CO2浓度升高对春小麦灌浆特性及产量的影响

为给在大气CO2浓度升高条件下春小麦高产栽培提供理论依据,利用农田开放式空气CO2浓度增高（Free Air CO2Enrichment,FACE）研究平台,以春小麦‘定西24号’为供试品种,研究了大气CO2浓度升高对春小麦灌浆特性及产量的影响。结果表明,随着CO2浓度的增加,春小麦干物质积累增加,最大积累速率出现的时间推迟,最大积累速率增大。随着CO2浓度的增加,千粒重增加,最大灌浆速率出现的日期推迟,最大灌浆速率升高;在不同CO2浓度条件下,灌浆速率与粒重呈显著正相关,但灌浆持续期天数与粒重关系不大。从灌浆的3个阶段来看,渐增期持续时间和渐增期灌浆速率对千粒重的影响作用更大;CO2处理小麦的籽粒产量分别比对照提高了15.62%、29.42%和36.98%,平均增产27.34%,均达极显著水平。本试验中CO2处理使春小麦显著增产主要是由于每穗粒数显著增加的缘故。     

大气CO2浓度升高对不同施氮棉田棉花生长的影响

通过大田试验研究不同CO2浓度处理下,不同施氮水平对棉花生长的影响。结果显示:C720和C360处理下,棉花打顶后(7月20日打顶),叶龄数仍呈现增加趋势;C540处理下棉花打顶后叶龄数趋于稳定。各处理中棉花现蕾数、开花数和结铃数并没有随着施氮量的增加而增加,C540-N20各指标平均值均表现最高。过高的大气CO2浓度和施氮量,不但不利于棉花生长,反而会降低其相关指标。     

大气CO2浓度升高背景下冬小麦冠层光谱特征和地上生物量估算

本研究旨在探究大气CO₂浓度升高对冬小麦全生育时期冠层光谱特征的影响,并基于筛选的敏感波段建立地上生物量(AGB)与光谱参数的定量关系。为此,在2021—2022年的冬小麦生长季,利用开放式CO₂富集系统(Mini-FACE),设定大气CO₂浓度(ACO₂,(420±20)μL L^-1)和高CO₂浓度(ECO₂,(550±20)μL L^-1)两个处理水平,分析了高CO₂浓度下光谱特征变化,基于连续投影算法(SPA)、逐步多元线性回归(SMLR)和偏最小二乘法回归(PLSR)筛选AGB敏感波段并构建估算模型。结果表明:CO₂浓度升高使冬小麦拔节期和开花期AGB显著增加。红边和近红边反射率及红边面积在拔节期增加,在开花期和灌浆期降低,蓝边、黄边和红边位置在不同生育时期均发生移动;AGB的敏感光谱波段主要分布在红边和近红边区域,CO₂浓度升高缩小了AGB...     

干旱胁迫下枇杷叶片的转录组分析

分析干旱胁迫下枇杷叶片的转录组,挖掘功能基因并对其差异表达基因进行筛选和分析,为枇杷抗旱提供理论依据。利用新一代高通量测序技术测序,对测序结果进行de novo拼接、功能注释和ORF预测,将差异表达基因在COG、GO和KEGG数据库中进行比对注释。测序结果表明,获得转录本共88 530个,平均长度为740.64 bp,ORF41 748条。COG、GO和KEGG数据库将转录本分别划分为24,54个功能类别及291条代谢通路中。25 197个差异表达的基因在30条代谢通路中显著富集,与酶活性、激素合成代谢和信号转导等相关的差异基因积极响应枇杷干旱,其中双萜类、油菜素类固醇和类胡萝卜素3条生物合成途径中的差异基因呈现出较为一致的表达。采用实时荧光定量(qRT-RCR)对选取的差异基因进行验证,其中过氧化物酶、蛋白激酶byr2、丝氨酸苏氨酸蛋白激酶、脱落酸8'-羟化酶、吲哚-3-乙酰乙酸合酶相关基因上调表达,细胞色素P450 734A1基因下调表达。为枇杷提供了较为全面的基因信息和代谢途径数据,为干旱胁迫下枇杷分子调控机制的深入研究奠定了基础。     

