CO2 Gain Research Articles

KUFRI DAKSH: A NEW WATER-USE EFFICIENT TABLE POTATO VARIETY WITH CROSS TOLERANCE TO HIGH TEMPERATURE STRESS

Kufri (K) Daksh is a main season, medium maturing, high yielding, water-use-efficient table potato variety that can be grown in regions with limited water availability. It is a clonal selection from the cross between CP1748, having high water use efficiency and LT-1 tolerating high temperature stress. Its plants are tall and vigorous with field resistance to late blight. Its tubers are white-cream (light yellow), ovoid with shallow to medium eyes and cream flesh with good keeping quality. It is fertilizer responsive and can yield 30-35 t/ha under low water (≤ 20%) availability in middle Gangetic plains. K Daksh has better trade-off for high CO2 gain and low water loss through optimization in plant canopy leaf area and plant height components. K Daksh can be an excellent choice to tolerate high temperature and water stress regimes in changing climatic scenarios.

Individual grain mass of inbred rice cultivars does not benefit from elevated [CO2]

Climate warming has led to a reduction of global crop yields. Elevated atmospheric [CO2] is believed to promote crop production by increasing photosynthesis, and thus partly offset the yield losses due to climate warming. However, photosynthetic acclimation may occur when the plant is exposed to long-term high [CO2] conditions, suggesting that elevated [CO2] (e[CO2]) might not bring benefits for cereal crops as the growing season proceeds. To assess the effect of long-term e[CO2] on rice yield, particularly on individual grain mass determined post-heading, we synthesized existing data from FACE (free-air CO2 enrichment) experiments across four locations in Japan and China. We also conducted a five-year field experiment with different [CO2] treatments using OTC (open-top chamber) facility. A novel experiment of pot replacement at heading was conducted in 2018 to evaluate the effect of post-heading e[CO2] on individual grain mass of rice. Meanwhile, we measured net photosynthetic rates under ambient [CO2] (a[CO2]) and e[CO2] (ambient + 200 μmol mol−1) at different developmental stages to identify the occurrence of photosynthetic acclimation. We show that FACE condition did not increase individual grain mass across thirty-six inbred rice cultivars at various rates of nitrogen application, and that the replacement of potted plants either from a[CO2] to e[CO2] or from e[CO2] to a[CO2] did not impact the individual grain mass. The yield benefit from e[CO2] was primarily attributed to an increase in the spikelet density determined pre-heading. We conclude that the individual grain mass of inbred rice does not benefit from e[CO2], which is most likely attributed to a loss of the advantage in CO2 gain induced by photosynthetic acclimation. Our findings suggest the necessity for selective breeding strategies to make better use of post-heading e[CO2] and for crop modelers to incorporate updated knowledge into models in the context of elevated [CO2].

Optimizing restoration duration to maximize CO2 uptake on the Tibetan Plateau

Grasslands cover one-third of the terrestrial area, though half of them have been degraded and primarily due to overgrazing. The Tibetan Plateau (TP) is home to the largest area of alpine grassland on Earth, experiencing a typical degradation-restoration story over the past three decades. With the large-scale implementation and long-term duration of ecological projects aimed at restoring degraded grasslands by fencing across the TP, there is considerable uncertainty regarding the direction and magnitude of changes in the carbon (C) sink function. To address this, we combined ten pairs of systematic field observations at the site scale with literature compilation, aiming to clarify whether restoration still contributes to C uptake and its driving factors. Our results show that after a decade of restoration, living biomass was enhanced by over 80 %, and litter accumulation increased by 3.68 ± 1.25 times across all ecosystem types, although these changes were barely reflected in soil C. Litter caused consistent negative impacts on CO2 uptake across all vegetation types, despite restoration having increased CO2 uptake by half in alpine steppes and alpine meadows. This negative impact was more evident in alpine wetlands, where the quantity of litter was double the living biomass. The thick layer of litter produced a shading effect that further limited the photosynthetic yield of living plants, regulating the restoration-induced CO2 gain or loss. Combining 246 cases across the TP further highlights the need to shorten the duration of restoration to maximize CO2 uptake while also benefitting sustainability, which is deserving of attention from both the scientific community and policy-makers.

