Reduced Ethylene Production Research Articles

Protective effects of 1-methylcyclopropene and salicylic acid on senescence regulation of gladiolus cut spikes

Reports indicate that senescence in cut flowers is accelerated. Therefore, the effects of 1-methylcyclopropene (1-MCP) or salicylic acid (SA) on the postharvest quality of gladiolus cut flowers and whether these treatments can regulate the flower senescence were investigated. Two concentrations of each 1-MCP (0.2 and 0.4gm−3) or SA (0.5 and 1mM) were studied. The control spikes were kept in distilled water. 1-MCP or SA treatments significantly prolonged the vase life and minimized the weight loss of gladiolus spikes compared with the control. Both treatments enhanced the relative water content (RWC) of leaves and maintained chlorophyll content compared with the control values, which were decreased. Ethylene production, proline accumulation and malondialdehyde content were increased in florets of untreated spikes. 1-MCP or SA reduced ethylene production, decreased both proline content and malondialdehyde level and hence maintained membrane stability. An increase in floret antioxidant enzyme activities (CAT, SOD and POX) was observed in 1-MCP- or SA-treated spikes compared with the control. The effects of 1-MCP or SA on floret senescence seemed not entirely limited due to their effects on ethylene, but they most likely had a sustainable impact on the above-tested physiological parameters.

Ethylene production in relation to nitrogen metabolism in Saccharomyces cerevisiae.

We have previously shown that ethylene production in Saccharomyces cerevisiae expressing the ethylene-forming enzyme (EFE) from Pseudomonas syringae is strongly influenced by variations in the mode of cultivation as well as the choice of nitrogen source. Here, we have studied the influence of nitrogen metabolism on the production of ethylene further. Using ammonium, glutamate, glutamate/arginine, and arginine as nitrogen sources, it was found that glutamate (with or without arginine) correlates with a high ethylene production, most likely linked to an observed increase in 2-oxoglutarate levels. Arginine as a sole nitrogen source caused a reduced ethylene production. A reduction of arginine levels, accomplished using an arginine auxotrophic ARG4-deletion strain in the presence of limiting amounts of arginine or through CAR1 overexpression, did however not correlate with an increased ethylene production. As expected, arginine was necessary for ethylene production as ethylene production in the ARG4-deletion strain ceased at the time when arginine was depleted. In conclusion, our data suggest that high levels of 2-oxoglutarate and a limited amount of arginine are required for successful ethylene production in yeast.

Precise spatio-temporal modulation of ACC synthase by MPK6 cascade mediates the response of rose flowers to rehydration.

Drought is a major abiotic stress that affects the development and growth of most plants, and limits crop yield worldwide. Although the response of plants to drought has been well documented, much less is known about how plants respond to the water recovery process, namely rehydration. Here, we describe the spatio-temporal response of plant reproductive organs to rehydration using rose flowers as an experimental system. We found that rehydration triggered rapid and transient ethylene production in the gynoecia. This ethylene burst serves as a signal to ensure water recovery in flowers, and promotes flower opening by influencing the expression of a set of rehydration-responsive genes. An in-gel kinase assay suggested that the rehydration-induced ethylene burst resulted from transient accumulation of RhACS1/2 proteins in gynoecia. Meanwhile, RhMPK6, a rose homolog of Arabidopsis thaliana MPK6, is rapidly activated by rehydration within 0.5h. Furthermore, RhMPK6 was able to phosphorylate RhACS1 but not RhACS2 in vitro. Application of the kinase inhibitor K252a suppressed RhACS1 accumulation and rehydration-induced ethylene production in gynoecia, and the protein phosphatase inhibitor okadaic acid had the opposite effect, confirming that accumulation of RhACS1 was phosphorylation-dependent. Finally, silencing of RhMPK6 significantly reduced ethylene production in gynoecia when flowers were subjected to rehydration. Taken together, our results suggest that temporal- and spatial-specific activation of an RhMPK6-RhACS1 cascade is responsible for rehydration-induced ethylene production in gynoecia, and that the resulting ethylene-mediated signaling pathway is a key factor in flower rehydration.

