Ethylene Evolution Research Articles

Amelioration of Salt Tolerance in Soybean (Glycine Max. L) by Plant-Growth Promoting Endophytic Bacteria Produce 1-Aminocyclopropane-1-Carboxylase Deaminase

Salinity is a major abiotic stress that can induce ethylene synthesis beyond the normal limits as plants response to stress and hence reduces crop productivity. The 1-aminocyclopropane-1-carboxylase deaminase (ACCD)-producing bacteria can reduce excessive ethylene synthesis by taking ACC (ethylene precursor) as a nitrogen source. This study showed the possibility of using endophytic bacteria in order to reduce the undesirable effects of salinity. Strain Pseudomonas putida PIR3C and Roultella terrigena PCM8 exhibited promising performance for promoting the growth of plant under salinity stress conditions. The results showed that bacterial inoculation was effective even in the presence of higher salinity levels. Strain P. putida PIR3C was the most efficient strain compared to the other strains and significantly increased shoot length, root length, dry weight, germination percentage, and reduced stem diameter. The role of ACCD in reducing ethylene production under salinity stress conditions was also studied by measuring the evolution of ethylene in vitro by soybean seeds treated with some ACCD bacterial strain. The maximum ethylene lowering capacity was observed in R. terrigena PCM8, the strain reduced ethylene production from 622.81 nmol.g-1(control) to 352.78 nmol.g-1 (43% reduction). The production of α-ketobutyrate, chlorophyll content and germination percentage from P. putida PIR3C was higher than other strains. The results suggested that strain P. putida PIR3C and R. terrigena PCM8 can be employed for salinity tolerance in soybean seedlings and may have better prospects for an amelioration of stress condition.

Flowering profile and ethylene production of a new carnation subspecies 'Mini-tiara'

Ethylene is involved in the senescence of carnation flowers. It is synthesized abundantly after full opening of the flowers and accelerates wilting of petals, which results in withering of the flowers. We investigated the possible involvement of ethylene production in the loss of display value of cut flowers of ‘Mini-tiara’ carnation, a new subspecies derived from Dianthus caryophyllus L. by interspecific cross with wild-type Dianthus species (wild pinks). Flowers of ‘Mini-tiara’ carnation have a unique morphology with pointed-shaped petals, some of which in the middle part of the flowers stand straight and build a dome throughout the display time, and lose their display value when the dome collapses by bending all petals outside (full opening of flowers). Ethylene evolution from ‘Mini-tiara’ carnation was not detected from flowers with upstanding petals, but occurred several days after the collapse of the dome (after full opening of the flowers), the time they already lost their display value. These findings indicated that ethylene production is not engaged in the loss of display value of ‘Mini-tiara’ carnation.

Changes in flavor-relevant compounds during vine ripening of tomato fruit and their relationship with ethylene production

Flavor quality is import for determining consumer perception and acceptance of tomato products. In this study, ‘Fendou’ tomato fruit were harvested at six ripening stages and sampled to investigate the development of flavor-relevant compounds during vine ripening. Results showed that upon the initiation of ripening there was an increase in respiration rate and concomitant ethylene evolution that was associated with increased membrane permeability. In accordance with these physiological changes, flavor-relevant compounds demonstrated different expression patterns as fruit ripened, which contributed to ‘red-ripe’ flavor characteristics of red-ripe fruit. Based on correlation analysis between ethylene evolution and the flavor-relevant compounds during ‘Fendou’ tomato ripening and the other researchers’ reports, the activation of System 2-dependent autocatalytic ethylene production plays an important role in the development of most flavor-relevant compounds during tomato vine ripening. Overall, our results suggested that most flavor-relevant compounds that accumulated the most during tomato fruit ripening at red stage could be under ethylene regulation and were among the most important contributors to the ‘red-ripe’ flavor. Due to the development of these compounds, the flavor quality at late ripening stages is different from that of fruit at early ripening stages.

