The influence of defoliation height on dry-matter partitioning and CO2 exchange of perennial ryegrass miniature swards

This study investigated the effects of defoliation intensity on the above- and below-ground plant mass, rates of CO₂ exchange and leaf appearance rate of ryegrass miniature swards maintained at constant cutting height ranging from 20 mm to 160 mm for 5 months. Total plant mass, above-ground herbage mass and root mass increased as cutting height increased from 20 to 120 mm. Further increase in cutting height did not increase total plant mass or its components. Leaf appearance rate and photosynthesis per unit of leaf dry matter (DM) decreased as defoliation height increased from 20 to 160 mm. Gross and net CO₂ uptake per unit soil surface area increased with cutting height to 120 mm. Further increase in cutting height to 160 mm decreased gross and net CO₂ uptake and herbage harvested. A multivariate canonical discriminant analysis indicated different responses of root and shoot mass to cutting height and a reduction in CO₂ uptake rate at the 160 mm cutting height. The implications of those responses to defoliation management of forage plants are discussed.     

Effects of elevated atmospheric CO2 on grain quality of wheat

Wheat (Triticum aestivum L.) is one of the most important agricultural crops worldwide. Due to its high content of starch and unique gluten proteins, wheat grain is used for many food and non-food applications. Although grain quality is an important topic for food and feed as well as industrial processing, the consequences of future increases in atmospheric carbon dioxide (CO₂) concentrations on quality parameters such as nutritional and bread-making rheological properties are still unclear. Wheat productivity increases under CO₂ enrichment. Concomitantly, the chemical composition of vegetative plant parts is often changed and grain quality is altered. In particular, the decrease in grain protein concentration and changes in protein composition may have serious economic and health implications. Additionally, CO₂ enrichment affects amino acid composition and the concentrations of macro- and micro-elements. However, experimental results are often inconsistent. The present review summarises the results from numerous CO₂ enrichment experiments using different exposure techniques in order to quantify the potential impacts of projected atmospheric CO₂ levels on wheat grain yield and on aspects of grain composition relevant to processing and human nutrition.     

Impacts of elevated atmospheric CO2 and temperature on plant community structure of a temperate grassland are modulated by cutting frequency

To determine the impacts of climate change and defoliation on the community structure and plant diversity of a semi‐natural temperate grassland, monoliths of a permanent grassland were exposed to ambient or elevated atmospheric CO₂ concentrations (ambient + 235 ppmv) and temperature (ambient + 3°C) from October 1998 to December 2000. The monoliths were subjected to two different cutting frequencies, either two or six cuts per year. The grassland community structure changed during the course of the experiment and was more responsive to changes in management than to changes in climate. Increased cutting frequency stimulated plant diversity by enhancing the number of forb species, but plant diversity was not significantly affected by climate change. The contribution of individual plant species to the vegetation cover revealed species‐specific responses to climate change and cutting frequency, but for most species significant interactions between climate change and cutting frequency were present. There were no clear‐cut effects of treatments on the total annual yield and the proportion of forbs present, as significant interactions between climate change and cutting frequency occurred. It is concluded that differential grassland management will modify plant species‐specific responses to climate change and resulting changes in the botanical composition of mixed‐species, temperate grasslands.     

The response of perennial ryegrass/white clover mini-swards to elevated atmospheric CO2 concentrations: effects on yield and fodder quality

In order to assess the effects of future elevated atmospheric CO₂ concentrations on yield, mineral content and the nutritive value of mixed swards of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), both species were grown as monocultures and as different mixtures and were exposed season-long to ambient (380 p.p.m.) and elevated (670 p.p.m.) CO₂ concentrations in open-top chambers. Mini-swards were cut four times at about monthly intervals at a height of 5 cm, dry-matter yields were determined and content of macroelements (N, P, K, S, Mg, Ca, Na) and crude fibre, crude protein and ash content were measured. The CO₂-related increase in seasonal yield amounted to 16–38% for white clover monocultures, 12–29% for mixed swards and 5–9% for ryegrass monocultures. The white clover content of all swards was significantly enhanced by elevated CO₂. The K and Na content of total yield was decreased by high CO₂ but did not fall below the minimum requirements for ruminants. As the Ca content of total yield was increased by elevated CO₂ and the P content was not changed, the Ca/P ratio of total yield was increased and exceeded values required for animal nutrition. The crude protein content of total yield was reduced by high CO₂ at the beginning of the growing season only and was increased by elevated CO₂ in the course of the experiment, whereas crude fibre content was decreased throughout the season, sometimes falling below the minimum requirement for ruminants. Removal of N, P, S, Mg and Ca by cutting was significantly enhanced because of CO₂ enrichment. The results show that, besides the positive effect of rising atmospheric CO₂ on dry-matter yield of white clover/ryegrass swards, impacts on the nutritive value should be expected. Possible changes in species composition and implications for grassland management are briefly discussed.     