Restrição hídrica como estratégia no cultivo de Talinum fruticosum (L.) Juss. (Talinaceae)

ABSTRACT Talinum fruticosum is a species confirmed to occur in the semi-arid region, considered an unconventional food plant with a high protein content and tolerant to temporary periods of water restriction. This study aimed to evaluate water deficit as a strategy for growing Talinum fruticosum, covering physiological and biochemical aspects. The experimental design adopted was entirely randomized, using six treatments and eight replications. The treatments were defined as water availability (WA) 0 (no water replenishment), 20, 40, 60, 80, and 100%, conducted in a greenhouse, with water replenishment every 7 days. After 21 days, the centesimal composition, water relations, gas exchange, and biochemical aspects were evaluated. The energy value of the dry biomass of T. fruticosum leaves was directly influenced by the water content in the soil, and the water deficit led to an increase in protein. Water restriction compromised the species' water status and performance, mainly limiting gas exchange by reducing the water content in the soil, compromising CO2 gain. It also led to increased biomolecules, with the highest contents seen in the treatments without water replacement (0%) and for 20% WA. Therefore, reducing the WA to 40% could be a strategy adopted to increase the protein content in the leaves of T. fruticosum, promoting an increase in the centesimal composition of proteins, a reduction in gas exchange, and an increase in the content of biomolecules.

Infant periodic breathing and apneic threshold.

A mathematical model was proposed to predict the role played by apneic threshold in periodic breathing in preterm infants. Prior models have mainly applied linear control theory which predicted instability but could not explain sustained periodic breathing. Apneic threshold to CO2 which has been postulated to play a major role in infant periodic breathing is a nonlinear effect and cannot be described by linear theory. Another previously unexplored nonlinear factor affecting instability is brain vascular volume change with CO2 which affects time delay to chemoreceptors. The current model explored the influences of apneic threshold, central and peripheral chemoreceptor gains, cardiac output, lung volume, and circulatory time delay on periodic breathing. Apneic threshold was found to play a major role in ventilatory responses to spontaneous sighs. Sighs led to apneic pauses followed by periods of periodic breathing with peripheral chemoreceptor CO2 gain, cardiac output, and lung volume were at reported normal levels. Apneic threshold when exceeded was observed to cause an asymmetry in the periodic breathing cycling and an increased periodic breathing frequency. Sighs in infants occur frequently enough to lead to repeated stimulation within the epoch duration of periodic breathing for a single sigh. Multiple sighs may then play a major role in promoting continuous periodic breathing in infants. Peripheral chemoreceptor gain estimated using endogenous CO2 led to validated predicted periodic breathing cycle duration as a function of age. Brain vascular volume increase with CO2 contributes to periodic breathing in very young (1-2 day old) preterm infants.

Biotechnical approach for a continuous simultaneous increase of indoor and outdoor air quality

Phytofiltration is the most sustainable way to achieve a better quality of inlet air in buildings in a polluted environment. But they don’t take into account the biorhythms of plants and pollute the inlet air with CO2 during breathing only time. We collected and analysed data about the biorhythms of plants. As a result, a new bi-directional phytofilter was offered for cleaning and oxygenation of the inlet ventilation air, and also to protect the environment by cleaning the exhaust air from different pollutants. The device has spaces with shifted illumination rhythms and a valve system. A controller directs the inlet air to the space(s), where plants release CO2. The outlet air runs through other spaces. Literature data show that in the less favourable case, the CO2 and oxygen emissions are balanced per day without overall CO2 gain to the environment. When plants are growing, they sequestrate CO2 to catch greenhouse gas emissions. Either natural light, artificial light, or a combination of the two can be used. While the second option simply demands one plant metabolism type, the first option needs a combination of CAM metabolism and other plants

Recent Trends and Variability in the Oceanic Storage of Dissolved Inorganic Carbon

