Normal CO2 Concentration Research Articles

Growth and actual leaf temperature modulate CO2responsiveness of monoterpene emissions from holm oak in opposite ways

Abstract. Climate change can profoundly alter volatile organic compound (VOC) emissions from vegetation and thus influence climate evolution. Yet, the short- and long-term effects of elevated CO2 concentrations on emissions in interaction with temperature are not well enough understood, especially for VOCs other than isoprene. To gain additional insight, we conducted a study on holm oak, which is known for its strong foliar monoterpene emissions that are directly linked to their synthesis. We measured CO2-response curves of emissions, CO2–H2O gas exchanges and chlorophyll fluorescence at two assay temperatures (30 and 35 ∘C) on saplings of four populations grown under normal and double CO2 concentrations combined with two temperature growth regimes differing by 5 ∘C (day/night: 25/15 and 30/20 ∘C). A stepwise reduction in CO2 resulted in a decrease in emissions, occasionally preceded by an increase, with the overall decrease in emissions being greater at 35 ∘C than at 30 ∘C assay temperature. During ramping to high CO2, emissions remained mostly unchanged at 35 ∘C, whereas at 30 ∘C they often dropped, especially at the highest CO2 levels (≥ 1200 ppm). In addition to the actual leaf temperature, the high CO2 responsiveness of emissions was modulated by the plant's growth temperature with warm-grown plants being more sensitive than cool-grown plants. In contrast, growth CO2 had no significant effect on the CO2 sensitivity of emissions, although it promoted plant growth and the leaf emission factor. Correlation analyses suggest that the emission response to CO2 depended primarily on the availability of energetic cofactors produced by photosynthetic electron transport. This availability was likely limited by different processes that occurred during CO2 ramping including photooxidative stress and induction of protective and repair mechanisms as well as competition with CO2 fixation and photorespiration. In addition, feedback inhibition of photosynthesis may have played a role, especially in leaves whose emissions were inhibited only at very high CO2 levels. Overall, our results confirm an isoprene-analogous behavior of monoterpene emissions from holm oak. Emissions exhibit a non-linear response curve to CO2 similar to that currently used for isoprene emission in the MEGAN model, with no difference between major individual monoterpene species and plant chemotype. Simulations estimating the annual VOC releases from holm oak leaves at double atmospheric CO2 indicate that the observed high-CO2 inhibition is unlikely to offset the increase in emissions due to the predicted warming.

Carbon Dioxide Footprint and Its Impacts: A Case of Academic Buildings

Carbon emissions have been considered a major reason behind climate change and global warming. Various studies report that rapid urbanization and the changing demands of 21st century life have resulted in higher carbon emissions. This study aims to examine the carbon footprints in an academic building to observe the carbon dioxide (CO2) levels at crucial landmarks and offices. A sensor-based automated system was designed and implemented for the collection of CO2 concentrations at selected locations. In the final stage, a CO2 footprint map was generated to highlight the vulnerable areas of CO2 in the academic building. It was concluded that offices have higher CO2 concentrations at both intervals (morning and afternoon), followed by the laboratory, corridors, and praying area. The CO2 concentration did not exceed 500 ppm at any location. Thus, all locations other than offices had normal CO2 concentration levels. Similarly, the humidity level was also satisfactory. The average humidity level was below 50%, which is below the permissible value of 65%. The recommended range for temperature values as per ASHRAE standards is 22.5 °C to 25.5 °C, except for prayer places. It was concluded that the selected academic institute is providing a good environment to the users of the building, but that may change once the academic institute becomes fully functional after COVID-19. This study assists the stakeholders in making guidelines and necessary actions to reduce CO2 concentration in academic buildings, as it is expected to rise once the human load increases in the next academic year. The suggested approach can be used in any other country and the results will vary based on the building type, building energy type, and building ventilation design.

Primary Metabolite Profile Changes in Coffea spp. Promoted by Single and Combined Exposure to Drought and Elevated CO2 Concentration.

Climate change scenarios pose major threats to many crops worldwide, including coffee. We explored the primary metabolite responses in two Coffea genotypes, C. canephora cv. Conilon Clone 153 and C. arabica cv. Icatu, grown at normal (aCO2) or elevated (eCO2) CO2 concentrations of 380 or 700 ppm, respectively, under well-watered (WW), moderate (MWD), or severe (SWD) water deficit conditions, in order to assess coffee responses to drought and how eCO2 can influence such responses. Primary metabolites were analyzed with a gas chromatography time-of-flight mass spectrometry metabolomics platform (GC-TOF-MS). A total of 48 primary metabolites were identified in both genotypes (23 amino acids and derivatives, 10 organic acids, 11 sugars, and 4 other metabolites), with differences recorded in both genotypes. Increased metabolite levels were observed in CL153 plants under single and combined conditions of aCO2 and drought (MWD and SWD), as opposed to the observed decreased levels under eCO2 in both drought conditions. In contrast, Icatu showed minor differences under MWD, and increased levels (especially amino acids) only under SWD at both CO2 concentration conditions, although with a tendency towards greater increases under eCO2. Altogether, CL153 demonstrated large impact under MWD, and seemed not to benefit from eCO2 in either MWD and SWD, in contrast with Icatu.

