Increase In CO2 Evolution Research Articles

Can Biochar Made from Rice Husk Affect Savanna Soils’ pH, Electrical Conductivity, and Soil Respiration?

Biochar is now gaining awareness as a sustainable tool for soil health improvement, boosting carbon (C) storage and the enhancement of nutrient cycling in agricultural soils. This study assesses the effects of biochar on soil respiration, pH, and electrical conductivity (EC) in savanna soils over a 45-day incubation trail in the laboratory. Four different biochar treatments (0, 2, 4, and 6 t/ha) were used in the study. The treatments were established at 26°C, and after 2, 5, and 10 days, the CO2 levels were recorded. After incubation for 0, 5, 10, and 45 days, the EC and pH were assessed. As the rate of application of biochar increased, the rate of CO2 evolution increased as well. During the first two days of incubation, the CO2 evolution rate rose by a value of 129 at 2 t/ha biochar, 146 at 4 t/ha biochar, and 168 ug CO2/g soil/d at 6 t/ha biochar above the 0 t/ha biochar. Following five days of incubation, the amounts of CO2 evolution that were higher than the control were 99 with 2 t/ha, 116 with 4 t/ha, and 120 ug CO2/g soil/d with 6 t/ha of biochar. The increase in CO2 evolution above the control treatment at 10 days of incubation was 61 with 2 t/ha, 79 with 4 t/ha, and 87 ug CO2/g soil/d with 6 t/ha of biochar. Analogously, rising patterns in CO2 emissions were noted. Throughout the whole incubation period, the biochar treatments' soil EC and pH were greater than those of the control treatment. After applying biochar, there were increases in the evolution of CO2, however after 10 days of incubation, the percentage of C evolved from the addition of biochar decreased as the rates of biochar increased. At two t/ha, four t/ha, and six t/ha, the percentage C developed was 1.74 %, 1.66%, and 0.82% of the applied biochar C, respectively. Although the CO2 evolved ratio to the total amount of biochar C typically reduced with increasing biochar rates, this study shows that the addition of biochar increases soil respiration, EC, and pH.

Resolving high potential structural deterioration in Ni-rich layered cathode materials for lithium-ion batteries operando

LixNi0.90Co0.05Al0.05O2 (NCA) extracted from an automotive battery cell is studied using a combination of in-house operando techniques to understand the correlation between gas evolution and structural collapse when NCA is cycled to high potentials in a lithium-ion battery configuration. The operando techniques comprise X-ray diffraction (XRD) and online electrochemical mass spectrometry (OEMS), and cycled using intermittent current interruption (ICI). The ICI cycling protocol is used to assess the dynamic change in resistance as well as to provide a validation of the operando setups. Both gas evolution and structural collapse have previously been observed as degradation mechanisms of Ni-rich electrodes including NCA, however, their causal link is still under debate. Here our presented results show a correlation between the decrease of the interlayer distance in NCA with both an increase in CO2 evolution and diffusion resistance above 4.1 V. Additionally, particle cracking, which is a mechanism often correlated with gas evolution, was found to be reversible and visible before gas evolution and Li diffusion resistance increase. The ICI technique is shown to be useful for the correlation of operando experiments on parallel setups and evaluation of mass transport dependent processes.

Mitigation of Greenhouse Gas Emissions with Biochar Application in Compacted and Uncompacted Soil

