Ethylene Emission Research Articles

Contributions of wood smoke and vehicle emissions to ambient concentrations of volatile organic compounds and particulate matter during the Yakima wintertime nitrate study

AbstractA multiple linear regression (MLR) chemical mass balance model was applied to data collected during an air quality field experiment in Yakima, WA, during January 2013 to determine the relative contribution of residential wood combustion (RWC) and vehicle emissions to ambient pollutant levels. Acetonitrile was used as a chemical tracer for wood burning and nitrogen oxides (NOx) as a chemical tracer for mobile sources. RWC was found to be a substantial source of gas phase air toxics in wintertime. The MLR model found RWC primarily responsible for emissions of formaldehyde (73%), acetaldehyde (69%), and black carbon (55%) and mobile sources primarily responsible for emissions of carbon monoxide (CO; 83%), toluene (81%), C2‐alkylbenzenes (81%), and benzene (64%). When compared with the Environmental Protection Agency's 2011 winter emission inventory, the MLR results suggest that the contribution of RWC to CO emissions was underestimated in the inventory by a factor of 2. Emission ratios to NOx from the MLR model agreed to within 25% with wintertime emission ratios predicted from the Motor Vehicle Emissions Simulator (MOVES) 2010b emission model for Yakima County for all pollutants modeled except for CO, C2‐alkylbenzenes, and black carbon. The MLR model results suggest that MOVES was overpredicting mobile source emissions of CO relative to NOx by a factor of 1.33 and black carbon relative to NOx by about a factor of 3.

Investigating Criteria and Organic Air pollutant Emissions from Motorcycles by Using Various Ethanol-Gasoline Blends

Studies on the correlation between ethanol-gasoline blends and pollutant emissions of small engine motorcycles are scant. This study examined the effects of ethanol-gasoline blends, containing various ethanol contents, on air pollutant emissions from two four-stroke fuel-injection motorcycles without engine adjustment. Three test blends, separately containing 15 (E15), 20 (E20), and 30 vol% (E30) ethanol in gasoline, were used to power the test motorcycles. Commercial unleaded gasoline was used as the reference fuel (as RF). The motorcycles were tested on a chassis dynamometer by using the Economic Commission for Europe test cycle. The target pollutants investigated in this study included criteria pollutants, volatile organic compounds (VOCs) and six species of organic air toxics. The results revealed that the emissions of CO, THC, total VOCs, alkanes, alkenes, and aromatic groups reduced when the ethanol-gasoline blends were used to fuel the motorcycles. E30 demonstrated approximately 1.2-fold increases in carbonyl group emissions compared with RF. Emissions of the target air toxics demonstrated a reduction potential on benzene, toluene, ethylbenzene, and xylene (BTEX), but increased the emissions of formaldehyde and acetaldehyde by 65% and 330%, respectively. Results also showed that the emission changes from fuel-injected motorcycle were generally smaller than the value of carburetor motorcycle. Fuel injection engine fueled with ethanol-gasoline blends may lead to emission reductions to CO, THC, and BTEX.

1-MCP Improved Diverse Sensorial, Biochemical and Physical Apple Traits during Cold Storage Based on Cultivar

Apple cultivars’ storability could be strengthened through known techniques of cold storage, advanced industries of control atmosphere or other routine usages like fruit pre-cooling followed by immersion in CA++ solution, depending on genetic potential of the plant material. At the end of pomology and cold storage assessments of 93 apple cultivars, two high yielding native "Dirras-e Mashhad" and "Wealthy" were treated by single and combined 1-MCP and ethylene nano-absorbent (ENA) to assess eventual improvements in cold storage span, fruit eating quality and role of cultivar. For this purpose, directs effects and interactions between all sources of variance were studied. Ethylene emission and CO2 amounts were measured. The results showed that reduced weight loss and flesh firmness, were registered in the treated samples of both cultivars compared with the control. Using of 1-MCP affected significantly (p 0.05) on these characteristics. The native apple "Dirras-e Mashhad" showed higher pH value than "Wealthy" under the combined treatment (ENA+1-MCP). Genetic source revealed significant difference through lower "Wealthy" storability. Ethylene emission increased to 53.64 ppm/Kg·hr after 5th month, which resulted in significant difference at p > 0.01 level related to the initial value of 3.26 ppm/Kg·hr. The combined treatment (ENA+1-MCP) affected significantly (p < 0.05) most of the fruit characteristics in both of the cultivars. The treatments demonstrated different results by cultivar.

