Inhibitor Of Ethylene Action Research Articles

Postharvest Longevity and Responsiveness of Guava Varieties with Distinctive Climacteric Behaviors to 1-Methylcyclopropene

The local guava (Psidium guajava) variety cultivated in Israel, named Ben Dov, emits a strong odor and suffers from a short postharvest life. To address these problems, we initiated a guava breeding program, and identified two new varieties, the pink-flesh King and the white/yellowish-flesh Omri, that have much better storage lives and emit fewer odors. Physiological characterization of their ripening process revealed that the traditional variety Ben Dov exhibited a classic climacteric behavior, whereas the new variety King had a suppressed-climacteric phenotype, and Omri was apparently nonclimacteric and did not exhibit any increases in respiration and ethylene production rates during ripening. Furthermore, differing concentrations of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were required to inhibit ripening in the various varieties: a high 1-MCP concentration of 500 nL·L−1 was required to delay ripening and to prolong postharvest storage life of the climacteric variety Ben Dov; a moderate concentration of 250 nL·L−1 inhibited ripening of the suppressed-climacteric variety King; and a low concentration of just 100 nL·L−1 was sufficient to inhibit ripening of the nonclimacteric variety Omri. The results of this study indicate that different guava varieties may pursue distinctive climacteric behaviors: the suppressed-climacteric variety and, to a greater extent, the nonclimacteric variety, have longer storage lives and are more sensitive to 1-MCP than the traditional variety.

Postharvest Longevity and Responsiveness of Guava Varieties with Distinctive Climacteric Behaviors to 1-Methylcyclopropene

The local guava (Psidium guajava) variety cultivated in Israel, named Ben Dov, emits a strong odor and suffers from a short postharvest life. To address these problems, we initiated a guava breeding program, and identified two new varieties, the pink-flesh King and the white/yellowish-flesh Omri, that have much better storage lives and emit fewer odors. Physiological characterization of their ripening process revealed that the traditional variety Ben Dov exhibited a classic climacteric behavior, whereas the new variety King had a suppressed-climacteric phenotype, and Omri was apparently nonclimacteric and did not exhibit any increases in respiration and ethylene production rates during ripening. Furthermore, differing concentrations of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were required to inhibit ripening in the various varieties: a high 1-MCP concentration of 500 nL·L−1 was required to delay ripening and to prolong postharvest storage life of the climacteric variety Ben Dov; a moderate concentration of 250 nL·L−1 inhibited ripening of the suppressed-climacteric variety King; and a low concentration of just 100 nL·L−1 was sufficient to inhibit ripening of the nonclimacteric variety Omri. The results of this study indicate that different guava varieties may pursue distinctive climacteric behaviors: the suppressed-climacteric variety and, to a greater extent, the nonclimacteric variety, have longer storage lives and are more sensitive to 1-MCP than the traditional variety.

Isolation of Rh-TIP1;1, an aquaporin gene and its expression in rose flowers in response to ethylene and water deficit

Flower opening is a process that involves water uptake by petal cells, during which aquaporins serve as the channels for water transport across the cell membranes. In this study, we isolated a TIP type aquaporin gene, Rh-TIP1;1, from rose ( Rosa hybrida cv. Samantha). The Rh-TIP1;1 transcript is 1142 bp in length and encodes a deduced protein of 253 amino acids. Through a prokaryotic expression system, we obtained a predominant ∼32 kDa protein band which is consistent with the predicted molecular weight of Rh-TIP1;1. Rh-TIP1;1 was mainly expressed in petals among all floral tissues at the fully opened bud stage. Its expression was maintained at a high level during rapid flower opening, and decreased when the flowers were fully opened. Ethylene and water deficit both decreased the expression of Rh-TIP1;1. Flowers treated with 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, maintained the transcript at a high level for longer than untreated controls. These results indicated that the effects of ethylene and water deficit on flower opening may be related to their influence on the expression of the Rh-TIP1;1 gene.