Biochar may offer a substantial potential as a climate change mitigation and soil improvement agent; however, little is known about its effects in fertile soils subjected to standard agricultural practices. The aim of this short-term (60 days) lab experiment, under controlled temperature and soil moisture regimes, was to investigate the interaction between soil compaction and fertiliser and biochar addition in relatively fertile Luvisol. Three different biochar types and two soil compaction levels were investigated to describe their interactive effect on soil greenhouse gas emission (GHG). A very strong effect of soil compaction on N2O emission (+280%) and an interaction with biochar were found. The cumulative N2O emissions from the compacted soil were higher (from +70 to +371%, depending on the biochar type) than the uncompacted soil. Soil compaction resulted in a faster onset and a faster decrease of N2O production. Biochar did not affect the temporal dynamics of N2O evolution from either soil. The addition of digestate/crop biomass biochar has resulted in a significant increase in CO2 evolution both in compacted and uncompacted soils, compared to softwood from spruce (mixture of branches and wood chips) and wood pallets from softwood (spruce without bark) biochar. In the compacted soil, NH4+ availability was positively related to N2O efflux, and CO2 emission was positively correlated to both NH4+ and SOC content. An increase in GHGs as a result of an increase in NH4+ availability was seen both in compacted and uncompacted soils, while the rates of N2O emission were modified by biochar type. Our results show a strong interaction between biochar and soil conditions and a strong effect of biochar type on GHG emissions from agricultural soils.

Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency

The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise well-drained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank rs = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (rs = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Fe-organic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with 13C nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Fe-organic interactions. In our incubation experiments, a doubling in short-term CO2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation.

Influence of organic residue addition on CO2 evolution and N mineralization in soil

A combination of pot culture experiment and incubation study was conducted at the soil science and agricultural chemistry section, college of agriculture, nagpur to assess the decomposition potential and rate of mineralization of nitrogen of different organic residues. Initially, the rate of CO2 evolution was near constant during 10 days of incubation peaking on 3rd day after incubation. There was a steep increase in CO2 evolution in all the treatments after 10 days, attaining its peak at 70 days after incubation thereafter it began to decrease in a non-uniform pattern upto 120 days. Cummulatively, maximum CO2 evolution was recorded in green gram stalks followed by sugarcane trash and lowest was found in control pot. Nitrogen mineralization in pot culture experiment was analysed at 4 monthly intervals viz. 30, 60, 90 and 120 days. There was a sharp increase in the rate of N mineralization at 60 days interval and altogether, there was a decreasing trend of nitrogen mineralization after 60 days of experimentation. The peak amount of mineralization was observed at 90 days in near about all the treatments. Subabul leaves mixture (T7) recorded maximum ammoniacal nitrogen (48.98 mg kg-1, 52.66 mg kg-1, 56.99 mg kg-1 and 44.99 mg kg-1) and nitrate nitrogen (26.25 mg kg-1, 38.02 mg kg-1, 30.01 mg kg-1 and 20.83 mg kg-1) throughout the experimentation. The results highly indicated that addition of all residues produced a significant increase in soil organic carbon and nitrogen but, leguminous residues showed a higher response.

Isolation and Characterization of Bacteria and Fungi Associated with Biodegradation of Municipal Solid Wastes in Abakaliki Metropolis, Nigeria

Microorganisms involved in the biodegradation of municipal solid waste (MSW) in Abakaliki dumps were isolated and characterized using standard microbiology technique. Five municipal solid waste dumpsites located within Abakaliki metropolis, Ebonyi State, Nigeria were used for this study. The potential of individual microbial isolate to grow on the MSW was also studied using nutrient broth supplemented with mineral salt media and thereafter five of the best microbial degraders were subjected to a 98 days biodegradation studies using weight loss, change in pH, density change and CO2 evolution as indices of success. The study showed that different dumpsites had different temperature readings, bacterial and fungal load, caused by the volume of waste dumped and the habits of the inhabitants. The bacteria population isolated from the dumpsites included Pseudomonas spp, Bacillus spp, Lactobacillus spp, Streptococcus spp, Staphylococcus spp and Micrococcus spp. Penicillum spp, Mucor spp, Aspergillus spp, Fusarum spp, Saccharomyces spp and Candida spp were the fungal species isolated from the dumpsites. The bacteria with the highest growth rate were Bacillus spp, Pseudomonas spp, while Aspergillus spp, Mucor spp, and Saccharomyces spp recorded the highest growth rate for the fungi isolates. The fungi group proved to be better microbial degraders than the bacteria population as a percent weight loss of 1.11 ± 0.03, 1.04 ± 0.05 and 1.23 ± 0.02 were achieved by Saccharomyces spp, Mucor spp and Aspergillus spp respectively. This was in comparison to the bacteria group, which recorded 0.89 ± 0.04 and 0.87 ± 0.03 percent weight loss by Pseudomonas spp and Bacillus spp. Increases in CO2 evolution was equally recorded by both the fungal and bacterial groups as well as increase in acidity. There was a positive correlation among CO2 evolution, weight loss and density for all the test organisms. However, there was no relationship between pH and CO2 evolution, weight loss and density.