Construction of an RNAi vector for knockdown of GM-ACS genes in the cotyledonary nodes of soybean

800x600 Background : Ethylene plays an important role in the regulation of floral organ development in soybean, and ACC synthase is a rate-limiting enzyme for ethylene biosynthesis. However, whether ACC synthase also regulates floral organ differentiation in soybean remains unknown. To address this, we constructed an RNAi vector to inhibit ACC synthase expression in cotyledonary nodes. Linear DNA cassettes of RNAi-ACS obtained by PCR were used to transform soybean cotyledonary nodes. Results : One hundred thirty-one of 139 transiently transformed plants acquired herbicide resistance and displayed GUS activities in the new buds. In comparison to untransformed seedling controls, a greater number of flower buds were differentiated at the cotyledonary node; GM-ACS1 mRNA expression levels and ethylene emission in the transformed buds were reduced. Conclusion : These results indicate that the cotyledonary node transient transformation system may be suitable for stable transformation, and that inhibition of ACC synthase expression may be an effective strategy for promoting floral organ differentiation in soybean.

Combustion and emission characteristics of diesel engine fueled with 2,5-dimethylfuran and diesel blends

Currently, worldwide interest has been triggered in the potential of 2,5-dimethylfuran (DMF) due to the discovery of improved production methods. However, the combustion and emission properties of DMF have been rarely characterized. Here we studied how the fuel properties and loads affected the combustion and emission of diesel–DMF blends or pure diesel in a four-cylinder direct-injection compression-ignition (DICI) engine. The experimental conditions were load from 0.13 to 1.13MPa brake mean effective pressure (BMEP) and constant speed at 1800rpm. We find at 0.38MPa BMEP, the maximum heat release rate (HRR) rises and the peak cylinder pressure decreases both significantly with the increase of DMF mass fraction in the blends. However, at 0.63MPa BMEP, the peak cylinder pressure and HRR both increased with the rise of DMF mass fraction. For each tested fuel, the emissions of 1,3-butadiene, benzene and acetaldehyde all declined with the increment of load. In addition, the DMF and diesel blending increased the acetaldehyde emission and reduced the benzene and 1,3-butadiene emissions. The nucleation mode greatly dominated the particle size distribution within the entire load range. The DMF and diesel blending tended to reduce particulate mass concentration and number concentration under most operating conditions. At 1.13MPa BMEP, however, the DMF and diesel blending tended to increase particulate number concentration.

Modelling bidirectional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

Abstract. The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem scale, a process not currently considered in regional- or global-scale atmospheric chemistry models.We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions, FORCAsT was able to successfully simulate the observed bidirectional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

Carbon Disulphide (CS2) Promotes Sprouting and Affects the Metabolism of Harvested Minitubers Grown from True Potato Seed

Chemical agents may be used to overcome dormancy in potato tubers so as to permit early planting. In this paper, the effect of carbon disulphide on sprouting and related metabolic processes in potato tubers grown from true potato seed (TPS) was investigated. Carbon disulphide was applied to potato tubers derived from TPS, at a rate of 20 ml m−3 container volume for 72 h. It accelerated tuber sprouting and increased tuber weight loss. It also caused an increase in the respiration rate, as well as ethylene emission from the tubers during the first 6 days after treatment. The respiration rate of carbon disulphide-treated tubers remained at a higher level than that of untreated controls for 35 days after treatment. In addition, carbon disulphide increased the concentrations of the soluble sugars sucrose and fructose, but not glucose, in the tuber tissues (buds, parenchyma). These findings suggest that carbon disulphide releases potato minitubers from dormancy and that dormancy breakage is associated with changes in tuber metabolism prior to the visible sprouting.

Ethylene Is Not Responsible for Phytochrome-Mediated Apical Hook Exaggeration in Tomato.