Simulation of the effects of genotype and N availability on rice growth and yield response to an elevated atmospheric CO2 concentration

The objective of this study was to identify physiological processes that result in genotypic and N fertilization effects on rice yield response to elevated atmospheric CO₂ concentrations ([CO₂]). This study conducted growth and yield simulations for 9 rice genotypes grown at 4 climatically different sites in Asia, assuming the current atmospheric [CO₂] (360 ppm) and elevated [CO₂] (700 ppm) using 5 levels of N fertilizer (4, 8, 12, 16, 20 g m⁻² N fertilizer). A rice growth model that was developed and already validated for 9 different genotypes grown under 7 sites in Asia was used for the simulation, integrating additional components into the model to explain the direct effect of [CO₂] on several physiological processes. The model predicted that the relative yield response to elevated [CO₂] (RY, the ratio of yield under 700 ppm [CO₂] to that under 360 ppm [CO₂]) increased with increasing N fertilizer, ranging from 1.12 at 4 g m⁻² N fertilizer to 1.22 at 20 g m⁻² N fertilizer, averaged overall genotypes and locations. The model also predicted a large genotypic variation in RY at the 20 g N treatment, ranging from 1.08 for ‘WAB450-I-B-P-38-HB’ to 1.41 for ‘Takanari’ averaged overall locations. Combining all genotypes grown at the 5N fertilization conditions, a close 1:1 relationship was predicted between RY and the relative [CO₂] response in spikelet number for crops with a small number of spikelets (less than 30,000 m⁻²) under the current atmospheric [CO₂] (n = 18, r = 0.89^***). In contrast, crops with a large number of spikelets under the current atmospheric [CO₂] showed a significantly larger RY than the relative [CO₂] response for spikelet number per unit area. The model predicted that crops with a larger number of spikelets under the current atmospheric [CO₂] derived great benefit from elevated [CO₂] by directly allocating increased carbohydrate to their large, vacant sink, whereas crops with a smaller number of spikelets primarily required an increased spikelet number to use the increased carbohydrate to fill grains. The simulation analyses suggested that rice with a larger sink capacity relative to source availability under the current atmospheric [CO₂] showed a larger yield response to elevated [CO₂], irrespective of whether genotype or N availability was the major factor for the large sink capacity under the current [CO₂]. The model predicted that the RY response to nitrogen was brought about through the N effects on spikelet number and non-structural carbohydrate accumulation. The genotypic variation in RY was related to differences in spikelet differentiation efficiency per unit plant N content. Further model validation about the effects of [CO₂] on growth processes is required to confirm these findings considering data from experimental studies.     

Effects of elevated atmospheric CO2 concentration on morphology of leaf blades in Chinese yam

ABSTRACT

The effects of elevated carbon dioxide concentration on the morphology of leaf blades in two Chinese yam lines under different temperature conditions were determined. Plants were grown under two [CO₂] levels, ambient (about 400 µmol mol^?1) and elevated (ambient + 200 µmol mol^?1) in the daytime, and two mean air temperature regimes, approximately ambient temperature (22.2°C) and high temperature (25.6°C). The palisade layer was thicker under elevated [CO₂] than under ambient [CO₂] in both temperature regimes, and the whole yam leaf blade was thicker under elevated [CO₂] than under ambient [CO₂] in the approximately ambient temperature regime. The numbers of chloroplasts per palisade cell and spongy cell as well as per unit profile area of palisade cell, number of starch grains per chloroplast, profile area of the starch grain, and starch-to-chloroplast area ratio in both palisade and spongy cells were higher under elevated [CO₂] than under ambient [CO₂] in both temperature regimes. Furthermore, the stomatal density on the abaxial side of the leaf blade in Chinese yam was greater under elevated [CO₂] than under ambient [CO₂] under both temperature regimes, and stomatal-pore length was higher under elevated [CO₂] than under ambient [CO₂] in the approximately ambient temperature regime. These results indicate that elevated [CO₂] positively affects the photosynthetic apparatus. The results of this study provide information for understanding the response characteristics of the leaf blade under elevated [CO₂] and a possible explanation for the positive photosynthetic responses of Chinese yam to elevated [CO₂] in our previous study.