高寒冷凉地区日光温室CO2浓度变化规律

为了解高寒冷凉地区日光温室内CO2浓度变化特征,预报温室内CO2浓度,调控温室内CO2浓度提供依据,根据2012年4月一2013年3月大通县国家现代农业示范园区节能日光温室内CO2浓度、温室内外气象要素观测资料,及大通县气象观测数据,分析高寒冷凉地区不同天气类型下日光温室CO2浓度变化规律。结果表明,试验期间CO2浓度在184~577mg／kg之间,日平均值为383mg／kg,日平均和最小值均呈极显著上升态势;不论何种天气类型,日光温室CO：浓度日变化均呈“u”型曲线,作物生长的旺盛期,自然通风无法避免CO2亏缺;CO2浓度最小值多云天与日地表温度最大值之间的相关性最好,晴天和阴天与日平均温度间的相关性最佳;除2013年3月外,各月均出现CO2亏缺现象,CO2亏缺时长与日C02浓度最小值间存在二次曲线关系。     

烯效唑浸种对干旱胁迫下大麻叶片的转录组调控分析

为了从转录组水平分析烯效唑缓解干旱胁迫的分子机制,以大麻品种‘汉麻2号’为材料,试验共设清水浸种的正常供水(CK),清水浸种的干旱处理(D),烯效唑浸种的干旱处理(SD) 3个处理,干旱胁迫处理4 d,利用RNA-Seq技术对叶片进行转录组测序分析并探讨半乳糖代谢、植物激素信号转导和氮代谢通路及相关基因。结果表明,CK vs D与D vs SD比较发现,全部差异表达基因有2 423个,其中不同处理共有差异表达基因1 109个。通过GO富集分析表明,两个比较中有1 402和1 144个差异表达基因在生物学过程、细胞组分和分子功能均有分布,且分类结果相似。差异基因GO主要富集在蛋白质折叠、氧化还原过程、胞浆、叶绿体包膜、水解酶活性、氧化还原酶活性等功能。KEGG富集结果表明,差异基因KEGG主要富集在半乳糖代谢、苯丙酸生物合成、植物激素信号转导、氮代谢、丙氨酸、天冬氨酸和谷氨酸代谢、氨基酸的生物合成等代谢途径。本研究主要分析了半乳糖代谢、植物激素信号转导和氮代谢途径,其中半乳糖代谢中UDP糖焦磷酸化酶基因,UDP葡萄糖4-差向异构酶基因,棉子糖合酶基因,水苏糖合酶基因,β-呋喃果糖苷酶基因等,植物激素信号转导中生长素响应蛋白,脱落酸受体,蛋白磷酸酶,脱落酸不敏感蛋白等,氮代谢中高亲和性硝酸盐转运蛋白,谷氨酸脱氢酶基因,谷氨酰胺合成酶基因和碳酸酐酶基因在烯效唑处理下表达水平发生变化。本研究为深入了解烯效唑处理对大麻响应干旱胁迫的分子调控机制、关键基因克隆以及功能验证等提供研究基础和理论依据。     

瞬时CO2浓度变化对杏属植物光合生理影响研究

为探讨CO2浓度瞬时变化对杏碳同化能力、水分利用能力的影响,进一步了解杏属植物在未来大气CO2浓度升高和全球变暖情况下的生长潜力和生态优势。作者利用Li-6400便携式光合测定仪对15个2年生杏品种进行瞬时CO2浓度倍降和倍升处理的光合参数测定。结果表明,瞬时CO2浓度变化显著影响杏属植物光合作用,在瞬时CO2浓度升高情况下,最大净光合速率(Amax)升高,呼吸速率(Rd)下降,光补偿点(LCP)降低,表光量子效率(AQY)提高,水分利用效率(WUE)显著增强,但光饱和点(LSP)变化不显著,不同品种Gs和Tr反应有一定差异。适当增加CO2浓度能提高杏属植物对弱光和水分的利用能力,促进光合作用,增加同化物积累,加速碳素循环。     