AbstractSeveral methods have been developed to quantify the oceanic accumulation of anthropogenic carbon dioxide (CO2) in response to rising atmospheric CO2. Yet, we still lack a corresponding estimate of the changes in the total oceanic dissolved inorganic carbon (DIC). In addition to the increase in anthropogenic CO2, changes in DIC also include alterations of natural CO2. Once integrated globally, changes in DIC reflect the net oceanic sink for atmospheric CO2, complementary to estimates of the air‐sea CO2 exchange based on surface measurements. Here, we extend the MOBO‐DIC machine learning approach by Keppler et al. (2020a, https://www.ncei.noaa.gov/access/metadata/landing-page/bin/iso?id=gov.noaa.nodc%3A0221526) to estimate global monthly fields of DIC at 1° resolution over the top 1,500 m from 2004 through 2019. We find that over these 16 years and extrapolated to cover the whole global ocean down to 4,000 m, the oceanic DIC pool increased close to linearly at an average rate of 3.2 ± 0.7 Pg C yr−1. This trend is statistically indistinguishable from current estimates of the oceanic uptake of anthropogenic CO2 over the same period. Thus, our study implies no detectable net loss or gain of natural CO2 by the ocean, albeit the large uncertainties could be masking it. Our reconstructions suggest substantial internal redistributions of natural oceanic CO2, with a shift from the midlatitudes to the tropics and from the surface to below ∼200 m. Such redistributions correspond with the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation. The interannual variability of DIC is strongest in the tropical Western Pacific, consistent with the El Nio Southern Oscillation.

The effect of renewable energy development, market regulation, and environmental innovation on CO2 emissions in BRICS countries.

The relationship between energy, environment, and economic growth has been received a lot of attention recently among scientific studies, but environmental sustainability remains a global issue. Renewable energy development, green technological innovations, and regulatory policy mechanisms can all help to reduce greenhouse gas emissions and support environmental sustainability. The purpose of this study was to look at the influence of renewable energy development, market regulation, and environment-related innovation on CO2 emissions in the BRICS countries from 1990 to 2020. For empirical analysis, it uses second-generation panel unit root test and updated linear and nonlinear cointegration techniques. To this end, this study employs symmetric and asymmetric approach to linear and nonlinear relationship among study variables. The findings indicate that there is long-run symmetric and asymmetric relationship between renewable energy development, market regulation, environment-related innovation, and CO2 emissions. The market regulation plays significant mediating role in relation between renewable energy development, environment-related innovation, and CO2 emissions. Our findings suggest that BRICS countries need to more focus on the environment-related innovation and renewable energy development. They should design market-based environmental regulation policies, emphasize on environmental taxes, expand renewable energy development, and environment-related innovations. Such strategies are key to limiting CO2 emissions and gain environmental sustainable.

干旱叠加海平面上升、氮负荷增加对河口潮汐沼泽生态系统净CO2交换的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱叠加海平面上升、氮负荷增加对河口潮汐沼泽生态系统净CO2交换的影响 DOI: 10.5846/stxb202106291727 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 福建省自然科学基金重点项目（2019J02008）；福建省林业科技项目（201916）；国家自然科学基金项目（41877335） Effects of combination of drought and sea-level rise, nitrogen enrichment on net ecosystem exchange of CO2 in an estuarine tidal marsh Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:河口潮汐沼泽湿地是全球重要的蓝碳生态系统之一。海平面上升和氮负荷增加是入海河流河口湿地面临的两个主要环境问题。近年来，干旱事件频发，干旱及其与海平面上升、氮负荷增加的叠加将如何影响河口潮汐沼泽湿地生态系统净CO2交换，目前还未见报道。2020年夏秋，福建沿海经历了数月严重的气象干旱，这为揭示干旱对河口潮汐沼泽湿地生态系统净CO2交换量（NEE）和生态系统呼吸（ER）的影响提供了一个契机。分别于2019年8-10月（正常天气）和2020年8-10月（干旱天气），在闽江河口微咸水短叶茳芏沼泽湿地运用光合作用测定仪+箱法测定不同处理（对照、模拟海平面上升、模拟氮负荷增加、模拟海平面上升＋模拟氮负荷增加）短叶茳芏湿地生态系统NEE和ER，以期揭示气象干旱与海平面上升、氮负荷增加的叠加对河口沼泽湿地生态系统净CO2交换的影响。与正常天气相比，干旱天气下各处理（包含对照）的NEE均显著降低（P<0.05）；对照、海平面上升以及氮负荷增加处理样地的ER显著减少（P<0.05），海平面上升＋氮负荷增加处理ER显著增加（P<0.05）。NEE （负值）与光合有效辐射（PAR）与呈显著负相关（P<0.05）。研究发现，气象干旱降低了河口潮汐沼泽生态系统固碳规模，且这种固碳规模的降低在叠加海平面上升或氮负荷增加的情景下仍将存在。 Abstract:Estuarine tidal marsh is one of the coastal blue carbon ecosystems in the world. Sea level rise and nitrogen enrichment are two major global environmental issues facing by estuarine wetlands. In recent years, meteorological drought events often occurred. The influences of drought, and combination of drought and sea-level rise, and nitrogen enrichment on net ecosystem exchange (NEE) of CO2 of estuarine tidal marshes remain poorly studied. A novel approach using the weirs for in-situ manipulating sea level rise (including the increase of depth and duration of flooding) at relatively larger spatial scale was developed in the journal of Methods in Ecology & Evolution, however at present, the method has not been actually used in-situ to study effects of sea level rise on carbon cycle in coastal tidal marsh ecosystem. In our study, we improved the weirs and used them to manipulate the sea level rise (SR) treatment in-situ, and meanwhile applied in-situ experimental manipulations of control, nitrogen enrichment (NE), and SR+NE in a tidal brackish marsh of Cyperus malaccensis in the Minjiang River estuary, southeastern China. In summer and autumn of 2020, the meteorological drought occurred in the coastal zone of Fujian Province, which provided an opportunity to determine the effects of drought, the combination of drought and simulated sea-level rise, nitrogen enrichment on the NEE and ecosystem respiration (ER). From August to October in 2019 and 2020, the NEE and ER were measured using transparent static chamber (or black cloth shading)+Licor-6800 method. Compared with 2019 (normal year), the NEE under each treatment (including control) was significantly reduced in 2020 (drought year), and the ER in the control, the SR, and the NE was also significantly decreased in 2020. NEE was significantly negatively correlated with the photosynthetically active radiation (PAR). The results indicate that drought event can reduce net CO2 gain in estuarine tidal marshes, and this decrease still occurs under combination of drought and sea-level rise, nitrogen enrichment. 参考文献 相似文献 引证文献