Effects of exogenously applied plant growth regulators on the physiology and anti-oxidant activity of wheat under water deficit condition

An experiment was conducted to know the effect of plant growth regulators, Thidiazuron; 0.01 µL L−1, Paclobutrazol; 30 µL L−1, Ascorbic acid; 100 µL L−1, on wheat genotypes under osmotic stress imposed with PEG 6000 and water-deficit stress in pots. Under osmotic stress with PEG6000, the total chlorophyll content and ethylene evolution were estimated from wheat seedling, and in pot experiment, detailed physiological studies were performed at different growth stages (pre-anthesis, anthesis and post anthesis) of wheat under water deficit stress and irrigated condition. Study revealed that the level of ethylene increased while the content of chlorophyll decreased under osmotic stress condition. Moreover, the higher level of ethylene and chlorophyll content were observed in C306 followed by in HD2987 as compared to HD2888 and HD2733 under control as well as in osmotic stress conditions. However, application of plant growth regulators (PGRs) led to the down-regulation of ethylene evolution from osmotic stressed wheat seedling while the chlorophyll content was improved across the wheat genotypes. Further, in pot experiment, PGRs application on water deficit stressed plants led to the improvement in ascorbic acid content and ascorbate peroxidase (APX) activity while the abscisic acid and thiobarbituric acid reactive substances (TBARS) content goes down in comparison to water deficit stress plants without PGRs application. Findings of the study indicated that due to simultaneous application of PGRs plant developed a sense of lower stress level thus lesser ethylene evolution and lipid peroxidation (TBARS content) was observed. Further PGRs application helped in maintenance of chlorophyll and ascorbic acid content with higher APX activity under water deficit condition indicating better tolerance level. The results of this study provide a synergetic effect of PGRs for abiotic stress tolerance.

Ethylene biosynthesis controlled by NON-RIPENING: A regulatory conflict between wounding and ripening

The phytohormone ethylene is involved in multiple aspects of morphological and physiological processes in plants. Tomato rapidly and transiently increases ethylene production during fruit ripening and in plant defense responses. The transcription factor non-ripening (NOR) has significant effects on fruit ripening via regulation of ethylene biosynthesis-related genes. The nor loss-of-function allele produces a basal level of ethylene during ripening, in contrast to the induced ethylene evolution observed upon Agrobacterium tumefaciens infection. The use of ACC deaminase represses ethylene production and significantly improves the efficiency of Agrobacterium-mediated T-DNA transfer in nor plants. Analyses of the transcription levels of the ethylene biosynthesis genes ACC synthase (ACS) and ACC oxidase (ACO) in nor plants revealed that the induced ethylene production was largely due to transcriptional accumulation of ACS2 and ACO1. Accumulation of ACS2 and ACO1 mRNA opposes NOR-mediated regulation in tomato fruit during ripening, and the feedback regulation of NOR is rendered ineffective by defense responses, thereby precluding the control of its own expression. The ethylene synthesis mechanisms respond properly to NOR-mediated transcriptional regulation that is differed through the wound-induced and ripening-induced signaling pathway.

Causes of irradiation-induced softening in peaches

Acceleration of ripening has been offered as a cause of irradiation-induced loss of firmness in peaches (Prunus persica). This work aimed to correlate softening with biochemical and physiological responses induced by irradiation in fresh peaches during subsequent storage. Freshly harvested and cooled ‘Mid Pride’peaches were treated with gamma irradiation at 1030 Gy, then stored at 1 °C for 7 days, and at 22 °C for another 6 days, during which time ripening and biochemical parameters were measured. The changes in respiration rate, ethylene, firmness, total soluble solids (TSS), titratable acidity (TA), water-soluble pectin (WSP) and activity of polygalacturonase (PG) and pectin methylesterase (PME) due to treatment and storage were evaluated. Firmness was significantly reduced immediately following irradiation treatment, whereas total pectin remained unaltered. WSP, however, increased upon irradiation and also during ripening. Despite an increase in respiration rate, ethylene evolution, TSS and TA were unaffected by irradiation. PG activity was not affected by irradiation, but, both PME and electrolyte leakage increased following irradiation treatment. For early ripe irradiated ‘Mid Pride’ peaches, softening during storage appears to be related to pectin hydrolysis, PME activity and electrolyte leakage, and not associated with ethylene evolution or exo-PG activity.

Evidence for the Involvement of Auxin, Ethylene and ROS Signaling During Primary Root Inhibition of Arabidopsis by the Allelochemical Benzoic Acid.