作物对大气CO2浓度升高生理响应研究进展

全球大气二氧化碳(CO₂)浓度不断升高对农业生产带来巨大影响。二氧化碳是作物光合作用的底物,其浓度的升高理论上有利于作物光合作用能力的提高,从而促进作物生物量和产量的形成。但已有研究表明,大气CO₂浓度升高对作物产量的促进作用小于预期,同时还存在使作物营养品质变劣的风险,相关机制尚不清楚。为此,本文从植物(作物)叶片对CO₂的吸收和固定生理基础入手,综述了不同类型作物关键光合生理指标如:净光合速率、叶片胞间CO₂浓度、Rubisco酶最大羧化速率及Rubp再生速率等对大气CO₂浓度的响应差异。以作物整株水平碳-氮代谢平衡为基础,总结了解释光合适应现象的2种主要假说,即"源-库"调节机制和N素抑制机制。综述了大气CO₂浓度升高对不同作物籽粒蛋白质、脂肪、矿质元素和维生素等关键营养指标浓度的影响。分析了未来大气CO₂浓度和温度升高的交互作用对作物生产所带来的潜在影响。展望了本领域未来需要关注的主要研究方向。该综述可以为准确评估未来气候条件...     

大气CO2浓度升高对夏大豆叶片生理生化性状的影响

研究大气CO2浓度升高对大豆生化指标的影响,有助于人们了解未来气候变化引起的大豆生理的变化。本研究利用FACE(Free Air CO2Enrichment)系统,在大田条件进行了夏大豆叶片中可溶性糖含量,蛋白质含量和SOD、POD活性变化受CO2浓度升高影响的试验。研究表明:大气CO2浓度升高后,夏大豆叶片中可溶性糖含量没有显著变化。蛋白含量和SOD、POD活性不同品种间有所差异。中黄13在开花期蛋白含量增加44.20%,中黄35在鼓粒期蛋白含量增加49.31%;中黄13在开花期SOD、POD活性分别降低17.35%,27.26%,在结荚期SOD活性下降22.38%,中黄35在鼓粒期SOD、POD活性分别降低50.85%,47.47%。这些结果说明,在大气CO2浓度升高下夏大豆叶片蛋白质代谢能力可能提高,但抗性降低,中黄35抗性下降幅度较中黄13大。     

温度和CO2浓度升高下双季稻茎蘖动态、成穗率与产量的关系

为明确气候变化下我国双季稻茎蘖动态与成穗特征的变化及其与产量的关系,利用开顶式气室(OTC)连续开展4年8个生长季的大田气候变化原位模拟试验,设置对照(CK)、增温2℃(ET)、CO₂浓度增加60μmol/mol(EC)、同时增温增CO₂浓度(ETEC)共4个处理,研究双季稻生育期内茎蘖动态、成穗率变化特征以及对产量的影响。结果表明,随着累积辐射量和生长度日(GDD)升高,水稻分蘖达到峰值后部分消亡,且早稻分蘖增长和消亡速率均大于晚稻。相比CK,ET、EC和ETEC条件下早稻最大分蘖数和无效分蘖数分别提高3.6%～14.2%和8.9%～134.2%,成穗率降低0.4%～9.3%,对产量形成具有不利影响;晚稻最大分蘖数提高2.9%～13.1%,无效分蘖数降低1.6%～64.8%,成穗率提高1.7%～22.1%,有助于产量增长。ETEC处理对双季稻最大分蘖具有正向协同的交互作用,而对无效分蘖和成穗率的交互作用不显著。总体而言,大气温度和CO₂浓度升高对早稻分蘖和成穗具有负效应,对晚稻表现为正效应,未来气候变化背景下提高水稻茎...     

New genes for resistance to Xanthomonas campestris pv. glycines in soybean [Glycine max (L.) Merr.] and their inheritance

Bacterial leaf pustule (BLP) caused by Xanthomonas campestris pv. glycines is an important disease of soybean. A new resistant source, P-4-2, showing an immune reaction in controlled conditions to BLP was crossed with the susceptible cultivar Monetta to study the inheritance of resistance. All F1 plants were susceptible. The F2 population segregated 15 susceptible: 1 resistant plants indicating the presence of duplicate recessive genes controlling resistance. This was further confirmed in the F3 generation. Two recessive genes conferring high levels of resistance in soybean to Xanthomonas campestris pv. glycines under controlled conditions are being reported here for the first time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis and identification of two soybean mosaic virus resistance genes in soybean [Glycine max (L.) Merr]

