Ethylene Evolution Research Articles

Pattern of phenolic content, antioxidant activity and senescence-related enzymes in granulated vs non-granulated juice-sacs of 'Kinnow' mandarin (Citrus nobilis x C. deliciosa).

'Kinnow' is a hybrid mandarin, developed at California (USA) but could not become successful there. However, it revolutionized citrus industry in India, Pakistan and Bangladesh. Recent reports indicate that like other citrus fruits, it also suffers from juice-sac granulation but exact cause of this malady is not known. Fully-mature 'Kinnow' fruits were harvested and observations on some physical and biochemical attributes were recorded and their relationship was established with occurrence of granulation. About 12.8% 'Kinnow' fruits were affected by juice-sac granulation. Granulated fruits had higher average weight (178±2.26g), peel thickness (3.72±0.23mm), and less soluble solids concentrates (7.4±0.21%) than non-granulated fruits. Granulated fruits exhibited lower concentrations of total phenolics compounds (4.3±0.56mg 100(-1)g gallic acid equivalent fresh weigh) and antioxidants activity (1.78±0.29μmol Trolox g(-1) FW) but produced higher rates of carbon dioxide and ethylene, and exhibited higher activities of senescent-related enzymes such as lipoxygenase (LOX) (1.3±0.31 μmoles min(-1)g(-1) FW) and pectin methylesterase (PME) (0.52±0.12μmol of NaOH g(-1) FW min(-1)) and had strong relationships with the occurrence of granulation. From this study, it can be concluded that total phenolics compounds, antioxidants and PAL enzyme activity have strongly negative co-relation; whereas, senescent-related enzymes such as LOX, and PME and rates of respiration or ethylene evolution have strongly positive relationships with the occurrence of granulation in 'Kinnow' mandarin.

Losses in litchi at various stages of supply chain and changes in fruit quality parameters

During May and June of 2012 and 2013, a study was conducted to assess losses at the farm, wholesale and retail levels in the supply chain of litchi in India. Changes in fruit quality parameters after harvest and the effectiveness of an improved corrugated fibre board (CFB) box versus conventional wooden box packaging to minimize postharvest losses were also studied. Farm-level samples were collected immediately after harvest from farmers' orchards in the Muzaffarpur district of Bihar state. Wholesale market samples were procured from the Delhi market, and retail samples from the Muzaffarpur and Delhi market. Real-time data on losses and quality parameters of fruits were recorded by transporting litchi from Muzaffarpur to Delhi (distance 1000 km) by truck. Studies indicated that the average loss (fruits discarded at sorting) apparent at the farm level during 2012 and 2013 was 30.4% and 25.8%, respectively. The average loss at the wholesale market level in Delhi was 15.8% and 12.4% during 2012 and 2013, respectively. The highest mean loss (up to 20.5%) was observed at the retail level. The mean fruit weight loss during transport to Delhi was 9.42% and 7.07% during 2012 and 2013, respectively. The mean total loss in the supply chain of litchi ranged from 35.3% to 43.8%. The total soluble solids, respiration and ethylene evolution in litchi fruits were found to increase after transport, whereas acidity and colour parameters (L*, a* and b* values) significantly decreased over time. The predominant pathogen associated with fruit decay was Alternaria alternata (Fr.) Keissler. CFB packaging significantly reduced various losses, thus indicating its effectiveness in its current use in non-refrigerated trucks for transport.

Abscisic Acid Antagonizes Ethylene Production through the ABI4-Mediated Transcriptional Repression of ACS4 and ACS8 in Arabidopsis

Increasing evidence has revealed that abscisic acid (ABA) negatively modulates ethylene biosynthesis, although the underlying mechanism remains unclear. To identify the factors involved, we conducted a screen for ABA-insensitive mutants with altered ethylene production in Arabidopsis. A dominant allele of ABI4, abi4-152, which produces a putative protein with a 16-amino-acid truncation at the C-terminus of ABI4, reduces ethylene production. By contrast, two recessive knockout alleles of ABI4, abi4-102 and abi4-103, result in increased ethylene evolution, indicating that ABI4 negatively regulates ethylene production. Further analyses showed that expression of the ethylene biosynthesis genes ACS4, ACS8, and ACO2 was significantly decreased in abi4-152 but increased in the knockout mutants, with partial dependence on ABA. Chromatin immunoprecipitation–quantitative PCR assays showed that ABI4 directly binds the promoters of these ethylene biosynthesis genes and that ABA enhances this interaction. A fusion protein containing the truncated ABI4-152 peptide accumulated to higher levels than its full-length counterpart in transgenic plants, suggesting that ABI4 is destabilized by its C terminus. Therefore, our results demonstrate that ABA negatively regulates ethylene production through ABI4-mediated transcriptional repression of the ethylene biosynthesis genes ACS4 and ACS8 in Arabidopsis.

