Infrared Gas Analyzer Research Articles

The effect of CO2 on the water-saturated solidus of K-poor peridotite between 4 and 6 GPa

The effect of various amounts of CO2 on the solidus of H2O–CO2-bearing peridotite was examined by determining the composition of H2O–CO2-bearing fluids and melts in equilibrium with garnet peridotite at 4–6GPa and 900–1100°C. Two capsules were placed in a rocking multi-anvil apparatus in each experiment. Both capsules contained a fertile peridotite with 10wt% H2O, one with 1 (CLZ1) and the other with 5wt% CO2 (CLZ5). In both capsules a diamond trap was placed on one end of the capsule as a fluid/melt trap. The H2O and CO2 content in the fluid or melt trapped in between the diamonds were measured using the quartz-tube-system technique by releasing the volatiles through infrared gas analyzer. The total dissolved solids in these phases were determined using the cryogenic laser-ablation – inductive couple plasma – mass spectrometry technique. The residual lherzolite consists of olivine, orthopyroxene, ±clinopyroxene, garnet, and ±magnesite as carbonate phase. The solidus of CLZ1 peridotite was located between 900 and 1000°C at 4GPa and between 1000 and 1100°C at 5 and 6GPa. CLZ5 peridotite melts below 900°C at 4GPa and between 900 and 1000°C at 5 and 6GPa. The results demonstrate a decrease in melting temperature of hydrous peridotite at pressures between 4 and 6GPa with increasing amount of CO2.The H2O–CO2-bearing fluids found in this study at 900–1000°C are similar in composition to low-Mg carbonatitic to silicic high-density fluids found in fluid inclusions in diamonds. With increasing temperature, the melts approach type II kimberlites. We propose that H2O–CO2-induced partial melting of metasomatized garnet lherzolite at 4–6GPa is a possible origin for group II kimberlites.

Carbon Sequestration and Photosynthesis in Newly Established Turfgrass Cover in Central Chile

Core Ideas Soil organic C varied for 3 yr and four seasons for the five cool season turfgrass species (C3) and the two warm season turfgrass species (C4) when compared to bare soil. The effect of turfgrass species was detected in all of the seasons, where turfgrass coverage increased soil organic C over time, primarily at the 0‐ to 10‐cm soil depth. Carbon dioxide fixation rate can be an adequate indicator of carbon sequestration potential in a short‐term period for turfgrass species. This study showed that Cynodon dactylon L. and Festuca arundinacea Schreb. were the most promising species to increase C sequestration and to better use the irrigation water in central Chile. Growth of the urban population in central Chile may have contributed to increased CO2 emissions, thus information regarding the role of turfgrass in public spaces and its ability to sequester CO2 would be valuable. The objectives of this study were to assess and compare the magnitude of C sequestration of seven newly established turfgrass species to bare soil using seasonal organic C stocks measurements aboveground (aboveground organic carbon [AOC]) and belowground (soil organic carbon [SOC]) and to associate these data with turfgrass seasonal photosynthetic behavior. Festuca arundinacea Schreb, Festuca rubra L. ssp. rubra, Cynodon dactylon L., Cynodon dactylon L. × Cynodon transvaalensis Burtt Davy, Poa pratensis L., P. trivialis L., and Lolium perenne L., and areas with bare soil were established during 2010. Soil samples from 10, 20, and 30 cm were collected over 2 yr. Cuttings from each turfgrass species were also collected seasonally after reaching higher than the 4 cm cutting height. The SOC and AOC were assessed using the Modified Mebius method. The CO2 assimilation rate, stomatal conductance and photosynthetic water use efficiency were measured seasonally over 2 yr using an infrared gas analyzer. Turfgrass species with high photosynthetic activity during the summer, such as C. dactylon and F. arundinacea ‘Bingo’, resulted in a high total SOC of 2.4 t SOC ha−1 and 2.7 t SOC ha−1, respectively, when compared with bare soil (0.9 t SOC ha−1) at the end of the study.

