Enhancement of petunia and dendrobium flower senescence by jasmonic acid methyl ester is via the promotion of ethylene production

Methyl jasmonate (JA-Me), applied to dendrobium and petunia flowers either as an aqueous solution through the cut stem or stigma, or as a gas, accelerated senescence. The rate of appearance of wilting symptoms was directly related to the amount of JA-Me applied to the flowers. JA-Me increased ethylene production by the flowers, irrespective of application method, and this effect was also proportional to the dose of the compound. In both dendrobium and petunia flowers, the JA-Me induced increases in ethylene production and 1-aminocyclopropane-1-carboxylic acid content followed similar patterns. Aminooxyacetic acid, an inhibitor of ACC-synthase, and silver-thiosulfate, an inhibitor of ethylene action, completely inhibited the effects of JA-Me. It is concluded that JA-Me enhances petunia and dendrobium flower senescence via the promotion of ACC and ethylene production.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AOA aminooxyacetic acid - Fl flower - JA jasmonic acid - JA-Me jasmonic acid methyl ester - LOX lipoxygenase - PLase A A-type phospholipase - STS silver-thiosulfate     

Ethylene and flower petal senescence: Interrelationship with membrane lipid catabolism

Accumulated experimental evidence suggests that the decline in the content of membrane components such as phospholipids (PL), is a key event in flower senescence. This loss of membrane integrity can be modulated by ethylene. The aim of this work was to examine the interrelationship between ethylene and one of the products of PL metabolism, diacylglycerol (DAG), during petunia ( Petunia hybrida ) flower senescence. DAG's role was studied using phorbol 12-myristate 13-acetate (PMA), which acts similarly in kinase activation. Our results demonstrate for the first time a senescence-related transient increase in the content of DAG in petunia plasma membranes. The climacteric-like ethylene rise associated with petal wilting appeared in petunia flowers well after PL degradation and DAG increase had commenced. The appearance and peak magnitude of the ethylene rise was enhanced or increased, respectively, by PMA treatment, thereby accelerating appearance and magnitude of all senescence parameters assayed. Conversely, suppression of ethylene action by silver thiosulfate (STS) resulted in retardation of flower wilting, as well as in abolishment of the PMA-enhancing effects on senescence. The results suggest an active role for lipid metabolites like DAG in enhancing flower senescence, through regulation of ethylene production and action, or possible activation of kinases. This sequence of events implies that ethylene is a mediator of flower senescence, rather than a trigger of the process.     

1-MCP对东方百合开放与衰老的影响

以东方系列百合（Lilium spp.）‘西伯利亚’品种为材料,研究了1-甲基环丙烯（1-MCP）对百合切花质膜透性、乙烯释放量、丙二醛含量、可溶性蛋白质含量等生理指标的影响。结果表明：1-MCP可延缓百合切花花瓣质膜相对透性的增加,延长百合切花瓶插寿命;降低百合花瓣乙烯释放量,推迟乙烯峰的出现;降低百合花瓣丙二醛含量,对可溶性蛋白含量的变化无明显影响。本研究结果说明1-MCP对东方百合切花的保鲜有一定效果,确定了1-MCP处理东方百合的最佳使用浓度为0.01μL/L。     

1-甲基环丙烯对百合采后切花某些生理指标的影响

百合切花经1-甲基环丙烯(1-MCP)处理后瓶插寿命延长,花朵发育和衰老进程延缓,乙烯峰出现时间推迟.经1-MCP处理的亚洲百合的乙烯峰值和细胞膜透性降低,而麝香百合可溶性蛋白质含量则不受影响.     