Substrate pH Impacts Efficacy of Ethephon Drenches on Growth of Herbaceous Perennials

Ethephon [(2-chloroethyl) phosphonic acid] is widely used as a growth regulator in floricultural crop production, with foliar sprays as the typical application method. Ethephon efficacy is determined by rate of uptake and subsequent ethylene evolution, which can be influenced by a number of factors, including solution pH. This study examines whether an ethephon substrate drench (100 mg⋅L−1 at a volume of 296 mL per 2.8-L container) would allow for plant uptake in two herbaceous perennials, Verbena bonariensis (L.) ‘Lollipop’ and Veronica spicata (L.) ‘Goodness Grows’, as measured by subsequent effects on shoot growth and days to flower. We also investigated substrate pH effects on ethephon drench efficacy by analyzing the shoot responses to ethephon applied at a range of starting substrate pH (4.5 to 7.0) compared with untreated plants grown under the same substrate pH conditions (controls). One or more measurements of shoot growth (height, width, shoot dry weight) were reduced in both taxa treated with ethephon as compared with controls. Veronica plant growth was not influenced by substrate pH in either the control or ethephon-drenched plants. For Verbena plants receiving the ethephon drench, as substrate pH increased, height and width increased. For example, when ethephon was applied at substrate pH 4.5, finished plant height averaged 32.0 cm, compared with 43.5 cm for those plants that received the drench at a substrate pH of 7.0. Increasing substrate pH conditions also influenced the days to flower in Verbena plants. Ethephon-treated plants at a substrate pH of 4.5 required an average of 6.5 days longer to flower than those at a substrate pH of 7.0. In summary, ethephon drench applications can result in significant growth regulation effects, as seen in both Veronica and Verbena. Furthermore, increasing substrate pH can reduce the efficacy of ethephon drench applications.

A structural and functional model for the 1-aminocyclopropane-1-carboxylic acid oxidase.

The hitherto most realistic low-molecular-weight analogue for the 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO) is reported. The ACCOs 2-His-1-carboxylate iron(II) active site was mimicked by a TpFe moiety, to which the natural substrate ACC could be bound. The resulting complex [Tp(Me,Ph) FeACC] (1), according to X-ray diffraction analysis performed for the nickel analogue, represents an excellent structural model, featuring ACC coordinated in a bidentate fashion-as proposed for the enzymatic substrate complex-as well as a vacant coordination site that forms the basis for the first successful replication also of the ACCO function: 1 is the first known ACC complex that reacts with O2 to produce ethylene. As a FeOOH species had been suggested as intermediate in the catalytic cycle, H2 O2 was tested as the oxidant, too, and indeed evolution of ethylene proceeded even more rapidly to give 65 % yield.

Genome-wide digital transcript analysis of putative fruitlet abscission related genes regulated by ethephon in litchi.

The high level of physiological fruitlet abscission in litchi (Litchi chinensis Sonn.) causes severe yield loss. Cell separation occurs at the fruit abscission zone (FAZ) and can be triggered by ethylene. However, a deep knowledge of the molecular events occurring in the FAZ is still unknown. Here, genome-wide digital transcript abundance (DTA) analysis of putative fruit abscission related genes regulated by ethephon in litchi were studied. More than 81 million high quality reads from seven ethephon treated and untreated control libraries were obtained by high-throughput sequencing. Through DTA profile analysis in combination with Gene Ontology and KEGG pathway enrichment analyses, a total of 2730 statistically significant candidate genes were involved in the ethephon-promoted litchi fruitlet abscission. Of these, there were 1867 early-responsive genes whose expressions were up- or down-regulated from 0 to 1 d after treatment. The most affected genes included those related to ethylene biosynthesis and signaling, auxin transport and signaling, transcription factors (TFs), protein ubiquitination, ROS response, calcium signal transduction, and cell wall modification. These genes could be clustered into four groups and 13 subgroups according to their similar expression patterns. qRT-PCR displayed the expression pattern of 41 selected candidate genes, which proved the accuracy of our DTA data. Ethephon treatment significantly increased fruit abscission and ethylene production of fruitlet. The possible molecular events to control the ethephon-promoted litchi fruitlet abscission were prompted out. The increased ethylene evolution in fruitlet would suppress the synthesis and polar transport of auxin and trigger abscission signaling. To the best of our knowledge, it is the first time to monitor the gene expression profile occurring in the FAZ-enriched pedicel during litchi fruit abscission induced by ethephon on the genome-wide level. This study will contribute to a better understanding for the molecular regulatory mechanism of fruit abscission in litchi.