Soybean mosaic virus (SMV) commonly affects soybean production worldwide, and the SC18 strain has been widespread in China. This study aimed to characterize and map the SC18 resistance genes present in soybean cultivars ‘Kefeng No. 1’ and ‘Qihuang 22’. Inheritance analysis revealed that two independent single dominant genes in Kefeng No. 1 and Qihuang 22 confer resistance to SC18. Using simple sequence repeat (SSR) markers and bulked segregant analysis, the Kefeng No. 1 and Qihuang 22 resistance genes were located on soybean chromosomes 2 and 13, respectively. We further screened two populations of recombinant inbred lines with 32 SSR markers in the target region, where the resistance gene in Kefeng No. 1 was fine mapped to an 80‐kb region containing six putative genes. Sequence and expression analyses of these genes revealed that SMV resistance in Kefeng No. 1 was probably attributable to three of the candidate genes (i.e. Glyma.02G127800, Glyma.02G128200 and Glyma.02G128300). Collectively, the results of this study will greatly facilitate the cloning of SC18 resistance genes and marker‐assisted breeding of SMV‐resistant soybean cultivars.     

Genomewide association analysis of salt tolerance in soybean [Glycine max (L.) Merr.]

Salinity is a common abiotic stress causing soybean [Glycine max (L.) Merr.] yield loss worldwide. The use of tolerant cultivars is an effective and economic approach to coping with this stress. Towards this, research is needed to identify salt‐tolerant germplasm and better understand the genetic and molecular basis of salt tolerance in soybean. The objectives of this study were to identify salt‐tolerant genotypes, to search for single‐nucleotide polymorphisms (SNPs) and QTLs associated with salt tolerance. A total of 192 diverse soybean lines and cultivars were screened for salt tolerance in the glasshouse based on visual leaf scorch scores after 15–18 days of 120 mM NaCl stress. These genotypes were further genotyped using the SoySNP50K iSelect BeadChip. Genomewide association mapping showed that 62 SNP markers representing six genomic regions on chromosomes (Chr.) 2, 3, 5, 6, 8 and 18, respectively, were significantly associated with salt tolerance (p < 0.001). A total of 52 SNP markers on Chr. 3 are mapped at or near the major salt tolerance QTL previously identified in S‐100 (Lee et al., 2014). Three SNPs on Chr. 18 map near the salt tolerance QTL previously identified in Nannong1138‐2 (Chen, Cui, Fu, Gai, & Yu, 2008). The other significant SNPs represent four putative minor QTLs for salt tolerance, newly identified in this study. The results above lay the foundation for fine mapping, cloning and molecular breeding for soybean salt tolerance.     

Genetic analysis for the leaf pubescence density and water status traits in soybean [Glycine max (L.) Merr.]

Leaf pubescence density (PD) is an important component for the adaptation of soybean [ Glycine max (L.) Merr.] to drought-prone environment. Quantitative trait loci (QTL) controlling PD on the upper surface of leaf blade (PDU), PD on the lower surface of leaf blade (PDL), leaf wilting coefficient (WC) and rate of excised leaf drying (ELD) were identified using recombinant inbred lines (RILs) population from the cross between soybean cultivars 'kefeng1' and 'nannong1138-2' at the field soil drought stress stage from the mid-end of stem elongation to onset of flowering. A total of 20 QTLs were detected on molecular linkage groups (MLGs) A2, D1b, E, H, G and I with individual QTL explained 4.49–23.56% of phenotypic variation by composite interval mapping. The QTLs for PD on MLG H were mapped to near Ps locus while the QTLs on MLG D1b were located near Rsc-7 . Three genome regions for PD and water status traits on MLGs A2, D1b and H were associated. This study revealed that leaf surface PD may play an important role in the soybean drought tolerance.     

Association analysis for detecting significant single nucleotide polymorphisms for phosphorus-deficiency tolerance at the seedling stage in soybean [Glycine max (L) Merr.]