Exogenous ethylene inhibits sprout growth in onion bulbs

Exogenous ethylene has recently gained commercial interest as a sprouting inhibitor of onion bulbs. The role of ethylene in dormancy and sprouting of onions, however, is not known. A cultivar (Allium cepa 'Copra') with a true period of dormancy was used. Dormant and sprouting states of onion bulbs were treated with supposedly saturating doses of ethylene or with the ethylene-action inhibitor 1-methylcyclopropene (1-MCP). Initial sprouting was determined during storage at 18 degrees C by monitoring leaf blade elongation in a specific size class of leaf sheaths. Changes in ATP content and sucrose synthase activity in the sprout leaves, indicators of the sprouting state, were determined. CO(2) and ethylene production of onion bulbs during storage were recorded. Exogenous ethylene suppressed sprout growth of both dormant and already sprouting onion bulbs by inhibiting leaf blade elongation. In contrast to this growth-inhibiting effect, ethylene stimulated CO(2) production by the bulbs about 2-fold. The duration of dormancy was not significantly affected by exogenous ethylene. However, treatment of dormant bulbs with 1-MCP caused premature sprouting. Exogenous ethylene proved to be a powerful inhibitor of sprout growth in onion bulbs. The dormancy breaking effect of 1-MCP indicates a regulatory role of endogenous ethylene in onion bulb dormancy.

Effect of 1-methylcyclopropene on expression of genes for ethylene biosynthesis enzymes and ethylene receptors in post-harvest broccoli

The effects of 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, on the senescence of broccoli (Brassica oleracea, L. var. italica) after harvest were studied, and its possible molecular mechanism was discussed. The results showed that 1-MCP treatment delayed the yellowing of broccoli florets, inhibited the activities of 1-aminocyclopropane-1-carboxylate acid (ACC) oxidase (ACO), and delayed the peaks in the ACC synthase (ACS) activity and ACC concentration. In addition, exogenous ethylene treatment did not accelerate yellowing in the florets pretreated with 1-MCP. The gene expression pattern of enzymes involved in ethylene biosynthesis and ethylene receptors in broccoli florets after harvest was investigated. 1-MCP treatment significantly decreased the expression of BO-ACS1, BO-ACS2, BO-ACO1, BO-ERS, BO-ETR1 and BO-ETR2. 1-MCP delayed the senescing process of broccoli by inhibiting the activities of enzymes involved in ethylene biosynthesis and gene expression of these enzymes and of ethylene receptors at the transcript level.

The effect of dialkylamine compounds and related derivatives of 1-methylcyclopropene in counteracting ethylene responses in banana fruit

Compounds that can block the ethylene receptor and be applied either as a gas or as a salt by spray or dip have been prepared and tested. Cyclopropenes with a methyl group in the 1-position, on which was attached a substituted amine, were allowed to evaporate in the presence of bananas that were treated with the gas. The minimum amount of a given compound required to inhibit chlorophyll degradation in the banana peel (an indicator of protective effect of the compound against ethylene action) that was subsequently exposed to ethylene, varied considerably depending on the compound, but N, N-dipropyl-(1-cyclopropenylmethyl)amine and N, N-di-(1-cyclopropenylmethyl)amine were the most effective. The degree of response to the ethylene inhibitory effect was similar for all of the compounds tested (32–34 d). The amount of cyclopropene compound required for inhibiting ethylene action following a 24 h exposure of bananas to the salt followed by a 15 h exposure to ethylene was higher than that required by the gas form used under the same conditions for the same effect. However, time of exposure could be much longer than 24 h with the salt than with the gas. The bananas treated with the salt do not need to be in an air-tight container, but could be used in open spaces. Only the banana peel appeared to be protected against ethylene during the 24 h interval when the salt was used. The pulp ripened upon exposure to ethylene.