外源乙烯及1-MCP对牡丹CTR基因表达的影响

采用RT-PCR法研究外源乙烯和1-MCP对牡丹品种洛阳红(Paeonia suffruticosa Luoyanghong)1级切花CTR基因家族3个成员基因表达的影响,以揭示乙烯在牡丹采后开花和衰老进程中的调控机制.结果表明,在花朵开放和衰老进程中,PsCTR1和PsCTR2类似组成型表达,PsCTR3随内源乙烯的增加表达增强.PsCTR2和PsCTR3表达受外源乙烯的促进,PsCTR1的表达仅在花朵开放后期受到外源乙烯的促进.1-MCP处理增加了PsCTR1和PsCTR2的表达,但对PsCTR3的表达起先促进后抑制的作用.复合处理的结果表明,1-MCP处理可以逆转乙烯处理对PsCTR1和PsCTR2的作用;在切花进入盛花期和衰老期后,乙烯处理可以逆转1-MCP处理对PsCTR1、PsCTR2和PsCTR3的作用.     

Effects of 1-MCP on the vase life and ethylene response of cut flowers

Pretreatment for 6 h with low concentrations of 1-MCP (1-Methylcyclopropene, formerly designated as SIS-X), a cyclic ethylene analog, inhibits the normal wilting response of cut carnations exposed continuously to 0.4 μl·l^?1 ethylene. The response to 1-MCP was a function of treatment concentration and time. Treatment with 1-MCP was as effective in inhibiting ethylene effects as treatment with the anionic silver thiosulfate complex (STS), the standard commercial treatment. Other ethylene-sensitive cut flowers responded similarly to carnations. In the presence of 1 μl·l^?1 ethylene, the vase life of 1-MCP-treated flowers was up to 4 times that of the controls.     

乙烯诱导西瓜果实的水渍化败坏

为了研究乙烯在西瓜(Citrullus lanatusThunb.Mansfeld)果实水渍化败坏过程中的作用,先将果实在5μL/L 1-甲基环丙烯(1-MCP)气体中处理18 h,然后在50 μL/L乙烯和20℃温度下贮藏.西瓜果实对乙烯处理的最初反应表现为胎座组织的电导率和游离汁液增加,同时出现组织软化和水渍化.水渍化的症状最初在靠近花萼端的内果皮中发生,在乙烯处理的第2天开始出现,ACC合成酶(ACS)和ACC氧化酶(ACO)的活性明显提高.1-MCP单独处理不产生任何明显的作用,但是会完全抑制外源乙烯诱导的水渍化败坏.没有经过乙烯处理的西瓜果实,贮藏2 d以后出现呼吸强度和乙烯释放量的高峰,10 d以后水渍化现象也零星出现.这些结果和1-MCP的预防效果说明,西瓜果实的水渍化败坏是一种由乙烯诱导的衰老现象.     

Effects of 1-MCP on the vase life and ethylene response of cut flowers

Pretreatment for 6 h with low concentrations of 1-MCP (1-Methylcyclopropene, formerly designated as SIS-X), a cyclic ethylene analog, inhibits the normal wilting response of cut carnations exposed continuously to 0.4 l·l^–1 ethylene. The response to 1-MCP was a function of treatment concentration and time. Treatment with 1-MCP was as effective in inhibiting ethylene effects as treatment with the anionic silver thiosulfate complex (STS), the standard commercial treatment. Other ethylene-sensitive cut flowers responded similarly to carnations. In the presence of 1 l·l^–1 ethylene, the vase life of 1-MCP-treated flowers was up to 4 times that of the controls.Abbreviations 1-MCP 1-Methylcyclopropene - STS silver thiosulfate     

Ethylene perception inhibitor 1-MCP decreases oxidative damage of leaves through enhanced antioxidant defense mechanisms in soybean plants grown under high temperature stress