Tolerance to low-phosphorus soil is a desirable trait in soybean cultivars. Previous quantitative trait locus (QTL) studies for phosphorus-deficiency tolerance were mainly derived from bi-parental segregating populations and few reports from natural population. The objective of this study was to detect QTLs that regulate phosphorus-deficiency tolerance in soybean using association mapping approach. Phosphorus-deficiency tolerance was evaluated according to five traits (plant shoot height, shoot dry weight, phosphorus concentration, phosphorus acquisition efficiency and use efficiency) comprising a conditional phenotype at the seedling stage. Association mapping of the conditional phenotype detected 19 SNPs including 13 SNPs that were significantly associated with the five traits across two years. A novel cluster of SNPs, including three SNPs that consistently showed significant effects over two years, that associated with more than one trait was detected on chromosome 3. All favorable alleles, which were determined based on the mean of conditional phenotypic values of each trait over the two years, could be pyramided into one cultivar through parental cross combination. The best three cross combinations were predicted with the aim of simultaneously improving phosphorus acquisition efficiency and use efficiency. These results will provide a thorough understanding of the genetic basis of phosphorus deficiency tolerance in soybean.     

Response of Soybean [Glycine max (L.) Merr.] Cultivars to Genistein-Preincubated Bradyrhizobium japonicum: Nodulation and Dry Matter Accumulation under Canadian Short-Season Conditions

The addition of genistein, a plant-to-bacteria signal molecule, to Bradyrhizobium japonicum cells prior to use as inocula has been shown to increase nodule number and promote soybean N₂ fixation at low root zone temperatures. Previous greenhouse and field experiments involving only two cultivars have indicated that soybean [ Glycine max (L.) Merr.] cultivars can vary in their response to genistein application. The objective of this study was to evaluate a range of soybean cultivars for response to genistein application under short-season cool-spring Canadian conditions. A 2-year field study was conducted in 1997 and 1998 with a range of soybean cultivars recommended for Quebec. The 11 cultivars tested represented a range of yield potentials and maturity groups. They were inoculated with genistein-preincubated B. japonicum inocula or regular inocula, applied into the furrow at the time of planting. The results of these experiments indicated that neither maturity nor yield was correlated with increases in nodulation, biomass, and plant total nitrogen content resulting from genistein treatment and that all maturity groups responded to genistein application in essentially the same way. Thus, response of soybean cultivars to genistein addition is regulated by genotype characteristics other than maturity or yield level.     

Interaction Amongst Soybean [Glycine max (L.) Merrill] Genotype, Soil Type and Inoculant Strain with Regard to N2 Fixation

The nitrogen (N₂)‐fixing bacterial inoculant strain for soybean [Glycine max (L.) Merrill] is not indigenous to South African soils. The interaction between soybean genotype, soil type and inoculant strain, however, has a definite influence on soybean production and compatibility should be optimized. This paper reports a growth chamber study using three different soybean genotypes (Barc‐9, Avuturda and Talana), three Bradyrhizobium japonicum inoculant strains (WB108, WB112 and WB1) and three soil types (Avalon, Arcadia and sand) to evaluate the effectiveness of N₂ fixation by different genotype × soil type × inoculant strain combinations, using different measuring parameters. These parameters included nodule fresh mass (NFM), amount of N₂ fixed (P_fix), as determined by the ureide method, seed protein content (SPC), average seed mass per plant (SMP) and average foliar N content (FNC). The comparison amongst the three‐way interactions, genotype × soil type × inoculant strain, did not differ significantly for the parameters used. Significant two‐way interactions were soil × inoculant for FNC, P_fix and SMP; soil × genotype for FNC and SMP, and inoculant × genotype for FNC (P < 0.05). The soil × inoculant strain interaction was significant for P_fix (P < 0.05). NFM, P_fix, FNC, SMP and SPC correlated positively with soil pH and negatively with soil clay content and soil NO₃^– and NH₄⁺ content (P < 0.05). SPC was significantly different (P < 0.05) for soil type, genotype and inoculant strain. P_fix and NFM did not reflect the protein content of the seeds, indicating that nodule evaluation should be used with caution as a N₂ fixation parameter. Low soil pH and high mineral N content inhibited N₂ fixation. NFM correlated negatively with the clay content of the soil. This finding confirms that soybean production in South Africa can be improved by appropriate selection of genotypes and inoculant strains for their compatibility in different soils.     

