0.30–0.60%, total aboveground biomass was reduced by 0.37–0.43%, and grain yield was reduced by 1.0–1.6%, but GPC was increased by 0.50% for cv Yangmai16 and 0.80% for cv Xumai30. The tested crop simulation models could reproduce some of the observed reductions in grain filling duration, final total aboveground biomass, and grain yield, as well as the observed increase in GPC due to heat stress. Most of the crop models tended to reproduce heat stress impacts better during grain filling than at anthesis. Some of the tested models require improvements in the response to heat stress during grain filling, but all models need improvements in simulating heat stress effects on grain set during anthesis. The observed significant genetic variability in the response of wheat to heat stress needs to be considered through cultivar parameters in future simulation studies.     

Fertilization regulates the response of wheat yield to interannual temperature variation in North China

Aims Understanding the effect of long-term fertilization on the sensitivity of grain yield to temperature changes is critical for accurately assessing the impact of global warming on crop production. In this study, we aim to assess the impacts of temperature changes on grain yields of winter wheat (Triticum aestivum L.) under different fertilization treatments in a long-term manipulative experiment in North China.Methods We measured grain yields of winter wheat under four fertilization treatments at the Yucheng Comprehensive Experimental Station each year from 1993 to 2012. We also measured air temperature at 0200, 0800, 1400 and 2000h each day since 1 January 1980. We then used the first-difference method and simple linear regression models to examine the relationship of crop yield changes to mean air temperature, mean daytime and nighttime air temperature in crop growing seasons.Important findings We found that increases in mean daily temperature, mean daytime temperature and mean nighttime temperature each had a positive impact on the grain yield of winter wheat. Grain yield increased by 16.7–85.6% for winter wheat in response to a 1°C increase in growing season mean daily temperature. Winter wheat yield was more sensitive to variations of nighttime temperature than to that of daytime temperature. The observed temperature impacts also varied across different fertilization treatments. Balanced fertilization significantly enhanced grain yields for winter wheat under a warming climate. Wheat plots treated with nitrogen and phosphorous balanced fertilization (NPK- and NP-treated plots) were more responsive to temperature changes than those without. This report provides direct evidence of how temperature change impacts grain yields under different fertilization treatments, which is useful for crop management in a changing global climate.     

未来10年黄土高原气候变化对农业和生态环境的影响

利用区域气候模式PRECIS输出的未来A2和B2气候情景及基准气候时段逐日资料,选择生态环境极其脆弱的黄土高原为研究区,分析了未来10a黄土高原气候变化特征及其对主要农作物和生态环境的影响。结果表明,未来10a,黄土高原光热资源增加,降水量减少。增温将对冬小麦和春玉米产量影响较大,对马铃薯产量的影响程度可能较小,但降水量减少对主要农作物的产量都有较大影响。在主要作物品种不发生较大变化的前提下,作物生育期太阳辐射和积温增加可能导致生育期需水量增加10%-15%,冬小麦、春玉米和马铃薯的播期分别延迟或提前1-3d,收获期提前1-2d,生育期缩短3-5d,可能引起冬小麦和春玉米气候产量下降50%-100%。未来10a,降水量减少可能导致草地盖度的增幅下降和人工林地稀疏化,引起黄土高原片状水力侵蚀程度下降。但突发性暴雨洪水和土地利用现状改变可能增强切沟溯源冲蚀能力,增加了黄土高原水土流失和农田及道路被冲毁的风险。     