Effect of disturbance by oil pollution on the diversity and activity of bacterial communities in biological soil crusts from the Sultanate of Oman

The impacts of oil pollution, unlike other disturbances, on the structure and activity of microorganisms in biological soil crusts have never been investigated. We exposed crust pieces from Wadi Al-Khoud, Sultanate of Oman to different oil concentrations and studied changes in their chlorophyll a (Chl a) content, bacterial communities and photosynthetic and respiration activities. Chl a concentrations did not change in dry oil-polluted crusts but increased in the crusts exposed to oil in the presence of water. Nevertheless, extended incubation with oil for ≥3 weeks or in the presence of higher concentrations resulted in a considerable decline in Chl a in the wet polluted crusts. A remarkable shift in the bacterial community composition of oil-polluted crusts was detected, with the replacement of Cyanobacteria by Firmicutes. Sequences affiliated to Firmicutes constituted 86% of total sequences after 96days of incubation with oil. This community shift was concomitant with alkanes degradation, as assessed by gas chromatography-mass spectrometry (GC–MS) analysis. Using oxygen microsensors, addition of oil to crusts was shown to result in an instantaneous decline in oxygen production but a quick recovery within hours of incubation. The net oxygen production and net photosynthesis decreased whereas the recovery time increased with increasing concentrations of oil. Recovery was not possible when crusts were exposed to ≥2000mg oilg−1 crust. Incubation of crust pieces at different oil concentrations in air-tight bottles in the dark showed an increase in CO2 evolution with increasing oil concentration. We conclude that oil pollution has drastic effects on crust microorganisms, and these effects depend on oil pollution levels, hydration conditions and duration of exposure.

Microwave-enhanced degradation of phenol over Ni-loaded ZnO nanorods catalyst

Nickel was loaded onto hydrothermally-grown ZnO nanorods on cordierite substrates and tested as catalysts in microwave-enhanced degradation of phenol from its aqueous solution (100ppm) at 70°C. Effects of metal loadings (1, 10 and 20mM impregnation solutions) on the degradation of phenol in aqueous solution was investigated. The catalyst performances were monitored based on phenol degradation, product distributions and carbon dioxide (CO2) evolutions. Based on the type of the catalysts, two different mechanistic pathways for the decomposition were observed—through catechol and/or hydroquinone as intermediates. It was found that the 10mM nickel loaded sample catalyzed the degradation through one pathway with hydroquinone as the benzenediol intermediate formed, while the 20mM nickel impregnated sample catalyzed the reaction through two pathways, producing catechol as well as hydroquinone by products. These differences in reaction pathways were attributed to the variation in the composition of the nickel compounds and surface structures between the two catalysts. Furthermore, the effect of hydrogen peroxide (H2O2) as an oxidant was explored. It was found that although addition of H2O2 led to an increase in the degree of phenol degradation, it also led to enhanced catalyst leaching. There was also an increase in CO2 evolution due to the addition of H2O2. It was observed that 20mM nickel-loaded sample without the addition of H2O2 exhibited optimum performance in terms of phenol degradation and CO2 evolution with no drawback of catalyst leaching. Catalytic microwave enhanced degradation is an effective means for the removal of dissolved organic compounds from wastewater.