Allelopathy is mediated by plant-derived secondary metabolites (allelochemicals) which are released by donor plants and affect the growth and development of receptor plants. The plant root is the first organ which senses soil allelochemicals this results in the production of a shorter primary root. However, the mechanisms underlying this process remain elusive. Here, we report that a model allelochemical benzoic acid (BA) inhibited primary root elongation of Arabidopsis seedlings by reducing the sizes of both the meristem and elongation zones, and that auxin signaling affected this process. An increase in auxin level in the root tips was associated with increased expression of auxin biosynthesis genes and auxin polar transporter AUX1 and PIN2 genes under BA stress. Mutant analyses demonstrated that AUX1 and PIN2 rather than PIN1 were required for the inhibition of primary root elongation during BA exposure. Furthermore, BA stimulated ethylene evolution, whereas blocking BA-induced ethylene signaling with an ethylene biosynthesis inhibitor (Co2+), an ethylene perception antagonist (1-methylcyclopropene) or ethylene signaling mutant lines etr1-3 and ein3eil1 compromised BA-mediated inhibition of root elongation and up-regulation of auxin biosynthesis-related genes together with AUX1 and PIN2, indicating that ethylene signal was involved in auxin-mediated inhibition of primary root elongation during BA stress. Further analysis revealed that the BA-induced reactive oxygen species (ROS) burst contributed to BA-mediated root growth inhibition without affecting auxin and ethylene signals. Taken together, our results reveal that the allelochemical BA inhibits root elongation by increasing auxin accumulation via stimulation of auxin biosynthesis and AUX1/PIN2-mediated auxin transport via stimulation of ethylene production and an auxin/ethylene-independent ROS burst.

Promotion of shoot regeneration of Swertia chirata by biosynthesized silver nanoparticles and their involvement in ethylene interceptions and activation of antioxidant activity

Chemically synthesized silver nanoparticles (AgNP) have been assessed on plant tissue cultures but the impact of biologically synthesized AgNP fabricated by different phytoconstituents has not been sufficiently investigated. In this study biogenic AgNP prepared from leaf extract of Swertia chirata was utilized to address the problems associated with conservation of endangered medicinal plant through plant tissue culture. Endangered as well as economically important medicinal plant considered for this analysis was the same plant S. chirata itself. Excessive deforestation and exploration of this plant had led to complete eradication of the natural reservoir. Thus in vitro plant tissue propagation had attained much importance for maintaining the plant species. Nano-sized particles of diameter 20 nm encapped by different phytochemicals applied on regenerating shoot cultures showed enhanced shoot induction and proliferation. Other forms of silver like AgNO3 (SN) and Ag2S2O3 (STS) showed improved regeneration in comparison to control samples. Ethylene precursors like 1-aminocyclopropane-1-carboxylic acid (ACC) and 2-chloroethylphosphonic acid (CEPA) downregulated the regeneration process considerably. Reactive oxygen species (ROS) status of the treated cultures were evaluated considering hydrogen peroxide and malondialdehyde (MDA) content in treated cells as wells as their antioxidant enzyme activity. Combined manipulation and coordination of ethylene evolution, maintenance of ROS balance and better bio-acceptance of AgNP were responsible for improvement in shoot regeneration of the plant. Phytoencapsulated and nano-dimensioned Ag was capable of changing the chemical reactions of different regulating players of plant regeneration. These findings will facilitate the understanding and future utilization of biofabricated AgNP in agriculture and plant sciences.

Acetaldehyde released by Lactobacillus plantarum enhances accumulation of pyranoanthocyanins in wine during malolactic fermentation

This study investigated the evolution of acetaldehyde and pyranoanthocyanins in wine during malolactic fermentation, and further evaluated the correlation between acetaldehyde and pyranoanthocyanins. Cabernet Gernischt wine after alcoholic fermentation was inoculated with four lactic acid bacteria strains. Malolactic fermentation kinetics and wine characteristics were compared. Results showed these strains exhibited different kinetics on wine malolactic fermentation. Wine with Lactobacillus plantarum had lower reducing sugar, total acid, and yellowness. Lactobacillus plantarum elevated the level of acetaldehyde in wine model medium and wine during malolactic fermentation. Malolactic fermentation using Lactobacillus plantarum significantly increased the concentration of pyranoanthocyanins, whereas O. oeni strain reduced the level of pyranoanthocyanins in wine. Polymerized anthocyanins percentage in wine was significantly enhanced after fermentation with Lactobacillus plantarum. Principal component analysis indicated that the characteristics of these strains inoculated wines after malolactic fermentation were segregated. The findings from this study could provide useful information on the wine color improvement through malolactic fermentation with suitable lactic acid bacteria strains.