Ethylene is a stress hormone involved in early senescence and abscission of vegetative and reproductive organs under stress conditions. Ethylene perception inhibitors can minimize the impact of ethylene-mediated stress. The effects of high temperature (HT) stress during flowering on ethylene production rate in leaf, flower and pod and the effects of ethylene inhibitor on ethylene production rate, oxidative damage and physiology of soybean are not understood. We hypothesize that HT stress induces ethylene production, which causes premature leaf senescence and flower and pod abscission, and that application of the ethylene perception inhibitor 1-Methyl cyclopropene (1-MCP) can minimize HT stress induced ethylene response in soybean. The objectives of this study were to (1) determine whether ethylene is produced in HT stress; (2) quantify the effects of HT stress and 1-MCP application on oxidative injury; and (3) evaluate the efficacy of 1-MCP at minimizing HT-stress-induced leaf senescence and flower abscission. Soybean plants were exposed to HT (38/28 °C) or optimum temperature (OT; 28/18 °C) for 14 d at flowering stage (R2). Plants at each temperature were treated with 1-MCP (1 μg L⁻¹) gas for 5 h or left untreated (control). High temperature stress increased rate of ethylene production in leaves, flowers and pods, production of reactive oxygen species (ROS), membrane damage, and total soluble carbohydrate content in leaves and decreased photosynthetic rate, sucrose content, F_v/F_m ratio and antioxidant enzyme activities compared with OT. Foliar spray of 1-MCP decreased rate of ethylene production and ROS and leaf senescence traits but enhanced antioxidant enzyme activities (e.g. superoxide dismutase and catalase). In conclusion, HT stress increased ethylene production rates, caused oxidative damage, decreased antioxidant enzyme activity, caused premature leaf senescence, increased flower abscission and decreased pod set percentage. Application of 1-MCP lowered ethylene and ROS production, enhanced antioxidant enzyme activity, increased membrane stability, delayed leaf senescence, decreased flower abscission and increased pod set percentage. The beneficial effects of 1-MCP were greater under HT stress compared to OT in terms of decreased ethylene production, decreased ROS production, increased antioxidant protection, decreased flower abscission and increased pod set percentage.     

Defence responses regulated by jasmonate and delayed senescence caused by ethylene receptor mutation contribute to the tolerance of petunia to Botrytis cinerea

Ethylene and jasmonate (JA) have powerful effects when plants are challenged by pathogens. The inducible promoter‐regulated expression of the Arabidopsis ethylene receptor mutant ethylene‐insensitive1‐1 (etr1‐1) causes ethylene insensitivity in petunia. To investigate the molecular mechanisms involved in transgenic petunia responses to Botrytis cinerea related to the ethylene and JA pathways, etr1‐1‐expressing petunia plants were inoculated with Botrytis cinerea. The induced expression of etr1‐1 by a chemical inducer dexamethasone resulted in retarded senescence and reduced disease symptoms on detached leaves and flowers or intact plants. The extent of decreased disease symptoms correlated positively with etr1‐1 expression. The JA pathway, independent of the ethylene pathway, activated petunia ethylene response factor (PhERF) expression and consequent defence‐related gene expression. These results demonstrate that ethylene induced by biotic stress influences senescence, and that JA in combination with delayed senescence by etr1‐1 expression alters tolerance to pathogens.     

Regulation of Senescence in Carnation (Dianthus caryophyllus): Effect of Abscisic Acid and Carbon Dioxide on Ethylene Production

Abscisic acid hastened senescence of carnation flowers and this was preceded by stimulation of accelerated ethylene production. Carbon dioxide delayed the onset of autocatalytic ethylene production in flowers regardless of treatment with abscisic acid. Flowers exhibited a low and transient climacteric of ethylene production without wilting while in 4% carbon dioxide and underwent accelerated ethylene production culminating in wilting when removed from carbon dioxide. Hypobaric ventilation, which lowers ethylene to hyponormal levels within tissues, extended flower longevity and largely negated enhancement of senescence by abscisic acid. Supplementing hypobarically ventilated flowers with ethylene hastened senescence irrespective of abscisic acid treatment. Collectively, the data indicate that abscisic acid hastens senescence of carnations largely as a result of advancing the onset of autocatalytic ethylene production.     