List of Abbreviations:[CO₂]: carbon dioxide concentration     

Effects of atmospheric CO2 enrichment on biomass,yield and low molecular weight metabolites in wheat grain

Spring wheat (Triticum aestivum L.) was grown in a free-air carbon dioxide (CO₂) enrichment (FACE) field experiment. Grain and biomass yield and its components were determined at maturity and the grain metabolome was analysed by gas chromatography-mass spectrometry (GC–MS). Elevated CO₂ (537 versus 409 μl l⁻¹) increased biomass production except for leaves. In total, levels of 16 grain metabolites were decreased and four were increased. CO₂ enrichment resulted in significant decreases of amino acids such as o-acetyl-L-homoserine, leucine, arginine, L-homoserine and the group of ornithine, arginine and citrulline and negative trends for norleucine, L-aspartate, proline, L-cysteine and tyrosine. The amines D/L-diaminopimelate and alpha-ketoaminobutyrate and the polyamine putrescine were significantly decreased. In contrast, the polyamine spermidine tended to increase under elevated CO₂. Among sugars and sugar derivatives, ribose-5-P was significantly increased, while gluconate-6-P was decreased. There were also negative CO₂-induced effects on sugar alcohols: significant for glycerol-2-P (P = 0.008) and almost significant for myo-inositol-P (P = 0.066). In contrast, organic acids such as pyruvate and glucuronic acid were significantly increased. Overall, the N-rich metabolites especially were reduced. CO₂ enrichment can markedly affect the physiology and metabolome of mature grains which may in turn lead to changes in nutritional status.     

Erratum to “Modeling the interactive effects of atmospheric CO2 and N on rice growth and yield” [Field Crops Res. 93 (2005) 237–251]

The publisher regrets that the following error has occurred in the above article: page 239, Table 1, and page 247, Table 5 should be replaced with below Tables in the original printing of the above-mentioned paper.     

Seasonal changes in the effects of free-air CO2 enrichment (FACE) on nitrogen (N) uptake and utilization of rice at three levels of N fertilization

Over time, the relative effect of elevated [CO₂] on the photosynthesis and dry matter (DM) production of rice crops is likely to be changed with increasing duration of CO₂ exposure, but the resultant [CO₂] effects on rice N concentration, uptake, efficiency and allocation remain unclear, especially under different soil N availability. Therefore, we conducted a free-air CO₂ enrichment (FACE) experiment at Wuxi, Jiangsu, China, in 2001–2003. A japonica cultivar with large panicle was grown at ambient or elevated (ca. 200 μmol mol⁻¹ above ambient) [CO₂] under three levels of N: low (LN, 15 g N m²), medium (MN, 25 g N m²) and high N (HN, 35 g N m² (2002, 2003)). The MN level was similar to that recommended to local farmers. Averaged across all N levels and years, shoot N concentration (dry base) was lower under FACE by 1.8%, 6.1%, 12.2%, 14.3%, 12.1%, and 6.9% at early-tillering, mid-tillering, panicle initiation (PI), booting, heading and grain maturity, respectively. Shoot N uptake under FACE was enhanced by 46%, 38%, 6% and 16% on average during the growth periods from transplanting to early-tillering (period 1), early-tillering to mid-tillering (period 2), mid-tillering to PI (period 3) and heading to grain maturity (period 5), respectively, but slightly decreased by 2% in the period from PI to heading (period 4). Seasonal changes in crop response to FACE in ratio of shoot N uptake during a given growth period to that over the whole season followed a similar pattern to that of shoot N uptake, with average responses of 33%, 26%, −3%, −11% and 10% in periods 1–5 of the growth period, respectively. As a result, FACE increased final aboveground N uptake by 9% at maturity. FACE greatly reduced the ratio of leaf to shoot N content over the season, while allocation of N to stems and spikes showed an opposite trend. FACE treatment resulted in the significant increase in N use efficiency for biomass (NUEp) over the season except at early-tillering and in N use efficiency for grain yield (NUEg) at grain maturity. These results indicate that, in order to maximize grain output in a future high [CO₂] environment, the recommended rates, proportion and timing across the season of N application should be altered, in order to take full advantage of strong N uptake capacity during the early growth period and facilitate N uptake after that.     

超临界CO2萃取人参脂溶性成分的GC-MS分析

目的 用超临界CO2萃取人参脂溶性成分,分析并测定提取物的主要成分和含量.方法 用超临界CO2萃取人参脂溶性成分.提取物用气相色谱质谱(GC-MS)联用法进行分析鉴定.使用面积归一法测定各成分相对含量.结果鉴定了44个化合物,主要为脂肪酸和酯(34)、挥发油.结论用超临界萃取人参,可以较好的获得其脂溶性成分.     