豆科作物-小麦轮作方式下旱地小麦花后干物质及养分累积、转移与产量的关系

研究旱作条件下豆科绿肥轮作影响旱地小麦产量变化的作物营养生态机制,对优化旱地作物种植施肥制度,促进水分资源高效利用、土壤培肥、作物增产有重要意义。通过两年定位试验,分析了与不同豆科作物轮作引起的后茬小麦产量变化及其与干物质、氮磷钾养分累积、转移的关系。结果表明:与秋豆轮作的第一季,小麦籽粒产量无显著变化,但第二季小麦产量提高23.4%;与绿豆轮作,两季产量分别降低19.2%和4.4%;与大豆轮作,产量无显著变化。与秋豆轮作增加了小麦花后干物质及氮、磷养分累积,和对照相比分别增加了35.1%,128.8%和14.0%,而与大豆和绿豆轮作花后干物质累积分别降低26.7%和17.0%,花后氮累积分别降低44.2%和24.4%,花后磷累积与对照相比无显著差异。与此对应,秋豆-小麦轮作,其后茬小麦花后干物质及养分累积对产量形成的贡献显著增加,茎叶花前累积氮、磷向籽粒的转移对产量的贡献明显小于大豆-小麦和绿豆-小麦轮作处理。与氮、磷不同,小麦茎叶花前累积钾素向籽粒转移的同时,花后植株钾素没有累积,反而明显损失,其中与秋豆轮作的小麦花后植株钾素损失量较小,为3.8 kg/hm2,籽粒钾素占转移钾的81.0%;休闲或与大豆、绿豆轮作的小麦花后植株钾素损失较多,分别为10.9,12.6和5.5kg/hm2,籽粒钾素占转移钾的52.9%,52.9%和66.8%。与秋豆-小麦轮作处理小麦增产的主要原因是花后植株能累积更多干物质和氮、磷养分,减少了花前累积于茎叶的钾素在花后的损失。     

Yield vs. Quality trade‐offs for wheat in response to carbon dioxide and ozone

Although it is established that there exist potential trade‐offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO₂) and ozone (O₃), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO₂ and O₃, we analysed 57 experiments with CO₂ or O₃ exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O₃ was associated with a change in grain protein yield of 8.1% (R² = 0.96), whereas a change in yield effect of 10% by CO₂ was linked to a change in grain protein yield effect of 7.5% (R² = 0.74). Superimposed on this effect, elevated CO₂, but not O₃, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO₂ restricts grain protein accumulation, which is absent for O₃. Grain mass, another quality trait, was more strongly affected by O₃ than grain number, whereas the opposite was true for CO₂. Harvest index was strongly and negatively influenced by O₃, but was unaffected by CO₂. We conclude that yield vs. protein trade‐offs for wheat in response to CO₂ and O₃ are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO₂ has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO₂‐induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade‐offs are very different in wheat exposed to elevated O₃ compared with elevated CO₂.     

玻璃温室与田间栽培小麦幼穗分化的比较

以河南省大面积种植的弱春性品种"郑麦9023"及半冬性品种"周麦18"为材料,开展了玻璃温室和田间栽培条件下小麦幼穗分化进程的比较研究。结果表明,在小麦全生育期,玻璃温室内平均温度高于田间环境,小麦幼穗分化所需时间极显著低于田间环境(P < 0.01)。温度和0 ℃以上积温升高,小麦幼穗分化进程加快。与田间种植小麦相比,玻璃温室内小麦幼穗分化缩短的时期主要集中在分化前期(出苗-伸长期、单棱期、二棱期)。玻璃温室内小麦幼穗分化持续时间和总积温均随播期推迟而降低,幼穗分化各阶段出现时间亦随播期的推迟而后延。小麦幼穗分化进程存在品种间差异,其中"郑麦9023"幼穗分化持续时间小于"周麦18",各阶段出现的时间亦早于"周麦18"。温度对幼穗分化各时期的影响存在品种间差异。温度升高对"郑麦9023"幼穗分化中期(二棱期、护颖分化期、小花分化期)影响较大,对"周麦18"幼穗分化前期和后期(单棱期、二棱期、药隔分化期)影响较大。积温对"郑麦9023"护颖分化期和"周麦18"药隔分化期、二棱期影响较大。     

黄土高原沟壑区粮食生产中的生态成本

以黄土高原沟壑区的陕西省长武县为研究对象,应用生态学和经济学方法,对粮食生产生态成本进行了初步研究.结果表明： 2008年该区粮食生产生态损失总价值相当于当年种植业总产值的7.2%;小麦和玉米生态成本已分别达到2.42和2.12元·kg^-1,而出售单价分别为1.70和1.28元·kg^-1,高成本低收益的情况对该区域生态经济可持续发展产生不利影响;利用灰色关联对粮食生产生态成本中各因素进行分析,单位产量、播种面积和农业机械费用是影响生态成本的重要因素,化肥费用和有机肥费用对其影响不大;在当前生产力水平下,适当加大科学技术投入水平,提高粮食产量,扩大家庭种植规模,可以降低生产单位粮食的生态成本.     