Characterization of hydrocarbon-degrading bacteria isolated from oil-contaminated sediments in the Sultanate of Oman and evaluation of bioaugmentation and biostimulation approaches in microcosm experiments

Two oil-polluted sediments (PD and KH) were sampled from a coastal region in Oman for the isolation of hydrocarbon-degrading bacteria and for testing different bioremediation approaches. Fourty strains were isolated, eighteen were affiliated to Marinobacter whereas the rest belonged to Pseudomonas, Halomonas, Hahella and Alcanivorax. All strains grew well at 2–7% salinity and between 20 and 60 °C. The strains exhibited a better growth on long chain than on short chain alkanes. Biostimulation and bioaugmentation were compared in both sediments and oil biodegradation was followed by measuring CO2 evolution and by gas chromatography (GC). The evolved CO2 reached 0.45 ± 0.02 and 2.23 ± 0.07 mg CO2 g−1 sediment after 88 days in the untreated PD and KH sediments, respectively. While the addition of inorganic nutrients resulted in 1.2–3.7 fold increase in CO2 evolution in both sediments, the addition of the bacterial consortium was only effective in the PD sediment. The maximum CO2 evolution was measured when both nutrients and bacteria were added and this corresponded to a total oil mineralization of 2.6 ± 0.12 and 1.49 ± 0.04% of the initial oil after 88 days in the PD and KH sediments, respectively. GC analysis confirmed the CO2 data and showed that most of the degraded compounds belonged to alkanes. We conclude that the Omani polluted sediments contain halotolerant and thermotolerant bacteria and biostimulation is more efficient than bioaugmentation for their cleanup.

Effects of intermittent mechanical mixing on solid-state fermentation of wet corn distillers grain with Trichoderma reesei

The influence of mixing on microorganism integrity and product formation is a critical design parameter for solid-state fermentation bioreactors. The effects of intermittent mechanical mixing on the solid-state fermentation of wet corn distillers grain with Trichoderma reesei NRRL 11460 for the production of cellulase were investigated. Experiments were conducted using the unbuffered media at mixing frequencies of 0, 1, 2, 3, and 6d−1 at 27.5°C with an initial moisture content of 50%. The results indicate that mixing caused about a tenfold increase in spore production compared to fermentations at static conditions. The cellulase enzyme activity produced was minimally affected by mixing with only a 5–10% decrease in filter paper activity for mechanically mixed fermentations compared to static fermentations. Mixing at lower frequencies of 1, 2, and 3d−1 caused an increase in CO2 evolution compared to static conditions and higher mixing frequencies of 6d−1. A correlation between substrate weight loss and cumulative CO2 evolution was established. The ability to intermittently mix a solid-state fermentation bioreactor with minimal detrimental effects increases the feasibility of onsite production of enzymes at biofuel facilities to lower the overall production costs of cellulosic biofuels.

Short-Term Metabolome Dynamics and Carbon, Electron, and ATP Balances in Chemostat-Grown Saccharomyces cerevisiae CEN.PK 113-7D following a Glucose Pulse

The in vivo kinetics in Saccharomyces cerevisiae CEN.PK 113-7D was evaluated during a 300-second transient period after applying a glucose pulse to an aerobic, carbon-limited chemostat culture. We quantified the responses of extracellular metabolites, intracellular intermediates in primary metabolism, intracellular free amino acids, and in vivo rates of O(2) uptake and CO(2) evolution. With these measurements, dynamic carbon, electron, and ATP balances were set up to identify major carbon, electron, and energy sinks during the postpulse period. There were three distinct metabolic phases during this time. In phase I (0 to 50 seconds after the pulse), the carbon/electron balances closed up to 85%. The accumulation of glycolytic and storage compounds accounted for 60% of the consumed glucose, caused an energy depletion, and may have led to a temporary decrease in the anabolic flux. In phase II (50 to 150 seconds), the fermentative metabolism gradually became the most important carbon/electron sink. In phase III (150 to 300 seconds), 29% of the carbon uptake was not identified in the measurements, and the ATP balance had a large surplus. These results indicate an increase in the anabolic flux, which is consistent with macroscopic balances of extracellular fluxes and the observed increase in CO(2) evolution associated with nonfermentative metabolism. The identified metabolic processes involving major carbon, electron, and energy sinks must be taken into account in in vivo kinetic models based on short-term dynamic metabolome responses.