Acetaldehyde adsorption on TiO2: Influence of NO2 preliminary adsorption

Titanium dioxide (TiO2) is a widespread metal oxide used in catalysis and photocatalysis, or coupled to non-thermal plasma for volatile organic compound (VOC) oxidation. Adsorption is a key step in the advanced heterogeneous oxidation processes; adsorption is partially addressed in that it is mainly investigated on fresh TiO2 surfaces. However, the treatment of real effluents combines various pollutants with VOCs; among them, NOx are characterized by reactive adsorption properties on TiO2 leading to irreversibly adsorbed species on the surface. The aim of this work is to determine the impact of NO2 preliminary adsorption on the subsequent adsorption of a model VOC: acetaldehyde. Breakthrough methods are used to (i) characterize acetaldehyde adsorption on fresh and NO2 covered TiO2 surface, (ii) control the coverage of TiO2 surface by irreversibly adsorbed NOx(ads)- species. In a first step, acetaldehyde adsorption on TiO2 has been characterized. In a second step, acetaldehyde adsorption has been achieved on TiO2 surface after NO2 exposure corresponding to different surface coverages. Then, acetaldehyde adsorption parameters have been determined. Subsequently, it has been possible to plot the evolution of acetaldehyde reversibly and irreversibly adsorbed quantities, and reversible fraction adsorption constant, as a function of TiO2 surface coverage by NOx(ads)- species, so called TiO2 surface NO2 ageing. Interestingly, both adsorbed acetaldehyde fractions are highly impacted by the presence of NOx(ads)- species on TiO2 surface. The irreversibly adsorbed fraction is considerably decreased since the lowest values of TiO2 surface coverage by NOx(ads)- species. Hypotheses related to competitive adsorption are not sufficient to explain the observed impact, suggesting that NOx(ads)- species modify TiO2 surface chemistry and acetaldehyde reactive adsorption. The reversibly adsorbed fraction of acetaldehyde is highly impacted as well; reversibly adsorbed amounts are decreased since the lowest surface coverage by NOx(ads)- species. The corresponding adsorption constants are abruptly increased as soon as TiO2 surface has been exposed to NO2, suggesting the formation of a new adsorption mode for acetaldehyde on NO2 exposed TiO2 surface. This paper evidences the considerable impact of NO2 on TiO2 adsorption properties regarding VOCs. Considering that NOx may accumulate on TiO2 the long term behaviour of such processes should be investigated further taking into account the NOx vs. VOC interaction for adsorption.

Delayed and prolonged ethylene treatment alleviates firmness asynchrony enhanced by 1-methylcyclopropene exposure in Guatemalan-West Indian avocado

Studies were conducted to determine the efficacy of a delayed and prolonged ethylene treatment in alleviating firmness asynchrony enhanced by 1-methylcyclopropene (1-MCP) exposure in avocado. ‘Booth 7’ and ‘Booth 8’ avocados, mid-season cultivars in Florida, were harvested and immersed in water (control) or aqueous 1-MCP at 16.7μmolL−1 a.i. (900μgL−1) for 1min at 20°C; all fruit were held at 20°C/89±2% relative humidity until ripe, based on whole fruit firmness, respiration and ethylene evolution. The effect of delayed and prolonged ethylene treatment was investigated by exposing 1-MCP-treated fruit to ethylene (100μLL−1) for 2 or 4d at 20°C upon reaching two progressive ripening stages (120N or 80N of whole fruit firmness, respectively).Ripe fruit (10–15N) from all treatments were assessed for peel color, pulp firmness and polygalacturonase (PG) activity. 1-MCP significantly delayed ripening of ‘Booth 7’ and ‘Booth 8’ avocado. Firmness asynchrony was confirmed in control fruit of both cultivars, with a difference of more than 20% in pulp firmness between apical and distal end segments regardless of ripeness stage. 1-MCP-treated fruit showed pronounced firmness asynchrony, with pulp firmness for apical end 10-fold higher than for distal end. PG activity was not directly related to firmness asynchrony, since even when strong asynchrony was observed for 1-MCP-treated fruit, PG activity did not differ from control. A 2-d delayed exposure of fruit at either 120N or 80N whole fruit firmness to ethylene was not consistently sufficient to promote ripening recovery (in terms of whole fruit firmness). However, a prolonged, 4-d ethylene treatment of fruit at either progressive ripening stages from both ‘Booth 7’ and ‘Booth 8’ effectively overcame the pronounced firmness asynchrony caused by 1-MCP treatment.