Ethylene and rooting of mung bean cuttings. The role of auxin induced ethylene synthesis and phase-dependent effects

We have re-examined the role of ethylene during rooting of mung bean cuttings. Cuttings were treated for 5 days with a low or a high concentration of NAA (naphthaleneacetic acid). During this 5 days period, we also applied STS (silverthiosulfate, an inhibitor of ethylene action) or ACC (1-aminocyclo-propane-l-carboxylic acid, a direct precursor of ethylene). At high NAA concentration, STS promoted and ACC inhibited rooting, respectively. At low NAA concentration, the effects were opposite, STS being inhibitory and ACC promotive. AVG (aminoethoxyvinylglycine, an inhibitor of ethylene synthesis) gave similar results as STS. Together, these data suggest supraoptimal and suboptimal ethylene levels in the tissue at high and low NAA concentration, respectively. We also examined whether the effect of ethylene varied during the successive phases of the rooting process. Thus, we gave 24 h pulses with either STS or ACC during the rooting treatment. During the first two days (0–48 h), ACC-pulses were promotive and STS-pulses inhibitory. Later on (48–168 h), the ACC-pulses were inhibitory and the STS-pulses promotive. Whether this effect was observed or not was dependent on the NAA concentration. These data indicate that ethylene promotes or inhibits rooting depending on the stage in the rooting process. When ACC was added only during the initial period, rooting was increased at all NAA concentrations in a NAA dose-response curve and the optimal NAA concentration remained the same. This suggests that ethylene renders more cells responsive to NAA.

1-Methylcyclopropene treatment modifies postharvest behavior of Fantasia nectarines

The effects of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, on the ripening and quality of Fantasia nectarines were examined. Fruit were harvested from two commercial orchards and subsequently exposed to 1 μL L-1 of 1-MCP for 24 h at 0°C. Following treatment, fruit were held at 0°C for 0, 2, or 4 wk, and then assessed for quality during a ripening period at 23°C. 1-MCP treatment improved postharvest firmness retention in nectarines after 0 and 2 wk at 0°C plus 4 days at 23°C. Soluble solids concentration (SSC) was lower in nectarines treated with 1 MCP and held for 0 or 4 wk at 0°C, compared with similar non-treated fruit. The peel ground color change from green to yellow was also delayed by 1-MCP. Nectarines treated with 1-MCP exhibited less CO2 and hydrophobic volatile production during 14 days at 23°C, compared with non-treated fruit. The overall inhibition of fruit ripening by 1-MCP appears transitory in Fantasia nectarines. Chilling injury was observed after 4 wk of storage at 0°C and 1-MCP-treated fruit had less visual chilling-related injury but greater chilling-induced flesh hardening. Further research is needed to determine the effects of 1-MCP on different chilling injury symptoms in nectarines. Key words: 1-MCP, fruit quality, ripening, storage, shelf-life, Prunus persica

Ethylene and ABA interactions in the regulation of flower induction in Pharbitis nil

Hormones are included in the essential elements that control the induction of flowering. Ethylene is thought to be a strong inhibitor of flowering in short day plants (SDPs), whereas the involvement of abscisic acid (ABA) in the regulation of flowering of plants is not well understood. The dual role of ABA in the photoperiodic flower induction of the SDP Pharbitis nil and the interaction between ABA and ethylene were examined in the present experiments. Application of ABA on the cotyledons during the inductive 16-h-long night inhibited flowering. However, ABA application on the cotyledons or the shoot apices during the subinductive 12-h-long night resulted in slight stimulation of flowering. Application of ABA also resulted in enhanced ethylene production. Whereas nordihydroguaiaretic acid (NDGA) - an ABA biosynthesis inhibitor - applied on the cotyledons of 5-d-old seedlings during the inductive night inhibited both the formation of axillary and of terminal flower buds, application of 2-aminoethoxyvinylglycine (AVG) and 2,5-norbornadiene (NBD) - inhibitors of ethylene action - reversed the inhibitory effect of ABA on flowering. ABA levels in the cotyledons of seedlings exposed to a 16-h-long inductive night markedly increased. Such an effect was not observed when the inductive night was interrupted with a 15-min-long red light pulse or when seedlings were treated at the same time with gaseous ethylene during the dark period. Lower levels of ABA were observed in seedlings treated with NDGA during the inductive night. These results may suggest that ABA plays an important role in the photoperiodic induction of flowering in P. nil seedlings, and that the inhibitory effect of ethylene on P. nil flowering inhibition may depend on its influence on the ABA level. A reversal of the inhibitory effect of ethylene on flower induction through a simultaneous treatment of induced seedlings with both ethylene and ABA strongly supports this hypothesis.