Leaf gas exchange and δ13C in cowpea and triticale under water stress and well-watered conditions

Leaf gas exchanges play a critical role in determining crop productivity as they control both CO2 gain and water loss. CO2 gain and water loss influence water use efficiency (WUE) and carbon isotope composition (δ13C). Responses in leaf gas exchanges to water stress are species-specific. However, the extent of this variation in C3 crops is less studied. A field study was carried out to investigate the influence of water stress on leaf gas exchanges of triticale and cowpea. Crops were grown under water stress and well-watered conditions and leaf gas exchanges were determined at flowering. The results showed that triticale maintained a higher stomatal conductance (gs), transpiration rate(E) and intercellular CO2 concentration (ci) compared to cowpea but did not differ in photosynthetic rate(A). As a result, triticale discriminated against 13C more than cowpea. These results suggest a higher influence of ci on δ13C than A. Despite triticale maintaining higher rates of ci, A and gs, it had lower WUE compared to cowpea. Consequently, triticale grain yield was more sensitive to water stress than cowpea. The findings of this study showed significant variation in leaf gas exchanges and δ13C between two drought-tolerant C3 crops suggesting differences in their response mechanism to water stress.

Photosynthetic activity increases with leaf size and intercellular spaces in an allomorphic lianescent aroid Rhodospatha oblongata.

This study aimed to investigate leaf anatomy, as well as photosynthetic gas exchange, that underlie the improvement in light foraging capacity, which appears to occur in aroid vines seeking light exposure. Three levels of plant height (soil level, 3 m and 6 m) were categorised for the aroid vine Rhodospatha oblongata Poepp. to represent the transition from ground to canopy. Compared with shaded leaves, leaves exposed to high light conditions were thicker, presenting a larger, spongy parenchyma characterised by a larger transversal area of intercellular spaces. In addition to the increase in maximum CO2 assimilation (Amax) and thicker and larger leaf lamina, we found an increased light saturation point, light compensation point and water use efficiency at 500 µmol PPFD. Nitrogen content per leaf dry mass remained constant across habitats, but Amax/N was 1.5-times greater in the canopy position than in the leaves at soil level, suggesting that CO2 gain did not rely on an N-related biochemical apparatus. The lower δ13C discrimination observed at high canopy leaves corroborated the higher photosynthesis. Altogether, these results suggest that the large and exposed aroid leaves maintained carbon gain coupled with light gain through investing in a more efficient proportion of intercellular spaces and photosynthetic cell surface, which likely allowed a less pronounced CO2 gradient in substomatal-intercellular space.

Light-Mediated Signaling and Metabolic Changes Coordinate Stomatal Opening and Closure.