Growth inhibition of pollen tubes by blocking the aromatic or branched-chain amino acid pathways of biosynthesis

A number of organic molecules that appear to block the ethylene receptor have been discovered recently. For example, on irradiation with visible light, diazocyclopentadiene (DACP), gives rise to some potent but as yet unidentified inhibitor compounds. Some synthetic cyclopropenes have been shown to bind to the ethylene receptor and prevent the physiological action of ethylene for extended periods. Cyclopropene (CP). 1-methylcyclopropene (1-MCP) and 3,3-dimethylcyclopropene (3,3-DMCP) have been shown to prevent ethylene effects in a number of plants. As low a concentration as 0.5 nl l⁻¹ of 1-MCP is sufficient to protect carnation ( Dianthus caryophyllus ) flowers for several days against ethylene, and 0.7 nl l⁻¹ 1-MCP or CP will prevent the ripening of banana ( Musa sapientum ) for 12 days at 24°C. Some plant organs require higher concentrations of these inhibitors. Complete inhibition of ethylene effects in pea seedlings requires treatment with 40 n1 1⁻¹ of 1-MCP. These novel inhibitors appear to be suitable for many commercial applications including extending the vase life of cut flowers and the display life of potted plants. Since 1-MCP apparently is non-toxic at concentrations that are active, it may in future be available for regulating the ripening of fruits and preventing the deleterious effects of ethylene in vegetables.     

Heterologous expression of the Arabidopsis etr1-1 allele inhibits the senescence of carnation flowers

The Arabidopsis thaliana etr1-1 allele, capable of conferring ethylene insensitivity in a heterologous host, was introduced into transgenic carnation plants. This gene was expressed under control of either its own promoter, the constitutive CaMV 35S promoter or the flower-specific petunia FBP1 promoter. In about half of the transgenic plants obtained flower senescence was delayed by at least 6 days relative to control flowers, with a maximum delay of 16 days, a 3-fold increase in vase life. These flowers did not show the petal inrolling phenotype typical of ethylene-dependent carnation flower senescence. Instead, petals remained firm and finally started to rot and decolorize.In transgenic plants with delayed flower senescence, expression of the Arabidopsis etr1-1 gene was detectable and the expression pattern followed the activity of the upstream promoter. In these flowers expression of the ACO1 gene, encoding the final enzyme in the ethylene biosynthesis pathway, ACC oxidase, was down-regulated. This indicates that the autocatalytic induction of ethylene biosynthesis, required to initiate and regulate the flower senescence process, is absent in etr1-1 transgenic plants due to dominant ethylene insensitivity.The delay in senescence observed in transgenic etr1-1 flowers was longer than in flowers pretreated with chemicals that inhibit either ethylene biosynthesis (amino-oxyacetic acid) or the ethylene response (silver thiosulfate). This may have important implications for post-harvest management of carnation flowers.     

Petunia flower longevity: the role of sensitivity to ethylene

Two petunia ( Petunia hybrida L.) lines, differing in their flower longevity, were studied, Similar tendencies were found in the changes of corolla fresh weight, electrolyte leakage and membrane microviscosity over the life spans of the two lines. Ethylene production by flowers of the two lines showed a similar pattern, peaking at 3 nl flower⁻¹ h⁻¹. However, in flowers of the short-lived line, ethylene production peaked at 6 days of age, but in the long-lived line, the peak appeared at 10 days of age. A large difference was found in the responsiveness of the flower to ethylene, Flowers of the short-lived line responded to a similar ethylene by immediate wilting, while those of the long-lived line responded to a similar ethylene treatment only after two days. Differences in sensitivity to ethylene were also, observed when the flowers were treated continuosly with (aminooxy)acetic acid, which blocks ethylene synthesis. Flowers of both lines responded to ethylene treatment by increased ethylene production to a similar rate. Differential sensitivity to ethylene, independent of ethylene production, seemingly governs flower longevity in the two petunia lines studied.     