DIEL MINERALIZATION PATTERNS OF STANDING-DEAD PLANT LITTER: IMPLICATIONS FOR CO2FLUX FROM WETLANDS

We examined the effects of environmental conditions on the microbially mediated CO2 evolution from standing-dead litter (leaf blades, leaf sheaths, and culms) of the common reed, Phragmites australis (Cav.) Trin. ex Steud., in two temperate littoral freshwater marshes. Water availability was the major factor affecting CO2 evolution rates. In the laboratory, microbial assemblages responded rapidly to controlled additions of water, with large increases in CO2 evolution occurring within five minutes after wetting of litter (e.g., leaf blades: 10–295 μg CO2-C·(g ash-free dry mass [AFDM])−1·h−1. Under field conditions, CO2 evolution in the absence of precipitation exhibited a pronounced diel periodicity, with the highest rates occurring during periods of increased water availability resulting from a temperature-induced rise in relative humidity (>95%) and corresponding litter water potential (>−2.0 MPa) during nighttime. For example, in October, rates of CO2 evolution over a 24-h cycle ranged from 5 to 223 μg CO2-C·(g AFDM)−1·h−1 for leaf blades and from 10 to 155 μg CO2-C·(g AFDM)−1·h−1 for leaf sheaths. Maximum rates of CO2 evolution from sheaths were consistently lower than those for leaf blades (by ∼25%), but were typically an order of magnitude higher than those observed from culm litter (e.g., 1.0–18 μg CO2-C·(g AFDM)−1·h−1 over a diel cycle in August) exposed to identical environmental conditions. Much of the differences in maximum CO2 evolution rates from different litter types were related (r2 = 0.72) to differences in litter associated fungal biomass (leaf blades 34–74 mg dry mass/g AFDM, leaf sheaths 16–67 mg dry mass/g AFDM, and culms 2–7 mg dry mass/g AFDM), which was estimated from litter ergosterol concentrations. Based on measured stocks of standing-dead plant litter, estimated daily CO2 flux from standing-dead shoots ranged between 51 and 570 mg C/m2 of wetland surface area. These values translate into a roughly estimated annual carbon mineralization equivalent to a mean of 8% (leaf blades), 29% (leaf sheaths), and 3% (culms) of net aboveground plant production. These data provide compelling evidence that microbial decomposition of plant litter in the aerial standing-dead phase can contribute appreciably to overall carbon flux from marshes to the atmosphere, even in cool temperate climates, where most wetlands occur.

Desiccation-induced loss of seed viability is associated with a 10-fold increase in CO2 evolution in seeds of the rare tropical rainforest tree Idiospermum australiense.

• Here the relationship was investigated between metabolic activity, state of hydration and seed viability in the desiccation-intolerant (recalcitrant) seeds of Idiospermum australiense, a rare and primitive angiosperm tree restricted to wet tropical forest. • Seed CO2 evolution rate, R, was monitored in fully hydrated (control) seeds and seeds that were allowed to desiccate under ambient conditions over a period of c.90d. • During desiccation R increased dramatically toward a peak at a seed relative water content of 39±3% (relative to maximum water content, which corresponded to 0.45±0.03g water g-1 d. wt) followed by a decline toward zero with total desiccation. This peak constituted a 10-fold increase in mean R, relative to the control. Exposing seeds to O2 -free air at this peak induced a further large, but transient, increase in CO2 evolution, indicating that the peak developed in the presence of oxidative phosphorylation, rather than due to the absence of it. • The magnitude and mode of the observed increase in CO2 evolution in response to desiccation is unlike any reported so far and thus adds new information about metabolic changes that may occur as the water content of desiccation-intolerant seeds declines.