The apical hook of tomato seedlings is exaggerated by phytochrome actions, while in other species such as bean, pea and Arabidopsis, the hook is exaggerated by ethylene and opens by phytochrome actions. The present study was aimed to clarify mainly whether ethylene is responsible for the phytochrome-mediated hook exaggeration of tomato seedlings. Dark-grown 5-day-old seedlings were subjected to various ways of ethylene application in the dark as well as under the actions of red (R) or far-red light (FR). The ethylene emitted by seedlings was also quantified relative to hook exaggeration. The results show: Ambient ethylene, up-to about 1.0 μL L-1, suppressed (opened) the hooks formed in the dark as well as the ones exaggerated by R or FR, while at 3.0–10 μL L-1 it enhanced (closed) the hook only slightly as compared with the most-suppressed level at about 1.0 μL L-1. Treatment with 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene biosynthesis, did not enhance the hook, only mimicking the suppressive effects of ambient ethylene. The biosynthesis inhibitor, CoCl2 or aminoethoxyvinylglycine, enhanced hook curvature, and the enhancement was canceled by supplement of ethylene below 1.0 μL L-1. Auxin transport inhibitor, N-1-naphthylphthalamic acid, by contrast, suppressed curvature markedly without altering ethylene emission. The effects of the above-stated treatments did not differentiate qualitatively among the R-, FR-irradiated seedlings and dark control so as to explain phytochrome-mediated hook exaggeration. In addition, ethylene emission by seedlings was affected neither by R nor FR at such fluences as to cause hook exaggeration. In conclusion, (1) ethylene suppresses not only the light-exaggerated hook, but also the dark-formed one; (2) ethylene emission is not affected by R or FR, and also not correlated with the hook exaggerations; thus ethylene is not responsible for the hook exaggeration in tomato; and (3) auxin is essential for the maintenance and development of the hook in tomato as is the case in other species lacking phytochrome-mediated hook exaggeration. A possible mechanism of phytochrome action for hook exaggeration is discussed.

Measuring NMHC and NMOG emissions from motor vehicles via FTIR spectroscopy

The determination of non-methane organic gases (NMOG) emissions according to United States Environmental Protection Agency (EPA) regulations is currently a multi-step process requiring separate measurement of various emissions components by a number of independent on-line and off-line techniques. The Fourier transform infrared spectroscopy (FTIR) method described in this paper records all required components using a single instrument. It gives data consistent with the regulatory method, greatly simplifies the process, and provides second by second time resolution. Non-methane hydrocarbons (NMHCs) are measured by identifying a group of hydrocarbons, including oxygenated species, that serve as a surrogate for this class, the members of which are dynamically included if they are present in the exhaust above predetermined threshold levels. This yields an FTIR equivalent measure of NMHC that correlates within 5% to the regulatory flame ionization detection (FID) method. NMOG is then determined per regulatory calculation solely from FTIR recorded emissions of NMHC, ethanol, acetaldehyde, and formaldehyde, yielding emission rates that also correlate within 5% with the reference method. Examples are presented to show how the resulting time resolved data benefit aftertreatment development for light duty vehicles.

METHOD FOR DETERMINING FRUIT HARVESTING MATURITY

Accurate identification of fruit harvest timing is quite a complicated issue. We know several methods of determining harvest maturity in climacteric fruits; these include measurement of: firmness, total solids contents, respiration rate, ethylene emission measurement as well starch tests. On the other hand non-climacteric fruits (no collective maturity phase) are identified as suitable for harvesting by evaluating their colour. The first three aforementioned basic methods can be combined into a single tool, the so-called Streiff index. All the characteristics identified herein, i.e.: starch assay, total solids (including sugars, tannins, vitamins, organic acids, etc.), as well as firmness, corresponding to protopectin-pectin conversion, produce caloric response. Hence, the correlation between fruit maturity and the caloric response of the material provides the basis for an innovative test enabling assessment of harvest maturity in fruit. Caloric response is largely impacted by the changing structure of fruit dry mass. The calorific content of fruit during maturation process decreases due to the conversion of the water-insoluble starch, with a calorific value of 4200 cal/g, into soluble monosaccharides 3750 cal / g. The study presents a novel calorimetric method of assessing harvest maturity in fruit and the presentation is based on fruit of selected varieties of apples, tomatoes and strawberries. The calorimetric maturity thresholds have been determined for these fruits at the following levels: apples – 3930 cal/g s.m., strawberries – 3880 cal/g s.m. and tomatoes - 3910 cal/g.