A mobile sensor network to map carbon dioxide emissions in urban environments

Abstract. A method for directly measuring carbon dioxide (CO2) emissions using a mobile sensor network in cities at fine spatial resolution was developed and tested. First, a compact, mobile system was built using an infrared gas analyzer combined with open-source hardware to control, georeference, and log measurements of CO2 mixing ratios on vehicles (car, bicycles). Second, two measurement campaigns, one in summer and one in winter (heating season) were carried out. Five mobile sensors were deployed within a 1 × 12. 7 km transect across the city of Vancouver, BC, Canada. The sensors were operated for 3.5 h on pre-defined routes to map CO2 mixing ratios at street level, which were then averaged to 100 × 100 m grid cells. The averaged CO2 mixing ratios of all grids in the study area were 417.9 ppm in summer and 442.5 ppm in winter. In both campaigns, mixing ratios were highest in the grid cells of the downtown core and along arterial roads and lowest in parks and well vegetated residential areas. Third, an aerodynamic resistance approach to calculating emissions was used to derive CO2 emissions from the gridded CO2 mixing ratio measurements in conjunction with mixing ratios and fluxes collected from a 28 m tall eddy-covariance tower located within the study area. These measured emissions showed a range of −12 to 226 CO2 ha−1 h−1 in summer and of −14 to 163 kg CO2 ha−1 h−1 in winter, with an average of 35.1 kg CO2 ha−1 h−1 (summer) and 25.9 kg CO2 ha−1 h−1 (winter). Fourth, an independent emissions inventory was developed for the study area using buildings energy simulations from a previous study and routinely available traffic counts. The emissions inventory for the same area averaged to 22.06 kg CO2 ha−1 h−1 (summer) and 28.76 kg CO2 ha−1 h−1 (winter) and was used to compare against the measured emissions from the mobile sensor network. The comparison on a grid-by-grid basis showed linearity between CO2 mixing ratios and the emissions inventory (R2 = 0. 53 in summer and R2 = 0. 47 in winter). Also, 87 % (summer) and 94 % (winter) of measured grid cells show a difference within ±1 order of magnitude, and 49 % (summer) and 69 % (winter) show an error of less than a factor 2. Although associated with considerable errors at the individual grid cell level, the study demonstrates a promising method of using a network of mobile sensors and an aerodynamic resistance approach to rapidly map greenhouse gases at high spatial resolution across cities. The method could be improved by longer measurements and a refined calculation of the aerodynamic resistance.

Factors influencing stomatal conductance in response to water availability in grapevine: a meta-analysis.

The main factors regulating grapevine response to decreasing water availability were assessed under statistical support using published data related to leaf water relations in an extensive range of scion and rootstock genotypes. Matching leaf water potential (Ψleaf ) and stomatal conductance (gs ) data were collected from peer-reviewed literature with associated information. The resulting database contained 718 data points from 26 different Vitis vinifera varieties investigated as scions, 15 non-V. vinifera rootstock genotypes and 11 own-rooted V. vinifera varieties. Linearised data were analysed using the univariate general linear model (GLM) with factorial design including biological (scion and rootstock genotypes), methodological and environmental (soil) fixed factors. The first GLM performed on the whole database explained 82.4% of the variability in data distribution having the rootstock genotype the greatest contribution to variability (19.1%) followed by the scion genotype (16.2%). A classification of scions and rootstocks according to their mean predicted gs in response to moderate water stress was generated. This model also revealed that gs data obtained using a porometer were in average 2.1 times higher than using an infra-red gas analyser. The effect of soil water-holding properties was evaluated in a second analysis on a restricted database and showed a scion-dependant effect, which was dominant over rootstock effect, in predicting gs values. Overall the results suggest that a continuum exists in the range of stomatal sensitivities to water stress in V. vinifera, rather than an isohydric-anisohydric dichotomy, that is further enriched by the diversity of scion-rootstock combinations and their interaction with different soils.

