μL CO2 Research Articles

Metaflumizone susceptibility baseline, reproduction, locomotion, and respiration responses on the Hypothenemus hampei

Coffee berry borer (CBB) is the world's primary coffee pest. Recently, metaflumizone was registered for the control of CBB. This study investigated the susceptibility baseline, reproduction, locomotion, and respiration responses in the CBB (Hypothenemus hampei) exposed to metaflumizone. Lethal concentration (LC10, LC50, and LC99) values for metaflumizone were determined for seventeen populations from Brazil. Coffea arabica fruits infested with the CBB were collected during 2020–2021 from regions with significant coffee production. Metaflumizone reduced the respiration rate of H. hampei from 0.51 to 0.22 μL CO2 h−1 at LC50 for up to 3 h after insecticide exposure. A low concentration (LC10) of metaflumizone showed a stable respiration rate for H. hampei. The locomotion and reproduction (number of eggs) of H. hampei were affected. The recommended diagnostic concentration for H. hampei was 58.0 mg a.i. L−1. Our findings suggest that metaflumizone-based insecticides can be an effective alternative for use in rotation with insecticides of different chemical groups to control this key pest.

Luxury Zinc Supply Prevents the Depression of Grain Nitrogen Concentrations in Rice (Oryza sativa L.) Typically Induced by Elevated CO2.

Rice (Oryza sativa L.) has inherently low concentrations of nitrogen (N) and zinc (Zn), and those concentrations are falling as the atmospheric concentration of carbon dioxide ([CO2]) increases, threatening the quality of human diets. We investigated the effect of two levels of Zn supply (marginal and luxury), on Zn and N concentrations in whole grain of two indica rice cvv. Differing in Zn-efficiency (IR26 (inefficient) and IR36 (efficient)), grown in sand culture at ambient (400 µL CO2 L-1 (a[CO2])) and elevated (700 µL CO2 L-1 (e[CO2])) CO2 concentrations. For both cvv., luxury Zn-supply increased vegetative growth, and the foliar and grain Zn concentrations; the increases in grain yield were greater at e[CO2]. The e[CO2] decreased grain Zn concentrations ([Zn]), as is consistently observed in other studies. However, unique to our study, luxury Zn-supply maintained grain N concentrations at e[CO2]. Our data also show that enhanced Zn uptake is the basis of the greater Zn-efficiency of IR36. Lastly, luxury Zn-supply and e[CO2] appreciably decreased the time to panicle emergence and, consequently, to maturity in both cvv. Since Zn-supply can be manipulated by both soil and foliar applications, these findings are potentially important for the quality and quantity of the global rice supply. That is, further investigation of our findings is justified. Key message: Luxury zinc supply maintains grain N concentration at 700 µL CO2 L-1.

Chemical Composition and Insecticidal Properties of Origanum vulgare (Lamiaceae) Essential Oil against the Stored Product Beetle, Sitophilus granarius

Although phosphides are utilized in stored pest control, efforts have been made to discover environmentally friendly insecticides. For insecticidal properties, essential oils (EOs) are considered to be novel alternatives for pesticide use. This study characterized the Origanum vulgare EO by gas chromatography–flame ionization detector (GC–FID) × gas chromatography–mass spectrometry (GC–MS) and assessed the insecticidal activities against Sitophilus granarius. Mortality, post-exposure survival, behavior, and respiration caused by this EO in S. granarius were investigated. The majority of the compounds were p-cymene, carvacrol, linalool, and thymol. In dose–mortality bioassays, the lethality of this EO (LD50 = 3.05 µg insect−1 and LD90 = 10.02 µg insect−1) was confirmed in S. granarius. The survival rate was 99.9% in adults not treated with O. vulgare EOs, reducing to 44.9% and 10.3% in weevils treated with 3.05 µg insect−1 and 10.02 µg insect−1, respectively. The O. vulgare EO alters the behavioral pattern in terms of walking distance and resting time, displaying repellency. Additionally, this EO reduced the gas exchange of weevils from 2.78 to 2.36 µL CO2 h−1 at 3.05 µg insect−1, after 3 h EO exposure. The results suggest that O. vulgare EOs affect different biological functions in the insect, and open new perspectives for controlling stored pests, representing a first step in the innovation of green pesticides.

Indoxacarb effects on non-target predator, Podisus distinctus (Hemiptera: Pentatomidae).