Role of 1, 3-Propane Sultone and Vinylene Carbonate in Solid Electrolyte Interface (SEI) Formation and Gas Generation

The cycling performance, ex-situ surface analysis, and in-situ gas analysis of lithium ion batteries containing the widely used electrolyte additives VC and PS has been investigated. All of the electrolytes have good cycling performance at 25°C. However, the electrolytes containing additives have better discharge capacity retention and coulombic efficiency upon cycling at 55°C. Analysis of the differential capacity plots suggest that both VC and PS are reduced prior to the carbonates and alter the structure of the anode SEI. Ex-situ surface analysis confirms structural differences of the anode SEI. Electrodes cycled in the presence of PS contain lithium alkyl sulphonate (RSO3Li) on the surface of the anodes. The presence of the lithium alkyl sulfonate leads to higher lithium ion conductivity of the anode SEI. Electrodes cycled with added VC contain poly(VC) in the anode SEI. The presence of the poly(VC) leads to improved stability of the SEI. Anodes cycled with both VC and PS contain lithium alkyl sulphonate and poly(VC) which leads to an SEI with both high conductivity and high thermal stability. In-situ gas analysis shows that both additives, VC and PS, are able to reduce the ethylene evolution during SEI formation by nearly 70 %. The formation of poly(VC) for electrodes cycled in VC is accompanied by CO2 evolution. The presence of the lithium sulfonate for PS leads to a lower onset potential of ethylene evolution. For VC, the only gaseous byproduct during reduction is CO2, while PS shows no gaseous reduction products. The combination of both additives leads to a superposition of the described phenomena. The reduction of gas evolution during SEI formation would allow a faster and easier industrial formation procedure for Li-ion batteries.

Nitrogen availability regulates proline and ethylene production and alleviates salinity stress in mustard (Brassica juncea)

Proline content and ethylene production have been shown to be involved in salt tolerance mechanisms in plants. To assess the role of nitrogen (N) in the protection of photosynthesis under salt stress, the effect of N (0, 5, 10, 20mM) on proline and ethylene was studied in mustard (Brassica juncea). Sufficient N (10mM) optimized proline production under non-saline conditions through an increase in proline-metabolizing enzymes, leading to osmotic balance and protection of photosynthesis through optimal ethylene production. Excess N (20mM), in the absence of salt stress, inhibited photosynthesis and caused higher ethylene evolution but lower proline production compared to sufficient N. In contrast, under salt stress with an increased demand for N, excess N optimized ethylene production, which regulates the proline content resulting in recovered photosynthesis. The effect of excess N on photosynthesis under salt stress was further substantiated by the application of the ethylene biosynthesis inhibitor, 1-aminoethoxy vinylglycine (AVG), which inhibited proline production and photosynthesis. Without salt stress, AVG promoted photosynthesis in plants receiving excess N by inhibiting stress ethylene production. The results suggest that a regulatory interaction exists between ethylene, proline and N for salt tolerance. Nitrogen differentially regulates proline production and ethylene formation to alleviate the adverse effect of salinity on photosynthesis in mustard.

Ethylene is all around.

Ethylene is all around.