Quality deterioration of cut carnation flowers involves in antioxidant systems and energy status

Adenosine triphosphate (ATP) has played an important role in regulating senescence of horticultural crops. The physiological mechanism of exogenous ATP to affect the senescence of cut carnation during vase life was investigated. Fresh cut carnation flowers were treated with distilled water (control), 0.1mM adenosine triphosphate (ATP) or 0.5mM 2,4-dinitrophenol (DNP, an agent for uncoupling oxidative phosphorylation) and then held at 25°C up to nine days. Exogenous ATP supply increased flower size, maintained fresh weight, extended vase life, reduced ethylene production rate and maintained membrane integrity. ATP treatment also reduced activities of phospholipase D (LD) and lipoxygenase (LOX), enhanced activities of superoxide dismutase (SOD) and catalase (CAT) and increased endogenous contents of ATP and adenosine diphosphate (ADP) and energy charge level at the later vase life. In comparison to control, exogenous application of DNP accelerated ethylene production and reduced vase life, increased membrane permeability, MDA content and activities of PLD and LOX and reduced activities of SOD and CAT. Furthermore, contents of ATP and ADP and energy charge level decreased in the DNP-treated flowers during vase life. Thus, exogenous ATP supply could maintain membrane integrity, increase antioxidant system and improve endogenous energy level, thereby suppressing ethylene production and retarding the senescence of cut carnation flower during vase life.

A Petunia Homeodomain-Leucine Zipper Protein, PhHD-Zip, Plays an Important Role in Flower Senescence

Flower senescence is initiated by developmental and environmental signals, and regulated by gene transcription. A homeodomain-leucine zipper transcription factor, PhHD-Zip, is up-regulated during petunia flower senescence. Virus-induced gene silencing of PhHD-Zip extended flower life by 20% both in unpollinated and pollinated flowers. Silencing PhHD-Zip also dramatically reduced ethylene production and the abundance of transcripts of genes involved in ethylene (ACS, ACO), and ABA (NCED) biosynthesis. Abundance of transcripts of senescence-related genes (SAG12, SAG29) was also dramatically reduced in the silenced flowers. Over-expression of PhHD-Zip accelerated petunia flower senescence. Furthermore, PhHD-Zip transcript abundance in petunia flowers was increased by application of hormones (ethylene, ABA) and abiotic stresses (dehydration, NaCl and cold). Our results suggest that PhHD-Zip plays an important role in regulating petunia flower senescence.

Effects of 1-MCP and ethylene on postharvest quality and expression of senescence-associated genes in cut rose cv. Sparkle

The aim of this study was to investigate the effects of 1-methylcyclopropene (1-MCP) and ethylene on postharvest quality of cut rose ‘Sparkle’ and expression of Laccase and Aquaporins genes. Cut flowers were pre-treated with 0, 0.5 or 1μLL−1 of 1-MCP concentrations for 12h and subsequently exposed to 8μLL−1 of exogenous ethylene for 6h. Control treatment was received neither 1-MCP nor ethylene. Molecular study was carried out on petals of flowers pre-treated with 0 or 1μLL−1 1-MCP exposed to 8μLL−1 ethylene. The results showed that 1-MCP treatment did not have significant effects on flower diameter, relative fresh weight, solution uptake, and water loss, while it reduced ethylene production and chlorophyll degradation, and increased postharvest longevity. Control and ethylene treated cut stems revealed 2 days differences in postharvest longevity of ‘Sparkle’. 1-MCP suppressed the expression of all investigated genes except RhPIP1. The expression of RhLAC and RhTIP1 was induced by ethylene. Physiological and molecular data showed that this cultivar is sensitive to exogenous ethylene, while 1-MCP treatment inhibited ethylene's detrimental effects. Therefore, applying 1-MCP or other ethylene blocking agents are recommended as a postharvest treatment for extending the postharvest quality of cut rose ‘Sparkle’.