Forestry pest management includes biological and chemical methods of pest control. Using insecticides and natural enemies can be compatible in forest pest management programs. The compatibility of the predatory stink bug Podisus distinctus with the insecticide indoxacarb, used in forestry, needs to be evaluated in Brazil. This study investigated the mortality, survival, respiration, preference, prey consumption, and locomotor activity of P. distinctus adults exposed to indoxacarb. In concentration-mortality bioassays, the lethality of indoxacarb (LC50 = 2.62g L-1 and LC90 = 6.11g L-1) was confirmed in P. distinctus adults. The survival rate was 100% in predator insects not exposed to indoxacarb, declining to 40.7% in predator insects exposed to 2.62g L-1 and 0.1% in predators treated with 6.11g L-1. Indoxacarb reduced the respiration of P. distinctus from 18.45 to 14.41 µL CO2 h-1 at 2.62g L-1 for up to 3h after insecticide exposure, inhibiting food consumption and displaying hyperexcitation. The harmful effects of indoxacarb to the natural enemy suggest that it should be better assessed for use with P. distinctus for pest management in forestry.

CO2 enrichment and supporting material impact the primary metabolism and 20-hydroxyecdysone levels in Brazilian ginseng grown under photoautotrophy

In vitro photoautotrophic propagation system has been successfully established for Pfaffia glomerata, a medicinal species that produces the phytoecdysteroid 20-hydroxyecdysone (20E) under forced ventilation and CO2 enrichment. For that, an adequate supporting material with high porosity in place of agar is required. In this study, we investigated metabolic and morpho-anatomical alterations of two accessions (Ac) of P. glomerata (Ac 22 and Ac 43) under photoautotrophy conditions, using two supporting materials (agar and Florialite®) and two CO2 concentrations (360 and 1000 µL CO2 L−1). High CO2 concentration and the use of Florialite® as supporting material enhanced the production of 20E, and influenced on the levels of amino acids, sugars, tricarboxylic acid cycle intermediates, stress related metabolites (aromatic amines and shikimate), and osmotic adjustment-related compounds (hydroxyproline, aspartate and myo-inositol). Interestingly, Ac 22 displayed less tolerance to stress caused by low photoautotrophy compared to Ac 43, as indicated by the higher total polyamines in Ac 22. Moreover, the accessions showed different metabolic responses under photoautotrophy. These findings provide a better understanding of how the supporting material and CO2 enrichment influence in vitro metabolism under photoautotrophic system in P. glomerata, wherein higher levels of gas exchange, enabled by use of Florialite® and CO2 enrichment, increased total sugars as well as the levels of 20E in the plants. This information will be fundamental to optimize the in vitro culture systems of P. glomerata for the production of 20E. Photoautotrophic propagation has the unique advantage of combining biological and environmental perspectives, resulting in morpho-physiologically well-adjusted plants grown in vitro or ex vitro. Our results revealed that the combined use of CO2 enrichment (1000 μL CO2 L−1) and supporting material (Florialite®) had great influence in the in vitro performance of P. glomerata and increased 20-hydroxyecdysone content. This combination also led to increased levels of amino acids, sugars, TCA cycle intermediates, and stress-related metabolites such as aromatic amines and shikimate, and osmotic adjustment-related compounds (hydroxyproline, aspartate, and myo-inositol).

Sequential mixture design optimization for divergent metabolite analysis: Enriched carbon dioxide effects on Coffea arabica L. leaves and buds

The first metabolic study of the impact of elevated CO2 (590 µL CO2 L−1) levels on the leaves and buds of Coffea arabica L. plants is reported. A novel sequential statistical mixture design strategy allowed optimization of both the extraction and mobile phase solvent systems to increase differences detected in metabolites of Coffea arabica L. plants and buds. Factor analysis showed that the 227 and 273 nm bands of the 1:1:1 ternary ethyl ether – dichloromethane – methanol mixture spectra resulted in discrimination of elevated CO2 extract samples from those obtained from leaves grown in a current level CO2 atmosphere (390 µL CO2 L−1) of leaf sample extracts. DAD-HPLC spectral peak evidence showed a 32% increase in absorbance of the 273 band for the enriched CO2 leaf extracts. This band has been assigned to caffeine-like substances and confirmed by the mass spectral signal at m/z 195 ([M + H]+). No enrichment band increases were found for kahweol, kaempferol and quercetin that had presence confirmed by mass spectral analysis. No epigenetic effect of this metabolic profile was found in new leaves after the addition of CO2 stopped. Enriched CO2 perturbation of the bud metabolite were much smaller than for the leaf samples. Absorbance increases in the 228 nm and decreases in the 235 nm bands play a prominent role in the discrimination of enriched CO2 buds from the controls in the pure dichloromethane extracting solvent. This global metabolome strategy allows the monitoring of chemical groups of plants susceptible to environmental changes as well as elucidate metabolic variations in complex matrices of biochemical responses.