Impact of Elevated CO2 on Leaf Gas Exchange, Carbohydrates and Secondary Metabolites Accumulation in Labisia pumila Benth

Aims: The aim of this study was to investigate different levels of CO 2 availability alters total phenolic and flavonoid, total available carbohydrate (TAC) and to determine how elevated CO 2 influences gas exchange of Labisia pumila seedlings. Study Design: The 3-months Labisia pumila seedlings of var Alata, var Pumila and var Lanceolata were put under 1 month to acclimatize in a nursery until ready for the treatment. Carbon dioxide enrichment treatments started when seedlings reached 4 months old by exposing them to three levels of CO 2 , viz., ambient CO 2 (400 µmol/mol), twice ambient (800 µmol/mol) and thrice ambient CO 2 (1200 µmol/mol). The split plot 3 x 3 factorial experiment was designed using randomized complete block design with CO 2 levels being the main plot and varieties as the sub-plot replicated Original Research Article Ibrahim et al.; ARRB, 19(6): 1-16, 2017; Article no.ARRB.36673 2 three times. Place and Duration of Study: Ladang 2, Universiti Putra Malaysia Glasshouse complex between July to November 2011. Methodology: The experiment was conducted for 15 weeks. The measurement of photosynthesis was obtained from a closed infra-red gas analyzer LICOR 6400XT Portable Photosynthesis System (IRGA, Licor Inc., USA). Total phenolics and flavonoid were determined using Follin-Ciocalteau reagent and total available carbohydrate using anthrone reagent. Results: It was found that the treatment effects were contributed by CO 2 levels in all weeks measured in leaf gas exchange properties (Net photosynthesis (A), stomatal conductance (g s), transpiration rate (E), intercellular CO 2 (C i) and Instantaneous water use efficiency, WUE). A combination of increases rates of A and E was responsible for enhancement of WUE by 50% in elevated treatment (800 and 1200 µmol/mol). Total available carbohydrate, total phenolics and flavonoid were also influenced by elevated CO 2 in all weeks of measurement. At end of 15 weeks after treatment (WAT), 44% increase in total available carbohydrate had increased total phenolic and flavonoid by 56% and 149% respectively than ambient treatment. At end of 15 WAT It was found, that the photosynthetic capacity of Labisia pumila was enhanced under elevated CO 2 by significantly have higher maximum electron transfer rate, J max and Rubisco CO 2 fixation capacity V cmax than ambient seedlings. Conclusion: In this work, it was observed that the increase in production of total phenolics and flavonoid in L. pumila might be due to increase in production of total available carbohydrate in the present study. The upregulation of photosynthesis in the present study was supported by enhancement of Maximum electron transfer rate, J max and Rubisco CO 2 fixation capacity V cmax than ambient seedlings that showed this plant has high sink strength to cope with high level of CO 2.

Impact of Carbon Dioxide and Increasing Nitrogen Levels on Growth, Photosynthetic Capacity, Carbohydrates and Secondary Metabolites in Kacip Fatimah (Labisia pumila)

