Ethylene production and antioxidant potential of five peach cultivars during maturation

Numerous biochemical processes are involved in fruit maturation, such as ethylene production, phenolic compounds accumulation, and antioxidant enzymes production. Therefore, the aim of the present work was the evaluation of ethylene production, and the bioactive compounds change in the exocarp and mesocarp of five peach [Prunus persica (L.)] cultivars during three ripening stages, (1) early ripening (ER), (2) commercial maturation, and (3) full ripening (FR) in order to establish the best stage to harvest each peach variety. The experiment was applied to five peach cultivars growing within an arid bioclimatic environment covering the whole peach production season: two early cultivars, Flordastar and Early Maycrest; one variety of mid-season Rubirich; and two late cultivars, Sweet Cap and O'Henry. Ethylene production, phenolic compounds, and oxidative stress through antioxidant enzyme activities (catalase, peroxidases [PODs] Class III, and ascorbate-POD), malondialdehyde (MDA), and hydrogen peroxide (H2 O2 ) production were determined in the exocarp and mesocarp of peach fruits. The results showed a significant increase in ethylene production during fruit ripening. However, a parallel decrease in the level of phenolic compounds as well as in antioxidant enzyme activities was observed. The FR stage was also characterized by an important accumulation of MDA and H2 O2 . In conclusion, important changes in fruit quality associated with the production level of ethylene were observed. Fruits harvested during the ER stage would be more suitable for delivering to distant markets and more appreciated by the peach industries due to their highest phenolic acid content, best antioxidant enzyme activities, and lowest oxidative stress indicator.

A comprehensive approach combining positive matrix factorization modeling, meteorology, and machine learning for source apportionment of surface ozone precursors: Underlying factors contributing to ozone formation in Houston, Texas

Ozone concentrations in Houston, Texas, are among the highest in the United States, posing significant risks to human health. This study aimed to evaluate the impact of various emissions sources and meteorological factors on ozone formation in Houston from 2017 to 2021 using a comprehensive PMF-SHAP approach. First, we distinguished the unique sources of VOCs in each area and identified differences in the local chemistry that affect ozone production. At the urban station, the primary sources were n_decane, biogenic/industrial/fuel evaporation, oil and gas flaring/production, industrial emissions/evaporation, and ethylene/propylene/aromatics. At the industrial site, the main sources were industrial emissions/evaporation, fuel evaporation, vehicle-related sources, oil and gas flaring/production, biogenic, aromatic, and ethylene and propylene. And then, we performed SHAP analysis to determine the importance and impact of each emissions factor and meteorological variables. Shortwave radiation (SHAP values are ∼5.74 and ∼6.3 for Milby Park and Lynchburg, respectively) and humidity (∼4.87 and ∼4.71, respectively) were the most important variables for both sites. For the urban station, the most important emissions sources were n_decane (∼2.96), industrial emissions/evaporation (∼1.89), and ethylene/propylene/aromatics (∼1.57), while for the industrial site, they were oil and gas flaring/production (∼1.38), ethylene/propylene (∼1.26), and industrial emissions/evaporation (∼0.95). NOx had a negative impact on ozone production at the urban station due to the NOx-rich chemical regime, whereas NOx had positive impacts at the industrial site. The study's findings suggest that the PMF-SHAP approach is efficient, inexpensive, and can be applied to other similar applications to identify factors contributing to ozone-exceedance events. The study's results can be used to develop more effective air quality management strategies for Houston and other cities with high levels of ozone.

Opuntia ficus indica mucilage coatings regulate cell wall softening enzymes and delay the ripening of banana fruit stored at retail conditions

Rapid ripening and softening due to cell wall polysaccharide degradation and disassembly pose major challenges in extending fruit storability. This study aimed to examine the efficacy of Opuntia ficus indica mucilage (OFIM) edible coating in minimizing softening in bananas under retail conditions. Mucilage was extracted from freshly harvested prickly pear cladodes and dried into a powder. Phenolic compounds in OFIM powder were quantified using liquid chromatography-mass spectrometry (LC-MS). OFIM concentrations (1, 2 and 3 % (w/v)) were prepared, and their physicochemical properties were examined. The prepared coatings were applied to harvested banana fruit by dipping and stored at room temperature for 12 days. During the experiment, several parameters were measured, including fruit weight loss, total soluble solids (TSS), titratable acidity (TA), peel color, pulp firmness, ethylene production, respiration rate, ion leakage, malondialdehyde (MDA) content, total chlorophyll and carotenoids, chlorophyll-degrading enzymes, protopectin content and water-soluble pectin (WSP) and softening-related enzymes in the peel. Results showed that mucilage treatments effectively delayed cell wall and chlorophyll degradation, as well as carotenoid accumulation, thus inhibiting ripening-associated processes compared to control fruit. OFIM-treated fruit exhibited significantly higher firmness, chlorophyll content, and TA, lower TSS content, ethylene production, respiration rate, MDA concentration, ion leakage and protopectin content than uncoated fruit. This suggests that OFIM edible coating has the potential to maintain quality and extend the shelf life of bananas by suppressing softening enzymes during storage.

A comparative study on the distribution behavior of microplastics through FT-IR analysis on different land uses in agricultural soils

Plastic materials have been variously exposed to arable land for decades through soil mulching, plastic housing, and sewage sludge composting. Their mechanical abrasion and biochemical degradation induce the proliferation of myriad microplastics that can further be broken into smaller nano-sized pieces that can be further accumulated in living organisms (including soil invertebrates, fruits, and vegetables); they can also be widely dispersed in neighboring environments. Despite the intensive use of plastics in agriculture, little is known about their origin of occurrence and environmental fate, especially with a size below 100 μm. Therefore, in this study, microplastics with a size in the range of 20-2,000 μm were investigated in soil samples obtained from three different conditions of land uses: tilled with plastic mulch, bare ground (i.e., uncultivated land), and in between the greenhouses of the farmland D located in Namyangju-si, Gyeonggi-do, Republic of Korea. They were primarily identified using Fourier transform infrared (FT-IR) spectroscopy coupled with a microscope. Prior to performing the analysis, microplastic extraction from the soil samples was validated using standardized high-density polyethylene (HDPE) microplastics of various sizes ranging from 20 to 500 μm. As a result, the number of microplastics was estimated to be (241 ± 52), (195 ± 37), and (306 ± 56) particles per kg of dry soil in tillage, bare ground, and in between greenhouses, respectively. They consist of polyethylene (PE), polypropylene (PP), and poly(ethylene terephthalate) (PET), which are the basic constituents of commonly used agricultural products. The particle size distribution depends on the type of plastic, the time elapsed since their usage, and the degree and duration of environmental exposure; the plastic particle sizes were smaller in tillage and around the greenhouses since agricultural films have been weathered for a long time, whereas those with relatively large sizes were found in the uncultivated.

LDPE/M-TiO2 composite films for modified atmosphere packaging to realize comprehensive preservation of strawberry (Fragaria × ananassa Duch.)

BACKGROUND

A shelf-life that is too short is the main problem with strawberries. Nano-TiO₂ can catalyze and oxidize ethylene under ultraviolet (UV) light irradiation to eliminate its ripening effect on fruits and prolong the freshness period.

RESULTS

In this work, nano-TiO₂ modified by methacryloxy propyl trimethoxyl silane (KH570) was blended with low-density polyethylene (LDPE) to prepare modified atmosphere packaging (MAP), and the influence of TiO₂ content on films was analyzed before and after UV treatment. The results show that the modified nano-TiO₂ (M-TiO₂ ) can be uniformly distributed in LDPE, improving its mechanical strength, hydrophobicity, oxygen barrier and UV shielding properties. A modified atmosphere with low ethylene, low O₂ and high CO₂ can be created to inhibit the ripening and spoilage of strawberries. The weight loss rate of fruit can be effectively reduced. The tendency of fruit firmness decline and nutrient loss can be slowed and stabilized, contributing to controllable shelf-life. Excellent freshness preservation function can be realized without special UV treatment.

CONCLUSION

Since UV treatment is rare in actual storage and transportation, LDPE/M-TiO₂ composite film has practical value as MAP for strawberry and similar non-climacteric fruits. © 2022 Society of Chemical Industry.

