乙烯与切花的衰老及保鲜

本文内容有四:(1)讨论了乙烯对切花的伤害作用及花瓣中乙烯的生物合成和变化动态;(2)介绍了乙烯作用机理的两种假说;(3)着重评述了乙烯合成抑制剂和作用拮抗剂在切花保鲜上的应用;(4)简述了乙烯和其它植物激素在调控切花衰老过程中的相互作用。     

花衰老相关的乙烯信号转导基因研究进展

乙烯在许多切花衰老过程中起着重要的调节作用,不同的植物乙烯信号转导组分在花衰老过程中有不同的转录调节特性。根据乙烯信号转导标准模式,通过调节乙烯信号转导基因表达能够调控花对乙烯的敏感性,深入研究乙烯信号转导机制;可能有多条途径可延缓切花衰老。综述了香石竹和月季等几种观赏植物在花衰老过程中乙烯受体和乙烯信号转导基因表达及特性。     

乙烯对蜡梅切花开放衰老及乙烯受体基因表达的影响

为探索乙烯是否参与蜡梅花朵开放衰老进程的调控,利用气相色谱法测定分析不同发育阶段花朵的乙烯释放情况,同时分析乙烯、1-甲基环丙烯(1-MCP)处理对切花开放衰老进程和乙烯受体基因表达的影响。结果表明:蜡梅花朵开放衰老过程中有微量乙烯的产生,在盛开期出现峰值;外源乙烯显著加快了花朵开放衰老进程,缩短切花瓶插寿命1.9 d,而1-MCP处理则延长瓶插寿命2.4 d;存在受乙烯和1-MCP影响其在蜡梅花朵中表达的乙烯受体基因成员CpETR-1、CpETR-2、CpETR-3,且3个基因的转录水平变化与开放衰老进程关联较为紧密。说明蜡梅乙烯释放量虽然很低,但乙烯参与了蜡梅花朵开放和衰老的调控,影响其进程和相关乙烯受体基因的表达。     

乙烯生物合成及信号转导途径中介导花衰老相关基因的研究进展

乙烯为植物重要内源激素,参与植物多项生命活动,在花发育及衰老进程中起重要调节作用。在花卉中,研究者可通过调控其乙烯生物合成及信号转导途径相关基因影响内源乙烯生成,继而影响其发育与衰老进程。目前,通过调控内源乙烯延长花期的研究主要应用于观赏花卉,对于药用等其他花类应用尚少。对乙烯生物合成和信号转导途径模型及其相关基因的互作模式、近年来乙烯反应中介导花发育与衰老相关基因克隆及调控的相关研究进行综述,以期将通过调控内源乙烯途径相关基因来延缓植物花期的研究应用于其他花期短的观赏切花、花类药材等,为从基因水平调控内源乙烯以获得花期延长的观赏、药用花类等优良育种提供参考。     

乙烯受体在果实成熟及花衰老中的研究进展

乙烯受体是乙烯信号转导网络的第一个转导元件,通过调控受体基因的表达,可以调节植物对乙烯的敏感性,以调控果实的成熟及花衰老进程的响应。随着人们对乙烯受体研究的深入,乙烯受体突变体及受体抑制剂在采后果实和切花保鲜上的应用已受到广泛关注。就近年来关于乙烯受体的相关研究进展进行综述,重点介绍了乙烯受体的分子调控机制及乙烯受体在果实成熟和花衰老中的应用,并对今后乙烯受体的研究方向作了展望,以期为进一步研究提供参考。     

月季切花衰老过程中多胺与乙烯的关系

月季切花瓶插过程中,内源腐胺在前2天略有增加,内源亚精胺、精胺、多胺总量则呈下降趋势,乙烯释放速率在第3天达到最高峰;多胺抑制剂甲基乙醛-双咪腙处理抑制了亚精胺、精胺的合成,增加了乙烯的释放速率;乙烯抑制剂氨氧乙酸处理推迟腐胺高峰的到来,降低了乙烯的释放速率,而且在瓶插期的前2天内源亚精胺、精胺含量较高。结果表明,具乙烯跃变型特征的月季切花衰老过程中,多胺与乙烯在其生物合成过程中相互竞争S-腺苷甲硫氨酸作为其合成的前体。     

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.     