Can Elevated Air [CO2] Conditions Mitigate the Predicted Warming Impact on the Quality of Coffee Bean?

Climate changes, mostly related to high temperature, are predicted to have major negative impacts on coffee crop yield and bean quality. Recent studies revealed that elevated air [CO2] mitigates the impact of heat on leaf physiology. However, the extent of the interaction between elevated air [CO2] and heat on coffee bean quality was never addressed. In this study, the single and combined impacts of enhanced [CO2] and temperature in beans of Coffea arabica cv. Icatu were evaluated. Plants were grown at 380 or 700 μL CO2 L-1 air, and then submitted to a gradual temperature rise from 25°C up to 40°C during ca. 4 months. Fruits were harvested at 25°C, and in the ranges of 30–35 or 36–40°C, and bean physical and chemical attributes with potential implications on quality were then examined. These included: color, phenolic content, soluble solids, chlorogenic, caffeic and p-coumaric acids, caffeine, trigonelline, lipids, and minerals. Most of these parameters were mainly affected by temperature (although without a strong negative impact on bean quality), and only marginally, if at all, by elevated [CO2]. However, the [CO2] vs. temperature interaction strongly attenuated some of the negative impacts promoted by heat (e.g., total chlorogenic acids), thus maintaining the bean characteristics closer to those obtained under adequate temperature conditions (e.g., soluble solids, caffeic and p-coumaric acids, trigonelline, chroma, Hue angle, and color index), and increasing desirable features (acidity). Fatty acid and mineral pools remained quite stable, with only few modifications due to elevated air [CO2] (e.g., phosphorous) and/or heat. In conclusion, exposure to high temperature in the last stages of fruit maturation did not strongly depreciate bean quality, under the conditions of unrestricted water supply and moderate irradiance. Furthermore, the superimposition of elevated air [CO2] contributed to preserve bean quality by modifying and mitigating the heat impact on physical and chemical traits of coffee beans, which is clearly relevant in a context of predicted climate change and global warming scenarios.

Structural and functional changes in coffee trees after 4 years under free air CO2 enrichment.

Climate forecasts suggest that [CO2] in the atmosphere will continue to increase. Structural and ecophysiological responses to elevated air [CO2] (e[CO2]) in tree species are contradictory due to species-dependent responses and relatively short-term experiments. It was hypothesized that long-term exposure (4 year) to e[CO2] would change canopy structure and function of Coffea arabica trees. Coffee plants were grown in a FACE (free air CO2 enrichment) facility under two air [CO2]: actual and elevated (actual + approx. 200 μL CO2 L-1). Plants were codified following the VPlants methodology to obtain coffee mock-ups. Plant canopies were separated into three 50 cm thick layers over a vertical profile to evaluate their structure and photosynthesis, using functional-structural plant modelling. Leaf area was strongly reduced on the bottom and upper canopy layers, and increased soil carbon concentration suggested changes in carbon partitioning of coffee trees under e[CO2]. Increased air [CO2] stimulated stomatal conductance and leaf photosynthesis at the middle and upper canopy layers, increasing water-use efficiency. Under e[CO2], plants showed reduced diameter of the second-order axes and higher investment in the youngest third to fifth-order axes. The responses of Arabica coffee grown under long-term exposure to e[CO2] integrated structural and functional modifications, which balanced leaf area loss through improvements in leaf and whole-plant photosynthesis.

Selection and Validation of Reference Genes for Accurate RT-qPCR Data Normalization in Coffea spp. under a Climate Changes Context of Interacting Elevated [CO2] and Temperature.