Storage performance of two ‘Pink Lady ® ’ clones differs, but 1-MCP treatment is beneficial, regardless of maturity at harvest

Abstract Determining optimal apple harvest time is important for effective postharvest treatments and also for maintenance of quality along the supply chain. A non-destructive instrument, the DA meter, was used to measure changes in absorbance near the upper chlorophyll-a absorption peak and to segregate commercially harvested fruit into two ripeness levels. DA meter readings were made at harvest and following cold (regular air) storage removals for two ‘Pink Lady®’ clones, ‘Cripps Pink’ and ‘Rosy Glow’. In addition, the destructive maturity and/or quality indicators of starch pattern index, fruit firmness, and soluble solids were determined and ethylene and CO2 production were monitored at harvest and at each removal, i.e. every 1.5 months for 7.5 months, and during a 14 d simulated shelf life per removal. The DA meter readings were a reliable non-destructive technology for determining ripeness levels throughout storage. Ethylene production patterns were similar up to 4.5 months of cold storage for the two cultivars, ‘Cripps Pink’ and ‘Rosy Glow’, but the rate was approximately double in ‘Rosy Glow’. Treatment with 1-methylcyclopropene (1-MCP) was effective at inhibiting ethylene evolution during cold storage and simulated shelf life, regardless of harvest maturity in both cultivars. However, this benefit only lasted until 4.5 months of cold storage for ‘Rosy Glow’, when ethylene production increased markedly after 7 d of simulated shelf life. The storage disorders, superficial scald and internal browning were more evident in ‘Rosy Glow’ fruit than in ‘Cripps Pink’, particularly after 6 months of cold storage. It is recommended that ‘Cripps Pink’ and its clone, ‘Rosy Glow’, be kept separately in storage and that ‘Rosy Glow’ not be stored for as long as ‘Cripps Pink’. Alternatively, the efficacy of additional 1-MCP treatments after 4 months of cold storage could be explored in ‘Rosy Glow’ to maintain reduced ethylene production during longer storage.

Grain density and its impact on grain filling characteristic of rice: mechanistic testing of the concept in genetically related cultivars

Physiological factors controlling assimilate partitioning was compared in relation to panicle architecture of lax- (Upahar) and compact-panicle (Mahalaxmi) rice cultivars. Grain number and ethylene production at anthesis are low, but filling rate is high in the former compared to high grain number and ethylene production and poor filling trait of the latter. Similar to Mahalaxmi, its progenitors Pankaj and Mahshuri, had attributes of high grain number and grain density, but grain filling was higher and ethylene evolution was lower. Disturbed genetic coherence owing to imbalance of gene groups brought in the cross combinations of Mahshuri and Pankaj could be responsible for high ethylene production leading to semi sterility of Mahalaxmi as the hormone slackened endosperm starch bio-synthesis enzyme activities. Mahalaxmi inherited grain compactness trait of its progenitors, but not the physiological attribute for reduced ethylene production, which impacted grain filling. Upahar, the progeny genotype of Mahalaxmi and IR62 cross, inherited the dominant allele for low ethylene production and good grain filling traits from the high yielding IR62. In conclusion grain filling in compact-panicle rice becomes poor subject to expression of recessive allele for high ethylene production, but the allele is amenable for suppression by corresponding dominant allele in a genetic breeding.