Involvement of ethylene biosynthesis and signalling in fruit set and early fruit development in zucchini squash (Cucurbita pepoL.)

BackgroundWe have identified a kind of parthenocarpy in zucchini squash which is associated with an incomplete andromonoecy, i.e. a partial conversion of female into bisexual flowers. Given that andromonoecy in this and other cucurbit species is caused by a reduction of ethylene production in the female flower, the associated parthenocarpic development of the fruit suggested the involvement of ethylene in fruit set and early fruit development.ResultsWe have compared the production of ethylene as well as the expression of 13 ethylene biosynthesis and signalling genes in pollinated and unpollinated ovaries/fruits of two cultivars, one of which is parthenocarpic (Cavili), while the other is non-parthenocarpic (Tosca). In the latter, unpollinated ovaries show an induction of ethylene biosynthesis and ethylene signal transduction pathway genes three days after anthesis, which is concomitant with the initiation of fruit abortion and senescence. Fruit set and early fruit development in pollinated flowers of both cultivars and unpollinated flowers of Cavili is coupled with low ethylene biosynthesis and signalling, which would also explain the partial andromonoecy in the parthenocarpic genotype. The reduction of ethylene production in the ovary cosegregates with parthenocarpy and partial andromonoecy in the selfing progeny of Cavili. Moreover, the induction of ethylene in anthesis (by ethephon treatments) reduced the percentage of bisexual parthenocarpic flowers in Cavili, while the inhibition of ethylene biosynthesis or response (by AVG and STS treatments) induces not only andromonoecy but also the parthenocarpic development of the fruit in both cultivars.ConclusionsResults demonstrate that a reduction of ethylene production or signalling in the zucchini flower is able to induce fruit set and early fruit development, and therefore that ethylene is actively involved in fruit set and early fruit development. Auxin and TIBA treatments, inducing fruit set and early fruit development in this species, also inhibit ethylene production and the expression of ethylene biosynthesis and response genes. A model is presented that discusses the crosstalk between ethylene and auxin in the control of fruit set and early fruit development in zucchini squash.

Increased 1‐aminocyclopropane‐1‐carboxylate deaminase activity enhances Agrobacterium tumefaciens‐mediated gene delivery into plant cells

Agrobacterium-mediated transformation is a useful tool for the genetic modification in plants, although its efficiency is low for several plant species. Agrobacterium-mediated transformation has three major steps in laboratory-controlled experiments: the delivery of T-DNA into plant cells, the selection of transformed plant cells, and the regeneration of whole plants from the selected cells. Each of these steps must be optimized to improve the efficiency of Agrobacterium-mediated plant transformation. It has been reported that increasing the number of cells transformed by T-DNA delivery can improve the frequency of stable transformation. Previously, we demonstrated that a reduction in ethylene production by plant cells during cocultivation with A. tumefaciens-expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase resulted in increased T-DNA delivery into the plant cells. In this study, to further improve T-DNA delivery by A. tumefaciens, we modified the expression cassette of the ACC deaminase gene using vir gene promoter sequences. The ACC deaminase gene driven by the virD1 promoter was expressed at a higher level, resulting in a higher ACC deaminase activity in this A. tumefaciens strain than in the strain with the lac promoter used in a previous study. The newly developed A. tumefaciens strain improves the delivery of T-DNA into Solanum lycopersicum (tomato) and Erianthus ravennae plants and thus may be a powerful tool for the Agrobacterium-mediated genetic engineering of plants.