World coffee production has faced increasing challenges associated with ongoing climatic changes. Several studies, which have been almost exclusively based on temperature increase, have predicted extensive reductions (higher than half by 2,050) of actual coffee cropped areas. However, recent studies showed that elevated [CO2] can strongly mitigate the negative impacts of heat stress at the physiological and biochemical levels in coffee leaves. In addition, it has also been shown that coffee genotypes can successfully cope with temperatures above what has been traditionally accepted. Altogether, this information suggests that the real impact of climate changes on coffee growth and production could be significantly lower than previously estimated. Gene expression studies are an important tool to unravel crop acclimation ability, demanding the use of adequate reference genes. We have examined the transcript stability of 10 candidate reference genes to normalize RT-qPCR expression studies using a set of 24 cDNAs from leaves of three coffee genotypes (CL153, Icatu, and IPR108), grown under 380 or 700 μL CO2 L−1, and submitted to increasing temperatures from 25/20°C (day/night) to 42/34°C. Samples were analyzed according to genotype, [CO2], temperature, multiple stress interaction ([CO2], temperature) and total stress interaction (genotype, [CO2], and temperature). The transcript stability of each gene was assessed through a multiple analytical approach combining the Coeficient of Variation method and three algorithms (geNorm, BestKeeper, NormFinder). The transcript stability varied according to the type of stress for most genes, but the consensus ranking obtained with RefFinder, classified MDH as the gene with the highest mRNA stability to a global use, followed by ACT and S15, whereas α-TUB and CYCL showed the least stable mRNA contents. Using the coffee expression profiles of the gene encoding the large-subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RLS), results from the in silico aggregation and experimental validation of the best number of reference genes showed that two reference genes are adequate to normalize RT-qPCR data. Altogether, this work highlights the importance of an adequate selection of reference genes for each single or combined experimental condition and constitutes the basis to accurately study molecular responses of Coffea spp. in a context of climate changes and global warming.

Protective Response Mechanisms to Heat Stress in Interaction with High [CO2] Conditions in Coffea spp.

Modeling studies have predicted that coffee crop will be endangered by future global warming, but recent reports highlighted that high [CO2] can mitigate heat impacts on coffee. This work aimed at identifying heat protective mechanisms promoted by CO2 in Coffea arabica (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown at 25/20°C (day/night), under 380 or 700 μL CO2 L−1, and then gradually submitted to 31/25, 37/30, and 42/34°C. Relevant heat tolerance up to 37/30°C for both [CO2] and all coffee genotypes was observed, likely supported by the maintenance or increase of the pools of several protective molecules (neoxanthin, lutein, carotenes, α-tocopherol, HSP70, raffinose), activities of antioxidant enzymes, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), catalase (CAT), and the upregulated expression of some genes (ELIP, Chaperonin 20). However, at 42/34°C a tolerance threshold was reached, mostly in the 380-plants and Icatu. Adjustments in raffinose, lutein, β-carotene, α-tocopherol and HSP70 pools, and the upregulated expression of genes related to protective (ELIPS, HSP70, Chape 20, and 60) and antioxidant (CAT, CuSOD2, APX Cyt, APX Chl) proteins were largely driven by temperature. However, enhanced [CO2] maintained higher activities of GR (Icatu) and CAT (Icatu and IPR108), kept (or even increased) the Cu,Zn-SOD, APX, and CAT activities, and promoted a greater upregulation of those enzyme genes, as well as those related to HSP70, ELIPs, Chaperonins in CL153, and Icatu. These changes likely favored the maintenance of reactive oxygen species (ROS) at controlled levels and contributed to mitigate of photosystem II photoinhibition at the highest temperature. Overall, our results highlighted the important role of enhanced [CO2] on the coffee crop acclimation and sustainability under predicted future global warming scenarios.

Formation of halogenated disinfection by-products in cobalt-catalyzed peroxymonosulfate oxidation processes in the presence of halides