Aims: This study was designed to investigate how CO2 and nitrogen availability alters growth, leaf gas exchange, primary and secondary metabolites production (total phenolics and flavonoid) in three varieties of L. pumila. namely var alata, var pumila and var lanceolata. under CO2 enrichment (1200 µmol mol-1) combined with four levels of nitrogen fertilization (0, 90, 180 and 270 kg N ha-1) for 15 weeks. Study Design: Three-month old L. pumila seedlings of var. alata, var. pumila and var. lanceolata were left for a month to acclimatize in a nursery until ready for the treatments. Carbon dioxide enrichment treatment started when the seedlings reached 4 months old where plants were exposed to 1200 µmol-1 mol-1 CO2 and fertilized with four levels of nitrogen concentrations viz. 0, 90, 180 and 270 kg N Ha-1. The fertilization with nitrogen levels were split into three applications. A control at ambient CO2 (400 µmol-1 mol-1) with standard N fertilization (180 kg N ha-1) was included to compare plant responses to high CO2 combined with different levels of N. Place and Duration of Study: Faculty of Agriculture Glasshouse Complex, Universiti Putra Malaysia from February to May 2011. Methodology: The seedlings were raised in specially constructed growth houses receiving 12-h photoperiod and average photosynthetic photon flux density of 300 µmol m-2 s-1. Carbon dioxide at 99.8% purity was supplied from a high–pressure CO2 cylinder and injected through a pressure regulator into fully sealed 2 m x 3 m growth houses at 2-h daily and applied continuous from 800 to 1000. Total plant biomass was taken by calculating the dry weight of root, stem and leaf per seedling. Total leaf area per plant was measured using a leaf area meter (LI-3100, Lincoln Inc, USA). The measurement of photosynthesis was obtained from a closed system of infra-red gas analyzer LICOR 6400 Portable Photosynthesis System. The response of net CO2 exchange (A) to changing intercellular CO2 concentration (Ci) was conducted at 27°C, 50% relative humidity and at light saturating conditions of 800 µmol m-2s-1. Anthrone method was used to determine the content of total available carbohydrate. Follin–Ciocalteau reagent was used to determine total phenolics and flavonoid using spectrophotometer. Results: In all parameters measured there were no significant was observed in the three varieties. As the levels of nitrogen increased from 0 to 270 kg N ha-1, plant growth, photosynthesis and total chlorophyll content was enhanced. However, carbohydrate, total phenolics and flavonoid was reduced with the increase in nitrogen fertilization. It was found that the high application of nitrogen can increased the photosynthetic capacity of L. pumila by having high Vcmax (RuBisCO CO2 fixation capacity), A sat (CO2 saturation point) and low dark respiration rate in the analysis of A/Ci curves. The production of secondary metabolites was related to increased total non-structural carbohydrate (TNC) under low nitrogen condition. Photosynthesis, displayed a significant negative relationship with secondary metabolites production. Total chlorophyll content exhibited very significant negative relationships with total soluble sugar, starch and total non-structural carbohydrate. Conclusion: This study demonstrated that enrichment with high levels of CO2 is able to enhance the production of plant secondary metabolites. However, increased nitrogen fertilization can reduce the production of these plant secondary metabolites under CO2 enrichment. When there were accumulation of TNC in plant leaves and reduction in photosynthesis, the production of plant secondary metabolites might be up-regulated. The increase in the production of plant secondary metabolites was indicated by reduction in chlorophyll contents.

Leaf anatomy, BVOC emission and CO2 exchange of arctic plants following snow addition and summer warming.

Climate change in the Arctic is projected to increase temperature, precipitation and snowfall. This may alter leaf anatomy and gas exchange either directly or indirectly. Our aim was to assess whether increased snow depth and warming modify leaf anatomy and affect biogenic volatile organic compound (BVOC) emissions and CO2 exchange of the widespread arctic shrubs Betula nana and Empetrum nigrum ssp. hermaphroditum METHODS: Measurements were conducted in a full-factorial field experiment in Central West Greenland, with passive summer warming by open-top chambers and snow addition using snow fences. Leaf anatomy was assessed using light microscopy and scanning electron microscopy. BVOC emissions were measured using a dynamic enclosure system and collection of BVOCs into adsorbent cartridges analysed by gas chromatography-mass spectrometry. Carbon dioxide exchange was measured using an infrared gas analyser. Despite a later snowmelt and reduced photosynthesis for B. nana especially, no apparent delays in the BVOC emissions were observed in response to snow addition. Only a few effects of the treatments were seen for the BVOC emissions, with sesquiterpenes being the most responsive compound group. Snow addition affected leaf anatomy by increasing the glandular trichome density in B. nana and modifying the mesophyll of E. hermaphroditum The open-top chambers thickened the epidermis of B. nana, while increasing the glandular trichome density and reducing the palisade:spongy mesophyll ratio in E. hermaphroditum CONCLUSIONS: Leaf anatomy was modified by both treatments already after the first winter and we suggest links between leaf anatomy, CO2 exchange and BVOC emissions. While warming is likely to reduce soil moisture, melt water from a deeper snow pack alleviates water stress in the early growing season. The study emphasizes the ecological importance of changes in winter precipitation in the Arctic, which can interact with climate-warming effects.