Effects of CO2 on transplantation of grape plantlets cultured in vitro by promoting photosynthesis

Plantlet in vitro is an indispensable step in micropropagation and breeding of grape (Vitis vinifera L.). However, the plantlets rely on the artificially controlled micro-environment, which is difficult to adapt to the field acclimation and transplantation, resulting in low survival rate and qualified plantlets rate. Studying the photosynthetic and growth characteristics of plantlets cultured with CO2 and sucrose as carbon sources presents important references for the acclimation and transplantation. In this context, "Pinot Noir" plantlets in vitro were cultured with S1: medium with 2% sucrose, normal carbon dioxide (CO2) concentration (380 μmol•mol−1), CS: medium with 2% sucrose, high CO2 concentration (1000 μmol•mol−1), C0: medium without sucrose, high CO2 concentration (1000 μmol•mol−1) and S0: medium without sucrose, normal CO2 concentration (380 μmol•mol−1). The results indicated that the growth status and survival rate (an average increase of 19.4%) of plantlets were significantly improved by high concentration CO2 treatments. The photosynthetic parameters of high-concentration CO2 treatments had a positive effect on photosynthetic products, which were consistent with the up-regulated trend of the relative expression of related synthesis and transport genes. Interestingly, the sugar content of photosynthetic products in leaves showed a trend from high to low at different carbon treatment stages, but the opposite trend was observed in stems. What's more, the main photosynthetic parameters of high concentration CO2 treatments were significantly increased, especially the photosynthetic fluorescence parameters of CS were the highest, and the relative expression of photosynthesis related genes were significantly up-regulated during acclimation and transplantation. Comprehensive principal component analysis method speculated that exogenous CO2 mainly laid a good foundation for the acclimation and transplantation by promoting the photosynthesis of plantlets and adjusting the source-sink relationship of leaf and stem photosynthetic products.

An Experimental Study of Greenhouse Gas Concentration on the Maximum Power Point of Solar PV Panels

The energy demand increases along with demographic and development growth. India is the second-most populous country in the world and most of its population needs more energy as its human and energy development indices are rather low. So, the country depends on cheaper sources of energy which have ample effects on the environment. Many energy sources are polluting, but solar energy is pollution-free and its availability is abundant with zero cost. Solar Photo Voltaic (PV) technology is the best technology to harness electricity. The effect of varying environmental factors regulates the performance factors of this technology. Its efficiency mainly depends on the concentration of greenhouse gases (GHGs), ambient temperature, module temperature, incoming solar radiation intensity, and PV material composition. To understand the behavior of solar panels on maximum power point under various GHGs concentrations, three experiments were conducted. One in normal atmospheric CO2 concentration and two in higher CO2 concentration chambers.

Exogenous Root Uptake of Glycine Betaine Mitigates Improved Tolerance to Salinity Stress in Avicenna germinans under Ambient and Elevated CO2 Conditions

In recent years, climate change has caused unpredictable variations in sea levels and an increase in atmospheric CO2 levels. Increasing temperatures and subsequent rates of evaporation have been demonstrated to cause increased coastal salinity in certain areas, which induces abiotic stress, in mangroves systems. The osmolyte, glycine betaine, has been shown in numerous studies to increase the tolerance of plants to environmental stressors, including salt stress. A handful of studies have demonstrated that increased CO2 concentrations confer increased salt tolerance and photosynthetic productivity of different mangrove species. Avicenna germinans, commonly referred to as the black mangrove, is native to Pacific and Atlantic coasts, and produces glycine betaine endogenously. This study sought to characterize the response of A. germinans exposed to increasing saline conditions, grown under normal and high CO2 concentrations. Elucidation of the role glycine betaine accumulation plays in tolerance to abiotic stress was investigated. A. germinans seedlings were subjected to increasing levels of salt stress (15–90 ppt) and treated with a dose response of glycine betaine (0–50 μM). Half of the seedlings were grown under ambient (400 ppm) CO2 conditions, and the other half were grown under elevated (800 ppm) CO2 conditions. Increased salinity tolerance and higher photosynthetic rates were observed among seedlings exposed to elevated CO2 conditions, as indicated by increased survival rates and qualitative health observations. This research may provide insights into potential consequences posed by climate change, as well as characterizing the glycine betaine signaling pathway in this mangrove species. Looking into the future, the knowledge obtained through this study may potentially contribute to our predictions of mangrove adaptability and therefore conferred protection of our coastlines in an ever‐changing world.