Putative role of cytokinin in differential ethylene response of two lines of antisense ACC oxidase cantaloupe melons

Two transgenic lines of ‘Cantaloupe’ melon derived from the same wild type genotype were previously generated using ACC oxidase antisense constructs from melon (pMEL1AS) and apple (pAP4AS). Both lines yielded fruit with reduced ethylene production and low ACC oxidase (ACCO) expression. ACCO antisense fruit also exhibited lower expression of ACC synthase genes, ACCS1 and ACCS3, indicating that these genes are positively regulated by ethylene and participate in the autocatalytic ethylene production process. In contrast, a higher expression of ACCS5 was observed in antisense lines when compared to the wild type indicating a negative feedback regulation of ACCS5 by ethylene. Fruit of both transformed lines exhibited delayed ripening and reduction in ester volatile production but differed in their response to exogenous ethylene supply. While postharvest ethylene application fully restored the ripening process in pMEL1AS melon, it only restored flesh softening of pAP4AS melon but not rind color change or aroma volatile production. Up-regulation of lipoxygenase pathway associated genes (hydroxyperoxide lyase, lipoxygenase, and alcohol acyl transferases 1, 3 and 4) occurred in ethylene-treated pMEL1AS fruit but not in pAP4AS melons. Polygalacturonase1 gene transcript accumulation increased in pMEL1AS and pAP4AS fruit upon ethylene supply. Zeatin and zeatin riboside content of roots and fruit (rind and flesh) of pAP4AS plants were 5-fold higher than the wild type and pMEL1AS counterparts. Higher relative transcript accumulation of a gene involved in the cytokinin synthesis and a gene involved in cytokinin response were also found in the roots and fruit of pAP4AS. In addition, polyamines, which are known to reduce sensitivity to ethylene, remained unchanged in all fruit. Collectively the results suggest a putative role for the increased endogenous cytokinin content in counteracting ethylene action in some aspects of the fruit ripening process.

Differential Suppression of Ethylene Biosynthesis and Receptor Genes in ‘Golden Delicious’ Apple by Preharvest and Postharvest 1-MCP Treatments

Harvista™, a sprayable formulation of 1-methylcyclopropene (1-MCP), has recently been developed for preharvest use on horticultural products, whereas SmartFresh™ is a widely used 1-MCP treatment for products after harvest. The effects of Harvista™ on apple fruit ripening when sprayed at different maturities and on expression patterns of ethylene biosynthesis and receptor genes during storage have been investigated. Harvista™ applied to on-tree maturing apple fruit at an average starch pattern index of 2.5 resulted in a higher at-harvest firmness value compared with those treated at a starch pattern index of 1.5 and 3.5. This indicates that the timing of the Harvista™ application is critical. An application of Harvista™ led to better postharvest fruit firmness retention as well as reduced ethylene production. In addition, both preharvest and postharvest 1-MCP treatments resulted in contrasting responses in the expression patterns of two ethylene biosynthesis genes and in differentially suppressing effects on four ethylene receptor genes. Furthermore, the combined application of Harvista™ + SmartFresh™ resulted in greater fruit firmness retention and longer ethylene suppression. The expression profiles of these genes during on-tree fruit maturation prior to Harvista™ application were also characterized. Different regulation patterns of receptor genes could contribute to differential effects by 1-MCP treatments. The potential roles of Harvista™ to manipulate the ripening process as well as the molecular mechanism influencing 1-MCP treatment efficacy are discussed.

Efficiency of Essential Oils, Citric Acid, Malic Aid and Nickel Reduced Ethylene Production and Extended Vase Life of Cut Lisianthus Flowers

Efficiency of Essential Oils, Citric Acid, Malic Aid and Nickel Reduced Ethylene Production and Extended Vase Life of Cut Lisianthus Flowers

Effect of hypobaric storage on flesh lignification, active oxygen metabolism and related enzyme activities in bamboo shoots

Freshly harvested bamboo (Phyllostachys violascens) shoots were stored for 35 days under various hypobaric conditions (101, 75, 50 and 25 kPa) at 2 ± 1 °C to investigate the effects of hypobaric storage on flesh lignifications. It was found that hypobaric storage at 50 kPa was most effective in preventing the increase in shoots firmness and allied accumulations of lignin and cellulose. Furthermore, the hypobaric storage at 50 kPa inhibited the ethylene production, reduced the rate of O2·− production and the accumulation of malondialdehyde (MDA) and H2O2, and maintained significantly higher activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), but restrained the activities of phenylalanine ammonia-lyase (PAL) and peroxidase (POD). These data indicate that the delay in flesh lignification of bamboo shoots by hypobaric storage was due to maintenance of higher antioxidant enzymes activities and reduced ethylene production, leading to less ROS accumulation and better cell-membrane integrity.