Nutrient deficiencies do not contribute to yield loss after waterlogging events in winter wheat (Triticum aestivum)

Frequent waterlogging increases the risk of possible harvest losses in winter wheat. The aim of this study was to analyse which developmental stage of wheat was impaired by waterlogging and whether yield losses can be explained by nutrient deficiences. A large‐scale container experiment was designed to evaluate growth, yield and nutrient status of two wheat cultivars after 14 days of waterlogging at two different developmental stages: DC 31 (first node visible) and DC 51 (beginning of ear emergence). Early waterlogging treatment impaired vegetative growth stages of winter wheat and nutrient uptake, leading to transient nutrient deficiencies, but yield was not significantly reduced. Late waterlogging at the beginning of ear emergence mainly affected generative growth stages and caused yield reductions ranging up to 61%. The main reason for yield loss was the significantly decreased thousand kernel weight in combination with a decreased number of grains per spike. Yield depressions in winter wheat depend on the timing of waterlogging. Early waterlogging transiently reduces vegetative growth through nutrient deficiencies, whereas late waterlogging results in an impaired grain development and associated therewith, yield losses.     

Satellite sun‐induced chlorophyll fluorescence detects early response of winter wheat to heat stress in the Indian Indo‐Gangetic Plains

Extremely high temperatures represent one of the most severe abiotic stresses limiting crop productivity. However, understanding crop responses to heat stress is still limited considering the increases in both the frequency and severity of heat wave events under climate change. This limited understanding is partly due to the lack of studies or tools for the timely and accurate monitoring of crop responses to extreme heat over broad spatial scales. In this work, we use novel spaceborne data of sun‐induced chlorophyll fluorescence (SIF), which is a new proxy for photosynthetic activity, along with traditional vegetation indices (Normalized Difference Vegetation Index NDVI and Enhanced Vegetation Index EVI) to investigate the impacts of heat stress on winter wheat in northwestern India, one of the world's major wheat production areas. In 2010, an abrupt rise in temperature that began in March adversely affected the productivity of wheat and caused yield losses of 6% compared to previous year. The yield predicted by satellite observations of SIF decreased by approximately 13.9%, compared to the 1.2% and 0.4% changes in NDVI and EVI, respectively. During early stage of this heat wave event in early March 2010, the SIF observations showed a significant reduction and earlier response, while NDVI and EVI showed no changes and could not capture the heat stress until late March. The spatial patterns of SIF anomalies closely tracked the temporal evolution of the heat stress over the study area. Furthermore, our results show that SIF can provide large‐scale, physiology‐related wheat stress response as indicated by the larger reduction in fluorescence yield (SIF_yield) than fraction of photosynthetically active radiation during the grain‐filling phase, which may have eventually led to the reduction in wheat yield in 2010. This study implies that satellite observations of SIF have great potential to detect heat stress conditions in wheat in a timely manner and assess their impacts on wheat yields at large scales.     