A Vegetation Climatic Unit for Studying the Impact on Higher Plants of an Increased CO2 Concentration in Comparison with the Atmospheric CO2 Concentration

An experimental vegetative climatic unit (VCU) consisting of two identical climatic chambers—experimental (CC-1) and control (CC-2)—was developed. The VCU allows long-term cultivation of higher plants under various constant microclimate conditions, moisture supply, and CO2 concentration. The basic scheme of the VCU and its parameters and operation are considered. As a result of a long (50 days) vegetation experiment in the VCU, we evaluated the effect of a double atmospheric CO2 concentration on СО2/Н2О gas exchange, the water status of leaves, and the biological productivity of pea (Pisum sativum L.) plants. The water status of the plant leaves of the experimental and control variants was evaluated based on the water potential value on the surface of the apoplast of the substomatal cavity. Compared to control plants under conditions of double CO2 concentration, a 1.5-fold increase in leaf, stem, and root weight was noted. The preservation of proportional organ growth under growing conditions at a double concentration of atmospheric CO2 in pea varieties with contrasting biological productivity—the highly productive Alpha variety and the unproductive Medovik variety—indicated the absence of varietal specificity of the pea growth reaction to increased CO2. The maximum yield of chlorophyll FSII fluorescence, photosynthetic CO2/H2O-gas exchange of intact leaves, measured at normal CO2 concentration, as well as the water status of the leaves, were the same in the plants of the experimental and control variants of the Medovik variety. With other conditions being equal, a double CO2 concentration of under nonlimiting by the water regime and mineral nutrition conditions of pea plant growing formed a leaf that does not differ from the leaf formed under a normal CO2 concentration. An increase in the biological productivity of peas under these conditions was provided by an increased photosynthetic carboxylation activity under increased atmospheric CO2 concentration and the formation of higher stem and leaf phytomass. As a result, it was concluded that the reaction of the photosynthetic and growth functions of pea plants to long-term cultivation under conditions of a double atmospheric CO2 concentration at nonlimiting by mineral nutrition and water supply conditions did not cause imbalances in growth and development. The reaction of the photosynthetic and growth functions of pea plants was within the physiological norm of the reaction of a pea plant to stress.

Provision of carbon skeleton for lipid synthesis from the breakdown of intracellular protein and soluble sugar in Phaeodactylum tricornutum under high CO2

BackgroundIncreasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. The physiological and biochemical processes of marine phytoplankton in response to ocean acidification have been reported, but have been mainly focused on growth and photosynthetic physiology. To acquire a thorough knowledge of the molecular regulation mechanisms, model species with clear genetic background should be selected for systematic study. Phaeodactylum tricornutum is a pennate diatom with the characteristics of small genome size, short generation cycle, and easy to transform. Furthermore, the genome of P. tricornutum has been completely sequenced.Results and discussionIn this study, P. tricornutum was cultured at high and normal CO2 concentrations. Cell composition changes during culture time were investigated. The 13C isotope tracing technique was used to determine fractional labeling enrichments for the main cellular components. The results suggested that when lipid content increased significantly under high CO2 conditions, total protein and soluble sugar contents decreased. The 13C labeling experiment indicated that the C skeleton needed for fatty acid C chain elongation in lipid synthesis under high CO2 conditions is not mainly derived from NaHCO3 (carbon fixed by photosynthesis).ConclusionThis study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration.

Effects of increased CO2 and temperature on the growth and photosynthesis in the marine macroalga Gracilaria lemaneiformis from the coastal waters of South China

The marine red macroalga Gracilaria lemaneiformis (Gracilariales, Rhodophyta) is one of the most important species for seaweed cultivation along the coastal waters of South China. In this study, G. lemaneiformis was incubated under present-day (390 ppm) or predicted-year CO2 levels (700 ppm), and under normal (20 °C) versus elevated temperatures (24 °C), to investigate possible effects of climate change conditions on the growth and photosynthesis. The chlorophyll a (Chl a), carotenoid (Car), and phycobiliprotein (PB) contents responded significantly to increased temperature under normal CO2 and high CO2 concentrations. However, CO2 enrichment in the culture had no significant impact on Chl a and Car but decreased the PB contents in G. lemaneiformis. The growth rates of G. lemaneiformis were significantly improved by increasing temperature, especially under concurrent increasing CO2 levels. Additionally, short-term exposure to high temperature stimulated the irradiance-saturated maximum photosynthetic rate (P max), and this stimulation was preserved with exposure to the high temperature in long-term incubations, with such stimulation being much more pronounced under normal CO2 concentrations than high CO2 concentrations. Results suggest that increased temperature exerted more pronounced effects on the growth and photosynthesis of G. lemaneiformis than increased CO2 concentrations did. We proposed that the sea cultivation of G. lemaneiformis would benefit from the ongoing climate change (increasing atmospheric CO2 concentrations and sea surface temperatures) through enhanced growth and carbon sequestration.