Estimation of Photorespiratory Fluxes by Gas Exchange.

Photorespiratory fluxes can be easily estimated by photosynthetic gas exchange using an infrared gas analyzer and applying the Farquhar, von Caemmerer, and Berry (Farquhar et al. Planta 149:78-90, 1980) photosynthesis model. For a more direct measurement of photorespiratory CO2 release from glycine decarboxylation, infrared gas analysis can be coupled to membrane-inlet mass spectrometry, capable of separating the total CO2 concentration into its 12CO2 and 13CO2 components in a continuous online fashion. This chapter discusses how to calculate rates of photorespiration from Rubisco kinetics and describes in detail a method for measuring the CO2 release from glycine decarboxylation using 13CO2.

Leaf gas exchange in cowpea and CO2 efflux in soil irrigated with saline water

ABSTRACT Leaf gas exchanges in plants and soil respiration are important tools for assessing the effects of salinity on the soil-plant system. An experiment was conducted with cowpea irrigated with saline water (0, 2.5, 5.0, 7.5, 10.0 and 12.5 dS m-1) prepared with two sources: NaCl and a mixture of Ca, Mg, Na, K and Cl ions in a randomized block design and a 6 x 2 factorial scheme, with four replicates, totaling 48 experimental plots. At 20 days after planting (DAP), plants were evaluated for net photosynthesis (A), stomatal conductance (gs) and transpiration (E) using the Infra-Red Gas Analyzer (Model XT6400- LICOR), and water use efficiency, intrinsic water use efficiency and instantaneous efficiency of carboxylation were calculated. At 60 DAP, the soil CO2 efflux (soil respiration) was determined with a camera (Model 6400-09- LICOR). Salinity caused reductions in A, gs and E. However, the salt source did not have significant effect on these variables. Soil CO2 efflux was reduced with the increase in the electrical conductivity, especially in the mixture of ions.

Physiological Response of Maize and Weeds in Coexistence

ABSTRACT This study aimed at evaluating the physiology of maize and weeds when living under different densities. The randomized block design with 4 replications was used. The factorial scheme 5 x 2 + 1 and 5 x 3 was adopted, for maize and weeds respectively, corresponding to weed species (Bidens pilosa, Commelina benghalensis, Urochloa brizantha, Sorghum arundinaceum and Ipomoea triloba) and infestation density (control, 15 and 30 plants m-2). Weeds were kept in coexistence with the maize hybrid DKB 390 PRO 2, with an additional treatment for maize plants absent of competition. It was kept in coexistence with maize hybrid DKB 390 PRO 2 besides an additional treatment with maize plants absent of competition. On day 45 and 60 after maize planting (DAP) physiological reviews were performed within the culture, and 38 days after weed transplanting (DAT), an infrared gas analyzer (IRGA) was used. There were physiological changes in maize due to the coexistence with weeds. On day 45 DAP, the competition, regardless of the weed species, caused less photosynthetic rate in maize coexisting with 15 plants m-2; the stomatal conductance was lower in both densities. On day 60 DAP, maize in competition with 15 and 30 plants m-2 showed lower transpiration rate. U. brizantha and S. arundinaceum showed reduction in photosynthesis and transpiration, due to increased density and coexistence with maize.