Diphenylamine Metabolism in ‘Braeburn’ Apples Stored under Conditions Conducive to the Development of Internal Browning

Diphenylamine metabolism and ethylene action were evaluated as factors influencing the development of 'Braeburn' apple internal browning and cavitation during cold storage. Apples treated with the antioxidant diphenylamine (DPA) and/or the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were held at 1 degrees C for up to 6 months in air or a controlled atmosphere (CA) containing 1 kPa of O2 and 3 kPa of CO2. Cortex tissues from fruit without disorders as well as from symptomatic and asymptomatic areas of fruit with disorders were analyzed for DPA and DPA derivative content. Internal browning and cavities developed in control and 1-MCP-treated fruit stored in CA, whereas air-stored and CA fruit treated with DPA or with DPA and 1-MCP prior to storage did not develop disorders. Depending on the storage regimen and duration, less DPA was detected in 1-MCP-treated fruit. The 4-hydroxydiphenylamine (4OHDPA) content of control fruit decreased during air storage duration but increased between 2 and 4 months in CA storage. 4OHDPA content in 1-MCP-treated fruit increased with storage duration in CA but not air. N-Nitrosodiphenylamine (NODPA) was detected after 2 months in control fruit stored in air or CA and in 1-MCP-treated fruit stored in CA, and NODPA content in control fruit was higher compared to that in 1-MCP-treated fruit. Accumulation of 4-methoxydiphenylamine (4MeODPA) in control fruit stored in air increased with storage duration, but 4MeODPA content did not change in 1-MCP-treated fruit stored in air or CA. 2-Nitrodiphenylamine content was reduced by prestorage treatment with 1-MCP, but storage environment and duration had no effect on its accumulation. The results indicate that CA storage increases the risk of disorder development in 'Braeburn' apples, that DPA can prevent disorder development, and that the content of DPA and DPA derivatives is influenced by storage environment and ethylene action. A clear relationship between DPA derivative formation and storage conditions that promote internal browning was not apparent.

Ethylene Receptor Antagonists: Strained Alkenes Are Necessary but Not Sufficient

Plants use ethylene as a hormone to control many physiological processes. Ethylene perception involves its binding to an unusual copper-containing, membrane-bound receptor. Inhibitors of ethylene action are valuable to study signaling and may have practical use in horticulture. Past investigation of alkene ligands for this receptor has identified strain as the key factor in antagonism of ethylene binding and action, consistent with known trends in metal-alkene complex stability. However, in this work, this principle could not be extended to other alkenes, prompting development of the proposal that a ring-opening reaction accounts for the unusual potency of cyclopropene ethylene antagonists. Another factor augmenting the affinity of alkenes for the copper binding site is pyramidalization, as in trans-cycloalkenes. The enantiomeric selectivity in the binding of one such alkene to the ethylene receptor demonstrates its protein-composed asymmetric environment.