Stomata are valves on the leaf surface controlling carbon dioxide (CO2) influx for photosynthesis and water loss by transpiration. Thus, plants have to evolve elaborate mechanisms controlling stomatal aperture to allow efficient photosynthesis while avoid excessive water loss. Light is not only the energy source for photosynthesis but also an important signal regulating stomatal movement during dark-to-light transition. Our knowledge concerning blue and red light signaling and light-induced metabolite changes that contribute to stomatal opening are accumulating. This review summarizes recent advances on the signaling components that lie between the perception of blue/red light and activation of the PM H+-ATPases, and on the negative regulation of stomatal opening by red light-activated phyB signaling and ultraviolet (UV-B and UV-A) irradiation. Besides, light-regulated guard cell (GC)-specific metabolic levels, mesophyll-derived sucrose, and CO2 concentration within GCs also play dual roles in stomatal opening. Thus, light-induced stomatal opening is tightly accompanied by brake mechanisms, allowing plants to coordinate carbon gain and water loss. Knowledge on the mechanisms regulating the trade-off between stomatal opening and closure may have potential applications toward generating superior crops with improved water use efficiency (CO2 gain vs. water loss).

Effects of Drought and Heat on Photosynthetic Performance, Water Use and Yield of Two Selected Fiber Hemp Cultivars at a Poor-Soil Site in Brandenburg (Germany)

Hemp currently regains certain importance as fiber, oil and medical crop not least because of its modest requirements of biocides, fertilizer and water. During recent years, crops were exposed to a combination of drought and heat, even in northern Central-Europe. Dynamic responses of photosynthesis and stomatal conductance to these stresses and their persistent effects had been studied, if at all, in controlled environment experiments. Comprehensive field studies on diurnal and long-term net photosynthesis and gas exchange, and yield properties of hemp during a drought prone, high-temperature season in northern Central-Europe are obviously missing. Thus, in whole season field trails, the essential actual physiological (rates of net photosynthesis and transpiration, stomatal conductance, water use efficiencies, ambient and internal CO2 concentrations) and the yield performance of modern high-yielding multi-purpose hemp cultivars, ‘Ivory’ and ‘Santhica 27’, were evaluated under extreme environmental conditions and highly limited soil water supply. This provides comprehensive information on the usability of these cultivars under potential future harsh production conditions. Plants of both cultivars differentially cope with the prevailing climatic and soil water conditions. While ‘Ivory’ plants developed high rates of CO2 gain and established large leaf area per plant in the mid-season, those of ‘Santhica 27’ utilized lower CO2 uptake rates at lower leaf area per plant most time. This and the higher germination success of ‘Santhica 27’ resulted in nearly twice the yield compared to ‘Ivory’. Although stomatal control of CO2 gain was pronounced in both cultivars, higher stomatal limitations in ‘Ivory’ plants resulted in higher overall intrinsic water use efficiency. Cultivation of both hemp cultivars with only basic irrigation during seed germination was successful and without large effects on yield and quality. This was valid even under extremely hot and dry climatic conditions in northern Central Europe.

On the CO2 gain in on-line hemodiafiltration.

The dialysis bath holds up to 90mmHg carbon dioxide (CO2 ) in order to keep pH low and salts in their soluble forms. CO2 crosses the dialyzer membrane and diffuses to patients. In post-dilution on-line hemodiafiltration (HDF) many liters of CO2 -containing dialysis bath - in the form of infusate - are delivered directly to patients bypassing the filtering membrane, but the precise amount of CO2 delivered is unknown. To gain insights on this issue 18 outpatients undergoing their regular on-line HDF were investigated by means of blood gas analysis. Arterial pre-dialysis samples show slight hypocapnia (35.40±3.22mmHg) consistent with the secondary compensatory response to metabolic acidosis. In blood coming back to patients (venous line of extracorporeal circuit) pCO2 doubled, amounting to 69±5.5mmHg (P<.0001 with respect to pre-dialysis values) hence in on-line HDF a CO2 gain does occur. Turning off the infusate flux pump, pCO2 decreased to 63.1±5.8mmHg (P=.004) meaning that delivery of infusate in post-dilution mode significantly contributes to CO2 gain, albeit by a small amount. On-line HDF is featured by CO2 delivery to patients, in part dragged by the infusate.