Basal Area Effects on Soil Respiration Rates of a Pinus densiflora Stand

This study was conducted to determine the relationship between stand and soil environmental factors, and soil respiration rates at various levels of basal area in a 40-year-old natural red pine(Pinus densiflora S. et Z.) stand in southern Korea. Soil respiration rates were measured monthly using an infrared gas analyzer system from six basal area treatments between 21.4 m2 ha-1 and 46.7 m2 ha-1 for one year. Soil respiration at various levels of basal area showed a clear monthly variation, which had a similar pattern to soil temperature. The mean annual soil respiration rates were positively correlated with increasing basal area(r=0.86, p 0.05) such as the mean annual soil temperature, soil water content, soil pH, and soil organic C content during the study period. The results indicate that it is important to understand the role of stand attributes in the mean annual soil respiration rates in a stand level.

Mapping QTLs for Physiological Traits Associated with Drought Tolerance in Rice (Oryza Sativa L.)

The present investigation mainly focused to study the physiological and molecular characterization of 101 Backcross Inbred Lines (BILs) of rice (BC1F5) for drought tolerance derived from the cross combination of Norungan // TKM9/ Norungan. The traits like photosynthetic rate, transpiration rate and stomatal conductance were observed using infrared gas analyzer (IRGA) and the population was phenotyped for other traits. Estimation of genetic parameters revealed that, among the physiological traits observed, the trait transpiration rate recorded higher value of heritability (0.28) and genetic advance (17.49). Association analysis recorded that, all the physiological traits studied under severe water deficit condition had high and significant positive correlation with plot yield. The trait photosynthetic rate had exhibited significant positive correlation with transpiration rate and stomatal conductance but recorded negative correlation with relative water content (RWC). Single marker analysis was performed with the genetic data and the trait mean values observed under stress condition. Among 167 SSR (microsatellite) markers surveyed, around 15 markers were identified and found to be linked to at least one of the investigated trait and many markers were reported to be linked with more than one trait. Characterization of Quantitative trait loci (QTLs) for drought tolerance in this study provides insight into an understanding of the mode of drought tolerance in rice and to perform MAS (Marker aided selection) aimed at the efficient pyramiding of favorable QTL alleles to improve drought tolerance in elite background of popular rice varieties.

Biological soil crust community types differ in photosynthetic pigment composition, fluorescence and carbon fixation in Shapotou region of China

In order to ensure the smooth operation of the Baotou-Lanzhou railway in Shapotou region of China (southeast edge of the Tengger Desert), vegetation protecting system was established, and then substantial biological soil crusts (BSCs) gradually developed there, however so far little study has focused on the refined crust community types and their related ecological functions. In this study, eight main crust community types were distinguished from the restoration region, and their pigment composition and photosynthetic performance were compared through spectrophotometry, chlorophyll fluorescence and infrared gas analysis technologies. The results showed that crust chlorophyll-a and carotenoids contents had a good linear relationship (R2=0.964; P<0.001), generally increased with the development and succession of BSCs, while crust scytonemin content was highest in cyanolichen soil crusts. When chlorophyll-a content was less than 15μgcm−2, crust original fluorescence (Fo) linearly increased with the increasing chlorophyll-a content (R2=0.758; P=0.001), providing a convenient approach to monitor crust photosynthetic biomass in situ, but without crust destruction. Compared with cyanobacterial and cyanolichen soil crusts, chlorolichen and moss soil crusts had the higher photosynthetic activities (Fv/Fm), although the chlorolichen soil crusts performed the lowest net photosynthetic carbon fixation (average 1.5–1.8mmol CO2 m−2h−1), while moss soil crusts had the greater carbon fixation efficiency, about 2.4–7.5 fold higher according to the different community types. Conclusively, a finely divided classification of BSCs will not only improve the estimation of crust carbon fixation, but also strengthen the accuracy and importance of crust community types at the landscape scale.