Effects of 1-MCP treatment on sprouting and preservation of ginger rhizomes during storage at room temperature

The purpose of this study was to explore the effects of 1-MCP on the sprouting and preservation of ginger rhizomes during storage at room temperature. Ginger rhizomes were treated with 1 µL L-1 1-methylcyclopropene (1-MCP) and stored at 23 ± 0.2 °C. Our data showed that application of 1-MCP reduced the rate of sprouting during storage compared with the control rhizome. Respiration rate and the reducing sugar content were also reduced following 1-MCP treatment, while the starch content increased. 1-MCP treatment increased the total phenol content and inhibited polyphenol oxidase (PPO) activity. 1-MCP treatment was also associated with a higher ascorbic acid content but a reduced crude fiber content. The generation of superoxide anion free radicals (O2-), hydrogen peroxide (H2O2) and malondialdehyde (MDA) was lower following 1-MCP treatment, while the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were higher compared with the controls. These results suggested that application of 1-MCP could reduce sprouting rates, decrease the accumulation of ROS, and maintain the quality of ginger rhizomes during storage at room temperature. It would be useful to further explore the role and mechanisms of action of ethylene in regulating the sprouting of ginger rhizomes.

Fourier transform and grating-based spectroscopy with a mid-infrared supercontinuum source for trace gas detection in fruit quality monitoring

We present a multi-species trace gas sensor based on a fast, compact home-built Fourier transform spectrometer (FTS) combined with a broadband mid-infrared supercontinuum (SC) source. The spectrometer covers the spectral bandwidth of the SC source (2 - 4 µm) and provides a best spectral resolution of 1 GHz in 6 seconds. It has a detection sensitivity of a few hundred of ppbv Hz^-1/2 for different gas species. We study the performance of the developed spectrometer in terms of precision, linearity, long-term stability, and multi-species detection. We use the spectrometer for measuring fruit-produced volatiles under different atmospheric conditions and compare the performance with a previously developed scanning grating-based spectrometer.

Sensors for the quantification, localization and analysis of the dynamics of plant hormones

Plant hormones play important roles in plant growth and development and physiology, and in acclimation to environmental changes. The hormone signaling networks are highly complex and interconnected. It is thus important to not only know where the hormones are produced, how they are transported and how and where they are perceived, but also to monitor their distribution quantitatively, ideally in a non-invasive manner. Here we summarize the diverse set of tools available for quantifying and visualizing hormone distribution and dynamics. We provide an overview over the tools that are currently available, including transcriptional reporters, degradation sensors, and luciferase and fluorescent sensors, and compare the tools and their suitability for different purposes.

Phytohormone production by the arbuscular mycorrhizal fungus Rhizophagus irregularis

Arbuscular mycorrhizal symbiosis is a mutualistic interaction between most land plants and fungi of the glomeromycotina subphylum. The initiation, development and regulation of this symbiosis involve numerous signalling events between and within the symbiotic partners. Among other signals, phytohormones are known to play important roles at various stages of the interaction. During presymbiotic steps, plant roots exude strigolactones which stimulate fungal spore germination and hyphal branching, and promote the initiation of symbiosis. At later stages, different plant hormone classes can act as positive or negative regulators of the interaction. Although the fungus is known to reciprocally emit regulatory signals, its potential contribution to the phytohormonal pool has received little attention, and has so far only been addressed by indirect assays. In this study, using mass spectrometry, we analyzed phytohormones released into the medium by germinated spores of the arbuscular mycorrhizal fungus Rhizophagus irregularis. We detected the presence of a cytokinin (isopentenyl adenosine) and an auxin (indole-acetic acid). In addition, we identified a gibberellin (gibberellin A₄) in spore extracts. We also used gas chromatography to show that R. irregularis produces ethylene from methionine and the α-keto γ-methylthio butyric acid pathway. These results highlight the possibility for AM fungi to use phytohormones to interact with their host plants, or to regulate their own development.

Combination of nZVI and DC for the in-situ remediation of chlorinated ethenes: An environmental and economic case study

Over the past two decades, the use of nanoscale zero-valent iron (nZVI) has emerged as a standard method of contaminated groundwater remediation. The effectiveness of this method depends on key intrinsic hydrogeological parameters, which can affect both reactivity of the nanoparticles and their migration in the aquifer. In the case of low hydraulic permeability, the migration of nanoparticles is limited, which negatively influences remediation. An application of nZVI reinforced with a DC electric field led to a significant increase in the efficiency of remediation, as demonstrated by long-term monitoring at a former industrial site in Horice (Czech Republic). For the method testing, a 12 × 9 m polygon was defined around well IS4, where the original contamination was predominantly composed of DCE (7300 μg/l), and with a total concentration of chlorinated ethenes of 8880 μg/l. During the first stage of the activities, 49 kg of nZVI was injected and monitored for two years. Subsequently, the electrodes were installed, and for three years, the synergistic action of nZVI within an applied DC field was monitored. Based on 32 monitoring campaigns performed over the six years, the combined method was compared with an application of the only nZVI in technical, environmental and economic terms. Technically, the method requires annual reinstallation of anodes as a result of their oxidative disintegration. Environmentally, the method provides significantly improved chlorinated ethane reduction, remediation of low permeable zones, and extended efficiency. Economically, the method is five times cheaper when compared to the nZVI used alone.

Phytohormone production by the arbuscular mycorrhizal fungus Rhizophagus irregularis

Arbuscular mycorrhizal symbiosis is a mutualistic interaction between most land plants and fungi of the glomeromycotina subphylum. The initiation, development and regulation of this symbiosis involve numerous signalling events between and within the symbiotic partners. Among other signals, phytohormones are known to play important roles at various stages of the interaction. During presymbiotic steps, plant roots exude strigolactones which stimulate fungal spore germination and hyphal branching, and promote the initiation of symbiosis. At later stages, different plant hormone classes can act as positive or negative regulators of the interaction. Although the fungus is known to reciprocally emit regulatory signals, its potential contribution to the phytohormonal pool has received little attention, and has so far only been addressed by indirect assays. In this study, using mass spectrometry, we analyzed phytohormones released into the medium by germinated spores of the arbuscular mycorrhizal fungus Rhizophagus irregularis. We detected the presence of a cytokinin (isopentenyl adenosine) and an auxin (indole-acetic acid). In addition, we identified a gibberellin (gibberellin A4) in spore extracts. We also used gas chromatography to show that R. irregularis produces ethylene from methionine and the α-keto γ-methylthio butyric acid pathway. These results highlight the possibility for AM fungi to use phytohormones to interact with their host plants, or to regulate their own development.

Electrokinetics applied in remediation of subsurface soil contaminated with chlorinated ethenes - A review

Electrokinetics is being applied in combination with common insituremediation technologies, e.g. permeable reactive barriers, bioremediation and in-situ chemical oxidation, to overcome experienced limitations in remediation of chlorinated ethenes in low-permeable subsurface soils. The purpose of this review is to evaluate state-of-theart for identification of major knowledge gaps to obtain robust and successful field-implementations. Some of the major knowledge gaps include the behavior and influence of induced transient changes in soil systems, transport velocities of chlorinated ethenes, and significance of site-specific parameters on transport velocities, e.g. heterogeneous soils and hydrogeochemistry. Furthermore, the various ways of reporting voltage distribution and transport rates complicate the comparison of transport velocities across studies. It was found, that for the combined EK-techniques, it is important to control the pH and redox changes caused by electrolysis for steady transport, uniform distribution of the electric field etc. Specifically for electrokinetically enhanced bioremediation, delivery of lactate and biodegrading bacteria is of the same order of magnitude. This review shows that enhancement of remediation technologies can be achieved by electrokinetics, but major knowledge gaps must be examined to mature EK as robust methods for successful remediation of chlorinated ethene contaminated sites.