Applicability and consequences of the integration of alternative models for CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; transfer velocity into a process-based lake model

Abstract. Freshwater lakes are important in carbon cycling, especially in the boreal zone where many lakes are supersaturated with the greenhouse gas carbon dioxide (CO2) and emit it to the atmosphere, thus ventilating carbon originally fixed by the terrestrial system. The exchange of CO2 between water and the atmosphere is commonly estimated using simple wind-based parameterizations or models of gas transfer velocity (k). More complex surface renewal models, however, have been shown to yield more correct estimates of k in comparison with direct CO2 flux measurements. We incorporated four gas exchange models with different complexity into a vertical process-based physico-biochemical lake model, MyLake C, and assessed the performance and applicability of the alternative lake model versions to simulate air–water CO2 fluxes over a small boreal lake. None of the incorporated gas exchange models significantly outperformed the other models in the simulations in comparison to the measured near-surface CO2 concentrations or respective air–water CO2 fluxes calculated directly with the gas exchange models using measurement data as input. The use of more complex gas exchange models in the simulation, on the contrary, led to difficulties in obtaining a sufficient gain of CO2 in the water column and thus resulted in lower CO2 fluxes and water column CO2 concentrations compared to the respective measurement-based values. The inclusion of sophisticated and more correct models for air–water CO2 exchange in process-based lake models is crucial in efforts to properly assess lacustrine carbon budgets through model simulations in both single lakes and on a larger scale. However, finding higher estimates for both the internal and external sources of inorganic carbon in boreal lakes is important if improved knowledge of the magnitude of CO2 evasion from lakes is included in future studies on lake carbon budgets.

CO2 emission and soil carbon sequestration from spring- and fall-applied poultry litter in corn production as simulated with RZWQM2

Poultry litter has increasingly been used as fertilizer in row crop production systems in the southeastern USA, leading to potential improvement of soil carbon (C) stocks. However, this improvement is accompanied by substantial losses of litter-derived C as CO2 emission, the balance of which has not been well investigated. A calibrated and validated Root Zone Water Quality Model (RZWQM2) with continuous 3-yr comprehensive field data was used to simulate and quantify soil CO2 emission and gain and loss of litter-derived C in a corn (Zea mays L.) production system in northern Mississippi USA. The corn field was fertilized with poultry litter (18,000 kg ha−1 yr−1) or NO3NH4 (202 kg ha−1 N yr−1) applied in the spring or fall over 3-yr. The results showed that simulated CO2 emissions from soil fertilized with litter averaged across years was approximately 0.8 times higher than soil fertilized with NH4NO3. Simulated CO2 emission loss from fall-applied litter was 16% higher than spring-applied litter when averaged across three years. The emission 59% of added litter C was lost as CO2 over the 3 yr course of the experiment, with an average loss rate of 7.53 kg C ha−1 d−1, implying 41% of C added remained in the soil profile. Relative to NH4NO3, litter increased soil total C by an average 1882 kg C ha−1 yr−1. The results overall show that, although the majority C applied to corn soil in the form of poultry litter may be lost as CO2, about 41% of it is stored in the soil in the short term may be contributing to the soil organic matter pool.

Facultative CAM photosynthesis (crassulacean acid metabolism) in four species of Calandrinia, ephemeral succulents of arid Australia.

Crassulacean acid metabolism (CAM) was demonstrated in four small endemic Australian terrestrial succulents from the genus Calandrinia (Montiaceae) viz. C. creethiae, C. pentavalvis, C. quadrivalvis and C. reticulata. CAM was substantiated by measurements of CO2 gas-exchange and nocturnal acidification. In all species, the expression of CAM was overwhelmingly facultative in that nocturnal H+ accumulation was greatest in droughted plants and zero, or close to zero, in plants that were well-watered, including plants that had been droughted and were subsequently rewatered, i.e. the inducible component was proven to be reversible. Gas-exchange measurements complemented the determinations of acidity. In all species, net CO2 uptake was restricted to the light in well-watered plants, and cessation of watering was followed by a progressive reduction of CO2 uptake in the light and a reduction in nocturnal CO2 efflux. In C. creethiae, C. pentavalvis and C. reticulata net CO2 assimilation was eventually observed in the dark, whereas in C. quadrivalvis nocturnal CO2 exchange approached the compensation point but did not transition to net CO2 gain. Following rewatering, all species returned to their original well-watered CO2 exchange pattern of net CO2 uptake restricted solely to the light. In addition to facultative CAM, C. quadrivalvis and C. reticulata exhibited an extremely small constitutive CAM component as demonstrated by the nocturnal accumulation in well-watered plants of small amounts of acidity and by the curved pattern of the nocturnal course of CO2 efflux. It is suggested that low-level CAM and facultative CAM are more common within the Australian succulent flora, and perhaps the world succulent flora, than has been previously assumed.