Inhibition of tomato fruit ripening by 1-MCP, wortmannin and hexanal is associated with a decrease in transcript levels of phospholipase D and other ripening related genes

Membrane deterioration is an inherent aspect of the advancement in senescence and loss in fruit quality during storage. Postharvest technologies used for extending shelf life and quality are targeted to reduce membrane damage through downregulating or blocking ethylene action. In this study, mature green tomato fruit were treated with inhibitors of ethylene receptor (ETR), phosphatidylinositol 3-kinase (PI3K) and phospholipase D (PLD), all recognized to be targets of regulation of fruit ripening. The inhibitors used included 1-methylcyclopropene (1-MCP, an ethylene receptor blocker), wortmannin (an inhibitor of PI3K), and hexanal (a PLD inhibitor). Fruit were treated at optimal levels of the inhibitors and were stored at 21 °C for 10 days. Color development was strongly delayed in wortmannin treated tomatoes just as in 1-MCP treated fruit; while, changes in respiration, firmness and ethylene evolution were very similar to that of control fruit. Hexanal delayed the initiation of these changes; while 1-MCP and wortmannin blocked the ripening process. Changes in expression levels of key genes involved in ethylene signalling, phosphoinositide metabolism, and lycopene synthesis that occurred in response to inhibitors, suggested potential roles for PI3K and PLD in ethylene signalling. Furthermore, fruit treated with all the three inhibitors showed a marked reduction in PLD transcript levels; suggesting that, regulation of PLD gene expression is a common critical regulatory point that regulates ripening. Lowered PLD levels may reduce membrane lipid catabolism and the generation of phosphatidic acid (PA), an intermediate in ethylene signalling regulation through downstream components.

Regulation of the protein and gene expressions of ethylene biosynthesis enzymes under different temperature during peach fruit ripening

Ethylene has profound effect on fruit development and ripening, and the role of ethylene biosynthesis enzymes involving 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS), ACC oxidase (ACO), and S-Adenosyl-l-methionine synthetase (SAMS) in peach fruit (cv. Xiahui-8) was characterized under 25 and 4 °C, respectively. All these enzymes in ethylene synthesis pathway were identified using 2-DE and real-time PCR. Both protein and gene expressions of ACO and SAMS were much higher at 25 °C than at 4 °C. Among five members of ACS family, PpaACS4 may belong to system II ethylene biosynthesis, while PpaACS3 involved in system I during development stage, and low temperature can induce PpaACS1 expression. The ethylene release and low expressions of proteins and genes of most enzymes indicated that low temperature can effectively postpone ripening stage by reducing ethylene evolution. High gene expression of PpaSAMS did not cause excessive expression of SAMS protein under low temperature, and over-expression of PpaACS1 at low temperature still did not induce increase of ethylene production. The mechanism underlying the phenomenon about how temperature affects ethylene release was also discussed.

Salicylic acid influences lenticel discolouration and physiological and biochemical attributes of mango (Mangifera indica L.) fruits

Lenticel discolouration (LD) has now emerged as a leading postharvest threat in mango, which interferes with the face value of fruits, thereby affecting the trade and causing huge monetary losses to our country. For its management, we designed an experiment using salicylic acid at 200, 400 and 600 ppm concentration along with control fruits, as a dip treatment for 5 min. Our results revealed that salicylic acid at 200 ppm was not only effective in reducing LD significantly but also reduced the activities of polyphenol oxidase (PPO) (0.397 ∆A410 O.D min−1 g−1 FW), peroxidase (POD) (0.050 ∆ A470 O.D min−1 g−1 FW), and lipoxigenase (LOX) (3.227 µmol min−1 g−1 FW) enzymes and helped in increasing the total phenolics (15.46 mg gallic acid equivalent 100 g−1). This treatment also suppressed the rates of ethylene evolution (0.521 µL kg−1 h−1) and respiration (34.46 mL CO2 kg−1 h−1) over untreated mango fruits. With respect to quality parameters, the significant decrease in postharvest decay (23.3%) occurred without any adverse effect on soluble solids concentrates (16° B) and total carotenoids (4.1 mg 100 g−1pulp). Thus, keeping all parameters (physical, physiological, biochemical and quality) in view, salicylic acid at 200 ppm was most effective as a postharvest dip treatment for reducing LD in mango during storage or marketing without adversely affecting the fruit quality.