Potential of Initial CA Condition on Quality Maintenance of 'Fuji' Apples during Export Simulation after Long-term Storage

Effects of initial controlled atmosphere (CA) treatment on quality maintenance of ‘Fuji’ apples were assessed and compared with 1-methylcyclopropene (1-MCP) treatment and continuous CA storage. Apples were harvested twice at different maturity, treated with 1 μLㆍL -1 1-MCP and then stored for 8 months at 0℃ under 3 conditions: air, CA for the first month followed by air (initial CA), and continuous CA (full CA). CA storage was performed with 1.5 ㎪ O₂ and ＜1.0 ㎪ (N₂ balance). Following long-term storage, export simulation, refrigerated shipment and local distribution, were performed by holding apples at 0℃ for 2 weeks and on the shelf at 20℃ for 7 days. Both the application of 1-MCP and CA storage reduced ethylene production and respiration rates. Initial CA storage was also effective on reducing the metabolism although the effects were not as noticeable as full CA. Full CA storage with or without 1-MCP treatment maintained titratable acidity, flesh firmness, and sensory quality at the acceptable to excellent level even after the export simulation following 8-month storage regardless of harvest maturity. In contrast, effects of initial CA storage were limited to the maintenance of firmness and texture in early-harvested apples. Overall results indicated that harvest maturity is the critical factor for export fruit quality after long-term storage when separate treatment of initial CA storage or 1-MCP treatment is applied as a postharvest program.

Postharvest Polyamine Application Alleviates Chilling Injury and Affects Apricot Storage Ability

Fruit of two apricot cultivars 'Bagheri' and 'Asgarabadi' were treated with putrescine (Put) or spermidine (Spd) at 1 mM and then were stored at 1 °C for 21 days. Fruit were sampled weekly and stored 2 days at 20 °C for shelf-life study. The treatments reduced ethylene production and maintained the firmness and color of the fruit. Peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), and polyphenol oxidase (PPO) activities and total phenol (TP) concentrations were measured during storage. Both cultivars showed chilling injury (CI) incidence, and the severity in control fruit was higher than either Put or Spd treatments. CI incidence in Spd-treated fruit was lower than that of Put-treated fruit. Polyamine (PA) treatment generally increased antioxidant enzyme activity of fruit during storage. PA treatments may help maintain the quality of apricot fruit during storage by inhibiting ripening and decreasing CI incidence.

Aplicação de 1-metilciclopropeno, estresse inicial com baixo oxigênio e armazenamento em ultrabaixo oxigênio na qualidade de maçã Fuji

O objetivo deste trabalho foi avaliar o efeito da aplicação de 1-MCP em combinação com condições de estresse inicial com baixo O2 e armazenamento em atmosfera controlada com pressões parciais ultrabaixas de O2 sobre a manutenção da qualidade de maçãs Fuji. Os tratamentos avaliados foram com e sem aplicação de 1-MCP (1.000nL L-1), combinado com cinco níveis do fator condição de armazenamento (sem estresse inicial + 0,6kPa O2, 1 estresse + 0,6kPa O2, 1 estresse + 0,8kPa O2, 2 estresses + 0,6kPa O2 e sem estresse inicial + 1,0kPa O2). Cada estresse inicial foi com 0,2kPa de O2 pelo período de 14 dias. Os frutos foram armazenados nessas condições durante oito meses a -0,5°C±0,2°C e UR de 96±1%, mais sete dias de exposição a 20±1°C. Em todos os tratamentos, o CO2 foi mantido abaixo de 0,5kPa. O armazenamento sem estresse inicial por baixo O2 associado a 1,0kPa ou 0,6kPa de O2 manteve a polpa mais firme e com maior acidez titulável. Além disso, proporcionou menor ocorrência de podridão após oito meses de armazenamento mais sete dias a 20°C. O 1-MCP proporcionou menor atividade da enzima ACC oxidase, no entanto, não foi eficiente para a redução da produção de etileno e para retardar a perda da firmeza e a ocorrência de podridão. O estresse inicial de 14 dias com 0,2kPa de O2 prejudicou a conservação de maçãs Fuji.