Simulation of Aldehyde Emissions from an Ethanol Fueled Spark Ignition Engine and Comparison with FTIR Measurements

This paper presents a mathematical model that calculates aldehyde emissions in the exhaust of a spark ignition engine fueled with ethanol. The numerical model for aldehyde emissions was developed using FORTRAN software, with the input data obtained from a dedicated engine cycle simulation software, AVL BOOST. The model calculates formaldehyde and acetaldehyde emissions, formed from the partial oxidation of methane, ethane and unburned ethanol. The calculated values were compared with experimental data obtained by Fourier Transform Infrared Spectroscopy (FTIR). The experiments were performed with a mid-size sedan powered by a 1.4-liter spark ignition engine on a chassis dynamometer. In general, the results demonstrate that the concentrations of aldehydes and the source elements increased with engine speed and exhaust gas temperature. A reasonable agreement between simulated and measured values was achieved.

Improvement of the Quality and the Shelf Life of Figs (Ficus carica) Using an Alginate–Chitosan Edible Film

The consumption of fresh figs (Ficus carica) has long been associated with longevity and health benefits. However, fresh figs are highly perishable. An alternative to extend the shelf life of this fruit might be the application of an edible film. Thus, in this study, fig fruits collected at two maturity stages (referred as stages III and IV) were coated with an alginate–chitosan bilayer edible (A–Ch BE) film and the main physiological and quality attributes were evaluated during storage at low temperature (6 °C) at 0, 3, 6, 9, 12, and 15 days of storage. Ethylene and CO2 productions were considered as physiological parameters, while firmness, color changes, weight loss, and visual infection were the quality attributes evaluated. The application of the film reduced CO2 production and increased ethylene emission, regardless of the maturity stage of the figs. Firmness for uncoated figs underwent a significant decrease during storage, exhibiting values lower than 1.0 N. On the contrary, for coated figs, firmness was not only maintained but also even increased up to 3 N, for figs of stage III, and up to 2.5 N for the more mature figs (stage IV). Furthermore, coated figs exhibited better external color retention (ΔE < 2), lower weight loss (∼8 %), and also lower visual fungal contamination (<5 %) than uncoated fruits during the 15 days of storage at 6 °C, regardless the maturity stage. Therefore, the results indicate that application of an A–Ch BE film not only can improve the overall quality of figs (F. carica var. Mission) stored at 6 °C but is also able to extend their shelf life.

Comparative dynamics of ethylene production and expression of the ACS and ACO genes in normal-ripening and non-ripening watermelon fruits

Watermelon fruit is traditionally classified as non-climacteric, but it has been reported to be hypersensitive to exogenous ethylene: resulting in accelerated softening and water-soaking. The previous studies have reported a modest, but significant increase in ethylene production in strawberry, grape, etc., which has stimulated interest in exploring the possible role of this hormone in ripening of non-climacteric fruits. In this study, both ethylene emission and content of internal ethylene (CIE) in watermelon fruit were determined, with tomato fruit used as the reference. Throughout the development and ripening, the average CIE levels in flesh was higher than the nearly undetectable ethylene emission from fruits, and revealed a distinct rise of ethylene production in flesh in normal-ripening line 97103, but not in non-ripening line PI296341-FR. In parallel with the patterns of CIE, the activity of 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) both increased in 97103 flesh as ripening progressed, but stayed at a constant and low level in PI296341-FR flesh. Eight ACS and eight ACO isoforms were identified in watermelon genome by full-length alignment and domain analysis of protein sequences, and among which, four ACS and four ACO genes were selected based on transcriptome profiling of the fruit development for further assay using qPCR. The expression of two ACS isoforms, Cla022653 and Cla011522, as well as two ACO isoforms, Cla014827 and Cla016287, were significantly up-regulated in 97103 flesh during ripening compared with PI296341-FR, indicating that these four genes could potentially play a more important role in ethylene biosynthesis in normal-ripening watermelon flesh.

An ACC Oxidase Gene Essential for Cucumber Carpel Development

Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests stamen development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase (ACO) converts ACC into ethylene; however, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsACO2, confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsACO2, resulting in 50% less ethylene emission from shoot tips. CsACO2 was expressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmACO3, the ortholog of CsACO2, showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWIP1, the ortholog of CmWIP1, could directly bind the promoter of CsACO2 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WIP1 transcription factor and ACO controls unisexual flower development in cucumber and melon.