Responses of banana fruit to treatment with 1-methylcyclopropene

Experiments were conducted to determine levels of 1-methylcyclopropene (1-MCP) exposure needed to prevent ethylene-stimulated banana fruit ripening, characterise responses of ethylene-treated fruit to subsequent treatment with 1-MCP, and to test effects of subsequent ethylene treatment on 1-MCP-treated fruit softening. Fruit softening was measured at 20°C and 90% relative humidity. One hour exposure at 20°C to 1000 nl 1-MCP/l essentially eliminated ethylene-stimulated ripening effects. Exposure for 12 h at 20°C to just 50 nl 1-MCP/l was similarly effective. Fruit ripening initiated by ethylene treatment could also be delayed with subsequent 1-MCP treatment. However, 1-MCP treatment only slowed down ripening of ethylene-treated fruit when applied at 1 day after ethylene and was ineffective when applied 3 or 5 days after ethylene treatment. The ripening response of fruit treated with 1-MCP and subsequently treated with ethylene varied with interval time between 1-MCP and ethylene treatments. As time increased, the response of 1-MCP-treated fruit to ethylene was enhanced. Responses to 0.1, 1, 10 or 100 µl ethylene/l concentrations were similar. Enzyme kinetic analysis applied to 1-MCP effects on ethylene-induced softening of banana fruit suggested that 1-MCP inhibition is by noncompetitive antagonism of ethylene binding.     

Roles of ethylene and 1-aminocyclopropane-1-carboxylic acid in pollination and wound-induced senescence of Petunia hybrida flowers

Normal senescence of Petunia hybrida L. (cv. Pink Cascade) was associated with a 10-fold increase in their ethylene production. Soon after pollination wounding of the stigma of detached flowers there was a burst of ethylene production by the gynoecium, which reached a maximum after 3 h. A subsequnt more gradual rise in ethylene production by the flowers was accompanied by blueing, wilting, and senescence of the corolla. Treatment with 1 μl ethylene 1⁻¹ accelerated the onset of senescence as measured first by color change and then by wilting of the corolla. These changes were further accelerated by using older flowers or higher concentrations of ethylene. Senescence was also hastened by supplying 1-aminocyclopropane-1-carboxylic acid (ACC) through the flower pedicel. Petunia pollen contained high concentrations of ACC (300 nmol g⁻¹); treatment of stigmas with ACC (1 m M ) caused a 4-fold increase in their ethylene production. Senescence, whether natural or hastened by pollination or piercing, was delayed by treating the flowers with the anionic silver thiosulfate complex.     

Role of the gynoecium in natural senescence of carnation (Dianthus caryophyllus L.) flowers

Although the role of the gynoecium in natural senescence of the carnation flower has long been suggested, it has remained a matter of dispute because petal senescence in the cut carnation flower was not delayed by the removal of gynoecium. In this study, the gynoecium was snapped off by hand, in contrast to previous investigations where removal was achieved by forceps or scissors. The removal of the gynoecium by hand prevented the onset of ethylene production and prolonged the vase life of the flower, demonstrating a decisive role of the gynoecium in controlling natural senescence of the carnation flower. Abscisic acid (ABA) and indole-3-acetic acid (IAA), which induced ethylene production and accelerated petal senescence in carnation flowers, did not stimulate ethylene production in the flowers with gynoecia removed (-Gyn flowers). Application of 1-aminocyclopropane-1-carboxylate (ACC), the ethylene precursor, induced substantial ethylene production and petal wilting in the flowers with gynoecia left intact, but was less effective at stimulating ethylene production in the -Gyn flowers and negligible petal in-rolling was observed. Exogenous ethylene induced autocatalytic production of the gas and petal wilting in the -Gyn flowers. These results indicated that ethylene generated in the gynoecium triggers the onset of ethylene production in the petals of carnation during natural senescence.