Australian wheat production expected to decrease by the late 21st century

Climate change threatens global wheat production and food security, including the wheat industry in Australia. Many studies have examined the impacts of changes in local climate on wheat yield per hectare, but there has been no assessment of changes in land area available for production due to changing climate. It is also unclear how total wheat production would change under future climate when autonomous adaptation options are adopted. We applied species distribution models to investigate future changes in areas climatically suitable for growing wheat in Australia. A crop model was used to assess wheat yield per hectare in these areas. Our results show that there is an overall tendency for a decrease in the areas suitable for growing wheat and a decline in the yield of the northeast Australian wheat belt. This results in reduced national wheat production although future climate change may benefit South Australia and Victoria. These projected outcomes infer that similar wheat‐growing regions of the globe might also experience decreases in wheat production. Some cropping adaptation measures increase wheat yield per hectare and provide significant mitigation of the negative effects of climate change on national wheat production by 2041–2060. However, any positive effects will be insufficient to prevent a likely decline in production under a high CO₂ emission scenario by 2081–2100 due to increasing losses in suitable wheat‐growing areas. Therefore, additional adaptation strategies along with investment in wheat production are needed to maintain Australian agricultural production and enhance global food security. This scenario analysis provides a foundation towards understanding changes in Australia's wheat cropping systems, which will assist in developing adaptation strategies to mitigate climate change impacts on global wheat production.     

气候变化对我国华北地区冬小麦发育和产量的影响

验证作物模型在我国华北冬小麦主产区是否适应的基础上,采用作物模型与气候模式相结合的研究方法,定量化地模拟预测了未来100年气候变化对华北冬小麦生产的影响.结果表明,从2000～2004年,华北地区冬小麦产量的模拟值与实测值的变化趋势基本一致,且生育期和产量变化不大.未来100年内华北地区冬小麦的生长期可能会有所缩短,平均缩短8.4 d;产量也会有不同程度的下降,平均减产10.1％.适当采取应对措施可以有效降低冬小麦的减产趋势.     

Effects of tillage systems on wheat and weed water relationships over time when growing together,in semiarid conditions

Water availability directly influences interactions and competition between weeds and crops. This article is based on the idea that relative water content (RWC) indicates the water uptake within plants and that it is possible to explain the water relationships between plants that are growing together. A field experiment carried out for 3 years (2013–2014, 2014–2015 and 2015–2016) compared the short-term effects of years and tillage systems on wheat grain yield, weed density, wheat-RWC, weed-RWC and soil water content (SWC), at tillering and flowering stages in a winter wheat monoculture system. The three tillage treatments were conventional tillage (CT), minimum tillage (MT) and no-tillage (NT). Wheat grain yield was low all years of study, because of low interannual rainfall, and we did not observe differences between tillage systems. Weed density was also affected by year and not by tillage systems. Lowest winter rainfall (73.4 mm from Nov to Feb) in the last year of the study (2015–2016), decreased the weed density in all tillage systems. Despite the rainfall variability over the 3 years of study, the NT system presented higher weed density (73 plants/m²) than MT and CT systems (39.83 and 46.33 plants/m²). We also observed a higher number of weed species for the NT system, facilitated by a high soil water storage in this system. The wheat-RWC, at tillering stage, varied with years and tillage systems; we found that high winter rainfall (2013–2014) led to higher values in CT (64.5%) compared with MT (52.9%) and NT plots (52.9%). Weed-RWC values did not vary and SWC was greater in NT than in CT and MT. At flowering stage, the year (2015–2016) with highest spring rainfall favoured higher wheat-RWC in NT (56.9%) compared with CT (48.3%). However, the lowest spring rainfall coincided with the lowest weed-RWC, (18% in NT plots) and SWC was always higher in NT soils. The results showed that climatic conditions affected the water competence dynamics between weeds and wheat in different ways. Seemingly, weeds can tolerate a lack of water availability until crop tillering stage independently of tillage system; however, the competition for water was not a problem as crops overcame the high weed density by flowering stage.     