QTL identification of kernel composition traits with popcorn using both F2:3 and BC2F2 populations developed from the same cross

Quantitative trait loci (QTL) influencing three main kernel composition traits, starch, protein and oil concentrations, in unselected F_2:3 and selected BC₂F₂ maize populations derived from the same cross of a dent corn inbred Dan232 × an elite popcorn inbred N04 under the same conditions were detected. Four and two QTL for starch, four and three QTL for protein, and four and one QTL for oil were detected in the two populations, respectively, with three QTL jointly detected. The proportion of phenotypic variation explained by a single QTL was 5.2–10.6%, 5.0–14.3%, and 6.2–8.5% for the three traits. Ten QTL had favorable alleles contributed by Dan232. Several QTL detected in this study had identical or similar chromosome regions to those previously identified with other maize germplasms. No QTL with opposite effects for kernel composition traits and popping characteristics were detected in the same or near marker intervals. This reflected that some QTL detected in this study seemed to contribute to trait variation in a diverse array of maize populations and environments, and the opportunity existed for improving popcorn's nutritional quality while maintaining acceptable popping characteristics. Inconsistent broad sense heritability and trait correlation estimates were also observed in the two populations.     

Impact of elevated CO2 concentration on inter-subspecific hybrid rice cultivar Liangyoupeijiu under fully open-air field conditions

Hybrid rice cultivar plays an important role in rice production system due to its high yield potential and resistance to environmental stress. Quantification of its responses to rising CO₂ concentration ([CO₂]) will reduce our uncertainty in predicting future food security and assist in development of adaptation strategies. Using free air CO₂ enrichment (FACE), we measured seasonal changes in growth and nitrogen (N) uptake of an inter-subspecific hybrid rice cultivar Liangyoupeijiu grown under two levels of [CO₂] (ambient and elevated by 200 μmol mol⁻¹) and two levels of N fertilization in 2005–2006. Average across the 2 years, FACE increased crop growth rate similarly by 22%, 24% and 23% in the periods from transplanting to panicle initiation (PI), PI to heading and heading to maturity, which was mainly attributed to an increase in green leaf area index rather than the greater net assimilation rate. Grain yield increased greatly under FACE as a result of similar contributions by panicle number per unit area, grain number per panicle and individual grain yield. Final aboveground N acquisition showed a 10.4% increase under FACE, which resulted from enhanced N uptake at both vegetative and reproductive growth stages. Compared with previous FACE studies on final productivity of two inbred japonica cultivars, inter-subspecific hybrid cultivar appears to profit more from elevated [CO₂], which mainly resulted from its greater enhancement in photosynthetic production during reproductive growth due to a lack of N limitations late in the season.     

Effects of cutting frequency on plant production, N-uptake and N2 fixation in above- and below-ground plant biomass of perennial ryegrass–white clover swards

Nitrogen (N), accumulating in stubble, stolons and roots, is an important component in N balances in perennial ryegrass–white clover swards, and the effects of cutting frequency on the biomass of above‐ and below‐harvest height were studied during two consecutive years. Total dry matter (DM) and total N production, and N₂ fixation, were measured at two cutting frequencies imposed in the summers of two years either by cutting infrequently at monthly intervals to simulate mowing or by frequent cutting at weekly intervals to simulate grazing. Total DM production harvested was in the range of 3000–7000 kg DM ha^?1 with lower DM production associated with the frequent cutting treatment, and it was significantly affected by the different weather conditions in the two years. The higher cutting frequency also reduced the biomass below harvest height but the different weather conditions between years had less effect on stubble and, in particular, biomass of roots. The biomass of roots of white clover was significantly lower than that of roots of perennial ryegrass and remained at a relatively constant level (200–500 kg DM ha^?1) throughout the experiment, whereas the biomass of perennial ryegrass roots increased from 2400 kg DM ha^?1 in the year of establishment to 10 200 kg DM ha^?1 in the infrequent cutting treatment and 6650 kg DM ha^?1 in the frequent cutting treatment by the end of the experiment, giving shoot:root ratios of 4·7–16·6 and 0·5–1·6 for white clover and perennial ryegrass respectively. Annual N₂ fixation was in the range of 28–214 kg N ha^?1, and the proportion of N fixed in stolons and roots was on average 0·28. However, as weather conditions affect the harvested DM production and the shoot:root ratio, care must be taken when estimating total N₂ fixation based on an assumed or fixed shoot:root ratio.     