Effect of Deep Placement of Slow-release Fertilizer (Lime Nitrogen) Applied at Different Rates on Growth, N2 Fixation and Yield of Soya Bean (Glycine max [L.] Merr.)

A new fertilization method with deep placement of slow‐release N fertilizers, such as coated urea and lime nitrogen (LN) (calcium cyanamide) at 20 cm depth was found to promote soy bean seed yield. In the present study, the effect of deep placement of LN was investigated on different parameters such as growth, N accumulation, N₂ fixation activity and yield of soy bean by applying LN at different rates in the rotated paddy field of Niigata, Japan. In addition to the basal fertilizer, ammonium sulphate (16 kg N ha^?1), deep placement of LN was conducted by applying various amounts such as 50 kg N ha^?1 (A50), 100 kg N ha^?1 (A100) and 200 kg N ha^?1 (A200) at 20 cm depth in separate plots. A ¹⁵N‐labelled LN fertilizer was also employed for each of the above treatments to calculate N utilization from LN in separate plots. Soya bean plant growth and N₂ fixation activity were periodically analysed. Both plant growth and N accumulation were found to increase with LN treatment compared with control plants. An increase in N₂ fixation activity was found in the A100 plots. The total seed yield was the highest in the deep placement of LN with A100 (73 g per plant) compared with other treatments. The visual quality of harvested seeds also showed that A100 enhanced the quality of seeds compared with other treatments. Thus, it is suggested that N fertilization management with particular reference to optimum amount of fertilizers is important for maximum growth, N₂ fixation and enhancement of seed yield of soy bean.     

Genetic analysis of antixenosis resistance to the common cutworm (Spodoptera litura Fabricius) and its relationship with pubescence characteristics in soybean (Glycine max (L.) Merr.)

The common cutworm (CCW, Spodoptera litura Fabricius) is one of the most serious pests of soybean (Glycine max (L.) Merr.). Previously, two quantitative trait loci (QTLs) for antibiosis resistance to CCW, CCW-1 and CCW-2, were detected in the resistant cultivar Himeshirazu. In this study, we conducted an anti-xenosis bioassay using a recombinant inbred population derived from a cross between a susceptible cultivar Fukuyutaka and Himeshirazu to perform QTL analysis. Two QTLs for antixenosis resistance, qRslx1 and qRslx2, were identified on Chrs 7 and 12, and the resistant alleles of qRslx1 and qRslx2 were derived from Himeshirazu and Fukuyutaka, respectively. The position of qRslx1 is similar to that of CCW-1. We also analyzed pubescence characteristics because they have been reported to be associated with soybean insect resistance. Two QTLs for pubescence length (on Chrs 7 and 12) and two QTLs for pubescence density (on Chrs 1 and 12) were identified. The pubescence QTLs on Chrs 7 and 12 were located near qRslx1 and qRslx2, respectively. These results suggest that the antixenosis resistance could be controlled genetically by the identified QTLs and that the pubescence characteristics might contribute to the soybean antixenosis resistance to CCW.     

Growth and marketable-yield responses of potato to increased CO2 and ozone

Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO₂ on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl l⁻¹ for 8 h, and ambient or elevated CO_2; targeted 680 μl l⁻¹ averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO₂ (550 μl l⁻¹) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 μl l⁻¹. Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 mm diameter, from ambient conditions ranged from 1 to 12 kg m⁻². There was no consistent (P>0.1) CO₂×O₃ interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P<0.05), particularly of the largest (>50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl l⁻¹ h over 40 nl l⁻¹, and with yields from chambered ambient-ozone treatments (P<0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P<0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO₂. Only green leaf number at the MLA harvest was reduced. The CO₂ responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO₂ treatment yields. Yield increases resulting from the 680 μl l⁻¹ and 550 μl l⁻¹ treatments were similar. Thus elevating [CO₂] from 550 to 680 μl l⁻¹ was less effective than elevating [CO₂] from ambient to 550 μl l⁻¹. On average, CO₂ elevation to 680 μl l⁻¹ increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO₂ and O₃ concentrations on the European potato crop would be an increase marketable yield.