Characterization of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) genes during nectarine fruit development and ripening

1-Aminocyclopropane-1-carboxylic acid synthases (ACS) are key regulatory enzymes involved in ethylene biosynthesis. In plants, ACS enzymes are encoded by a multigene family. In our study, six Pp-ACS genes were identified in nectarine (Prunus persica var. nectarina) based on the recently released peach genome sequence. To gain a better understanding of the nectarine ACS genes in fruit ethylene biosynthesis networks, ethylene evolution and the accumulation patterns of six Pp-ACS transcripts during fruit development and ripening in nectarine ‘CN13’ (melting type) and ‘CN16’ (stony hard type) cultivars were examined. Of the six Pp-ACS cDNAs isolated, two genes (Pp-ACS1 and Pp-ACS4) showed ripening-related increased expression during fruit development and ripening in nectarine ‘CN13’. Lack of Pp-ACS1 expression was solely responsible for low levels of ethylene production in nectarine ‘CN16’. The expression of Pp-ACS5 decreased during fruit development. The effects of phytohormones (auxin and ethylene) and low temperature (4 °C) on the levels of different Pp-ACS mRNAs were investigated. Finally, a model is proposed describing the critical regulation of Pp-ACS genes and their relationships to ethylene biosynthesis during nectarine fruit development and ripening.

Cinnamyl alcohol dehydrogenases in the mesocarp of ripening fruit of Prunus persica genotypes with different flesh characteristics: changes in activity and protein and transcript levels.

Development of fruit flesh texture quality traits may involve the metabolism of phenolic compounds. This study presents molecular and biochemical results on the possible role played by cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) during ripening [S3, S4 I (pre-climacteric) and S4 III (climacteric) stages] of peach [Prunus persica (L.) Batsch] fruit with different flesh firmness [non-melting flesh (NMF) 'Oro A'/melting flesh (MF) 'Springcrest' and 'Sanguinella'] and color (blood-flesh Sanguinella). A total of 24 putative full-length PRUPE_CAD genes were identified (in silico analysis) in the peach genome. The most abundant CAD isoforms, encoded by genes located on scaffolds 8 and 6, were probed by specifically developed anti-PRUPE_CAD sc8 and by anti-FaCAD (PRUPE_CAD sc6) polyclonal antibodies, respectively. PRUPE_CAD sc8 proteins (SDS-PAGE and native-PAGE/western blot) appeared responsible for the CAD activity (in vitro/in-gel assays) that increased with ripening (parallel to PRUPE_ACO1 transcripts accumulation and ethylene evolution) only in the mesocarp of Oro A and blood-flesh Sanguinella. Accumulation of PRUPE_CAD sc8 transcripts (semi-quantitative RT-PCR) occurred in all three cultivars, but in Oro A and Springcrest it was not always accompanied by that of the related proteins, suggesting possible post-transcriptional regulation. Flesh firmness, as well as levels of lignin, total phenolics and, where present (Sanguinella), anthocyanins, declined with ripening, suggesting that, at least in the studied peach cultivars, CAD activity is related to neither lignification nor differences in flesh firmness (NMF/MF). Further studies are necessary to clarify whether the high levels of CAD activity/expression in Sanguinella play a role in determining the characteristics of this blood-flesh fruit.

Effect of Activebag® modified atmosphere packaging on the postharvest characteristics of mango fruits, <i>Mangifera indica</i> L, cultivar Tommy Atkins

Objective: This was to evaluate the efficacy of MAP in maintaining the postharvest quality of mango fruits.Methodology and results: The fruits were harvested from a commercial orchard, (Karurumo Orchards) located in Embu county of Eastern province. The fruits were harvested at advanced maturity during the pre-climacteric rise phase when most of the flesh had turned yellow. They were selected for uniformity in colour, size and shape and randomly separated into three equal batches of 50 fruits each. The first batch was packaged in Activebag®, second batch in ordinary (commercially used) polythene bags while the third batch was left unpackaged as control. Five fruits from each treatment were sampled every three days during the shelf life period and evaluated for various physiological and physicochemical parameters associated with mango ripening and quality including ethylene evolution, respiration rate, cumulative weight loss, firmness, hue angle, total soluble solids, total titratable acid, soluble sugars, ascorbic acid and beta-carotene. MAP whether in Activebag® or ordinary polythene was effective in maintaining the quality of mango fruits compared to the unpackaged controls. Slow ripening changes of Activebag® fruits was accompanied by a delayed respiratory climacteric and generally lower respiration rates compared to ordinary bag and unpackaged fruits. At the end of the observation period, Activebag® fruits were 16% firmer compared to unpackaged fruits. The initial average weight was 635g and modified atmosphere packaging had a remarkable effect on cumulative weight loss with fruits packaged in the ordinary polythene bag and Activebag® fruits losing only 7.4% of the initial weight compared to 12% in the case of unpackaged fruits (control). Higher levels of total soluble solids (°brix) 5.5g/100g and total soluble sugars (6g/100g) observed at the beginning of storage (6 days after packaging) signalled advanced ripening of unpackaged fruits. However as the storage time progressed, the levels of each of the soluble sugars evaluated were higher in Activebag® fruits. Similarly, Activebag® fruits retained higher levels of titratable acidity (0.39%and ascorbic acid compared to ordinary bag fruits (0.36%).Conclusion: Packaging mangoes in Activebag® after harvest at ripe stage was effective in delaying most of the ripening related changes in mango fruits thereby maintaining the quality and extending their shelf life. Although ordinary polythene packaging maintained quality of the fruits better than unpackaged fruits, the positive effects were negated by high incidences of rotting.Key words: Mango, MAP, postharvest, quality, shelf life