Sulfate radicals (SO4−) generated by activation of peroxymonosulfate (PMS) and persulfate (PS) are highly oxidative and applied to degrade various organic pollutants. This research was designed to investigate formation of halogenated by-products in Co2+ activated PMS process in the presence of halides and natural organic matter (NOM). It was revealed that no halogenated by-products were detected in the presence of Cl− while 189 μg/L bromoform and 100.7 μg/L dibromoacetic acid (DBAA) were found after 120 h when 2 mg/L NOM, 0.1 mM Br−, 1.0 mM PMS, and 5 μL Co2+ were present initially. These products are known as disinfection by-products (DBPs) since they are formed in water disinfection processes. Formation of DBPs was even more significant in the absence of Co2+. The data indicate that both PMS and SO4− can transform Br− to reactive bromine species which react with NOM to form halogenated by-products. Less DBP formation in Co2+-PMS systems was due to the further destruction of DBPs by SO4−. More DBPs species including chlorinated ones were detected in the presence of both Cl− and Br−. However, more brominated species produced than chlorinate ones generally. The total DBP yield decreased with the increase of Cl− content when total halides kept constant. This is one of the few studies that demonstrate the formation of halogenated DBPs in Co2+/PMS reaction systems, which should be taken into consideration in the application of SO4− based oxidation technologies.

Long-term elevated air [CO2 ] strengthens photosynthetic functioning and mitigates the impact of supra-optimal temperatures in tropical Coffea arabica and C.canephora species.

The tropical coffee crop has been predicted to be threatened by future climate changes and global warming. However, the real biological effects of such changes remain unknown. Therefore, this work aims to link the physiological and biochemical responses of photosynthesis to elevated air [CO2 ] and temperature in cultivated genotypes of Coffea arabica L. (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown for ca. 10 months at 25/20°C (day/night) and 380 or 700 μl CO2 l(-1) and then subjected to temperature increase (0.5°C day(-1) ) to 42/34°C. Leaf impacts related to stomatal traits, gas exchanges, C isotope composition, fluorescence parameters, thylakoid electron transport and enzyme activities were assessed at 25/20, 31/25, 37/30 and 42/34°C. The results showed that (1) both species were remarkably heat tolerant up to 37/30°C, but at 42/34°C a threshold for irreversible nonstomatal deleterious effects was reached. Impairments were greater in C. arabica (especially in Icatu) and under normal [CO2 ]. Photosystems and thylakoid electron transport were shown to be quite heat tolerant, contrasting to the enzymes related to energy metabolism, including RuBisCO, which were the most sensitive components. (2) Significant stomatal trait modifications were promoted almost exclusively by temperature and were species dependent. Elevated [CO2 ], (3) strongly mitigated the impact of temperature on both species, particularly at 42/34°C, modifying the response to supra-optimal temperatures, (4) promoted higher water-use efficiency under moderately higher temperature (31/25°C) and (5) did not provoke photosynthetic downregulation. Instead, enhancements in [CO2 ] strengthened photosynthetic photochemical efficiency, energy use and biochemical functioning at all temperatures. Our novel findings demonstrate a relevant heat resilience of coffee species and that elevated [CO2 ] remarkably mitigated the impact of heat on coffee physiology, therefore playing a key role in this crop sustainability under future climate change scenarios.

Effects of GC temperature and carrier gas flow rate on on-line oxygen isotope measurement as studied by on-column CO injection.

Although deemed important to δ18 O measurement by on-line high-temperature conversion techniques, how the GC conditions affect δ18 O measurement is rarely examined adequately. We therefore directly injected different volumes of CO or CO-N2 mix onto the GC column by a six-port valve and examined the CO yield, CO peak shape, CO-N2 separation, and δ18 O value under different GC temperatures and carrier gas flow rates. The results show the CO peak area decreases when the carrier gas flow rate increases. The GC temperature has no effect on peak area. The peak width increases with the increase of CO injection volume but decreases with the increase of GC temperature and carrier gas flow rate. The peak intensity increases with the increase of GC temperature and CO injection volume but decreases with the increase of carrier gas flow rate. The peak separation time between N2 and CO decreases with an increase of GC temperature and carrier gas flow rate. δ18 O value decreases with the increase of CO injection volume (when half m/z 28 intensity is <3 V) and GC temperature but is insensitive to carrier gas flow rate. On average, the δ18 O value of the injected CO is about 1‰ higher than that of identical reference CO. The δ18 O distribution pattern of the injected CO is probably a combined result of ion source nonlinearity and preferential loss of C16 O or oxygen isotopic exchange between zeolite and CO. For practical application, a lower carrier gas flow rate is therefore recommended as it has the combined advantages of higher CO yield, better N2 -CO separation, lower He consumption, and insignificant effect on δ18 O value, while a higher-than-60 °C GC temperature and a larger-than-100 µl CO volume is also recommended. When no N2 peak is expected, a higher GC temperature is recommended, and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.