NAA and STS effects on potted bougainvillea: Early flower death allows delayed bract abscission

The effects of silver thiosulfate (STS) and naphthalene acetic acid (NAA) (0.45% NAA+1.2% NAA-amide at 500mgL−1) on flowering bud development, anthesis duration, bract longevity, and bract photosynthetic rate were studied in Bougainvillea spectabilis ‘Killie Campbell’ plants, under interior conditions. The relationships between bract longevity and the above parameters were also investigated.NAA induced longer bract longevity, shorter flower anthesis duration, and lower percentage of flowers reaching anthesis. STS alone increased duration of flower anthesis but did not affect completely developed bract abscission, as compared to the water treatment. Depending on the experiment, adding STS to NAA delayed or had no effect on bract abscission. Longer bract longevity was related to shorter flower anthesis and lower percentage of flowers reaching anthesis. Manual removal of flowers from the bract+flower unit increased bract longevity. Despite the low level of irradiance, bracts photosynthesized and plants treated with NAA (alone or with STS) had lower bract photosynthetic rates. Bract photosynthetic activity, although with relevant rates (similar to leaves and most probably capable of covering respiration expenditure) did not seem important as an energy source for bract longevity since bracts that lasted longer had lower photosynthetic rates. In the water control, percentage of flowers reaching anthesis positively correlated with bract photosynthetic rates.In potted bougainvillea under low light conditions, flower senescence and bract abscission are under different types of control. In addition to the classical effect of auxin reducing ethylene production, and/or sensitivity of the abscission zone to ethylene, NAA delays bougainvillea bract abscission via early interruption of flower development.

Qualidade pós-colheita de quivi 'Hayward' tratado com 1-MCP e armazenado sob diferentes atmosferas

Este trabalho teve por objetivo avaliar o efeito do 1-MCP sobre o amadurecimento e a qualidade pós-colheita de quivi 'Hayward' armazenado sob diferentes atmosferas. Foram conduzidos dois experimentos, com frutos colhidos em pomar comercial localizado em Fraiburgo-SC. No experimento 1, os frutos foram tratados com três doses de 1-MCP (0,0; 0,5 ou 1,0 µL L-1) e armazenados sob atmosfera controlada (AC, contendo 2,0kPa de O2 + 4,5kPa de CO2, a 0ºC ± 0,5ºC, 92 ± 3% UR, e com <40 ηL L-1 de etileno no ambiente), durante 90 e 120 dias, mais sete dias de vida de prateleira a 23ºC. No experimento 2, os frutos foram tratados com 0,0 ou 0,7 µL L-1 de 1-MCP e armazenados sob atmosfera ambiente (AA, contendo 21 kPa de O2 + 0,03 kPa de CO2, a 0 ± 0,5ºC, 90 ± 3% UR, e com 200 a 250 ηL L-1 de etileno no ambiente, durante 30, 60, 90 e 120 dias, mais um e sete dias de vida de prateleira a 23ºC) ou AC (contendo 2,0 kPa de O2 + 4,5 kPa de CO2, a 0ºC ± 0,5ºC, 92 ± 3% UR, e com <40 ηL L-1 de etileno no ambiente, durante 60, 90, 120 e 150 dias, mais um e sete dias de vida de prateleira a 23ºC). Os benefícios do tratamento com 1-MCP sobre a conservação da qualidade foram observados tanto para frutos armazenados sob AA quanto sob AC. No experimento 1, não houve diferença entre as doses de 1-MCP de 0,5 e 1,0 µL L-1 sobre o controle do amadurecimento e manutenção da qualidade dos frutos armazenados em AC. No experimento 2, o tratamento com 1-MCP retardou o aumento na taxa de produção de etileno após remoção de câmara fria. A redução da taxa de produção de etileno nos frutos tratados com 1-MCP foi associada ao aumento na conservação da firmeza da polpa sob AC e AA, e redução na incidência de pericarpo translúcido sob AA. O potencial de armazenamento foi aumentado pelo tratamento com 1-MCP em aproximadamente 60 e 30 dias, nos frutos armazenados sob AA e AC, respectivamente.