Oxidation of P700 in Photosystem I Is Essential for the Growth of Cyanobacteria.

The photoinhibition of photosystem I (PSI) is lethal to oxygenic phototrophs. Nevertheless, it is unclear how photodamage occurs or how oxygenic phototrophs prevent it. Here, we provide evidence that keeping P700 (the reaction center chlorophyll in PSI) oxidized protects PSI. Previous studies have suggested that PSI photoinhibition does not occur in the two model cyanobacteria, Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942, when photosynthetic CO2 fixation was suppressed under low CO2 partial pressure even in mutants deficient in flavodiiron protein (FLV), which mediates alternative electron flow. The lack of FLV in Synechococcus sp. PCC 7002 (S. 7002), however, is linked directly to reduced growth and PSI photodamage under CO2-limiting conditions. Unlike Synechocystis sp. PCC 6803 and S. elongatus PCC 7942, S. 7002 reduced P700 during CO2-limited illumination in the absence of FLV, resulting in decreases in both PSI and photosynthetic activities. Even at normal air CO2 concentration, the growth of S. 7002 mutant was retarded relative to that of the wild type. Therefore, P700 oxidation is essential for protecting PSI against photoinhibition. Here, we present various strategies to alleviate PSI photoinhibition in cyanobacteria.

Quantification of the soil organic carbon balance in the Tai-Lake paddy soils of China

Rising temperatures and elevated atmospheric CO2 are two factors that simultaneously affect the dynamics of soil organic carbon (SOC). This study separately examines the effects arise from these two factors in Tai-Lake Paddy soils using DeNitrification–DeComposition (DNDC) model, with the currently most detailed soil database for the paddy region of China. The soil database is at a scale of 1:50,000, containing 52,034 paddy soil polygons derived from 1107 unique paddy soil profiles. Our simulations indicate that, the SOC in the top soils (0-30cm) increases 0.83, 1.09, 1.32, and 1.51Tg C under conventional management (3.44Tg C) in the 2.32Mha paddy soils of the Tai-Lake region from 2001 to 2019, respectively, with the atmospheric CO2 concentration increases at 1.5, 2.0, 2.5, and 3.0 times the normal rate (1.9ppmyear−1). By contrast, with rising air temperature of 0.5, 1.0, 1.5, 2.0, 3.0, and 4°C, the SOC decreases 0.09, 0.54, 0.69, 1.13, 1.80, and 2.51Tg C under conventional management, respectively. Thus, the effect of carbon sink induced from CO2 fertilization at the 2.0 times normal CO2 concentration increase rate could generally offset the effect of carbon source resulted from a 2.0°C air temperature increase. In addition, the paddy soils in this region tend to persistently be a sink of atmospheric CO2 under warming and elevated CO2 scenarios, even if when the air temperature has increased by 4°C. These results suggest that SOC storage in paddy soils of this region is prone to benefit from future global climate change and this carbon sequestration potential in the agro-ecosystems is likely to contribute to climate mitigation under current agricultural practices, despite any negative effects derived from warming. As a representative of paddy soils in eastern China, the insights gained from the Tai-Lake region may be potentially transferable to other paddy soils in eastern China where 95% of the total of China is located.