中国北方气候暖干化对粮食作物的影响及应对措施

东北、华北和西北50a来的平均气温增幅高于全国平均水平,气候变暖明显,尤其冬季增温最显著。区域增暖的极端最低气温远比极端最高气温的贡献大。东北、华北大部、西北东部降水量明显减少,平均每10a减少20—40mm,尤其春夏季减少最明显。这种趋势一直延续到20世纪90年代以后,干旱化趋势非常突出。在综述我国北方现代气候变化基本特征是暖干化的基础上,重点阐述了喜凉作物冬小麦、春小麦、马铃薯和喜温作物水稻、玉米、谷子、糜子等7种主要粮食作物的生长发育、品种熟性、种植区域与面积、产量与品质等对气候暖干化的响应特征。揭示了气候暖干化使春播作物播期提早,苗期生长发育速度加快,营养生长期提前,生殖生长期和全生育期延长;秋作物发育期推迟,生殖生长期和全生长期延长;越冬作物播期推迟,越冬死亡率降低,种植风险减少,春初提前返青,生殖生长期提早,全生育期缩短。使作物适宜种植区域向高纬度高海拔扩展;品种熟性向偏中晚熟高产品种发展;喜温作物和越冬作物以及冷凉气候区的作物种植面积迅速扩大;在旱作区种植不较耐旱的玉米、春小麦等作物种植面积受到制约。对雨养农业区的作物气候产量影响严重,尤其对不够耐旱的小麦和玉米的气候产量受影响最大;对较耐旱的谷子、糜子、马铃薯等影响较轻。从作物属性而言,对喜温作物水稻、玉米和越冬作物冬小麦有利于气候产量提高;对喜凉作物春小麦和马铃薯的气候产量将产生不利影响。同时,提出了从5个方面应对气候暖干化的技术措施,调整作物种植结构,确保粮食生产安全;根据不同气候年型调整各种作物种植比例;针对不同气候区域发展优势作物和配置作物种植格局;采取不同栽培技术和管理模式应对气候变化;采取综合配套技术提髙抵御灾害能力。为粮食作物安全生产和种植结构调整与布局提供科学依据。     

耕作播种方式对稻茬小麦生长和养分吸收利用的影响

2016—2018年,在四川省广汉市分析了深旋耕播种(DRT)、浅旋耕播种(SRT)和免耕带旋播种(NT)3种耕播方式对稻茬小麦生长和养分吸收利用的影响。结果表明:与DRT相比,SRT和NT处理提高了小麦分蘖、成穗能力。2016—2017年,处理间产量无显著差异;2017—2018年,NT处理产量显著高于DRT,增幅10.9%。处理间干物质积累的差异主要在苗期。NT处理下植株对氮的吸收量高于DRT,平均增幅9.9%,而氮收获指数DRT高于NT;各处理植株磷吸收量差异不显著;NT处理对钾的吸收量显著高于DRT。与传统的深旋耕播种方式相比,免耕带旋播种技术是提高稻茬小麦产量和养分吸收的有效途径。     

Contributions of climatic and crop varietal changes to crop production in the North China Plain,since 1980s

The North China Plain (NCP) is the most important agricultural production area in China. Crop production in the NCP is sensitive to changes in both climate and management practices. While previous studies showed a negative impact of climatic change on crop yield since 1980s, the confounding effects of climatic and agronomic factors have not been separately investigated. This paper used 25 years of crop data from three locations (Nanyang, Zhengzhou and Luancheng) across the NCP, together with daily weather data and crop modeling, to analyse the contribution of changes in climatic and agronomic factors to changes in grain yields of wheat and maize. The results showed that the changes in climate were not uniform across the NCP and during different crop growth stages. Warming mainly occurred during the vegetative (preflowering) growth stage of wheat and maize, while there was a cooling trend or no significant change in temperatures during the postflowering stage of wheat (spring) or maize (autumn). If varietal effects were excluded, warming during vegetative stages would lead to a reduction in the length of the growing period for both crops, generally leading to a negative impact on crop production. However, autonomous adoption of new crop varieties in the NCP was able to compensate the negative impact of climatic change. For both wheat and maize, the varietal changes helped stabilize the length of preflowering period against the shortening effect of warming and, together with the slightly reduced temperature in the postflowering period, extend the length of the grain‐filling period. The combined effect led to increased wheat yield at Zhengzhou and Luancheng; increased maize yield at Nanyang and Luancheng; stabilized wheat yield at Nanyang, and a slight reduction in maize yield at Zhengzhou, compared with the yield change caused entirely by climatic change.     