Ethylene is involved in high air humidity promoted stomatal opening of tomato (Lycopersicon esculentum) leaves.

High relative air humidity (RH) promotes stomatal opening in tomato leaves. This study examined the role of the plant hormones abscisic acid (ABA) and ethylene in high RH induced stomatal opening. Plants were grown in high (90%) and moderate (60%) RH or transferred from moderate to high RH. ABA levels were only slightly, but significantly decreased during darkness by increasing RH. However, a significantly higher ethylene evolution was found in high RH compared with moderate RH. Ethephon increased conductance and stomatal aperture in moderate RH. Treatment with amino-ethoxyvinylglycine (AVG) suppressed stomatal opening when plants were transferred from moderate to high RH. Similarly, blocking the ethylene receptor or using an ethylene-insensitive mutant (NR) reduced the response to high RH. These results demonstrate that both ethylene production and sensitivity play a role in high RH-induced stomatal opening in tomato leaves. The increased conductance found when plants were transferred to high RH could be counteracted by exogenous ABA spray. The ABA deficient mutant 'Flacca' produced high levels of ethylene irrespective of the RH and the difference in water loss and conductance between high and moderate grown 'Flacca' plants was attenuated compared with WT. The results indicate that both ABA and ethylene play a role in air humidity control of stomatal movement in tomato.

Comparative storage behaviour of the pods from a large-fruiting and small-fruiting okra cultivar

Weight loss of pods of small-fruiting okra cv. Boyiatiou stored at 10°C was higher than that of large-fruiting cv. Clemson spineless. Enclosure in plastic film reduced weight loss, but in Clemson spineless caused surface discoloration. In both cultivars, respiration and ethylene evolution increased during storage, while firmness and colour intensity decreased. Subsequent transfer of pods to room temperature (22°C) for three days increased loss of weight, firmness and colour, especially if the film was removed. We conclude that the small pods of cv. Boyiatiou may only be stored satisfactorily at 10°C if enclosed in plastic film, and for a period of > 5 days pods should not be subsequently subjected to shelf life at 22°C. The larger pods of Clemson spineless, however, store better in air at 10°C. Thus, recommendations for storage should take into account cultivar and pod size.

Effect of surface coatings on postharvest quality of Kinnow mandarin

The study was conducted to observe the effect of surface coatings such as lac based wax, Citrashine®, P-104® and NiprofreshTM on Kinnow mandarin with the objective to extend its shelf-life. For this, Kinnow fruit were treated with different surface coatings and stored at 5o ± 1oC temperature and 85–90% RH. Our results indicated that all surface coatings maintained a very good profile of quality parameters, but the surface coating of lac based wax was the best followed by Citrashine®, P-104® and NiprofreshTM. All surface coatings influenced all the studied attributes significantly but lac based wax was the most effective in maintaining lowest physiological loss in weight (9.7%), fruit firmness (6.5 N), respiration rate (1.3 ml CO2 kg−1 h−1), and ethylene evolution rate (1.5 μl kg−1 h−1). Similarly, all the surface coatings used could retain quality attributes (souble solids content, titratable acidity and ascorbic acid content) of the fruits without any adverse effect. Results suggested that surface coatings have potential to enhance shelf-life of Kinnow mandarin as its fruits could be successfully stored for 60 days under cold storage conditions with highly acceptable sensory quality. The non-coated fruits, on the other hand, maintained postharvest shelf-life of 45 days in cold storage. The surface coatings of indigenous origin (lac-based wax & P-104) can also recommended owning to their cheaper cost and reasonable effect on storage life.