黄河三角洲贝壳堤岛叶底珠叶片光合作用对CO2浓度及土壤水分的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 黄河三角洲贝壳堤岛叶底珠叶片光合作用对CO2浓度及土壤水分的响应 DOI: 10.5846/stxb201305060935 作者: 作者单位: 山东农业大学,山东省黄河三角洲生态环境重点实验室,山东农业大学林学院、山东省土壤侵蚀与生态修复重点实验室,山东农业大学林学院、山东省土壤侵蚀与生态修复重点实验室,山东省邹平水务局,山东省黄河三角洲生态环境重点实验室 作者简介: 通讯作者: 中图分类号: Q945.1 基金项目: 国家自然科学基金（31100468）；山东省高校科研发展计划项目（J13LC03）；山东省优秀中青年科学家科研奖励基金（BS2013NY010）；山东省黄河三角洲生态环境重点实验室开放基金项目（2012KFJJ04） Photosynthetic responses to changes in CO2 concentration and soil moisture in leaves of Securinega suffruticosa from shell ridge islands in the Yellow River Delta, China Author: Affiliation: Shandong Agricultural University,Shandong Provincial Key Laboratory of Eco-Environmental Science for Yellow River Delta,Binzhou University,Shandong SProvincialS key SLaboratoryS of soil erosion and ecological restoration,Shandong SProvincialS key SLaboratoryS of soil erosion and ecological restoration,Zouping Water Conservancy Department,Zouping,Shandong Provincial Key Laboratory of Eco-Environmental Science for Yellow River Delta,Binzhou 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:为阐明黄河三角洲贝壳砂生境叶底珠叶片光合作用对CO2浓度的响应规律，明确其光合生产力与土壤水分的定量关系，以2年生叶底珠（Securinega suffruticosa）苗木为材料，采用旱棚人工控水试验，利用光合测定系统测定分析了不同水分条件下叶底珠叶片光合作用的CO2响应特征。结果表明，叶底珠叶片净光合速率（Pn）和光合作用特征参数对土壤水分（SRWC）变化具有阈值效应。维持叶底珠叶片较高光合生产力的SRWC为50.3%-83.2%，CO2浓度为700-1100 μmol/mol，其中最适宜的SRWC为70.5%，最大值出现在CO2浓度为900 μmol/mol，而正常CO2浓度和倍增CO2浓度下维持叶底珠叶片较高光合生产力水平的SRWC范围分别为45.5%-90.0%和47.0%-92.6%。叶底珠叶片表观最大净光合速率（Pmax，c）和羧化效率（CE）随着SRWC的增加而呈抛物线变化。CO2补偿点（Г）呈现与Pmax，c和CE相反的变化规律，在SRWC为70.5%时，Г达到最低值（51.3 μmol/mol）。光呼吸速率（Rp）在SRWC为50.3%时达到最小值（2.62 μmol·m-2·s-1），随着SRWC的增加，Rp增加缓慢。说明黄河三角洲贝壳砂生境条件下，叶底珠叶片光合作用对CO2浓度和土壤水分具有宽泛的适应范围，对贝壳砂生境经常出现的干湿交替逆境表现出一定适应能力，在黄河三角洲贝壳堤岛可引种栽培。 Abstract:Atmospheric CO2 concentrations, soil moisture, and photosynthetically active radiation are the major factors limiting plant growth and photosynthetic productivity in large areas of the world. These factors affect agricultural and forest production and the distribution and composition of vegetation. Human activities have resulted in increased CO2 concentrations in the atmosphere, leading to changes in temperature, water cycling, and radiation. CO2 is required for photosynthesis, and the ongoing increases in atmospheric CO2 concentrations could eventually lead to higher temperatures and greater evaporative demands. Hence, droughts will be more frequent, intense, and erratic, and may affect regions that are not currently affected by drought. The effect of changes in CO2 concentrations and soil water content on plants is an important theme in studies on global change. To date, few studies have assessed the effects of continuous increases in CO2 concentration and soil moisture on photosynthesis. Securinega suffruticosa is one of the dominant drought-tolerant species growing on the shell islands in the Yellow River Delta region. To investigate the carbon and water cycles of the ecological system in this region, it is important to investigate the photosynthetic responses of S. suffruticosa to changes in CO2 concentrations and soil moisture conditions. This has important practical significance both in terms of food safety and for constructing, improving, and managing a functional ecological environment as the global climate changes.The study materials were 2-year-old plants of S. suffruticosa, originally from the shell islands in the Yellow River Delta. These plants were obtained from a nursery. The plants were subjected to seven different levels of water supply using an artificial water control system in a covered shed, and to a series of CO2 concentrations controlled using a LI-COR 6400 portable photosynthesis system. The objective of this study was to investigate photosynthetic responses to CO2 concentrations and determine whether photosynthetic productivity was quantitatively related to soil moisture content. The photosynthetic rate (Pn) and characteristic parameters of photosynthesis showed threshold-value responses to variations in soil relative water content (SRWC). S. suffruticosa plants were able to maintain higher photosynthetic productivity in the range of 50.3% to 83.2% RWC; in this range, the range of suitable CO2 concentrations was 700 to 1100 μmol/mol, and Pn increased with increasing CO2 concentrations. The most suitable SRWC was 70.5%, and Pn peaked at the CO2 concentration of 900 μmol/mol. The characteristic parameters of photosynthesis showed different responses to changes in SRWC. Under normal and double CO2 concentrations, the ranges of SRWC in which S. suffruticosa maintained higher photosynthetic productivity were 45.5%-90.0% and 47.0%-92.6%, respectively, indicating that S. suffruticosa was highly adaptable to changes in soil moisture content. The apparent maximum photosynthesis rate (Pmax,c) and carboxylation efficiency (CE) increased with increasing SRWC, peaking at 70.5% SRWC and then decreasing slowly at higher SRWC. The CO2compensation point showed the opposite trend to that of Pmax,c and CE, and reached a minimum value (approx. 51.3 μmol/mol) at 70.5% SRWC. The photorespiration rate increased slowly with increasing SRWC and peaked at approximately 2.6175 μmol·m-2·s-1 at 50.3% SRWC.We concluded that photosynthesis in leaves of S. suffruticosa is widely adaptable to changes in CO2 concentrations and soil moisture, and that this species has the typical physiological characteristics of a water-tolerant and drought-tolerant plant. Thus, S. suffruticosa has the potential for cultivation on the shell ridge islands of the Yellow River Delta, China. 参考文献 相似文献 引证文献