The impact of free-air CO2 enrichment (FACE) and nitrogen supply on grain quality of rice

Because CO₂ is needed for plant photosynthesis, the increase in atmospheric CO₂ concentration ([CO₂]) has the potential to enhance the growth and yield of rice (Oryza sativa L.), but little is known regarding the impact of elevated [CO₂] on grain quality of rice, especially under different N availability. In order to investigate the interactive effects of [CO₂] and N supply on rice quality, we conducted a free-air CO₂ enrichment (FACE) experiment at Wuxi, Jiangsu, China, in 2001–2003. A long-duration rice japonica with large panicle (cv. Wuxiangging 14) was grown at ambient or elevated (ca. 200 μmol mol⁻¹ above ambient) [CO₂] under three levels of N: low (LN, 15 g N m²), medium (MN, 25 g N m²) and high N (HN, 35 g N m² (2002, 2003)). The MN level was similar to that recommended to local farmers. FACE significant increased rough (+12.8%), brown (+13.2%) and milled rice yield (+10.7%), while markedly reducing head rice yield (−13.3%); FACE caused serious deterioration of processing suitability (milled rice percentage −2.0%; head rice percentage −23.5%) and appearance quality (chalky grain percentage +16.9%; chalkiness degree +28.3%) drastically; the nutritive value of grains was also negatively influenced by FACE due to a reduction in protein (−6.0%) and Cu content (−20.0%) in milled rice. By contrast, FACE resulted in better eating/cooking quality (amylose content −3.8%; peak viscosity +4.5%, breakdown +2.9%, setback −27.5%). These changes in grain quality revealed that hardness of grain decreased with elevated [CO₂] while cohesiveness and resilience increased when cooked. Overall, N supply had significant influence on rice yield with maximum value occurring at MN, whereas grain quality was less responsive to the N supply, showing trends of better appearance and eating/cooking quality for LN or MN-crops as compared with HN-crops. For most cases, no [CO₂] × N interaction was detected for yield and quality parameters. These data suggested that the current recommended rates of N fertilization for rice production should not be modified under projected future [CO₂] levels, at least for the similar conditions of this experiment.     

皂化麦麸对重金属Cd~(2+)的吸附作用及吸附机理研究

为扩大纤维素类生物吸附剂的开发利用资源,采用五因子二次回归正交旋转组合设计方法对影响皂化麦麸吸附Cd2+的因子进行优化,得出在吸附时间为1h、加入量为0.20g、pH=6、温度20℃、浓度2.00mg·L-1时,皂化麦麸有最大吸附率(YMax=99.19%)。对比试验表明,皂化麦麸对Cd2+的吸附优于活性炭,纤维素在吸附中起主要作用。扫描电镜下皂化麦麸表面显示粗糙和多褶皱的物理吸附特征,红外光谱显示皂化麦麸中-OH、-CH3、C≡C、C=C、C=O、C-O基团可能参与吸附作用。吸附等温线和吸附动力学模型显示,皂化麦麸对Cd2+吸附符合Freundlich等温式和二级动力学模型。皂化麦麸经过解吸附可以反复使用。     

混播比例对热研2号柱花草和飞机草早期生长竞争能力的影响

为明确热研2号柱花草(Stylosanthes guianensis cv.Reyan No.2)与飞机草(Chromolaena odorata(L.)R.M.KingH.Robinson)生长早期的竞争关系,探索飞机草替代控制的途径和管理策略。设置总株数固定(8株),5种柱花草和飞机草分株数混播比例(柱∶飞=8∶0、6∶2、4∶4、2∶6、0∶8)盆栽试验,就各混播比例下2种植物在浇水频率1次/2 d、生长30 d的生长情况和相对竞争能力进行定量分析。结果表明:随着柱花草混播株数的减少,柱花草和飞机草的相对株高、相对平均生长速度、相对单株总生物量和总生物量分配至根、茎和叶的相对生物量均逐渐降低;但飞机草的相对根长、相对根冠比和根生物量质量分数均逐渐减小、茎生物量质量分数无显著变化、叶生物量质量分数逐渐增大,而柱花草的各对应指标反之。柱花草比例较高时(柱∶飞为6∶2)2种植物的相对产量总和显著大于1,2种植物间无种间竞争现象,4∶4和2∶6时相对产量总和均与1相比无显著差异,2种植物间存在资源竞争;混播群落中柱花草的竞争平衡指数均显著小于0,说明生长早期柱花草的相对竞争能力比飞机草弱。下一步进行生长中期、晚期竞争试验和肥力、刈割等其他因素影响试验来确定柱花草替代控制飞机草的可能性。