Root-derived bicarbonate assimilation in response to variable water deficit in Camptotheca acuminate seedlings.

Water deficit is one of the key factors that limits the carbon (C) assimilation and productivity of plants. The effect of variable water deficit on recently root-derived bicarbonate assimilation in Camptotheca acuminate seedlings was investigated. Three-month-old seedlings were subjected to three water regimes, well-watered (WW), moderate stress (MS), and severe stress (SS) induced by polyethyleneglycol, in conjunction with relatively high (H) and low (L) natural 13C-abundance of NaHCO3-labeled treatments in hydroponics for 14 days. The δ13C of the newly expanded leaves in H were generally more enriched in heavy isotopes than were those in L, indicative of the involvement of bicarbonate in aboveground tissues. The C isotope fractionation of newly expanded leaves relative to air (∆13Cair-leaves) ranged from 17.78 to 21.78‰ among the treatments. The ∆13Cair-leaves under the MS and SS treatments in H were both more negative than was that in L. A linear regression between Ci/Ca and ∆13Cair-leaves in both L and H were different from the theoretical regression. On the basis of the two end-member mixing model, the proportion of fixed CO2 supplied from bicarbonate contributing to the total photosynthetically inorganic C assimilation were 10.34, 20.05 and 16.60% under the WW, MS, and SS treatments, respectively. These results indicated that the increase in water deficit decreased the atmospheric CO2 gain but triggered a compensatory use of bicarbonate in C. acuminate seedlings.

高CO2浓度对杂交水稻光合作用日变化的影响——FACE研究

PDF HTML阅读 XML下载 导出引用 引用提醒 高CO2浓度对杂交水稻光合作用日变化的影响——FACE研究 DOI: 10.5846/stxb201509261974 作者: 作者单位: 扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心;扬州大学 环境科学与工程学院;中国科学院 南京土壤研究所;中国科学院 南京土壤研究所,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 环境科学与工程学院,扬州大学 环境科学与工程学院,中国科学院 南京土壤研究所;中国科学院 南京土壤研究所,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心,扬州大学 江苏省作物遗传生理国家重点实验室培育点/粮食作物现代产业技术协同创新中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（31571597，31371563，31171460）；国家自然科学基金国际（地区）合作与交流项目（31261140364）；中国博士后科学基金资助项目（2015M581870）；江苏省博士后科研资助计划（1501077C）；江苏高校优势学科建设工程项目资助 Effect of increasing atmospheric CO2 concentration on photosynthetic diurnal variation characteristics of hybrid rice: a FACE study Author: Affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology/ Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University,Jiangsu Key Laboratory of Crop Genetics and Physiology/ Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University,,,,,,Jiangsu Key Laboratory of Crop Genetics and Physiology/ Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:大气二氧化碳（CO2）浓度增高导致全球变暖，但作为光合作用底物促进绿色作物的光合作用。为了明确高CO2浓度对杂交水稻结实期光合日变化的影响，2014年利用稻田FACE（Free Air CO2 Enrichment）平台，以生产上曾创高产纪录的两个杂交稻新组合甬优2640和Y两优2号为供试材料，设置环境CO2和高CO2浓度（增200 μmol/mol）两个水平，测定杂交稻抽穗期和灌浆中期光合作用日变化和成熟期生物量。结果表明，高CO2浓度环境下两组合抽穗期叶片净光合速率均大幅增加（全天平均52%），但灌浆中期的平均增幅减半，其中Y两优2号这种光合下调表现更为明显。大气CO2浓度升高使两杂交稻组合抽穗和灌浆中期叶片气孔导度均大幅下降，导致蒸腾速率下降而水分利用效率大幅增加，Y两优2号气孔导度和蒸腾速率对CO2的响应上午大于下午，而甬优2640表现相反。尽管大气CO2浓度升高使杂交稻结实期不同时刻胞间CO2浓度均大幅增加，但对气孔限制值特别是胞间CO2与空气CO2浓度之比多无显著影响，两品种趋势一致。大气CO2浓度升高对甬优2640地上部生物量及其组分的影响明显大于Y两优2号，CO2与品种间多存在互作效应。以上结果表明，与甬优2640相比，Y两优2号最终生产力从高CO2浓度环境中获益较少可能与该品种生长后期存在明显的光合适应有关，但这种光合适应似乎不是由气孔限制造成的。 Abstract:The rising of atmospheric carbon dioxide (CO2) concentration has been blamed for global warming, but it promotes the leaf photosynthesis of crops because CO2 is the main substrate for photosynthesis. In order to understand the effect of elevated CO2 concentration on diurnal courses of CO2 uptake of hybrid rice, a paddy field experiment utilizing free air CO2 enrichment (FACE) technology was undertaken to determine diurnal courses of leaf photosynthesis at heading and middle grain filling stages, and its association with the final productivity of rice at maturity. Two hybrid rice variety Yongyou 2640 (YY 2640) and YLiangyou No.2 (YLY 2) were grown in the ambient CO2 and the elevated CO2 concentration (200 μmol/mol above ambient) from plant transplanting until grain maturity. Elevated CO2 concentration significantly increased net photosynthetic CO2 assimilation of flag leaves of two hybrids by 52% on average at heading, but the enhancement was reduced to half at the middle grain filling stage. This photosynthesis acclimation was more pronounced in YLY 2. Elevated CO2 concentration significantly decreased stomatal conductance of two hybrids at both heading and grain filling stages, resulting in lower transpiration and higher water use efficiency. Greater CO2 responses of leaf transpiration and stomatal conductance were observed in the morning for YLY 2, but YY 2640 showed higher CO2 effects in the afternoon. Growth at elevated CO2 concentration significantly increased intercellular CO2 concentration, but had no clear effects on the ratio of intercellular to air CO2 concentration and stomata limitation value, and the same trend was observed for the two varieties. The CO2 effects on the above-ground biomass and its components were greater in YY 2640 than YLY 2, and it was reflected in the significant CO2 by variety interactions. The results indicated that compared with YY 2640, the lower CO2 gain on final productivity of YLY 2 might result from photosynthesis acclimation at the late growth stage, and this down-regulation in leaf photosynthesis was not caused by stomatal limitation. 参考文献 相似文献 引证文献