Transcriptome and hormone analyses provide insights into hormonal regulation in strawberry ripening

The possible molecular mechanisms regulating strawberry fruit ripening were revealed by plant hormone quantification, exogenous hormone application, and RNA-sequencing. Fruit ripening involves a complex interplay among plant hormones. Strawberry is a model for studies on non-climacteric fruit ripening. However, the knowledge on how plant hormones are involved in strawberry ripening is still limited. To understand hormonal actions in the ripening process, we performed genome-wide transcriptome and hormonal analysis for the five major hormones (abscisic acid and catabolites, auxins, cytokinins, gibberellins, and ethylene) in achenes and receptacles (flesh) at different ripening stages of the woodland strawberry Fragaria vesca. Our results demonstrate that the pre-turning stage (a stage with white flesh and red achenes defined in this study) is the transition stage from immature to ripe fruits. The combinatorial analyses of hormone content, transcriptome data, and exogenous hormone treatment indicate that auxin is synthesized predominantly in achenes, while abscisic acid (ABA), bioactive free base cytokinins, gibberellins, and ethylene are mainly produced in receptacles. Furthermore, gibberellin may delay ripening, while ethylene and cytokinin are likely involved at later stages of the ripening process. Our results also provide additional evidence that ABA promotes ripening, while auxin delays it. Although our hormone analysis demonstrates that the total auxin in receptacles remains relatively low and unchanged during ripening, our experimental evidence further indicates that ABA likely enhances expression of the endoplasmic reticulum-localized auxin efflux carrier PIN-LIKES, which may subsequently reduce the auxin level in nucleus. This study provides a global picture for hormonal regulation of non-climacteric strawberry fruit ripening and also evidence for a possible mechanism of ABA and auxin interaction in the ripening process.

Application of palladium-modified zeolite for prolonging post-harvest shelf life of banana

BACKGROUND

The marketability of banana is limited by the rapid rate of ripening. However, the traditional post-harvest technologies may not be desirable. The aim of this study was to investigate the potential of a reusable material for the food preservation industry.

RESULTS

The nanocomposite-based palladium (Pd)-modified zeolite (Pd/zeolite) was prepared by impregnating Pd into zeolite. Pd/zeolite had a Brunauer-Emmett-Teller dinitrogen specific surface area of 475 m² g^-1 with crystal structure similar to Y-zeolite. Transmission electron microscopy images showed the dispersion of Pd particles over the multi-pore zeolite support. Pd/zeolite uniquely acted as an adsorbent and a catalyst and was able to remove ethylene even after reaching breakthrough point. To prove Pd/zeolite is reusable, a 99 ± 0.8% ethylene removal efficiency still remained even after five consecutive cycles with repeated use of Pd/zeolite. The presence of Pd/zeolite significantly decreased the ethylene concentration during 18 days of storage at 20 ± 2 °C.

CONCLUSIONS

Pd/zeolite could delay the ripening of banana and improve its firmness and the peel color significantly. Findings indicated that the as-prepared Pd/zeolite is an effective adsorbent/catalyst with high potential for practical application in ethylene removal, especially for the post-harvest period. © 2019 Society of Chemical Industry.

Extending storage potential of de-hulled fresh pistachios in passive-modified atmosphere

BACKGROUND

The effects of passive modified-atmosphere packaging (passive-MAP) on the postharvest quality of de-hulled fresh pistachios (Pistacia vera L. cv. Kerman) stored at cold temperature (0 ± 0.5 °C) and 90 ± 1% relative humidity was investigated with fruits under ambient air condition as the control treatment. The fruit quality parameters measured included kernel firmness, color values (L^* , a^* , b^* , h°, and C^* ), weight loss, fungal decay and marketability, ethylene production, respiration rate, and sensory characteristics at 0, 30, 60, and 105 days of storage. The carbon dioxide (CO₂ ) and oxygen (O₂ ) concentrations in the package headspace were monitored during storage.

RESULTS

A modified atmosphere of 0.95-3.35% O₂ and 23.17-29.82% CO₂ was achieved in the passive-MAP treatment. Fruit respiration rates increased significantly relative to controls throughout storage (P ≤ 0.01). However, storage had no significant effect on ethylene production rates. Additionally, passive-MAP-stored fruits maintained firmness, shell lightness, kernel color, and sensory quality with minimum weight loss and fungal decay, compared with the control.

CONCLUSION

These results demonstrate storage life of fresh pistachios in passive-MAP can be extended up to 105 days, compared with 30 days in ambient conditions. © 2019 Society of Chemical Industry.

Ethylene Measurements from Sweet Fruits Flowers Using Photoacoustic Spectroscopy

Ethylene is a classical plant hormone and has appeared as a strong molecule managing many physiological and morphological reactions during the life of a plant. With laser-based photoacoustic spectroscopy, ethylene can be identified with high sensitivity, at a high rate and with very good selectivity. This research presents the dynamics of trace gases molecules for ethylene released by cherry flowers, apple flowers and strawberry flowers. The responses of distinctive organs to ethylene may fluctuate, depending on tissue sensitivity and the phase of plant development. From the determinations of this study, the ethylene molecules at the flowers in the nitrogen flow were established in lower concentrations when the value is correlated to the ethylene molecules at the flowers in synthetic air flow.

Role of maturity stages and modified-atmosphere packaging on the quality attributes of cornelian cherry fruits (Cornus mas L.) throughout shelf life

BACKGROUND

A study was conducted to determine the effects of modified-atmosphere packaging (MAP) treatments on fruit quality attributes and bioactive compounds of cornelian cherry fruits (Cornus mas L.) harvested at two different maturity stages - maturity (M): M-1, skin red color <10%; M-2, skin red color >90% - throughout the shelf life. Fruits were stored at 0 ± 0.5 °C and 90 ± 5% relative humidity (RH) for 30 days, and then kept at 22 ± 0.5 °C and 80 ± 5% RH over 3 days for shelf life.

RESULTS

In the measurements performed at harvest, MS-2 fruits had significantly greater respiration rate, soluble solids content, acidity, anthocyanin, flavonoids, and phenolics and significantly lower ethylene productions, firmness, L^* , chroma, and hue angle values than MS-1 fruits. In the last measurement period, MAP-treated fruits had significantly greater firmness, total flavonoids, and total phenolics and significantly lower respiration rates, ethylene productions, and decay rates than the untreated fruits. While color parameters of MS-2 fruits were significantly lower than the color values of MS-1 fruits, they had greater vitamin C and anthocyanin contents.

CONCLUSION

It was concluded that the cornelian cherry fruits harvested at MS-2 stage of maturity and preserved in MAP better maintained quality attributes throughout their shelf life. © 2018 Society of Chemical Industry.

Rapid and Visual Detection and Quantitation of Ethylene Released from Ripening Fruits: The New Use of Grubbs Catalyst

Herein, we report on fluorophore-tagged Grubbs catalysts as turn-on fluorescent probes for the sensitive detection and quantitation of ethylene, a plant hormone that plays a critical role in many phases of plant growth and fruit ripening. The ruthenium-based weak fluorescent probes were prepared handily through the metathesis reaction between the first-generation Grubbs catalyst and selected fluorophores that have high quantum yields and contain terminal vinyl groups. Upon exposure to ethylene, fluorescence enhancement was observed via the release of fluorophore from the probe. Our probe shows an excellent limit of detection for ethylene at 0.9 ppm in air and was successfully applied for monitoring ethylene released during the fruit-ripening process. Our work opens up a new avenue of application of Grubbs catalysts for bioanalytical chemistry of ethylene, which is critically important in plant biology, agriculture, and food industry.

Supraoptimal Cytokinin Content Inhibits Rice Seminal Root Growth by Reducing Root Meristem Size and Cell Length via Increased Ethylene Content

Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In this study, treatments of lovastatin (an inhibitor of CK biosynthesis) and kinetin (KT; a synthetic CK) were found to inhibit rice seminal root growth in a dose-dependent manner, suggesting that endogenous CK content is optimal for rapid growth of the seminal root in rice. KT treatment strongly increased ethylene level by upregulating the transcription of ethylene biosynthesis genes. Ethylene produced in response to exogenous KT inhibited rice seminal root growth by reducing meristem size via upregulation of OsIAA3 transcription and reduced cell length by downregulating transcription of cell elongation-related genes. Moreover, the effects of KT treatment on rice seminal root growth, root meristem size and cell length were rescued by treatment with aminoethoxyvinylglycine (an inhibitor of ethylene biosynthesis), which restored ethylene level and transcription levels of OsIAA3 and cell elongation-related genes. Supraoptimal CK content increases ethylene level by promoting ethylene biosynthesis, which in turn inhibits rice seminal root growth by reducing root meristem size and cell length.