Changes in photosynthesis caused by adaptation of maize seedlings to short-term drought

Detached leaf is in the state of increasing water deficit; it is a good experimental model for looking into the hardening effect of adaptation of eight-day-old maize (Zea mays L.) seedlings to short-term drought (five days without watering). The light stage of photosynthesis and photosynthetic CO2/H2O exchange in detached leaves were studied. Specific surface density of leaf tissue (SSDL), the content of chlorophylls a and b, proline, MDA as well as photosynthetic parameters: quantum yield of photosystem II fluorescence, assimilation of CO2, and transpiration at room temperature and light saturation (density of PAR quantum flux of 2000 μmol/(m2 s)) at normal and half atmospheric CO2 concentration were determined. The leaves of seedlings exposed to short-term drought differed from control material by a greater SSDL and higher content of proline. The hardening effect of the stress agent on the dark stage of photosynthesis was detected; it was expressed in the maintenance of the higher photosynthetic CO2 assimilation against control material due to the elevation of stomatal conductance for CO2 diffusing into the leaf. Judging from the lack of differences in the MDA content, short-term drought did not injure photosynthetic membranes. In detached leaves of experimental maize seedlings, photosynthesis was maintained on a higher level than in control material.

Effect of acute acid-base disturbances on ErbB1/2 tyrosine phosphorylation in rabbit renal proximal tubules

The renal proximal tubule (PT) is a major site for maintaining whole body pH homeostasis and is responsible for reabsorbing ∼80% of filtered HCO3(-), the major plasma buffer, into the blood. The PT adapts its rate of HCO3(-) reabsorption (JHCO3(-)) in response to acute acid-base disturbances. Our laboratory previously showed that single isolated perfused PTs adapt JHCO3(-) in response to isolated changes in basolateral (i.e., blood side) CO2 and HCO3(-) concentrations but, surprisingly, not to pH. The response to CO2 concentration can be blocked by the ErbB family tyrosine kinase inhibitor PD-168393. In the present study, we exposed enriched rabbit PT suspensions to five acute acid-base disturbances for 5 and 20 min using a panel of phosphotyrosine (pY)-specific antibodies to determine the influence of each disturbance on pan-pY, ErbB1-specific pY (four sites), and ErbB2-specific pY (two sites). We found that each acid-base treatment generated a distinct temporal pY pattern. For example, the summated responses of the individual ErbB1/2-pY sites to each disturbance showed that metabolic acidosis (normal CO2 concentration and reduced HCO3(-) concentration) produced a transient summated pY decrease (5 vs. 20 min), whereas metabolic alkalosis produced a transient increase. Respiratory acidosis (normal HCO3(-) concentration and elevated CO2 concentration) had little effect on summated pY at 5 min but produced an elevation at 20 min, whereas respiratory alkalosis produced a reduction at 20 min. Our data show that ErbB1 and ErbB2 in the PT respond to acute acid-base disturbances, consistent with the hypothesis that they are part of the signaling cascade.

Short- and long-term consequences of larval stage exposure to constantly and ephemerally elevated carbon dioxide for marine bivalve populations

Abstract. While larval bivalves are highly sensitive to ocean acidification, the basis for this sensitivity and the longer-term implications of this sensitivity are unclear. Experiments were performed to assess the short-term (days) and long-term (months) consequences of larval stage exposure to varying CO2 concentrations for calcifying bivalves. Higher CO2 concentrations depressed both calcification rates assessed using 45Ca uptake and RNA : DNA ratios in Mercenaria mercenaria and Argopecten irradians larvae with RNA : DNA ratios being highly correlated with larval growth rates (r2>0.9). These findings suggested that high CO2 has a cascading negative physiological impact on bivalve larvae stemming in part from lower calcification rates. Exposure to elevated CO2 during the first four days of larval development significantly depressed A. irradians larval survival rates, while a 10-day exposure later in larval development did not, demonstrating the extreme CO2 sensitivity of bivalve larvae during first days of development. Short- (weeks) and long-term (10 month) experiments revealed that individuals surviving exposure to high CO2 during larval development grew faster when exposed to normal CO2 as juveniles compared to individuals reared under ambient CO2 as larvae. These increased growth rates could not, however, overcome size differences established during larval development, as size deficits of individuals exposed to even moderate levels of CO2 as larvae were evident even after 10 months of growth under normal CO2 concentrations. This "legacy effect" emphasizes the central role larval stage CO2 exposure can play in shaping the success of modern-day bivalve populations.