English

Calcium carbide (CaC2) is a well-known source of acetylene and ethylene gases. Its use as a plant growth regulator could be an innovative approach for vegetable production if applied in suitable formulation. Different rates of CaC2 (10, 20, 30 and 40 mg plate) were evaluated regarding seed germination and morphological characteristics under controlled conditions. The results showed that germination rate was significantly improved by using low rates of CaC2 (10 to 30 mg CaC2 plate) while the highest rate of CaC2 (40 mg plate) suppressed germination rate of cucumber seeds. Likewise, lower rates of CaC2 were also found effective in enhancing the root and hypocotyl lengths, number of lateral roots and fresh weight of seedling while the highest rate of CaC2 was proved inhibitory. It was recorded that the CaC2 induced improvement in seed germination was significantly correlated (r = 0.75) with magnitude of ethylene production during imbibition. Moreover, a pot experiment was conducted under natural conditions to select optimum rate and coating material of CaC2 regarding growth and yield parameters of cucumber. It was found that all rates of CaC2, irrespective of coating materials, exhibited new primary branches, early female flowering and fruit maturity. Maximum response regarding female flower count, fruit yield and ethylene emission was obtained by the application of paint coated CaC2 at 300 mg pot, which resulted in 34% more fruit yield compared to control plants. © 2016 Friends Science Publishers

Emission analysis of a modern Tier 4 DI diesel engine fueled by biodiesel-diesel blends with a cold flow improver (Wintron Synergy) at multiple idling conditions

A direct injection (DI) diesel engine is tested in this work with biodiesel-diesel and biodiesel-diesel cold flow additive blends for emissions at idling conditions. Biodiesel is produced from pure canola oil by transesterification process and the effect of a cold flow additive, Wintron Synergy in different proportions is examined for cold flow property (cloud point) and engine emissions. Systematic tests are undertaken over different engine speeds (800, 1000 and 1200rpm), with 0, 20, 50 and 100vol% of biodiesel in biodiesel-diesel and 0.25, 0.5, 1 and 2vol% of Wintron Synergy in biodiesel-diesel-additive blends. The emission of carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NOx), hydrocarbon (HC), acetaldehyde and formaldehyde from different blends are measured and compared to neat diesel emissions. Test results show that B20S2 has the lowest cloud point of the fuel blends at −34.8°C. Biodiesel and Synergy are found to be effective in reducing both CO and HC emissions. Biodiesel and Synergy content can increase NOx emissions. After warmup, acetaldehyde emissions remain the same for all tests at 5ppm and formaldehyde emissions increases for all fuel blends and neat diesel. It is also found that Synergy can change the crystal size and structure of biodiesel-diesel blend B20.

Metabolic activity, microbial growth and sensory quality of arugula leaves (Eruca vesicaria Mill.) stored under non-conventional modified atmosphere packaging

Arugula compositional characteristics linked to vitamin content, polyphenols and other health beneficial compounds have increased consumer interest to include it in the diet. This leafy vegetable is very susceptible to yellowing and dehydration, reducing its shelf life period. This study evaluated the effects of non-conventional modified packaging atmospheres, i.e. Argon (75–80% Ar+10–11% O2, balance N2), Nitrogen (10–11% O2+89–90%N2), High Oxygen (85–90% O2+10–15%N2), Helium (75–80% He+10–11% O2, balance N2) and Nitrous Oxide (75–80%N2O+10–11% O2, balance N2), on metabolic activity, microbiological growth and sensory characteristics of fresh cut arugula (Eruca vesicaria Mill.) leaves. The High Oxygen atmospheres reduced the respiration rate until 5days of storage, but there were no differences among treatments at the end of the storage period. There were no differences in ethylene emission among treatments at any of the evaluation dates. Non-conventional atmospheres had 0.5–1 log unit lower microbial growth counts than air packaging after 8days of storage. Color and sensory characteristics were not affected by the storage conditions. The non-conventional atmospheres maintained some quality characteristics of arugula leaves, suggesting it could be an alternative to conventional modified atmosphere used to maintain arugula shelf life.