A genetic screen for plant mutants with altered nodulation phenotypes in response to rhizobial glycan mutants

Nodule primordia induced by rhizobial glycan mutants often remain uninfected. To identify processes involved in infection and organogenesis we used forward genetics to identify plant genes involved in perception and responses to bacterial glycans. To dissect the mechanisms underlying the negative plant responses to the Mesorhizobium loti R7AexoU and ML001cep mutants, a screen for genetic suppressors of the nodulation phenotypes was performed on a chemically mutagenized Lotus population. Two mutant lines formed infected nitrogen-fixing pink nodules, while five mutant lines developed uninfected large white nodules, presumably altered in processes controlling organogenesis. Genetic mapping identified a mutation in the cytokinin receptor Lhk1 resulting in an alanine to valine substitution adjacent to a coiled-coil motif in the juxta-membrane region of LHK1. This results in a spontaneous nodulation phenotype and increased ethylene production. The allele was renamed snf5, and segregation studies of snf5 together with complementation studies suggest that snf5 is a gain-of-function allele. This forward genetic approach to investigate the role of glycans in the pathway synchronizing infection and organogenesis shows that a combination of plant and bacterial genetics opens new possibilities to study glycan responses in plants as well as identification of mutant alleles affecting nodule organogenesis.

Impacts of exogenous pollutant bisphenol A on characteristics of soybeans

Bisphenol A (BPA) is an endocrine disruptor that is ubiquitous in the environment. Previous studies have focused on the effects of BPA on plants to assess the ecological risk of BPA in the environment. To evaluate the effects of BPA on plant biological characters more systematically, we investigated the biological characters of above-ground and under-ground organs of soybean plants exposed to BPA. Meanwhile, the mechanisms for the observed changes were also analyzed from the view of hormone levels and photosynthesis. The results showed that after exposure to 0.8 mg L-1 BPA for three days, indole-3-acetic acid (IAA) and gibberellic acid levels in roots increased significantly, and the IAA level increased in leaves, so the character indices of roots and leaves both increased. The IAA and ethylene levels in stems increased, but the character indices of stems did not increased. With higher BPA concentrations, especially exposure to 17.2 mg L-1 BPA, the levels of IAA, gibberellic acid, and zeatin decreased (except for the increased zeatin in leaves), and abscisic acid and ethylene levels increased; thus, all of the character indices significantly decreased. By comparing the changes in various biological characters, we found that leaf area, root surface area, and root length changed most significantly. In addition, changes in photosynthetic parameters provided initial causes for plant growth changes, and impacted biological characters. The changes of character indices were stronger when the BPA exposure time was prolonged, and after the removal of BPA, the character indices showed some recovery. Therefore, BPA exposure can regulate the changes in plant characters by influencing hormone levels and photosynthesis, and root surface area, root length, and leaf area were the most sensitive to BPA.

Parallel online determination of ethylene release rate by Shaken Parsley cell cultures using a modified RAMOS device

BACKGROUND

Ethylene is an important plant hormone that controls many physiological processes in plants. Conventional methods for detecting ethylene include gas chromatographs or optical mid-infrared sensors, which are expensive and, in the case of gas chromatographs, are hardly suitable for automated parallelized online measurement. Electrochemical ethylene sensors are cheap but often suffer from poor resolution, baseline drifting, and target gas oxidation. Thus, measuring ethylene at extremely low levels is challenging.

RESULTS

This report demonstrates the integration of electrochemical ethylene sensors into a respiration activity monitoring system (RAMOS) that measures, in addition to the oxygen transfer rate, the ethylene transfer rate in eight parallel shake flasks. A calibration method is presented that is not prone to baseline drifting and considers target gas oxidation at the sensor. In this way, changes in ethylene transfer rate as low as 4 nmol/L/h can be resolved. In confirmatory experiments, the overall accuracy of the method was similar to that of gas chromatography-mass spectrometry (GC/MS) measurements. The RAMOS-based ethylene determination method was exemplified with parsley suspension-cultured cells that were primed for enhanced defense by pretreatment with salicylic acid, methyl jasmonate or 4-chlorosalicylic acid and challenged with the microbial pattern Pep13. Ethylene release into the headspace of the shake flask was observed upon treatment with salicylic acid and methyl jasmonate was further enhanced, in case of salicylic acid and 4-chlorosalicylic acid, upon Pep13 challenge.

CONCLUSION

A conventional RAMOS device was modified for simultaneous measurement of the ethylene transfer rate in eight parallel shake flasks at nmol/L/h resolution. For the first time electrochemical sensors are used to provide a medium-throughput method for monitoring ethylene release by plants. Currently, this can only be achieved by costly laser-based detection systems and automated gas chromatographs. The new method is particularly suitable for plant cell suspension cultures. However, the method may also be applicable to intact plants, detached leaves or other plant tissues. In addition, the general principle of the technology is likely extendable to other volatiles or gases as well, such as nitric oxide or hydrogen peroxide.

Dynamics in the concentrations of health-promoting compounds: lupeol, mangiferin and different phenolic acids during postharvest ripening of mango fruit

BACKGROUND

Mango fruit (Mangifera indica L.) is renowned for its pleasant taste and as a rich source of health beneficial compounds. The aim of this study was to investigate the changes in concentrations of health-promoting compounds, namely ascorbic acid, carotenoids, antioxidants, lupeol, mangiferin, total phenols and individual phenolic acids, as well as ethylene production and respiration rates during climacteric ripening in 'Kensington Pride' and 'R2E2' mango fruit.

RESULTS

The climacteric ethylene and respiration peaks were noted on the third day of the fruit ripening period. The concentrations of total carotenoids in the pulp, total antioxidants in both pulp and peel, and total phenols of the peel, lupeol and mangiferin were significantly elevated, whereas the concentration of ascorbic acid declined during post-climacteric ripening. Gallic, chlorogenic and vanillic acids were identified as the major phenolic acids in both pulp and peel of 'Kensington Pride' and 'R2E2' mangoes. The concentrations of phenolic acids (gallic, chlorogenic, vanillic, ferulic and caffeic acids) also increased during the post-climacteric phase. The concentrations of all phenolic compounds were several-fold higher in the peel than pulp.

CONCLUSION

Mangoes at post-climacteric ripening phase offer the highest concentrations of health-promoting compounds. Peel, at this stage of fruit ripening, could be exploited as a good source for extraction of these compounds. © 2017 Society of Chemical Industry.

Gas Chromatography-Based Ethylene Measurement of Arabidopsis Seedlings

Plants tightly regulate the biosynthesis of ethylene to control growth and development and respond to a wide range of biotic and abiotic stresses. To understand the molecular mechanism by which plants regulate ethylene biosynthesis as well as to identify stimuli triggering the alteration of ethylene production in plants, it is essential to have a reliable tool with which one can directly measure in vivo ethylene concentration. Gas chromatography is a routine detection technique for separation and analysis of volatile compounds with relatively high sensitivity. Gas chromatography has been widely used to measure the ethylene produced by plants, and has in turn become a valuable tool for ethylene research. Here, we describe a protocol for measuring the ethylene produced by dark-grown Arabidopsis seedlings using a gas chromatograph.

Dynamics of Ethylene Production in Response to Compatible Nod Factor

Establishment of symbiotic nitrogen-fixation in legumes is regulated by the plant hormone ethylene, but it has remained unclear whether and how its biosynthesis is regulated by the symbiotic pathway. We established a sensitive ethylene detection system for Lotus japonicus and found that ethylene production increased as early as 6 hours after inoculation with Mesorhizobium loti This ethylene response was dependent on Nod factor production by compatible rhizobia. Analyses of nodulation mutants showed that perception of Nod factor was required for ethylene emission, while downstream transcription factors including CYCLOPS, NIN, and ERN1 were not required for this response. Activation of the nodulation signaling pathway in spontaneously nodulating mutants was also sufficient to elevate ethylene production. Ethylene signaling is controlled by EIN2, which is duplicated in L. japonicus We obtained a L. japonicus Ljein2a Ljein2b double mutant that exhibits complete ethylene insensitivity and confirms that these two genes act redundantly in ethylene signaling. Consistent with this redundancy, both LjEin2a and LjEin2b are required for negative regulation of nodulation and Ljein2a Ljein2b double mutants are hypernodulating and hyperinfected. We also identified an unexpected role for ethylene in the onset of nitrogen fixation, with the Ljein2a Ljein2b double mutant showing severely reduced nitrogen fixation. These results demonstrate that ethylene production is an early and sustained nodulation response that acts at multiple stages to regulate infection, nodule organogenesis, and nitrogen fixation in L. japonicus.