Decomposition of biodegradable packing materials jute, Biopol, BAK and their composites in soil

We investigated the effects of the biodegradable polymers jute, Biopol and BAK 2195 and their composites on the mineralisation activity and biomass of microorganisms in soil and on the fungal component of the microbial community. Two different pre-treatments of jute were used to produce the composites, treatment of the fibres with sodium hydroxide (SH-jute) and co-polymerisation with acrylonitrile (AN-jute). All products tested were highly degradable, as indicated by the increase in CO2 evolution after amendment. The additional amount of CO2-C evolved after polymer incorporation into the soil corresponded to between 21% and 34% of the added C after 85 days incubation at 25°C. The extra CO2-C evolved decreased in the order BAK > jute > Biopol. Composites of AN-jute were less mineralisable than those of SH-jute. Degradation of jute is characterised by a rapid increase, then a slow decline of microbial respiratory activity. In contrast, in the Biopol treatments, and especially in the BAK treatments, maximum CO2 evolution rates occurred considerably later, indicating that the soil microorganisms needed some time to colonise the polymer particles. All polymers and composites tested increased the soil microbial biomass in the order jute ≤ Biopol < BAK. The net increase in microbial biomass C was 3% of the added polymer C in the jute treatment, an average of 4% in the three Biopol treatments, and 7% in the three BAK treatments. The content of ergosterol, an indicator for fungal biomass, was also increased by all amendments, but the effect on ergosterol content was much more pronounced than on microbial biomass C.

Effects of lime and phosphate additions on changes in enzyme activities, microbial biomass and levels of extractable nitrogen, sulphur and phosphorus in an acid soil

The effects of adding lime and/or phosphate to an acid, phosphate-deficient soil on microbial activity, enzyme activities and levels of biomass and extractable N, S and P were studied under laboratory conditions. Following rewetting there was, as expected, an initial flush in microbial growth and activity, as shown by large increases in CO2 evolution, in levels of biomass N, S and P and by accumulation of extractable mineral N and sulphate in the soil. Following rewetting, additions of lime and phosphate further stimulated mineralization of C, N and S. In the first 4 weeks of incubation, the mineralized N accumulated in the soil as ammonium N and there was a concomitant rise in soil pH. After this initial period, nitrification increased substantially and soil pH decreased again. Additions of lime generally increased protease and sulphatase activities but decreased phosphatase activity. Additions of phosphate decreased the activities of all three enzymes. The positive effect of liming on protease and sulphatase activities persisted for the duration of the experiment while accumulation of mineral N and sulphate effectively ceased after about 4 weeks. Furthermore, although phosphate additions decreased the activities of protease and sulphatase they increased the accumulation of mineral N and sulphate. Thus, protease and sulphatase activities were not reliable indicators of the relative amounts of mineral N and sulphate accumulated in the soil during incubation. Some uncertainty surrounded the validity of biomass S and P values estimated by the chloroform fumigation technique because differing proportions of the sulphate and phosphate released from the lysed cells may have been extracted from the different treatments.

Development of Cyanide-resistant Respiration in Carnation Flower Petals

Abstract Cyanide-resistant respiration in carnation (Dianthus caryophyllus L.) petal tissue increased daily until 3 days after flowers were harvested. Mitochondria from petals exhibited only cyanide-resistant respiration when malate and pyruvate were provided as substrate. Although intact petals from freshly harvested flowers exhibited little cyanide-resistant respiration, mitochondria isolated from them were highly cyanide-resistant in their respiration if malate and pyruvate were provided as substrate. Pyruvate, in mitochondria, was capable of releasing mitochondria inhibited by cyanide in the presence of malate. Pentose-phosphate pathway activity was significant throughout the postharvest period, but was maximum 5 days after flowers were harvested. The gas exchange quotient (GEQ) was 1 for the first 3 days after harvest, declining on days 4 and 5 and dramatically increasing on day 6 as a result of a climacteric increase in CO2 evolution accompanying flower wilting.