Root cap-mediated evaluation of soil resistance towards graviresponding roots of maize (Zea mays L.) and the relevance of ethylene

Besides biological and chemical impacts, mechanical resistance represents an important obstacle that growing roots face. Graviresponding roots must assess the mechanical resistance of the substrate and take decisions on whether they change growth direction and grow around obstacles or tolerate growth conditions impaired to varying degrees. To test the significance of the root cap, we measured pressure and growth behaviour of single intact, as well as decapped, roots encountering diverse mechanical obstacles. We examined ethylene emission in intact roots as well as roots without a root cap, thereby lacking the capacity to deviate. Roots of fixed seedlings were grown vertically onto diverse mechanical obstacles. Developing pressure profiles of vertically growing roots encountering horizontal mechanical obstacles were measured employing electronic milligram scales, with and without root caps in given local environmental conditions. The evolution of root-borne ethylene was measured in intact roots and roots without the root cap. In contrast to decapped roots, intact roots develop a tentative, short-lasting pressure profile, the resolution of which is characterized by a definite change of growth direction. Similarly, pressure profiles and strengths of roots facing gradually differing surface resistances differ significantly between the two. This correlates in the short term with root cap-dependent ethylene emission which is lacking in roots without caps. The way gravistimulated and graviresponding roots cope with exogenous stimuli depends on whether and how they adapt to these impacts. With respect to mechanical hindrances, roots without caps do not seem to be able to evaluate soil strengths in order to respond adequately. On encountering resistance, roots with intact caps emit ethylene, which is not observed in decapped roots. It therefore appears that it is the root cap which specifically orchestrates the resistance needed to overcome mechanical resistance by specifically inducing ethylene.

AVG, NAA, boron, and magnesium influence preharvest fruit drop and fruit quality of ‘Honeycrisp’ apples

Preharvest fruit drop (PFD) of apple (Malus domestica Borkh.) can cause significant losses resulting in up to 50% reduction in yield in some years. In a 2-yr study, ‘Honeycrisp’ trees were treated with six foliar treatments including 20 mg·L−1 1-naphthaleneacetic acid (NAA) 2 wk before anticipated harvest (WBAH), 125 mg·L−1 aminoethoxyvinylglycine hydrochloride (AVG) 4 WBAH, AVG plus NAA 2 WBAH, and repeat sprays of 200 mg·L−1 B, and 2000 mg·L−1 Mg applied 48–93 d after full bloom to evaluate their effect on PFD and fruit quality. Fruit drop associated with broken pedicels and physiological causes was monitored. During a year with ∼43% PFD on untreated control trees, AVG retained up to ∼35% and NAA retained up to ∼27% of the total fruit number, relative to the control trees. The combination of AVG plus NAA had similar PFD compared with AVG alone, while B and Mg were similar to the control. The proportion of PFD associated with broken pedicels was ∼5%. Aminoethoxyvinylglycine delayed starch degradation, ethylene evolution, and blush skin colour development of fruit. This study supports the use of AVG 4 WBAH and NAA 2 WBAH to manage ‘Honeycrisp’ PFD, which may offer economic advantages for growing quality apples. Foliar sprays of Mg or B failed to reduce PFD.

De-hulling facilitates seed germination and ethylene production in dormant and non-dormant rice genotypes

SUMMARYThe hull or husk of rice, comprising the lemma and palea, provides a fitting enclosure for the caryopsis. The physiological significance of the hull in seed dormancy has been examined by comparing the effects of its removal on germination, seed vigour, assimilate mobilization and ethylene production in germinating seeds of six rice genotypes; two each belonging to dormant, semi-dormant and non-dormant groups. Hull removal promoted the above parameters in all three categories of seeds, but the effect was relatively higher in dormant seeds compared with less dormant categories. Ethylene production in non-dormant seeds was initiated after imbibition of water, normally before visible emergence of the radicle. It peaked when the radicle began to protrude and declined thereafter. In comparison, dormant seeds produced very low levels of ethylene during germination; however, hull removal resulted in a dramatic rise in its production. Overall, ethylene evolution at the radicle protrusion stage correlated negatively with germination time. It was concluded that ethylene production starts with breaking of the caryopsis coat and peaks when the radicle ruptures it completely, at the stage of radicle visible emergence. Removal of the hull facilitates germination and ethylene production can be a good indicator for the progress of germination.