Carbon Mineralization and Water-Extractable Organic Carbon and Nitrogen as Predictors of Soil Health and Nitrogen Mineralization Potential

ABSTRACTThe United States Department of Agriculture Natural Resources Conservation Service (NRCS) launched a national “Soil health initiative” in 2012; as a part of that effort, a soil health index (SHI) has been developed. The SHI is calculated using results of three soil tests: 24-h carbon mineralization following rewetting of air-dried soil (Cmin, by the “Solvita” proprietary method) and water-extractable organic carbon (C) and nitrogen (N). These tests are being promoted both as the inputs into the SHI calculation and as predictors of soil N mineralization potential. Soil was collected from 35 California fields in annual crop rotations; 20 fields were under certified organic management and the other 15 under conventional management, to provide a range of soil properties and management effects. Carbon mineralization was determined by the Solvita method, and by a comparison method utilizing head space carbon dioxide (CO2) monitoring by infrared gas analyzer (IRGA); additionally, two soil wetting protocols were compared, capillary wetting (the Solvita method) and wetting to 50% water-filled pore space (WFPS). Both water-extractable C (WEOC) and N (WEON) were determined using NRCS-recommended protocols. Net N mineralization (Nmin) was also determined after a 28-day aerobic incubation at 25°C. Solvita Cmin was highly correlated with the IRGA method using capillary wetting (R2 = 0.81). However, capillary soil wetting resulted in high gravimetric water content that significantly suppressed Cmin compared to the 50% WFPS method. Nmin was correlated with Solvita Cmin (r = 0.54) and with WEOC and WEON (r = 0.62 for each comparison); combining these three measurements into the SHI slightly improved the correlation with Nmin. The organically managed soils scored higher than the conventional soils on the SHI, with a minority of organic soils and the majority of conventional soils scoring below the NRCS target threshold. SHI and soil organic matter were correlated, suggesting an inherent bias that would complicate the application of a national SHI standard.

Real-Time Soil CO2 Respiration Rate Determination and the Comparison between the Infrared Gas Analyzer and Microrespirometer (MicroRes®) Methods

ABSTRACTSoil carbon dioxide (CO2) respiration is one of the important soil health parameters that provides a general assessment of soil microbial activity and soil quality. Soil respiration rates, however, have not been widely applied in soil testing protocols mainly because the traditional methods are either inconvenient, technically cumbersome or too expensive. Currently, only two methods are available for a true real-time soil respiration rate determination (<2 h): the infrared gas analyzer (IRGA) and the microrespirometer (MR or MicroRes®) methods. We analyzed the real-time soil respiration rates of 20 soil samples from fifteen states after various periods of incubation using the IRGA method and the MR method. The measured soil respiration rates ranged from 0.4 µL CO2/h/g to 9.0 µL CO2/h/g. Both methods show precision in soil respiration determinations (CV = 12.7% and 11.9%, respectively). Comparison of the results between the IRGA and MR methods indicates high degrees of agreement (r2 = 0.914). This study shows that the MR method is a simpler and more cost-effective alternative for real-time soil respiration rate determinations.

LiDAR and thermal images fusion for ground-based 3D characterisation of fruit trees

The thermal behaviour of an orchard is intrinsically related to the plant physiological status and it is commonly observed using thermal imagery, in most cases, provided by a drone or by a satellite. Such remote sensing methods are currently popular since they allow to analyse large amounts of land data with few sensor readings. However, they are restricted by the spatial resolution of the images, which always correspond to top views of the canopies. The latter does not allow for a side recording or analysis of the orchard. In this work, we design and evaluate a portable ground-based system for a manual thermal and geometrical characterisation of an orchard, merging thermal images with LiDAR-based range readings in order to obtain a 3D thermal reconstruction of the crop to overcome the previously mentioned issues. The proposed system can work in Global Navigation Satellite System (GNSS) denied environments and delivers multiple views of the orchard, offering the user a three-dimensional view of the thermal behaviour of the grove. Further, the implemented algorithm classifies points from the LiDAR measurements which correspond to the canopy using a supervised classifier. Later, a matching procedure is performed between such points and the thermal information provided by the thermal camera. In order to reconstruct the entire orchard or only a section of the grove, several frames are registered using the Iterative Closest Point algorithm. The system was tested in two conditions: in laboratory and in field within a plantation of Hass avocado, which is one of the main fruit trees growing in Chile, and its performance is compared with an LI-6400 Infra-red Gas Analyser (IRGA) portable photosynthesis system (LI-COR, Lincoln, NE).