Drought-induced changes and recovery of photosynthesis in two bean cultivars<br>(Phaseolus vulgaris L.)

The effects of soil drought on photosynthesis and chlorophyll fluorescence in the leaves of two common bean (Phaseolus vulgaris L.) cultivars ? Zarya and Tangra were studied, as well as recovery of photosynthesis after re-watering. Drought was imposed 14 days after the emergency by withholding water for 10 days in which soil water potential reached -0.9 MPa. Water stress led to a noticeable decrease in both the initial slope of the An/Ci curve and Amax in the primary leaf of the studied cultivars. The most marked reduction in leaf gas exchange was observed in cv. Tangra. ? was reduced more than three folds and Amax - more than six folds. Exposure of bean plants to soil drought and provoked leaf water deficit resulted in a dramatic reduction (with an 84.17%) of An at normal ambient CO2 concentration (Ca=370 ?mol mol-1 ). The lower reduction in leaf gas exchange parameters were observed in cv. Zarya. Drought stress induces an increase of F0 accompanied by a decrease of Fm in the studied cultivars, being cv. Zarya less affected. The Fv/Fm ratio was significantly decreased in cv. Tangra and only showed a slight tendency to a decrease in cv. Zarya. Cv. Tangra presented a decrease of 56% in qP in the primary leaf, while in cv. Zarya qP decreased with 32%. Accordingly, Y strongly decreased in cv. Tangra, while in cv. Zarya Y was less affected. 3 days after re-watering photosynthesis of cv. Zarya was about 87% from the control plants, while in cv. Tangra photosynthesis was only 68% from control. Chlorophyll fluorescence parameters were recovered to the greater extent. On the basis of the data obtained we could arrange photosynthetic apparatus of cv. Zarya as relatively drought tolerant and that of cv. Tangra as drought sensitive.

Cork oak (Quercus suber L.) seedlings acclimate to elevated CO2 and water stress: photosynthesis, growth, wood anatomy and hydraulic conductivity

Leaf gas-exchange, leaf and shoot anatomy, wood density and hydraulic conductivity were investigated in seedlings of Quercus suber L. grown for 15 months either at elevated (700 μmol mol−1) or normal (350 μmol mol−1) ambient atmospheric CO2 concentrations. Plants were grown in greenhouses in a controlled environment: relative humidity 50% (±5), temperature similar to external temperature and natural light conditions. Plants were supplied with nutrients and two water regimes (WW, well watered; WS, water stress). After 6 months exposure to CO2 enrichment an increase in photosynthetic rate, a decrease in stomatal conductance and a decrease in carbon isotope discrimination (Δ13C) were observed, along with enhanced growth and an increase in the number of branches and branch diameter. Over the same period, the shoot weight ratio increased, the root weight ratio decreased and the leaf weight ratio was unaffected. The specific leaf area increased due to an increase in total leaf thickness, mainly due to the palisade parenchyma and starch. However, after 9 and 15 months of elevated CO2 exposure, the above-mentioned physiological and morphological parameters appeared to be unaffected. Elevated CO2 did not promote changes in vessel lumen diameter, vessel frequency or wood density in stems grown in greenhouse conditions. As a consequence, xylem hydraulic efficiency remained unchanged. Likewise, xylem vulnerability to embolism was not modified by elevated CO2. In summary, elevated CO2 had no positive effect on the ecophysiological parameters or growth of water stressed plants.