Stratification of chlorinated ethenes natural attenuation in an alluvial aquifer assessed by hydrochemical and biomolecular tools

Biomolecular and hydrochemical tools were used to evaluate natural attenuation of chlorinated ethenes in a Quaternary alluvial aquifer located close to a historical source of large-scale tetrachloroethylene (PCE) contamination. Distinct stratification of redox zones was observed, despite the aquifer's small thickness (2.8 m). The uppermost zone of the target aquifer was characterised by oxygen- and nitrate-reducing conditions, with mixed iron- to sulphate-reducing conditions dominant in the lower zone, along with indications of methanogenesis. Natural attenuation of PCE was strongly influenced by redox heterogeneity, while higher levels of PCE degradation coincided with iron- to sulphate reducing conditions. Next generation sequencing of the middle and/or lower zones identified anaerobic bacteria (Firmicutes, Chloroflexi, Actinobacteria and Bacteroidetes) associated with reductive dechlorination. The relative abundance of dechlorinators (Dehalococcoides mccartyi, Dehalobacter sp.) identified by real-time PCR in soil from the lower levels supports the hypothesis that there is a significant potential for reductive dechlorination of PCE. Local conditions were insufficiently reducing for rapid complete dechlorination of PCE to harmless ethene. For reliable assessment of natural attenuation, or when designing monitoring or remedial systems, vertical stratification of key biological and hydrochemical markers should be analysed as standard, even in shallow aquifers.

Modeling 3D-CSIA data: Carbon, chlorine, and hydrogen isotope fractionation during reductive dechlorination of TCE to ethene

Reactive transport modeling of multi-element, compound-specific isotope analysis (CSIA) data has great potential to quantify sequential microbial reductive dechlorination (SRD) and alternative pathways such as oxidation, in support of remediation of chlorinated solvents in groundwater. As a key step towards this goal, a model was developed that simulates simultaneous carbon, chlorine, and hydrogen isotope fractionation during SRD of trichloroethene, via cis-1,2-dichloroethene (and trans-DCE as minor pathway), and vinyl chloride to ethene, following Monod kinetics. A simple correction term for individual isotope/isotopologue rates avoided multi-element isotopologue modeling. The model was successfully validated with data from a mixed culture Dehalococcoides microcosm. Simulation of Cl-CSIA required incorporation of secondary kinetic isotope effects (SKIEs). Assuming a limited degree of intramolecular heterogeneity of δ³⁷Cl in TCE decreased the magnitudes of SKIEs required at the non-reacting Cl positions, without compromising the goodness of model fit, whereas a good fit of a model involving intramolecular CCl bond competition required an unlikely degree of intramolecular heterogeneity. Simulation of H-CSIA required SKIEs in H atoms originally present in the reacting compounds, especially for TCE, together with imprints of strongly depleted δ²H during protonation in the products. Scenario modeling illustrates the potential of H-CSIA for source apportionment.

Investigation into the role of endogenous abscisic acid during ripening of imported avocado cv. Hass

BACKGROUND

The importance of ethylene in avocado ripening has been extensively studied. In contrast, little is known about the possible role of abscisic acid (ABA). The present work studied the effect of 1-methylcyclopropene (1-MCP) (0.3 μL L^-1 ), e+® Ethylene Remover and the combination thereof on the quality of imported avocado cv. Hass fruit stored for 7 days at 12 °C. Ethylene production, respiration, firmness, colour, heptose (C7) sugars and ABA concentrations in mesocarp tissue were measured throughout storage.

RESULTS

Treatment with e+® Ethylene Remover reduced ethylene production, respiration rate and physiological ripening compared with controls. Fruit treated with 1-MCP + e+® Ethylene Remover and, to a lesser extent 1-MCP alone, had the lowest ethylene production and respiration rate and hence the best quality. Major sugars measured in mesocarp tissue were mannoheptulose and perseitol, and their content was not correlated with ripening parameters. Mesocarp ABA concentration, as determined by mass spectrometry, increased as fruit ripened and was negatively correlated with fruit firmness.

CONCLUSIONS

Results suggest a relationship between ABA and ethylene metabolism since blocking ethylene, and to a larger extent blocking and removing ethylene, resulted in lower ABA concentrations. Whether ABA influences avocado fruit ripening needs to be determined in future research. © 2017 Society of Chemical Industry.

Ethylene, an early marker of systemic inflammation in humans

Ethylene is a major plant hormone mediating developmental processes and stress responses to stimuli such as infection. We show here that ethylene is also produced during systemic inflammation in humans and is released in exhaled breath. Traces of ethylene were detected by laser spectroscopy both in vitro in isolated blood leukocytes exposed to bacterial lipopolysaccharide (LPS) as well as in vivo following LPS administration in healthy volunteers. Exposure to LPS triggers formation of ethylene as a product of lipid peroxidation induced by the respiratory burst. In humans, ethylene was detected prior to the increase of blood levels of inflammatory cytokines and stress-related hormones. Our results highlight that ethylene release is an early and integral component of in vivo lipid peroxidation with important clinical implications as a breath biomarker of bacterial infection.

Non-invasive quantification of ethylene in attached fruit headspace at 1 p.p.b. by gas chromatography-mass spectrometry

Ethylene is a gaseous plant hormone involved in defense, adaptations to environmental stress and fruit ripening. Its relevance to the latter makes its detection highly useful for physiologists interested in the onset of ripening. Produced as a sharp peak during the respiratory burst, ethylene is biologically active at tens of nl L^-1 . Reliable quantification at such concentrations generally requires specialized instrumentation. Here we present a rapid, high-sensitivity method for detecting ethylene in attached fruit using a conventional gas chromatography-mass spectrometry (GC-MS) system and in situ headspace collection chambers. We apply this method to melon (Cucumis melo L.), a unique species consisting of climacteric and non-climacteric varieties, with a high variation in the climacteric phenotype among climacteric types. Using a population of recombinant inbred lines (RILs) derived from highly climacteric ('Védrantais', cantalupensis type) and non-climacteric ('Piel de Sapo', inodorus type) parental lines, we observed a significant variation for the intensity, onset and duration of the ethylene burst during fruit ripening. Our method does not require concentration, sampling times over 1 h or fruit harvest. We achieved a limit of detection of 0.41 ± 0.04 nl L^-1 and a limit of quantification of 1.37 ± 0.13 nl L^-1 with an analysis time per sample of 2.6 min. Validation of the analytical method indicated that linearity (>98%), precision (coefficient of variation ≤2%) and sensitivity compared favorably with dedicated optical sensors. This study adds to evidence of the characteristic climacteric ethylene burst as a complex trait whose intensity in our RIL population lies along a continuum in addition to two extremes.

LeEIX2 Interactors' Analysis and EIX-Mediated Responses Measurement

Plant-pathogen interactions involve a large number of wide regulatory systems, necessary for plant defense responses against pathogen attack. The fungal protein ethylene-inducing xylanase (EIX) elicits defense responses in specific cultivars of tobacco and tomato. The response to EIX is controlled by a single locus encoding for LeEIX2, a leucine-rich-repeat receptor-like-protein (LRR-RLP). As an RLP, LeEIX2 does not possess an obvious cytoplasmic signaling moiety such as a kinase domain. To study LeEIX2 mode of action, it is essential to identify the potential interactors involved after EIX perception. Here, we describe the in vivo co-IP methodology used for protein interaction verification and ethylene and ROS (reactive oxygen species) measurements used for physiological effects assessment.