Respiration, worker body size, tempo and activity in whole colonies of ants

Ants are social, and their metabolism should be measured on at least two levels: (i) the individual workers and brood of which the colony is composed and (ii) the colony in its entirety. Whole colony respiration, tempo (size‐free running speed in body lengths per second) and whole colony activity were simultaneously measured for 15 species of ants in four subfamilies, and these data are related to average worker and whole‐colony weight, activity, percentage brood and percentage fat. Across all 15 species, whole colony respiration rate (μL CO2 h−1) is linearly related to whole colony live weight (log–log slope = 1.0). Colonies composed of large workers respire less than colonies composed of an equal live weight of small workers, and colonies with high tempos respire more than lower tempo colonies of equal weight. The tempos and respiration rates of smaller ants tend to be higher, and a higher tempo exacts a cost in higher respiration independent of the effect of small body size. Individual worker respiration (μL CO2 h−1) scales to worker live weight with an exponent of 0.76. Whole colony specific respiration rate (μL CO2 g−1 h−1) is unrelated to colony live weight. The regressions of respiration rates against colony and worker dry weight, lean weight and metabolic weight have similar slopes to those of live weight but different intercepts. Respiration is not related to worker percentage fat, percentage brood or activity. Ant ecology, tempo, body size, polymorphism and colony size are discussed in relation to respiration.

Perspectives on the potential impacts of climate changes on coffee plant and bean quality

The atmosphere CO2 concentration increased from ca. 280, prior to the Industrial Revolution up to ca. 400 μL CO2 L-1 in our days, rising nearly 2 ppm per year actually. The Intergovernmental Panel on Climate Changes (IPCC) estimates at the end of 21st century the [CO2] could reach values between 445 and 1130 μL CO2 L-1, with a potential impact on global temperature and changes in water availability: These changes will have major agricultural and ecological implications. Here are presented some perspectives concerning the potential impacts of these environmental changes on the physiology and, consequently, on the production of Coffea arabica and C. canephora species, which together account for about 99% of the worldwide yielded coffee bean, considering the coffee plant’s requirements mostly focused in temperature.

Combined effects of elevated [CO2] and high temperature on leaf mineral balance in Coffea spp. plants

Modelling studies predicted that climate change will have strong impacts on the coffee crop, although no information on the effective impact of elevated CO2 on this plant exists. Here, we aim at providing a first glimpse on the effect of the combined impact of enhanced [CO2] and high temperature on the leaf mineral content and balance on this important tropical crop. Potted plants from two genotypes of Coffea arabica (cv. Icatu and IPR 108) and one from C. canephora (cv. Conilon Clone 153) were grown under 380 or 700 μL CO2 L−1 air, for 1 year, after which were exposed to an stepwise increase in temperature from 25/20 °C (day/night) up to 42/34 °C, over 8 weeks. Leaf macro − (N, P, K, Ca, Mg, S) and micronutrients (B, Cu, Fe, Mn, Zn) concentrations were analyzed at 25/20 °C (control), 31/25 °C, 37/30 °C and 42/34 °C. At the control temperature, the 700 μL L−1 grown plants showed a moderate dilution effect (between 7 % and 25 %) in CL 153 (for N, Mg, Ca, Fe) and Icatu (for N, K and Fe), but not in IPR 108 (except for Fe) when compared to the 380 μL L−1 plants. For temperatures higher than control most nutrients tended to increase, frequently presenting maximal contents at 42/34 °C (or 37/30 °C), although the relation between [CO2] treatments did not appreciably change. Such increases offset the few dilution effects observed under high growth [CO2] at 25/20 °C. No clear species responses were found considering [CO2] and temperature impacts, although IPR 108 seemed less sensitive to [CO2]. Despite the changes promoted by [CO2] and heat, the large majority of mineral ratios were kept within a range considered adequate, suggesting that this plant can maintain mineral balances in a context of climate changes and global warming.

TRANSPIRATION INFLUENCES CADMIUM UPTAKE BY BABY LEAF SPINACH (&lt;i&gt;SPINACIA OLERACEA&lt;/i&gt; L.)