エチレン処理に対するカンキツ果実の呼吸量の変化

Several kinds of citrus fruit, including satsuma mandarin (Citrus unshiu Marc.), hassaku orange (Citrus hassaku Hort.) and natsudaidai (Citrus natsudaidai Hayata), responded to 10ppm ethylene treatment by increases in CO2 evolution at 20°C.When ethylene treatments were continued for more than 3 days, maximum rates of CO2 evolution were reached during days 1 to 3, the rates of CO2 evolution declining there after.When 1-day treatments with ethylene were repeated every other day, the fruit showed an increase in respiration rate to the first 3 to 5 treatments, but responded little to the subsequent treatments.When the treatment of 3 days of ethylene and 1 day of air was repeated, the 2nd and the 3rd cycles did not induce any response in the fruits.When the treatment of 2 days of ethylene and 1 day of air was repeated, the first 2 cycles induced a response but subsequent ones had little effect.When the treatments with ethylene for 3 or 6 days and air for 3 days were repeated, the fruits responded to the 2nd cycle.In view of these results, it was thought that citrus fruit(non-climacteric type of fruit) has a certain ability to respond to ethylene for a limited time and that this ability can be recovered during a period of several days without treatment.

Microbial decomposition of ferulic acid in soil

The suppression of plant growth by different phenolic acids is well known. This work was designed to determine if ferulic acid, a known phenolic inhibitor of plant growth, accumulates in the soil and if soil microorganisms could be isolated that metabolize it. Over 99% of the extractable ferulic acid was lost from decaying hackberry leaves in 300 days. During this time the amount in the top 15 cm of soil remained fairly constant at about 30 ppm, except for the March sample which was significantly higher than the rest. Addition of ferulic acid to soil caused an increase in CO2 evolution and in numbers of a select group of microorganisms.Rhodotorula rubra andCepnalosporium curtipes, which actively metabolize ferulic acid, were isolated, but the metabolic pathways employed appear to be different from the reported one. The reported pathway for ferulic acid breakdown is ferulic acid to vanillic acid to protocatechuic acid to β-keto-adipic acid.Rhodotorula Rubra was found to convert ferulic acid to vanillic acid, but no evidence was found for utilization of the rest of the pathway.Cephalosporium curtipes appears to use a different pathway or to metabolize intermediate compounds rapidly without accumulating them, because no phenolic compounds were found during the breakdown of ferulic acid. The presence in the soil of microorganisms that metabolize ferulic acid and other phenolic acids is ecologically significant because such organisms prevent long-term accumulations of these substances, which are toxic to many other microorganisms and higher plants.

Ozone Induced Carbon Dioxide Evolution in Tobacco Callus Cultures

AbstractCallus derived from Bel–W3 and Bel–B tobacco plants when exposed to ozone turned brown as a consequence of surface cell destruction. Ozone fumigations above a threshold concentration of 0.10 μl/1 for two hoars caused an increase in the rate of tissue carbon dioxide (CO2) evolution. The maximum increase in CO2 evolution was about 65 percent for both the ozone sensitive Bel–W3 and resistant Bel–B callus. However, the ozone dosage required to attain maximum increase in CO2 evolution was approximately two times greater for the resistant variety. Callus cultures that grew roots were observed to be more resistant to ozone. The addition of the antioxidant N,N'dipnenyl–p–phenylenediamine (DPPD) m the nutrient medium retarded ozone induced CO2 evolution.

Ethylene and carbon dioxide as mediators in the response of the bean hypocotyl hook to light and auxins

Ethylene inhibits hook opening in the bean hypocotyl and at high concentrations induces closure of the hook. Indoleacetic acid and 2,4-dichlorophenoxyacetic acid, whose inhibitory effect on hook opening resembles that of ethylene, stimulate ethylene production from the hook tissue, and this ethylene production is physiologically active in inhibiting hook opening. It is concluded that the inhibition of opening by auxin is due at least in a major part to auxin-induced ethylene production by the hook tissue.Carbon dioxide promotes hook opening, apparently by antagonizing the action of endogenous ethylene. The concentration of respiratory CO2 in the internal gas space of the hook tissue is high enough to play a role in the regulation of hook opening.Red light causes a decrease in ethylene production and an increase in CO2 evolution from the hook tissue. These effects are partially reversible by far-red light. It is concluded that both ethylene and CO2 serve as natural growth regulators which mediate the hypocotyl hook-opening response to light in bean seedlings.