Ethylene Biosynthesis and Signaling Is Required for Rice Immune Response and Basal Resistance Against Magnaporthe oryzae Infection

Recent studies have suggested that ethylene enhances host resistance to fungal pathogen Magnaporthe oryzae, the causal agent of rice blast disease. Among the six 1-aminocyclopropane-1-carboxylic acid synthase genes in rice, OsACS1 and OsACS2 are induced within 24 h of inoculation by M. oryzae. This induction occurs simultaneously with an increase in ethylene production that is noticeable 12 h postinoculation. The purpose of this study was to examine the dynamics of ethylene production and signaling in wild type and RNA interference-mediated suppression lines deficient in ethylene production (acs2) or signaling (eil1) after challenge with M. oryzae as well as fungal cell-wall elicitors. Ethylene-insensitive mutant lines show an attenuated basal defense response including lower basal expression of the genes encoding a chitin-binding receptor, pathogenesis-related (PR) proteins, and the enzymes involved in the synthesis of diterprenoid phytoalexins, a reduction on early hypersensitive response (HR)-like cell death, and reduced incidence of callose deposition. Ethylene-deficient mutants showed an intermediate phenotype, with a significant reduction in expression of defense-related genes and callose deposition, but only a slight reduction in HR-like cell death. As a result, all ethylene-insensitive mutants show increased susceptibility to M. oryzae, whereas the ethylene-deficient lines show a slight but less significant increase in disease severity. These results show that ethylene signaling and, to some extent, ethylene production are required for rice basal resistance against the blast fungus Magnaporthe oryzae.

C, Cl and H compound-specific isotope analysis to assess natural versus Fe(0) barrier-induced degradation of chlorinated ethenes at a contaminated site

Compound-specific isotopic analysis of multiple elements (C, Cl, H) was tested to better assess the effect of a zero-valent iron-permeable reactive barrier (ZVI-PRB) installation at a site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). The focus was on (1) using (13)C to evaluate natural chlorinated ethene biodegradation and the ZVI-PRB efficiency; (2) using dual element (13)C-(37)Cl isotopic analysis to distinguish biotic from abiotic degradation of cis-dichloroethene (cis-DCE); and (3) using (13)C-(37)Cl-(2)H isotopic analysis of cis-DCE and TCE to elucidate different contaminant sources. Both biodegradation and degradation by ZVI-PRB were indicated by the metabolites that were detected and the (13)C data, with a quantitative estimate of the ZVI-PRB efficiency of less than 10% for PCE. Dual element (13)C-(37)Cl isotopic plots confirmed that biodegradation was the main process at the site including the ZVI-PRB area. Based on the carbon isotope data, approximately 45% and 71% of PCE and TCE, respectively, were estimated to be removed by biodegradation. (2)H combined with (13)C and (37)Cl seems to have identified two discrete sources contributing to the contaminant plume, indicating the potential of δ(2)H to discriminate whether a compound is of industrial origin, or whether a compound is formed as a daughter product during degradation.

Quantitative Ethylene Measurements with MOx Chemiresistive Sensors at Different Relative Air Humidities

The sensitivity of two commercial metal oxide (MOx) sensors to ethylene is tested at different relative humidities. One sensor (MiCS-5914) is based on tungsten oxide, the other (MQ-3) on tin oxide. Both sensors were found to be sensitive to ethylene concentrations down to 10 ppm. Both sensors have significant response times; however, the tungsten sensor is the faster one. Sensor models are developed that predict the concentration of ethylene given the sensor output and the relative humidity. The MQ-3 sensor model achieves an accuracy of ±9.2 ppm and the MiCS-5914 sensor model predicts concentration to ±7.0 ppm. Both sensors are more accurate for concentrations below 50 ppm, achieving ±6.7 ppm (MQ-3) and 5.7 ppm (MiCS-5914).

Ethylene Biosynthesis Is Promoted by Very-Long-Chain Fatty Acids during Lysigenous Aerenchyma Formation in Rice Roots

In rice (Oryza sativa) roots, lysigenous aerenchyma, which is created by programmed cell death and lysis of cortical cells, is constitutively formed under aerobic conditions, and its formation is further induced under oxygen-deficient conditions. Ethylene is involved in the induction of aerenchyma formation. reduced culm number1 (rcn1) is a rice mutant in which the gene encoding the ATP-binding cassette transporter RCN1/OsABCG5 is defective. Here, we report that the induction of aerenchyma formation was reduced in roots of rcn1 grown in stagnant deoxygenated nutrient solution (i.e. under stagnant conditions, which mimic oxygen-deficient conditions in waterlogged soils). 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is a key enzyme in ethylene biosynthesis. Stagnant conditions hardly induced the expression of ACS1 in rcn1 roots, resulting in low ethylene production in the roots. Accumulation of saturated very-long-chain fatty acids (VLCFAs) of 24, 26, and 28 carbons was reduced in rcn1 roots. Exogenously supplied VLCFA (26 carbons) increased the expression level of ACS1 and induced aerenchyma formation in rcn1 roots. Moreover, in rice lines in which the gene encoding a fatty acid elongase, CUT1-LIKE (CUT1L; a homolog of the gene encoding Arabidopsis CUT1, which is required for cuticular wax production), was silenced, both ACS1 expression and aerenchyma formation were reduced. Interestingly, the expression of ACS1, CUT1L, and RCN1/OsABCG5 was induced predominantly in the outer part of roots under stagnant conditions. These results suggest that, in rice under oxygen-deficient conditions, VLCFAs increase ethylene production by promoting 1-aminocyclopropane-1-carboxylic acid biosynthesis in the outer part of roots, which, in turn, induces aerenchyma formation in the root cortex.

Optimal intensity and biomass density for biofuel production in a thin-light-path photobioreactor

Production of competitive microalgal biofuels requires development of high volumetric productivity photobioreactors (PBRs) capable of supporting high-density cultures. Maximal biomass density supported by the current PBRs is limited by nonuniform distribution of light as a result of self-shading effects. We recently developed a thin-light-path stacked photobioreactor with integrated slab waveguides that distributed light uniformly across the volume of the PBR. Here, we enhance the performance of the stacked waveguide photobioreactor (SW-PBR) by determining the optimal wavelength and intensity regime of the incident light. This enabled the SW-PBR to support high-density cultures, achieving a carrying capacity of OD730 20. Using a genetically modified algal strain capable of secreting ethylene, we improved ethylene production rates to 937 μg L(-1) h(-1). This represents a 4-fold improvement over a conventional flat-plate PBR. These results demonstrate the advantages of the SW-PBR design and provide the optimal operational parameters to maximize volumetric production.

Study on the kinetic characteristics of trace harmful gases for a two-person-30-day integrated CELSS test

A two-person-30-day controlled ecological life support system (CELSS) integrated test was carried out, and more than 30 kinds of trace harmful gases including formaldehyde, benzene, and ammonia were measured and analyzed dynamically. The results showed that the kinds and quantities of the trace harmful gases presented a continuously fluctuating state during the experimental period, but none of them exceed the spacecraft maximum allowable concentration (SMAC). The results of the Pre-Test (with two persons without plants for 3 days) and the Test (with two persons and four kinds of plants for 30 days) showed that there are some notable differences for the compositions of the trace harmful gases; the volatile organic compounds (VOCs) such as toluene, hexane, and acetamide were searched out in the Pre-Test, but were not found in the Test. Moreover, the concentrations of the trace harmful gases such as acetic benzene, formaldehyde, and ammonia decreased greatly in the Test more than those in the Pre-Test, which means that the plants can purify these gases efficiently. In addition, the VOCs such as carbon monoxide, cyclopentane, and dichloroethylene were checked out in the Test but none in the Pre-Test, which indicates that these materials might be from the crew's metabolites or those devices in the platform. Additionally, the ethylene released specially by plants accumulated in the later period and its concentration reached nearly ten times of 0.05 mg m(-3) (maximum allowed concentration for plant growth, which must have promoted the later withering of plants). We hoped that the work can play a referring function for controlling VOCs effectively so that future more CELSS integrating tests can be implemented smoothly with more crew, longer period, and higher closure.