Cadmium (Cd) is a toxic heavy metal whose concentration in soils is rising. This study investigated the effect of transpiration on Cd uptake by plants using soil conditions akin to those experienced by field crops. Two experiments were performed using baby leaf spinach ( Spinacia oleracea L.) grown in soil containing Chloride (Cl) at a typical concentration of 70 mg kg �1 . Experiment 1 explored plant response to Cd over the range ~0.04 to 10 mg kg �1 so that a non-toxic concentration could be selected for Experiment 2. Experiment 2 tested the hypothesis that transpiration and Cd uptake were related using soil amended to 70 mg Cl kg �1 and 0.24 mg Cd kg. Differences in transpiration were achieved by manipulating atmospheric CO 2 (~400 and ~640 µL CO 2 L �1 ) and air temperature (22/14, 26/18 and 30/22°C day/night). In Experiment 1, Cd in the foliage variedfrom ~2 to ~100 mg kg �1 DW, yet there was no evidence of Cd toxicity. In Experiment 2, temperature and [CO 2] caused large differences in plant growth. [Cd] was lower in chambers with increased temperature and higher in those with elevated CO 2. Despite differences in growth, transpiration and foliar Cd uptake were positively and strongly correlated, even when both parameters were expressed on a DW basis. The data are consistent with Cd transport by mass flow towards the roots being a substantial contributor to Cd uptake. Higher [Cd] at elevated CO 2 raises concerns about future chronic dietary exposure to Cd. The findings challenge the interpretation of earlier studies on the effects of CO 2 and temperature on Cd uptake and may partly explain the inter-seasonal variation in Cd uptake by field crops.

半干旱地区不同土地利用方式下土壤团聚体的微生物量属性

团聚体是土壤基本结构单元,是土壤质量和肥力的基础,研究了解不同土地利用方式下,不同团聚体的生物学属性,有助于深入了解土壤肥力本质,以及不同土壤肥力差异的根本原因.采集半干旱地区林地、旱地、灌溉耕地和草地4种土壤利用类型的表层土壤,用干筛法获得6级团聚体,测定微生物量碳(MBC)、三磷酸腺苷(ATP)含量、基础呼吸速率(BR)和基质诱导呼吸量(SIR)等指标.结果表明:土壤微生物量ATP浓度在7.79-9.26 μmol ATP/g C_mic,灌溉耕地最高、林地最低;微生物代谢熵(<em>q</em>CO₂)和SIR分别为0.35-0.69 μL CO₂ g^-1C_mic d^-1和88.7-132.2 μg CO₂ g^-1 d^-1,灌溉耕地最高、旱地最低.土壤团聚体的微生物量ATP浓度在6.54-9.32 μmol/g C_mic之间,平均值为8.22 μmol/g C_mic;<em>q</em>CO₂和SIR分别为0.29-0.71 μL/g C_mic和64-120 μg CO₂/g土,大团聚体含量总体上高于小团聚体,可能暗示不同团聚体土壤微生物群落活性及生理状态存在差异.土壤ATP含量、SIR和<em>q</em>CO₂与微生物量碳呈显著相关性 (<em>r</em>=0.929、0.865、0.885, <em>P</em> < 0.01),SIR和BR之间也有存在较高的相关性 (<em>r</em>=0.828、<em>P</em> < 0.01),说明尽管各级团聚体微生物学属性的绝对值存在很大的差异,但相互关系并未随团聚体大小而变化.;Soil aggregates are the basic units of soil structure and play an important role in soil quality and fertility. It is thus meaningful to investigate the natures and differences in biochemical properties of different soil aggregates. Moreover, it may be benefit to understand the essence of soil fertility and fundamental reason for the difference in fertility of different soils. In this study, 4 surface soils were sampled from woodland, none-irrigated cropland, irrigated cropland, and grassland in semi-arid region of Inner Mongolia. Six classes of soil aggregates with different diameters were collected with dry sieving method. The measured parameters included soil basic properties such as clay, organic matter, total nitrogen, K₂SO₄ extracted carbon, and soil microbial biomass C (MBC), ATP, basal respiration and substrate-induced respiration. The results showed that the irrigated soil had highest clay and organic matter contents, about 32.2 g/kg and 29.93 g/kg respectively, but lowest values in grassland soil, only 12.2 g/kg and 12.48 g/kg. The irrigated soil contained microbial biomass C of 336.03 mg/kg, but the woodland soil and none-irrigated cropland soil had about 207.53 mg/kg and 216.11 respectively. The ATP content in soils ranged 0.0016 - 0.0031 μmol/g soil, higher in the irrigated soil, lower in the woodland soil. The soil microbial biomass ATP concentration was the highest in the irrigated soil, about 9.26 μmol ATP/g C_mic, but lowest in the woodland soil, only 7.79 μmol ATP/g C_mic. The soil basal respiration and substrate-induced respiration were the highest in the irrigated soil, 10.31 μg CO₂-C g^-1soil d^-1 and 132.2 μg CO₂ g^-1 d^-1 respectively, but very low in the no-irrigated soil, only 3.33 μg CO₂-C g^-1soil d^-1 and 88.66 μg CO₂ g^-1 d^-1. The microbial biomass metabolic quotient (<em>q</em>CO₂) was high in the irrigated soil, about 0.69μg CO₂-C g^-1soil d^-1 but very low in the none-irrigated cropland soil, about 0.35 μL CO₂-C g^-1soil d^-1. The result showed that the microbial activity in the irrigated soil was higher than other soils, which might be linked with the quantity and quality of organic C input, water soluble carbon content and water content. Different soil aggregates had different natures of microbial biochemical properties. The basal respiration, <em>q</em>CO₂ and substrate-induced respiration in different soil aggregates were 0.29-0.71 μL/g C_mic, 0.29-0.71 μL/μg C_mic and 64-120 μg CO₂/g soil, respectively. The ATP content in soil aggregates changed among 0.83-3.02 nmol/g soil. The soil microbial biomass ATP concentration in soil aggregates were fallen within the range of 6.54-9.32 μmol/g C_mic. In general, the larger the soil aggregates, the higher values of those biochemical parameters were measured, which may imply the difference in microbial community and physiological activity among the soil aggregates. It may also indicate that microorganisms in larger aggregates (> 0.25 mm) have higher carbon utilization efficiency than those of smaller aggregates (< 0.25 mm). Soil microbial biomass ATP concentration, soil basal respiration and substrate-induced respiration were significantly and positively correlated with the soil microbial biomass C(<em>r</em>=0.929, 0.865, 0.885, <em>P</em> < 0.01). There was also a significant correlation between basal respiration and substrate-induced respiration (<em>r</em>=0.828, <em>P</em> < 0.01). It is evident that the relationships among the soil microbial parameters does not change with soil aggregates though dramatically different in the absolute values.