Effect of chitosan coating on postharvest life and quality of plum during storage at low temperature

Abstract The effect of chitosan coating on the storage life and quality of ‘Santa Rosa’ plum was investigated. The plum fruits were treated with 2% chitosan coating and stored at 1 ± 1 °C under 90 ± 5% RH. During storage, observations on weight loss, fruit firmness, colour, rates of respiration and ethylene evolution, biochemical and quality attributes were recorded at weekly interval. Our experiment yielded that chitosan had a significant effect in maintaining fruit firmness (∼78%), retarding weight loss (∼52%), respiration and ethylene evolution rates and delaying the colour change as compared to non-coated fruits. Furthermore, at the end of 35 days of storage at low temperature, a significant reduction in pectin methylesterase activity (∼44%) and malondialdehyde production (∼21%) was observed. Similarly, anthocyanin content (∼24%) was significantly retarded in chitosan-coated ‘Santa Rosa’ plums. Thus, postharvest application of chitosan as an edible coating can effectively maintain the quality and extend the storage life of plum up to 35 days under low temperature storage condition.

Enological tannins affect acetaldehyde evolution, colour stability and tannin reactivity during forced oxidation of red wine

SummaryThe addition of enological tannins is a practice admitted and widely used to improve wine phenolic compositions. Although wine ageing is an oxidative process involving phenolic compounds and acetaldehyde production and consumption, the effect of enological tannins on the acetaldehyde and chromatic and phenolic changes of a red wine during oxidation is still not known. In this study, three enological tannins preparations containing gallotannins GT, ellagitannins ET and condensed tannins CT were added to a young commercial Lambrusco red wine in order to obtain wines with three different phenolic compositions. Samples were then treated with hydrogen peroxide to trigger oxidation. All added tannins have determined a production of acetaldehyde greater than control. Acetaldehyde was then consumed in 30 days. The samples treated with CT and ET showed, after oxidation, an increase in colour intensity, determined as the sum of 420, 520 and 620 nm absorbances. A simultaneously increase in polymeric pigments was detected. No significant variation of the Saliva Precipitation Index (SPI), an index useful to give an indirect measure of wine astringency, was observed after 30 days of treatment of CT and ET samples. Results highlight that the addition of CT and ET can help to stabilise colour without affecting wine reactivity towards salivary proteins. A significant role of acetaldehyde has been even detected. These are the first data showing the effect of different enological tannins on the production and consumption of acetaldehyde formation during an oxidation process.

Heat stress differentially modifies ethylene biosynthesis and signaling in pea floral and fruit tissues.

Ethylene biosynthesis is regulated in reproductive tissues in response to heat stress in a manner to optimize resource allocation to pollinated fruits with developing seeds. High temperatures during reproductive development are particularly detrimental to crop fruit/seed production. Ethylene plays vital roles in plant development and abiotic stress responses; however, little is known about ethylene's role in reproductive tissues during development under heat stress. We assessed ethylene biosynthesis and signaling regulation within the reproductive and associated tissues of pea during the developmental phase that sets the stage for fruit-set and seed development under normal and heat-stress conditions. The transcript abundance profiles of PsACS [encode enzymes that convert S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylic acid (ACC)] and PsACO (encode enzymes that convert ACC to ethylene), and ethylene evolution were developmentally, environmentally, and tissue-specifically regulated in the floral/fruit/pedicel tissues of pea. Higher transcript abundance of PsACS and PsACO in the ovaries, and PsACO in the pedicels was correlated with higher ethylene evolution and ovary senescence and pedicel abscission in fruits that were not pollinated under control temperature conditions. Under heat-stress conditions, up-regulation of ethylene biosynthesis gene expression in pre-pollinated ovaries was also associated with higher ethylene evolution and lower retention of these fruits. Following successful pollination and ovule fertilization, heat-stress modified PsACS and PsACO transcript profiles in a manner that suppressed ovary ethylene evolution. The normal ethylene burst in the stigma/style and petals following pollination was also suppressed by heat-stress. Transcript abundance profiles of ethylene receptor and signaling-related genes acted as qualitative markers of tissue ethylene signaling events. These data support the hypothesis that ethylene biosynthesis is regulated in reproductive tissues in response to heat stress to modulate resource allocation dynamics.