Experimental and kinetic modeling study of diethyl ether flames

Diethyl ether (DEE, C4H10O) is being considered as a promising biofuel. However, its combustion chemistry has not been well studied. Particularly lacking are quantitative intermediate species profiles in flames that provide a stringent test for kinetic models, and flame speed data at elevated pressures. In the present paper, we obtain species distributions in low-pressure flames and measure flame speeds at elevated pressure to gain insights into high-temperature combustion chemistry of DEE. Specifically, a fuel-rich DEE flame (ϕ∼1.8) with 25% argon dilution at 4kPa was investigated by using a dedicated combination of electron ionization (EI) molecular-beam mass spectrometry (MBMS) with gas chromatography (GC) and tunable synchrotron vacuum ultraviolet (VUV) photoionization (PI) MBMS. High-pressure flame speeds of DEE were measured in a constant-volume cylindrical chamber at an initial temperature of 298K at an equivalence ratio of ϕ=1.4 and pressure up to 507kPa. Moreover, a new detailed kinetic model for DEE combustion was developed, with the most noticeable advances over the solely existing model by Yasunaga et al., 2010 being a more complete description of the reactions of DEE radicals and the use of accurate theoretical methods, i.e. CBS-QB3, to determine the rate constants for important primary reactions. In contrast to the previously published one, the present model includes reactions of DEE radicals that directly involve the formation of ethyl vinyl ether (EVE), an addition supported by identification and quantification of EVE by PI-MBMS in the flame experiment. Finally, the results showed that DEE flames yield low concentrations of aromatic species. However, high acetaldehyde emission was observed, originating from the dominant pathways of DEE consumption via H-abstractions from C-α positions followed by β-scissions.

Determination of the Optimum Harvest Window for Apples Using the Non-Destructive Biospeckle Method.

Determination of the optimum harvest window plays a key role in the agro-food chain as the quality of fruit depends on the right harvesting time and appropriate storage conditions during the postharvest period. Usually, indices based on destructive measurements are used for this purpose, like the De Jager Index (PFW-1), FARS index and the most popular Streif Index. In this study, we proposed a biospeckle method for the evaluation of the optimum harvest window (OHW) of the “Ligol” and “Szampion” apple cultivars. The experiment involved eight different maturity stages, of which four were followed by long cold storage and shelf life to assist the determination of the optimum harvest window. The biospeckle activity was studied in relation to standard quality attributes (firmness, acidity, starch, soluble solids content, Streif Index) and physiological parameters (respiration and ethylene emission) of both apple cultivars. Changes of biospeckle activity (BA) over time showed moderate relationships with biochemical changes during apple maturation and ripening. The harvest date suggested by the Streif Index and postharvest quality indicators matched with characteristic decrease in BA. The ability of biospeckle method to characterize the biological state of apples was confirmed by significant correlations of BA with firmness, starch index, total soluble solids and Streif Index, as well as good match with changes in carbon dioxide and ethylene emission. However, it should be noted that correlations between variables changing over time are not as meaningful as independent observations. Also, it is a well-known property of the Pearson’s correlation that its value is highly susceptible to outlier data. Due to its non-selective nature the BA reflected only the current biological state of the fruit and could be affected by many other factors. The investigations showed that the optimum harvest window for apples was indicated by the characteristic drop of BA during pre-harvest development. Despite this, at the current state of development the BA method cannot be used as an indicator alone. Due to rather poor results for prediction in OHW the BA measurements should be supported by other destructive methods to compensate its low selectivity.

Comprehensive Analysis of ABA Effects on Ethylene Biosynthesis and Signaling during Tomato Fruit Ripening.

ABA has been widely acknowledged to regulate ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism underlying the interaction between these two hormones are largely unexplored. In the present study, exogenous ABA treatment obviously promoted fruit ripening as well as ethylene emission, whereas NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) application showed the opposite biological effects. Combined RNA-seq with time-course RT-PCR analysis, our study not only helped to illustrate how ABA regulated itself at the transcription level, but also revealed that ABA can facilitate ethylene production and response probably by regulating some crucial genes such as LeACS4, LeACO1, GR and LeETR6. In addition, investigation on the fruits treated with 1-MCP immediately after ABA exposure revealed that ethylene might be essential for the induction of ABA biosynthesis and signaling at the onset of fruit ripening. Furthermore, some specific transcription factors (TFs) known as regulators of ethylene synthesis and sensibility (e.g. MADS-RIN, TAGL1, CNR and NOR) were also observed to be ABA responsive, which implied that ABA influenced ethylene action possibly through the regulation of these TFs expression. Our comprehensive physiological and molecular-level analysis shed light on the mechanism of cross-talk between ABA and ethylene during the process of tomato fruit ripening.