Spermidine application to young developing peach fruits leads to a slowing down of ripening by impairing ripening‐related ethylene and auxin metabolism and signaling

Peach (Prunus persica var. laevis Gray) was chosen to unravel the molecular basis underlying the ability of spermidine (Sd) to influence fruit development and ripening. Field applications of 1 mM Sd on peach fruit at an early developmental stage, 41 days after full bloom (dAFB), i.e. at late stage S1, led to a slowing down of fruit ripening. At commercial harvest (125 dAFB, S4II) Sd-treated fruits showed a reduced ethylene production and flesh softening. The endogenous concentration of free and insoluble conjugated polyamines (PAs) increased (0.3-2.6-fold) 1 day after treatment (short-term response) butsoon it declined to control levels; starting from S3/S4, when soluble conjugated forms increased (up to five-fold relative to controls at ripening), PA levels became more abundant in treated fruits, (long-term response). Real-time reverse transcription-polymerase chain reaction analyses revealed that peaks in transcript levels of fruit developmental marker genes were shifted ahead in accord with a developmental slowing down. At ripening (S4I-S4II) the upregulation of the ethylene biosynthetic genes ACO1 and ACS1 was dramatically counteracted by Sd and this led to a strong downregulation of genes responsible for fruit softening, such as PG and PMEI. Auxin-related gene expression was also altered both in the short term (TRPB) and in the long term (GH3, TIR1 and PIN1), indicating that auxin plays different roles during development and ripening processes. Messenger RNA amounts of other hormone-related ripening-regulated genes, such as NCED and GA2-OX, were strongly downregulated at maturity. Results suggest that Sd interferes with fruit development/ripening by interacting with multiple hormonal pathways.

방울토마토의 호흡 및 에틸렌 발생에 미치는 자외선 LED의 효과

경남대학교 정보통신학과UV light irradiation is known to give beneficial effects on fresh produce preservation. A container system equipped with UV-LED was fabricated for storing cherry tomatoes under computer-controlled conditions of intermittent on-off cycles (1 hour on/1 hour off). Wavelength (365 and 405 nm) and physical location of the LED (2 and 5 cm above fruit) were studied as variables affecting the respiration, ethylene production and quality preservation of the fruits at 10 and 20. 365 nm wavelength gave much higher radiation intensity than 405 nm, and intensity on surface decreased in inverse proportion to square of distance from LED. When compared to non-irradiated control, UV-LED irradiation decreased the respiration by 5-10% at 10while there was no obvious effect at 20. Ethylene production was reduced when the fruits were placed at 5 cm distance, while there was no significant difference from control at 2 cm location. The reduction of ethylene production at 5 cm was more pronounced at 20. UV-LED irradiation was shown to have delayed increase or lower concentration in carotenoids compared to control treatment. Any negative effect of UV-LED irradiation on ascorbic acid content and firmness was not observed.Key wordscherry tomato, UV-LED, respiration, ethylene, quality

Longkong fruit abscission and its control

Longkong fruit abscission was found to be sensitive to external ethylene at concentrations as low as 0.05 μL L −1. Ethylene induced fruit drop at the junction between the main peduncle and the calyx, at a clear abscission zone. Fruit drop at the junction between calyx and the fruit, however depended on an external force. There may or may not be an abscission zone at this site. Dipping longkong fruit in 200 μL L −1 NAA solution delayed fruit abscission and slightly reduced ethylene production. NAA application was also found to reduce the effect of external ethylene treatment. Applications of 1 μL L −1 1-MCP for 6 h minimized the effect of external ethylene and almost doubled storage life of longkong. The combination of NAA and 1-MCP treatment did not give a synergistic effect.