Effects of elevated CO2 and water stress on physiological responses of Perilla frutescens var. japonica HARA

The aim of the present study was to investigate the interactive effects of expected environmental constraints, specifically elevated CO2 and drought conditions, on the physiological responses of Perilla frutescens var. japonica Arum. Perilla frutescens var. japonica ‘Arum’ was exposed to 700 μmol mol−1 of CO2 under both well-watered and water-stressed conditions. Photosynthetic rate was higher under elevated CO2 conditions. Stomatal resistance increased while transpiration rates declined, which suggests that water-use efficiency rose under elevated CO2 conditions. Under water-stressed conditions, elevated CO2 concentrations induced much higher stomatal resistance than ambient CO2 levels. This result implies that elevated CO2 concentrations might increase plant sensitivity to water stress, thereby providing plants with increased protection against drought. Furthermore, elevated CO2 concentrations alleviated drought-induced photosynthetic decline in the early stages of drought, although this effect was not sustainable. Water stress also elevated ascorbate peroxidase (APX) activity but had little effect on glutathione reductase activity. Water stress-induced APX activity was much lower under elevated CO2 conditions compared to ambient CO2 levels. Therefore, elevated CO2 concentrations might increase plant resistance to water stress. Moreover, there is a possibility that increased ethylene evolution under elevated CO2 conditions could improve the capacity of plants to scavenge reactive oxygen species by enhancing APX activity.

Plant-Agrobacterium interaction mediated by ethylene and super-Agrobacterium conferring efficient gene transfer.

Agrobacterium tumefaciens has a unique ability to transfer genes into plant genomes. This ability has been utilized for plant genetic engineering. However, the efficiency is not sufficient for all plant species. Several studies have shown that ethylene decreased the Agrobacterium-mediated transformation frequency. Thus, A. tumefaciens with an ability to suppress ethylene evolution would increase the efficiency of Agrobacterium-mediated transformation. Some studies showed that plant growth-promoting rhizobacteria (PGPR) can reduce ethylene levels in plants through 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, which cleaves the ethylene precursor ACC into α-ketobutyrate and ammonia, resulting in reduced ethylene production. The whole genome sequence data showed that A. tumefaciens does not possess an ACC deaminase gene in its genome. Therefore, providing ACC deaminase activity to the bacteria would improve gene transfer. As expected, A. tumefaciens with ACC deaminase activity, designated as super-Agrobacterium, could suppress ethylene evolution and increase the gene transfer efficiency in several plant species. In this review, we summarize plant–Agrobacterium interactions and their applications for improving Agrobacterium-mediated genetic engineering techniques via super-Agrobacterium.

Shedding light on ethylene metabolism in higher plants.

Ethylene metabolism in higher plants is regulated by a wide array of endogenous and environmental factors. During most physiological processes, ethylene levels are mainly determined by a strict control of the rate-limiting biosynthetic steps responsible for the production of 1-aminocyclopropane-1-carboxylic acid (ACC) and its subsequent conversion to ethylene. Responsible for these reactions, the key enzymes ACC synthase and ACC oxidase are encoded by multigene families formed by members that can be differentially regulated at the transcription and post-translational levels by specific developmental and environmental signals. Among the wide variety of environmental cues controlling plant ethylene production, light quality, duration, and intensity have consistently been demonstrated to influence the metabolism of this plant hormone in diverse plant tissues, organs, and species. Although still not completely elucidated, the mechanisms underlying the interaction between light signal transduction and ethylene evolution appears to involve a complex network that includes central transcription factors connecting multiple signaling pathways, which can be reciprocally modulated by ethylene itself, other phytohormones, and specific light wavelengths. Accumulating evidence has indicated particular photoreceptors as essential mediators in light-induced signaling cascades affecting ethylene levels. Therefore, this review specifically focuses on discussing the current knowledge of the potential molecular mechanisms implicated in the light-induced responses affecting ethylene metabolism during the regulation of developmental and metabolic plant responses. Besides presenting the state of the art in this research field, some overlooked mechanisms and future directions to elucidate the exact nature of the light–ethylene interplay in higher plants will also be compiled and discussed.