Ammonia and ethylene biomarkers in the respiration of the people with schizophrenia using photoacoustic spectroscopy

Oxidative stress has become an exciting area of schizophrenia (SCZ) research, and provides ample opportunities and hope for a better understanding of its pathophysiology, which may lead to new treatment strategies. The first objective of the present study was to analyze the oxidative stress markers in breath samples of patients with SCZ before and after the treatment with Levomepromazine. The second objective was to analyze the deficiency of amino acids marker in breath samples of patients with SCZ before and after the treatment. Exhaled breath was collected from 15 SCZ patients and 19 healthy controls; subsequently, CO2 laser photoacoustic spectroscopy was used to assess the exhaled breath compounds of the study subjects. One of the main breath biomarkers of the oxidative stress is ethylene, while one of the main breath biomarkers of the amino acids deficiency is ammonia. The breath biomarkers in the exhalation of SCZ patients exhibited significant differences from the breath biomarkers in the exhalation of healthy controls. Analysis of breath ethylene and breath ammonia provides a related model of SCZ exhalation that could represent an effective and convenient screening method for this intellectual disability.

Modelling microbial dechlorination of trichloroethene: investigating the trade-off between quality of fit and parameter reliability

This work puts forth a heuristic approach for investigating compromises between quality of fit and parameter reliability for the Monod-type kinetics employed to model microbial reductive dechlorination of trichloroethene. The methodology is demonstrated with three models of increasing fidelity and complexity. Model parameters were estimated with a stochastic global optimization algorithm, using scarce and inherently noisy experimental data from a mixed anaerobic microbial culture, which dechlorinated trichloroethene to ethene completely. Parameter reliability of each model was assessed using a Monte Carlo technique. Finally, an alternate quantity of applied interest was evaluated in order to assist with model discrimination. Results from the application of our approach suggest that the modeler should examine the implementation of conceptually simple models, even if they are a crude abstraction of reality, as they can be computationally less demanding and adequately accurate when model performance is assessed with criteria of applied interest, such as chloroethene elimination time.

Detection of Golden apples' climacteric peak by laser biospeckle measurements

In this paper, we report a study in which a laser biospeckle technique is used to detect the climacteric peak indicating the optimal ripeness of fruits. We monitor two batches of harvested Golden apples going through the ripening phase in low- and room-temperature environments, determine speckle parameters, and measure the emitted ethylene concentration using gas chromatography as reference method. Speckle results are then correlated to the emitted ethylene concentration by a principal component analysis. From a practical point of view, this approach allows us to validate biospeckle as a noninvasive and alternative method to respiration rate and ethylene production for climacteric peak detection as a ripening index.

Multiple phytohormones and phytoalexins are involved in disease resistance to Magnaporthe oryzae invaded from roots in rice

Blast, caused by the fungus Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. Phenylalanine ammonia lyase (PAL) is a key enzyme in the phenylpropanoid pathway, which leads to the biosynthesis of defense-related phytohormone salicylic acid (SA) and flavonoid-type phytoalexins sakuranetin and naringenin. However, the roles and biochemical features of individual rice PALs in defense responses to pathogens remain unclear. Here, we report that rice OsPAL06, which can catalyze the formation of trans-cinnamate using l-phenylalanine, is involved in rice root-M. oryzae interaction. OsPAL06-knockout mutant showed increased susceptibility to M. oryzae invaded from roots and developed typical leaf blast symptoms, accompanied by nearly complete disappearance of sakuranetin and naringenin and a two-third reduction of the SA level in roots. This mutant also showed compensatively induced expression of chalcone synthase, which is involved in flavonoid biosynthesis, isochorismate synthase 1, which is putatively involved in SA synthesis via another pathway, reduced jasmonate content and increased ethylene content. These results suggest that OsPAL06 is a positive regulator in preventing M. oryzae infection from roots. It may regulate defense by promoting both phytoalexin accumulation and SA signaling that synergistically and antagonistically interacts with jasmonate- and ethylene-dependent signaling, respectively.

Spatial and temporal variations in mango colour, acidity, and sweetness in relation to temperature and ethylene gradients within the fruit

Managing fruit quality is complex because many different attributes have to be taken into account, which are themselves subjected to spatial and temporal variations. Heterogeneous fruit quality has been assumed to be partly related to temperature and maturity gradients within the fruit. To test this assumption, we measured the spatial variability of certain mango fruit quality traits: colour of the peel and of the flesh, and sourness and sweetness, at different stages of fruit maturity using destructive methods as well as vis-NIR reflectance. The spatial variability of mango quality traits was compared to internal variations in thermal time, simulated by a physical model, and to internal variations in maturity, using ethylene content as an indicator. All the fruit quality indicators analysed showed significant spatial and temporal variations, regardless of the measurement method used. The heterogeneity of internal fruit quality traits was not correlated with the marked internal temperature gradient we modelled. However, variations in ethylene content revealed a strong internal maturity gradient which was correlated with the spatial variations in measured mango quality traits. Nonetheless, alone, the internal maturity gradient did not explain the variability of fruit quality traits, suggesting that other factors, such as gas, abscisic acid and water gradients, are also involved.

Effects of cold storage and 1-methylcyclopropene treatments on ripening and cell wall degrading in rabbiteye blueberry (Vaccinium ashei) fruit

The effect of postharvest 1-methylcyclopropene and/or cold storage application on texture quality parameters during storage was determined. The changes in fruit quality (including weight loss, firmness, total soluble solids content, and ethylene production), cell wall material (including water-soluble fraction, ethylenediaminetetraacetic acid-soluble fraction, Na2CO3-soluble fraction, 4% KOH-soluble fraction, and 14% KOH-soluble fraction), and cell wall hydrolase activities (including polygalacturonase, endo-1,4-beta-D-glucanase, pectinesterase, alpha-L-arabinofuranosidase, and beta-galactosidase) were periodically measured up to 25 days after postharvest treatments. The application of cold storage reduced weight loss, ethylene production, and delayed ripening of blueberry fruit. The inhibition of senescence was associated with suppressed increase in cell wall hydrolase activities and retarded solubilization of pectins and hemicelluloses. Furthermore, no obvious differences in firmness, weight loss, ethylene production, and cell wall hydrolase activities between fruits with or without 1-methylcyclopropene application were observed, while significant lower levels of the detected parameters were found in cold storage fruit compared with fruit stored in room temperature. Thus, cold storage can be viewed as an effective means to extend the shelf life of blueberry fruit.

Hydrogen sulfide extends the postharvest life and enhances antioxidant activity of kiwifruit during storage

BACKGROUND

Exogenous hydrogen sulfide (H₂S) treatment can prolong the postharvest life of cut flowers and strawberries. Little work has been done to explore the effects of H₂S on respiratory climacteric fruits such as kiwifruits during storage. Therefore the aim of the present study was to evaluate the effects of H₂S treatment at concentrations of 15–1000 µmol L⁻¹ on the postharvest life of kiwifruit during 25 °C storage and the role of H₂S in regulating the antioxidant defensive system of kiwifruit.

RESULTS

Treatments with 45 and 90 µmol L⁻¹ H₂S significantly inhibited the increase in soluble sugar content and the decrease in vitamin C (Vit C), chlorophyll content and firmness, inhibited ethylene production and both superoxide production rate (O(·2)⁻) and hydrogen peroxide content. Kiwifruits with 45 and 90 µmol L⁻¹ H₂S exhibited significantly higher activities of superoxide dismutase, catalase and peroxidase. Treatment with 180 µmol L⁻¹ H₂S promoted the ripening of kiwifruits.

CONCLUSION

Treatments with 45 and 90 µmol L⁻¹ H₂S could delay the maturation and senescence of kiwifruits and maintain higher titratable acid (TA) and Vit C during eating-ripe storage by inhibiting ethylene production, improving protective enzyme activities and decreasing the accumulation of reactive oxygen species to protect the cell membrane during storage.