Postharvest Senescence and Deterioration of ‘Thoroughbred’ and ‘Carlo’ Green Beans (Phaseolus vulgaris L.) in Response to 1-Methylcyclopropene

Nonclimacteric commodities produce low levels of ethylene yet remain quite sensitive to the growth regulator. 1-Methylcyclopropene (1-MCP; SmartFresh Quality System), an inhibitor of ethylene action, allows analysis of the effects of endogenous ethylene on the senescence of nonclimacteric commodities during storage. Two commercial cultivars (Thoroughbred and Carlo) of fresh green beans (Phaseolus vulgaris L.) were treated with 0.5 μL·L−1 1-MCP followed by storage at 7 °C. 1-MCP was effective in delaying color change, brown spot incidence, and watersoaking in both cultivars. 1-MCP was effective at delaying yellowing as indicated by a decline in surface hue and chroma; however, lightness was not significantly different between control and 1-MCP-treated beans. Respiration in both cultivars was suppressed, but ethylene production was stimulated late during storage in response to 1-MCP. The appearance of brown spot, a surface disorder possibly reflecting low-temperature injury, was delayed by ≈5 days, and the progression of the disorder was reduced in 1-MCP-treated beans. The incidence of watersoaking in ‘Carlo’ was reduced by 50% in 1-MCP-treated compared with control beans. 1-MCP alleviated symptoms of senescence and chill injury of green beans during long-term storage, implicating a role for endogenous ethylene in the senescence of nonclimacteric commodities after harvest.

Storage Life and Deterioration of Intact Cantaloupe (Cucumis melo L. var. reticulatus) Fruit Treated with 1-Methylcyclopropene and Fresh-cut Cantaloupe Prepared from Fruit Treated with 1-Methylcyclopropene Before Processing

A study was conducted to determine the influence of the ethylene action inhibitor, 1-methylcyclopropene (1-MCP), on the shelf life and deterioration during storage at 5 °C of intact netted muskmelon (Cucumis melo L. var. reticulatus) fruit and fresh-cut cubes prepared from those fruit. ‘Durango’, ‘Magellan’, and ‘7920’ fruit (3/4 to full-slip stage) were treated with 1-MCP (1.0 μL·L−1) for 24 h at 20 °C. Preliminary research with ‘Athena’ muskmelon had shown that the more physiologically advanced distal pericarp tissue developed significantly more watersoaking than the less advanced proximal and center portions during 5 °C storage; therefore, after treatment with 1-MCP and cooling to 5 °C, the center portions of the fruit were used to prepare the fresh-cut samples. Fresh-cut cubes and intact fruit were stored for 12 d at 5 °C. Intact fruit of all tested cultivars responded to 1-MCP application with improved firmness retention during storage, but no watersoaking was observed in intact fruit. The effect of 1-MCP treatment on the firmness retention and watersoaking of fresh-cut cubes from the different cultivars was inconsistent. Exposure of muskmelon fruit to 1-MCP did not significantly influence the flesh color or soluble solid contents of either intact fruit or fresh-cut cubes during storage at 5 °C.

Assessment of the potency of 1-substituted cyclopropenes to counteract ethylene-induced processes in plants

A study was undertaken to assess the potency of 1-methylcyclopropene (1-MCP) analogues to block the ethylene receptor and thereby inhibit ethylene action. Eight structural analogues of 1-MCP with substitution in the 1-position and a side chain containing 2–10 carbons were synthesized and their potency to inhibit ethylene-induced plant processes was tested on climacteric fruit like avocado, and tomato, on ethylene-induced growth modification in etiolated pea seedlings and on abscission in citrus leaf explants. High concentrations of ethylene were used under conditions which hasten ethylene-induced processes. The results showed differences in the responses of the various tissues tested as related to the concentrations of the inhibitors. Some required much higher concentration to exert the same effect, while some, when applied at the same concentration, blocked the receptor for a longer period of time than the others. Fruits responded differently than other plant organs to the same inhibitor, indicating possible differences in characteristics and availability of the ethylene receptors in the various tissues. The potency of the inhibitors was greatly affected by their molecular structure and size. The highest potency of a given inhibitor was obtained when the treatment was applied before the onset of ethylene action. The relationship between ethylene and the inhibitors was found to be of an apparent non-competitive nature. All the fruits treated with the various inhibitors resumed normal ripening after recovery from the inhibition which is crucial when considering the putative inhibitors for practical use.