Abiotic contribution to total soil CO2 flux across a broad range of land-cover types in a desert region

As an important component of ecosystem carbon (C) budgets, soil carbon dioxide (CO2) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiotic component can be important in total soil CO2 flux (Rtotal), its relative importance has never been systematically assessed. In this study, after comparative measurements of CO2 fluxes on sterilized and natural soils, the Rtotal was partitioned into biotic flux (Rbiotic) and abiotic flux (Rabiotic) across a broad range of land-cover types (including eight sampling sites: cotton field, hops field, halophyte garden, alkaline land, reservoir edge, native saline desert, dune crest and interdune lowland) in Gurbantunggut Desert, Xinjiang, China. The relative contribution of Rabiotic to Rtotal, as well as the temperature dependency and predominant factors for Rtotal, Rbiotic and Rabiotic, were analyzed. Results showed that Rabiotic always contributed to Rtotal for all of the eight sampling sites, but the degree or magnitude of contribution varied greatly. Specifically, the ratio of Rabiotic to Rtotal was very low in cotton field and hops field and very high in alkaline land and dune crest. Statistically, the ratio of Rabiotic to Rtotal logarithmically increased with decreasing Rbiotic, suggesting that Rabiotic strongly affected Rtotal when Rbiotic was low. This pattern confirms that soil CO2 flux is predominated by biotic processes in most soils, but abiotic processes can also be dominant when biotic processes are weak. On a diurnal basis, Rabiotic cannot result in net gain or net loss of CO2, but its effect on transient CO2 flux was significant. Temperature dependency of Rtotal varied among the eight sampling sites and was determined by the predominant processes (abiotic or biotic) of CO2 flux. Specifically, Rbiotic was driven by soil temperature while Rabiotic was regulated by the change in soil temperature (ΔT). Namely, declining temperature (ΔT 0) resulted in positive Rabiotic (i.e., CO2 released from soil). Without recognition of Rabiotic, Rbiotic would be overestimated for the daytime and underestimated for the nighttime. Although Rabiotic may not change the sum or the net value of daily soil CO2 exchange and may not directly constitute a C sink, it can significantly alter the transient apparent soil CO2 flux, either in magnitude or in temperature dependency. Thus, recognizing the fact that abiotic component in Rtotal exists widely in soils has widespread consequences for the understanding of C cycling.