Modeling the effects of naturally occurring organic carbon on chlorinated ethene transport to a public supply well

The vulnerability of public supply wells to chlorinated ethene (CE) contamination in part depends on the availability of naturally occurring organic carbon to consume dissolved oxygen (DO) and initiate reductive dechlorination. This was quantified by building a mass balance model of the Kirkwood-Cohansey aquifer, which is widely used for public water supply in New Jersey. This model was built by telescoping a calibrated regional three-dimensional (3D) MODFLOW model to the approximate capture zone of a single public supply well that has a history of CE contamination. This local model was then used to compute a mass balance between dissolved organic carbon (DOC), particulate organic carbon (POC), and adsorbed organic carbon (AOC) that act as electron donors and DO, CEs, ferric iron, and sulfate that act as electron acceptors (EAs) using the Sequential Electron Acceptor Model in three dimensions (SEAM3D) code. SEAM3D was constrained by varying concentrations of DO and DOC entering the aquifer via recharge, varying the bioavailable fraction of POC in aquifer sediments, and comparing observed and simulated vertical concentration profiles of DO and DOC. This procedure suggests that approximately 15% of the POC present in aquifer materials is readily bioavailable. Model simulations indicate that transport of perchloroethene (PCE) and its daughter products trichloroethene (TCE), cis-dichloroethene (cis-DCE), and vinyl chloride (VC) to the public supply well is highly sensitive to the assumed bioavailable fraction of POC, concentrations of DO entering the aquifer with recharge, and the position of simulated PCE source areas in the flow field. The results are less sensitive to assumed concentrations of DOC in aquifer recharge. The mass balance approach used in this study also indicates that hydrodynamic processes such as advective mixing, dispersion, and sorption account for a significant amount of the observed natural attenuation in this system.

Ethylene detection in fruit supply chains

Ethylene is a gaseous ripening phytohormone of fruits and plants. Presently, ethylene is primarily measured with stationary equipment in laboratories. Applying in situ measurement at the point of natural ethylene generation has been hampered by the lack of portable units designed to detect ethylene at necessary resolutions of a few parts per billion. Moreover, high humidity inside controlled atmosphere stores or containers complicates the realization of gas sensing systems that are sufficiently sensitive, reliable, robust and cost efficient. In particular, three measurement principles have shown promising potential for fruit supply chains and were used to develop independent mobile devices: non-dispersive infrared spectroscopy, miniaturized gas chromatography and electrochemical measurement. In this paper, the measurement systems for ethylene are compared with regard to the needs in fruit logistics; i.e. sensitivity, selectivity, long-term stability, facilitation of automated measurement and suitability for mobile application. Resolutions of 20-10 ppb can be achieved in mobile applications with state-of-the-art equipment, operating with the three methods described in the following. The prices of these systems are in a range below €10 000.

An integrative analysis of the transcriptome and proteome of the pulp of a spontaneous late-ripening sweet orange mutant and its wild type improves our understanding of fruit ripening in citrus

Fruit ripening is a complex, genetically programmed process that occurs in conjunction with the differentiation of chloroplasts into chromoplasts and involves changes to the organoleptic properties of the fruit. In this study, an integrative analysis of the transcriptome and proteome was performed to identify important regulators and pathways involved in fruit ripening in a spontaneous late-ripening mutant ('Fengwan' orange, Citrus sinensis L. Osbeck) and its wild type ('Fengjie 72-1'). At the transcript level, 628 genes showed a 2-fold or more expression difference between the mutant and wild type as detected by an RNA sequencing approach. At the protein level, 130 proteins differed by 1.5-fold or more in their relative abundance, as indicated by iTRAQ (isobaric tags for relative and absolute quantitation) analysis. A comparison of the transcriptome and proteome data revealed some aspects of the regulation of metabolism during orange fruit ripening. First, a large number of differential genes were found to belong to the plant hormone pathways and cell-wall-related metabolism. Secondly, we noted a correlation between ripening-associated transcripts and sugar metabolites, which suggests the importance of these metabolic pathways during fruit ripening. Thirdly, a number of genes showed inconsistency between the transcript and protein level, which is indicative of post-transcriptional events. These results reveal multiple ripening-associated events during citrus ripening and provide new insights into the molecular mechanisms underlying citrus ripening regulatory networks.

The impact of bioaugmentation on dechlorination kinetics and on microbial dechlorinating communities in subsurface clay till

A molecular study on how the abundance of the dechlorinating culture KB-1 affects dechlorination rates in clay till is presented. DNA extracts showed changes in abundance of specific dechlorinators as well as their functional genes. Independently of the KB-1 added, the microbial dechlorinator abundance increased to the same level in all treatments. In the non-bioaugmented microcosms the reductive dehalogenase gene bvcA increased in abundance, but when KB-1 was added the related vcrA gene increased while bvcA genes did not increase. Modeling showed higher vinyl-chloride dechlorination rates and shorter time for complete dechlorination to ethene with higher initial concentration of KB-1 culture, while cis-dichloroethene dechlorination rates were not affected by KB-1 concentrations. This study provides high resolution abundance profiles of Dehalococcoides spp. (DHC) and functional genes, highlights the ecological behavior of KB-1 in clay till, and reinforces the importance of using multiple functional genes as biomarkers for reductive dechlorination.

Germination of salt-stressed seeds as related to the ethylene biosynthesis ability in three Stylosanthes species

Stylosanthes, a genus of tropical forage legume, is known to exhibit good persistence in saline soils, yet mechanisms for regulation of seed germination under salt stress are poorly understood. This study was carried out to evaluate the mode of action of salt stress on seed germination of Stylosanthes. 1-Aminocyclopropane-1-carboxylic acid (ACC) increased ethylene biosynthesis and germination of NaCl-inhibited seeds in a dose-dependent manner. Contents of ACC and germination of Stylosanthes humilis seeds increased following transfer from NaCl solution to deionised water, but not after transfer to l-α-(2-aminoethoxyvinyl)-glycine (AVG) solution, an inhibitor of ethylene biosynthesis. Ethylene biosynthesis was much larger in NaCl-treated seeds of Stylosanthes guianensis than in seeds of S. humilis and Stylosanthes capitata, a fact which was reflected in higher germination rates. S. guianensis seedlings also displayed higher growth and survival rates than S. humilis and S. capitata under salt stress. Moreover, smaller ACC levels, as well as reduced ethylene biosynthesis of S. capitata seeds were accompanied by lower germination under salt stress. In addition, S. capitata seedlings treated with NaCl solutions exhibited relatively lower growth and survival rates in comparison with S. humilis and S. guianensis. Thus, different abilities to synthesize ethylene by S. guianensis, S. humilis and S. capitata seeds explain the differences in tolerance to salt stress of the three species.

Proteomic analysis and polyamines, ethylene and reactive oxygen species levels of Araucaria angustifolia (Brazilian pine) embryogenic cultures with different embryogenic potential

Somatic embryogenesis is an important biotechnological tool in the large-scale propagation of elite genotypes and ex situ conservation of conifer species. Protocols for the induction and proliferation of embryogenic cultures (ECs) of Brazilian pine (Araucaria angustifolia (Bert.) O. Ktze) are well established, although the proper formation of mature somatic embryos (SEs) is still problematic. Thus, the identification of molecular markers for the screening of ECs able to respond to maturation conditions (abscisic acid and osmotic agents) is highly desirable. To develop molecular markers for the early detection of ECs able to develop well-formed SEs under maturation conditions, we analyzed the proteins found during the proliferation phase of A. angustifolia cell lines with different embryogenic capabilities, with one cell line being responsive to maturation conditions (R cell line), and one cell line that presented blocked development of SEs (B cell line). In addition, based on the peptides identified, polyamine levels (free and conjugate), ethylene production and reactive oxygen species (ROS) emission were analyzed using both EC lines (R and B cell lines). A marked difference in the biochemistry of ECs between these two cell lines was observed. Eleven proteins that were differentially expressed in the cell lines were identified by the combination of two-dimensional electrophoresis (2-DE) and MALDI-TOF/TOF mass spectrometry. Among these, S-adenosylmethionine synthase, the enzyme associated with polyamines and ethylene biosynthesis, was observed exclusively in the R cell line, while a protein linked to the oxidative stress subunit F of NADH dehydrogenase was observed exclusively in the B cell lines. Additionally, B cell lines showed higher levels of diamine putrescine and lower levels of ethylene. Higher values of ethylene and ROS were observed for the cell line that showed normal development of SEs. Altogether, our results open new perspectives in the optimization of culture conditions for A. angustifolia somatic embryogenesis, as well as establishing biochemical markers for the early selection of ECs during maturation trials.