Performance Evaluation of an Integrated Open-Path Eddy Covariance System in a Cold Desert Environment

AbstractPerformance evaluation of an integrated eddy covariance (EC) instrument called the IRGASON, with a separated EC for reference, was conducted in a desert riparian Populus euphratica stand in the lower Tarim River basin in northwestern China. The separated EC consisted of an open-path gas analyzer and a sonic anemometer separated by 20 cm. The IRGASON integrates an open-path gas analyzer and a sonic anemometer into the same sensing volume, thus eliminating sensor separation in comparison to the traditional open-path EC setup. Integrating the infrared gas analyzer’s sensing head into the sensing volume of the sonic anemometer had negligible effects on wind speed and friction velocity observations of the IRGASON. Physiologically unreasonable daytime CO2 uptake was observed by both systems during the cold winter season (mean air temperature of −6.7°C), when the trees were dormant without any photosynthetic activities. The mean midday CO2 flux was −1.65 and −1.61 μmol m−2 s−1 for the IRGASON and the separated EC setup, respectively. No evidence was found for sensor self-heating as the cause of the apparent uptake CO2 flux. Instead, the uptake CO2 flux appeared to be an artifact of the spectroscopic effect of the IRGASON’s gas analyzer. After adjusting for this spectroscopic effect using a relationship with the sensible heat flux, the wintertime IRGASON CO2 flux became physiologically reasonable (mean value of −0.04 μmol m−2 s−1).

Genetic engineering of polyamine metabolism changes Medicago truncatula responses to water deficit

In the current scenario of climate change and increasing water scarcity there is an increased need to combine research efforts for the development of abiotic stress resistant crops, specifically plants able to support water deficit (WD). Polyamines (PAs) have been described as being involved in the regulation of many physiological processes and a variety of stress responses in plants. Arginine decarboxylase (ADC) is considered a key enzyme of the polyamine (PA) biosynthetic pathway. In this study, a T2 transgenic homozygous line of Medicago truncatula expressing the oat Adc under the control of CaMV 35S was obtained and was shown to have higher leaf accumulation of putrescine, spermidine and norspermidine compared to wild type plants. The photosynthetic parameters, leaf internal CO2 concentration (Ci), net CO2 assimilation rate (A), transpiration (E) and stomatal conductance (gs) of transformed and untransformed lines during WD and water deficit recovery experiments were measured by IRGA (infrared gas analyzer) and compared over time. Two light intensities were used, growth light intensity (391 μmol m−2 s−1) and saturating light intensity (1044 μmol m−2 s−1). Independently of the light intensity, and under WD, the transgenic line stood out with increased Ci, A, E and gs; suggesting a possible benefit of the augmented PAs under such disturbing environmental conditions. We showed that the constitutive expression of the oat Adc gene improve the physiological responses to WD and that WD recovered transgenic plants had higher seed yield, suggesting a possible benefit of PA metabolism manipulation in legumes.

A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO2 and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO2 flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO2 for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO2 exposure, photosynthesis increased with CO2 as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO2, such as temperature, irradiance and nutrients.

Investigation on the Reduction Behavior of Coal Composite Pellet at Temperatures between 1373 and 1573 K

The influence of different coal types on the reduction of composite pellet is investigated. Three Australian coals representing high volatile, medium volatile, and low volatile coal are analyzed and used for pellet preparation. High temperature behavior is investigated by Thermo-Gravimetric Analyzer (TGA) at temperature range from 1373 K (1100 °C) to 1573 K (1300 °C). CO and CO2 gases released from the reaction measured by Infrared (IR) gas analyzer are used for kinetic analysis. Reaction rates at different temperatures are investigated by kinetic models considering Boudouard reaction and surface area change during the reduction reaction.