PHYSIOLOGICAL CHANGE ASSOCIATED WITH TUBEROSE CUT FLOWERS SENESCENCE IN RESPONSE TO ANTI ETHYLENE AND HOLDING SOLUTIONS

Various postharvest treatments were evaluated for their effect on longevity and quality of cut Polianthus tuberose cv. Double, spikes which were harvested when the basal 4 flowers were opened. Spikes were pulsed in silver thiosulfate (STS) 1:4 mM, for 10 minutes at 24 °C. They were treated for 24 hours at 24°C with control (without treatment), 10 and 100 nI/L1 1-MCP. The flowers were stored for 0,3 and 5 days at 5°C then were placed in jars of a holding solution (500 ml) containing 30 g/I sucrose, 200 mg/I 8- hydroxyquinoline dtrate and 150 mg/I citric acid until the end of experiment. The results indicated that all pretreatments increased vase life compared with the control. The highest percentage of fully opened florets, fresh weight and water uptake were obtained in 100 WU' 1-MCP compared with the other treatments. The life of the flowers was significantly increased by inhibiting ethylene action using pretreatinent with either 1-MCP or silver thiosulfate (STS). 1-MCP was more effective than STS in maintaining flower quality. Increasing storage duration from 3 up to 5 days decreased vase life and flower quality. The flowers pretreated with 1-MCP at 100 n1/1:I then stored for 0 or 3 days produced the highest longevity and flower quality.

Elevated H2O2 production via overexpression of a chloroplastic Cu/ZnSOD gene of lily (Lilium oriental hybrid ‘Marco Polo’) triggers ethylene synthesis in transgenic potato

Transgenic potato plants (SS2 and SS4) that overexpressed a chloroplastic copper/zinc superoxide dismutase lily gene were utilized as an H(2)O(2)-inducible system in order to study the role of H(2)O(2) as a signaling molecule in the biosynthesis of ethylene. SS2 and SS4 plants grown in vitro under sealed microenvironment (SME) conditions displayed anomalous phenotypes including reduction of stem elongation, radial stem growth, and promotion of root hair formation in the generated root, which were similar to ethylene-induced responses. In addition, SS4 plants showed severe vitrification in developing leaves and elevated ethylene production under SME conditions. After the ethylene action inhibitor AgNO(3), 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) inhibitor CoCl(2), and ACC synthase inhibitor L -aminoethoxyvinylglycine were added to the growth media, the anomalous phenotypes in SS4 plants reverted to their normal phenotype with a concurrent decrease in ethylene production. Northern blot analysis showed that ACO transcripts in SS4 plants were constantly at high levels under normal and SME conditions, indicating that a high level of H(2)O(2) in SS4 plants up-regulates ACO transcripts. Moreover, the direct treatment of H(2)O(2) in potato plants confirmed the elevated expression of the ACO gene. Taken together, these data suggest that the high concentration of H(2)O(2) in transgenic potato plants stimulates ethylene biosynthesis by activating ACO gene expression.

Suppression of Ethylene Responses Through Application of 1-Methylcyclopropene: A Powerful Tool for Elucidating Ripening and Senescence Mechanisms in Climacteric and Nonclimacteric Fruits and Vegetables

The discovery of 1-methylcyclopropene (1-MCP) as an inhibitor of ethylene action has provided yet another effective tool for understanding the role of this hormone in the development of higher plants. In the nearly 12 years since the description of the effects of this growth regulator on ethylene action, the subsequent introduction of stable formulations has resulted in an explosive increase in 1-MCP-targeted research, particularly, although not exclusively, in the discipline of postharvest science. The vicinal relationship between 1-MCP and postharvest biology is understandable in view of the established roles of ethylene, both beneficial and detrimental, in the handling and storage behaviors of a vast majority of harvested fruit and vegetative organs. The use of 1-MCP is proving to be supplemental to molecular approaches for identifying and understanding the spectrum of senescence and ripening processes under the direct control of ethylene perception. Climacteric fruits have served as the predominant target for investigations of 1-MCP, and the responses of these fruits have confirmed that the antagonist operates in opposition to ethylene. Studies of nonclimacteric fruits challenged with 1-MCP and other ethylene action inhibitors have identified both ethylene-dependent and ethylene-independent ripening processes and have posed interesting questions regarding the canonical distinctions between climacteric and nonclimacteric fruits.