Sustained photosynthetic performance of Coffea spp. under long-term enhanced [CO2

Coffee is one of the world’s most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but these studies have not anticipated possible mitigating effects of the elevated atmospheric [CO2] because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m-2 s-1), RH (75%) and 380 or 700 μL CO2 L-1 for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high [CO2] treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth [CO2], the net rate of CO2 assimilation increased (34-49%) when measured at 700 than at 380 μL CO2 L-1. This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated [CO2], although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to [CO2] supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated [CO2] were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data suggest that Coffea spp. plants may successfully cope with high [CO2] under the present experimental conditions.

Influence of Global Atmospheric Change on the Feeding Behavior and Growth Performance of a Mammalian Herbivore, Microtus ochrogaster

Global atmospheric change is influencing the quality of plants as a resource for herbivores. We investigated the impacts of elevated carbon dioxide (CO2) and ozone (O3) on the phytochemistry of two forbs, Solidago canadensis and Taraxacum officinale, and the subsequent feeding behavior and growth performance of weanling prairie voles (Microtus ochrogaster) feeding on those plants. Plants for the chemical analyses and feeding trials were harvested from the understory of control (ambient air), elevated CO2 (560 µl CO2 l−1), and elevated O3 (ambient × 1.5) rings at the Aspen FACE (Free Air CO2 Enrichment) site near Rhinelander, Wisconsin. We assigned individual voles to receive plants from only one FACE ring and recorded plant consumption and weanling body mass for seven days. Elevated CO2 and O3 altered the foliar chemistry of both forbs, but only female weanling voles on the O3 diet showed negative responses to these changes. Elevated CO2 increased the fiber fractions of both plant species, whereas O3 fumigation elicited strong responses among many phytochemical components, most notably increasing the carbon-to-nitrogen ratio by 40% and decreasing N by 26%. Consumption did not differ between plant species or among fumigation treatments. Male voles were unaffected by the fumigation treatments, whereas female voles grew 36% less than controls when fed O3-grown plants. These results demonstrate that global atmospheric change has the potential to affect the performance of a mammalian herbivore through changes in plant chemistry.