刈割对冬小麦再生积温需求及其籽粒产量和品质的影响

对黄土高原塬区冬小麦‘陇育216’于分蘖期、拔节期及孕穗期进行刈割处理,以不刈割为对照,测定冬小麦再生生长发育的积温需求及籽粒产量及其品质,探究刈割利用时间对冬小麦再生生长积温需求及产量构成的影响。结果表明:(1)分蘖中期(6个分蘖)前刈割利用,小麦再生各阶段的有效积温需求较对照无显著差异,在收获小麦青干草0.9～1.5t/hm2的同时,能保证籽粒、秸秆产量及其品质较对照均无显著下降;分蘖期后期(9个分蘖)及其后刈割利用,拔节至开花及成熟期的有效积温需求显著减少,尽管较分蘖期可多收获60%的青干草,但籽粒、秸秆产量较对照均显著降低。(2)通径分析发现,刈割主要通过降低再生植株高度及减少单位面积穗数而导致冬小麦籽粒减产。研究表明,为维持冬小麦再生生长节律、籽粒产量及品质形成的稳定,冬小麦刈割利用的时期应不迟于分蘖中期(6个分蘖)。     

Response of wheat restricted‐tillering and vigorous growth traits to variables of climate change

The response of wheat to the variables of climate change includes elevated CO₂, high temperature, and drought which vary according to the levels of each variable and genotype. Independently, elevated CO₂, high temperature, and terminal drought affect wheat biomass and grain yield, but the interactive effects of these three variables are not well known. The aim of this study was to determine the effects of elevated CO₂ when combined with high temperature and terminal drought on the high‐yielding traits of restricted‐tillering and vigorous growth. It was hypothesized that elevated CO₂ alone, rather than combined with high temperature, ameliorates the effects of terminal drought on wheat biomass and grain yield. It was also hypothesized that wheat genotypes with more sink capacity (e.g. high‐tillering capacity and leaf area) have more grain yield under combined elevated CO₂, high temperature, and terminal drought. Two pairs of sister lines with contrasting tillering and vigorous growth were grown in poly‐tunnels in a four‐factor completely randomized split‐plot design with elevated CO₂ (700 µL L^?1), high day time temperature (3 °C above ambient), and drought (induced from anthesis) in all combinations to test whether elevated CO₂ ameliorates the effects of high temperature and terminal drought on biomass accumulation and grain yield. For biomass and grain yield, only main effects for climate change variables were significant. Elevated CO₂ significantly increased grain yield by 24–35% in all four lines and terminal drought significantly reduced grain yield by 16–17% in all four lines, while high temperature (3 °C above the ambient) had no significant effect. A trade‐off between yield components limited grain yield in lines with greater sink capacity (free‐tillering lines). This response suggests that any positive response to predicted changes in climate will not overcome the limitations imposed by the trade‐off in yield components.     

Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment

Spring wheat ( Triticum aestivum L. cv. TRISO) was grown for three consecutive seasons in a free-air carbon dioxide (CO₂) enrichment (FACE) field experiment in order to examine the effects on crop yield and grain quality. CO₂ enrichment promoted aboveground biomass (+11.8%) and grain yield (+10.4%). However, adverse effects were predominantly observed on wholegrain quality characteristics. Although the thousand-grain weight remained unchanged, size distribution was significantly shifted towards smaller grains, which may directly relate to lower market value. Total grain protein concentration decreased significantly by 7.4% under elevated CO₂, and protein and amino acid composition were altered. Corresponding to the decline in grain protein concentration, CO₂ enrichment resulted in an overall decrease in amino acid concentrations, with greater reductions in non-essential than essential amino acids. Minerals such as potassium, molybdenum and lead increased, while manganese, iron, cadmium and silicon decreased, suggesting that adjustments of agricultural practices may be required to retain current grain quality standards. The concentration of fructose and fructan, as well as amounts per area of total and individual non-structural carbohydrates, except for starch, significantly increased in the grain. The same holds true for the amount of lipids. With regard to mixing and rheological properties of the flour, a significant increase in gluten resistance under elevated CO₂ was observed. CO₂ enrichment obviously affected grain quality characteristics that are important for consumer nutrition and health, and for industrial processing and marketing, which have to date received little attention.