Enriquecimento e alocação de 13C em plantas de eucalipto

Nas últimas décadas, a utilização de isótopos estáveis em várias áreas de pesquisa vem se destacando, como na análise de fluxos e rotas metabólicas, análise de efeitos de estresses em plantas e, em grande escala, no estudo da matéria orgânica do solo (MOS). Estudos de alterações e dinâmica da MOS usando a variação da abundância natural do 13C requerem mudanças na razão isotópica do C. Quando não existe essa possibilidade, uma das alternativas é enriquecer o material vegetal (planta) com 13C, via fixação de 13CO2, de modo que a razão isotópica seja distinta daquela da MOS original. O objetivo deste trabalho foi investigar a magnitude e a homogeneidade do enriquecimento em 13C em diferentes componentes da planta de eucalipto. No processo de marcação, três plantas de eucalipto, com 4 meses de idade, cultivadas em solução nutritiva foram expostas a uma atmosfera enriquecida com 13CO2, em uma câmara de vidro (448 dm³), com temperatura em torno de 24 ºC. A concentração de CO2 e a razão 13C/12C foram monitoradas por um espectrômetro de massa de razão isotópica (IRMS) em amostras de ar retiradas ao longo do processo (126 dias com três pulsos de 13CO2 semanais). Após o período de marcação, as plantas foram separadas em folha (folha-fonte e folha-dreno), galho, casca, lenho e raiz e analisadas em IRMS. O resultado foi expresso em partes por mil (‰) em relação ao padrão internacional de C denominado Pee-Dee Belemnite (PDB), obtendo-se a δ13C PDB delas: folha-fonte (828,07 ‰), folha-dreno (645,72 ‰), galho (672,49 ‰), casca (691,86 ‰), lenho (632,02 ‰) e raiz (536,55 ‰). O padrão de alocação e enriquecimento de 13C entre os componentes das plantas foi homogêneo, embora com diferenças numéricas da ordem de 291 ‰ na δ13C PDB. As plantas de eucalipto mantiveram alta taxa de absorção de CO2 e, consequentemente, alta taxa fotossintética em concentrações de CO2 muito acima (180,4 mmol L-1 - 7.934 ppmv) da encontrada na atmosfera (8,64 mmol L-1 - 380 ppmv). O 13C fixado durante o dia foi liberado em menor escala na respiração noturna, em comparação com o 12C. O grau de enriquecimento com 13C obtido indica que a técnica empregada permite o enriquecimento suficiente do material para traçar o C em estudos de decomposição e estabilização de litter de eucalipto em frações da MOS.

Does enhanced photosynthesis enhance growth? Lessons learned from CO2 enrichment studies.

Plants typically convert only 2-4% of the available energy in radiation into new plant growth. This low efficiency has provided an impetus for trying to genetically manipulate plants in order to achieve greater efficiencies. But to what extent can increased photosynthesis be expected to increase plant growth? This question is addressed by treating plant responses to elevated CO2 as an analogue to increasing photosynthesis through plant breeding or genetic manipulations. For plants grown optimal growth conditions and elevated CO2, photosynthetic rates can be more than 50% higher than for plants grown under normal CO2 concentrations. This reduces to 40% higher for plants grown under the average of optimal and sub-optimal conditions, and over the course of a full day, average photosynthetic enhancements under elevated CO2 are estimated to be about 30%. The 30% enhancement in photosynthesis is reported to increase relative growth rate by only about 10%. This discrepancy is probably due to enhanced carbohydrate availability exceeding many plant9s ability to fully utilise it due to nutrient or inherent internal growth limitations. Consequently, growth responses to elevated CO2 increase with plant9s sink capacity and nutrient status. However, even a 10% enhancement in relative growth rate can translate into absolute growth enhancements of up to 50% during the exponential growth phase of plants. When space constraints and self-shading force an end to exponential growth, on-going growth enhancements are likely to be closer to the enhancement of relative growth rate. The growth response to elevated CO2 suggests that increases in photosynthesis almost invariably increase growth, but that growth response is numerically much smaller than the initial photosynthetic enhancement. This lends partial support to the usefulness of breeding plants with greater photosynthetic capacity, but dramatic growth stimulation should not be expected. The usefulness of increasing photosynthetic capacity can be maximised through changes in management practices and manipulation of other genetic traits to optimise the conditions under which increased photosynthesis can lead to maximal growth increases.

Effects of in vitrorooting environments and irradiance on growth and photosynthesis of strawberry plantlets during acclimatization

Strawberry (Fragaria ananassaDuch. cv. Fengxiang) plantlets were cultured under two in vitroenvironments for rooting, and then acclimatized under two ex vitroirradiance conditions. At the end of rooting stage plant height, fresh weight and specific leaf area of T1-plants grown under high sucrose concentration (3 sucrose), low photosynthetic photon flux density (30 μ mol m−2 s−1) and normal CO2 concentration (350–400 μl l−1) were significantly higher than those of T2-plantlets grown under low sucrose concentration (0.5), high photosynthetic photon flux density (90 μ mol m−2 s−1) and elevated CO2 concentration (700–800 μl l−1). But T2-plantlets had higher net photosynthetic rate (Pn), effective photochemical quantum yield of PSII (ΦPSII), effective photosynthetic electron transport rate (ETR), photochemical quenching (qP) and ratio of chlorophyll fluorescence yield decrease (Rfd). After transfer, higher irradiance obviously promoted the growth of plantlets and was beneficial for the development of photosynthetic functions during acclimatization. T2-plantlets had higher fresh weight, leaf area, ΦPSII and ETR under higher ex vitroirradiance condition.