A Brief History of 1-Methylcyclopropene

Research that led to the discovery of 1-methylcyclopropene (1-MCP) started with efforts to understand the effects of controlled atmosphere storage and continued with studies that examined the nature of the ethylene binding site. Although some researchers focused on the use of silver ion for inhibiting ethylene action, Sisler and his colleagues focused on analogs of olefins that had a similar effect. Efforts to tag the binding site using activation tagging with diazocyclopentadiene led to the discovery of the dramatic effects of cyclopropenes, which were identified as products of its photooxidation. The story is a testament to the value of fundamental research and the collegiality and unique intellectual and technical abilities of the primary inventor, Edward C. Sisler.

Effect of pre-harvest and post-harvest conditions and treatments on plum fruit quality.

Abstract Plums belong to the Rosaceae family and include the European species ( Prunus domestica L.), which is consumed fresh or dried, and the Japanese species ( Prunus salicina Lindell), mainly freshly consumed. Plums are considered climacteric, although some plum cultivars do not show the typical increase in ethylene production and respiration until late ripening. They respond to exogenous ethylene, which is a key ripening regulator, while treatments with 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, are effective in delaying fruit ripening. Plum fruit is characterized by high softening rate and, so far, the sequence of events leading to cell wall degradation, as well as changes in the proteins responsible for these modifications, has not been thoroughly investigated. Post-harvest diseases (brown rot, grey mould and Rhizopous rot) are also a main concern in plum post-harvest handling and storage. Prompt cooling and low-temperature storage (0°C) are recommended to delay ripening and maintain plum fruit quality. However, when the fruit is held for long periods at low temperature, chilling injury (CI) symptoms, usually manifested as translucency, bleeding, flesh browning and/or failure to ripen, might develop. Although softening can be delayed by controlled and modified atmospheres, this technology is not widely used commercially, since the benefits are not as pronounced as in other fruit species. Other post-harvest strategies tested to date with apparent usefulness at a laboratory scale include heat treatment, ozone, polyamine and calcium treatments, as well as fumigation with environmentally friendly compounds; such strategies might be useful under particular circumstances to complement other post-harvest treatments. Pre-harvest treatments, such as application of synthetic auxins and calcium, regulation of canopy light conditions and orchard soil management, have been reported to affect plum fruit quality and its post-harvest behaviour. Overall, the present review discusses the influence of field and post-harvest practices on plum fruit quality and market life.

1-Alkenes: Ethylene action compounds or ethylene competitive inhibitors in plants

Ethylene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 1-dodecene were tested as ethylene action compounds and also as ethylene competitive inhibitors using a pea growth and a banana ripening assay method. Ethylene, propene, and 1-butene gave a growth inhibition ethylene response in etiolated pea seedlings. 1-Pentene, 1-hexane, 1-octene, 1-decene, and 1-dodecene were inactive as ethylene action compounds but were active as competitive inhibitors of ethylene action in peas. 1-Butene was also active as a competitive inhibitor of ethylene action in pea growth. Ethylene and propene gave a typical ethylene ripening response in bananas, but 1-butene did not induce ripening. It did compete with ethylene and inhibited ethylene action in bananas. 1-Pentene, 1-hexene, 1-octene, 1-decene, and 1-dodecene also were inactive in mimicking ethylene action in bananas, but were competitive inhibitors of ethylene action, and their effectiveness increased as the chain length increased. It is clear that ethylene action inducing compounds and ethylene action competitive inhibitors are reaching the receptor, and the binding site does not appear to be restricted.