香石竹花瓣中乙烯诱导合成的60kD蛋白功能的初步研究

越来越多的研究表明植物器官的衰老与蛋白质合成密切相关[1～3]。乙烯在许多花卉衰老和一些水果的成熟过程中起重要作用[1,3],实验结果显示花对乙烯的反应依赖于新的蛋白质合成[2～5]。深入研究那些与衰老相关的蛋白质,特别是乙烯诱导合成的蛋白质的生化功能,对于了解掌握...     

月季切花衰老过程中多胺与乙烯的关系

月季切花瓶插过程中,内源腐胺在前２天略有增加,内源亚精胺,精胺、多胺总量则呈下降趋势,乙烯释放速率在第３天达到最高峰;多胺抑制剂甲基乙醛－双咪腙处理抑制了亚精胺,精胺的合成,增加了乙烯的释放速率;乙烯抑制剂氨氧乙酸处理推迟腐胺高峰的到来,降低了乙烯的释放速率,而且在瓶插期的前２天内业精胺、精胺含量较高,结果表明,具乙烯跃变型特征的月季切花衰老过程中,多与乙烯在其生物合成过程中相互竞争Ｓ－腺苷甲硫氨     

香石竹花瓣对乙烯的敏感性与蛋白质合成

基因转录抑制剂α-amanitin和蛋白质合成抑制剂cycloheximide完全抑制了香石竹(Dianthuscaryophyllus L.cvs.White Sim and Sandrosa)花瓣对乙烯反应的症状,包括花瓣卷曲和细胞膜离子渗漏增加。观察到花中蛋白质合成能力随着花的衰老而降低,花对乙烯的敏感性随花的衰老而增加。但是用乙烯合成抑制剂aminooxyacetic acid(AOA)预处理切花,则改变了花对乙烯敏感性的变化趋势。常用的香石竹品种D.caryophyllus L.cv.White Sim花经AOA处理后,对乙烯的敏感性随着花的衰老而下降。这些结果揭示花对乙烯的敏感性可能受蛋白质合成能力影响。     

Roles of pollination and short-chain saturated fatty acids in flower senescence

Pollination induced an immediate increase in ethylene production in Dianthus caryophyllus and Petunia hybrida. In Cymbidium, a lag of several hours was observed. In all three species, pollination induced premature flower senescence. Treatment of the stigmatic surface with aminoethoxyvinylglycine prior to pollination effectively blocked the increase in ethylene production and alleviated the detrimental effect of pollination on flower life.In all three tested species, octanoic and decanoic acids, when applied to the stigmatic surface, had no effect on ethylene production and flower life. In isolated Cymbidium lips placed with their cut base in solutions containing these fatty acids, no effects on red colouration, ethylene production, and ethylene forming enzyme activity were observed. In addition, ethylene sensitivity of isolated lips was not affected. The putative regulatory role of short-chain saturated fatty acids in (pollination-induced) flower senescence is discussed.     

Inhibition of wilting and autocatalytic ethylene production in cut carnation flowers by cis-propenylphosphonic acid

The effect of cis-propenylphosphonic acid (PPOH), a structural analoge of ethylene, on flower wilting and ethylene production was investigated using cut carnation flowers which are very sensitive to ethylene. Wilting (petal in-rolling) of the flowers was delayed by continuously immersing the stems in a 5–20 mM PPOH solution. In addition, the continuous treatment with PPOH markedly reduced autocatalytic ethylene production of the petals accompanying senescence. This reduction of autocatalytic ethylene production was considered responsible for the inhibitory effect of PPOH on flower wilting. The inhibitory activity of trans-propenylphosphonic acid (trans-PPOH), on both flower wilting and the autocatalytic ethylene production accompanying senescence was markedly lower than that of PPOH, suggesting that PPOH action is stereoselective. PPOH may be of interest as a new, water-soluble inhibitor of wilting and autocatalytic ethylene production in cut carnation flowers.     

The Relationship Between the Change of Calmodulin Content and Ethylene Biosynthesis of Carnation Flower During Its Senescence

The relationship between the change of calmodulin content and the ethylene hiosynthesis in cut carnation flower (Dianthus caryophyllus ‘sun besm’ ) during its senescence was studied. Ethylene releasing was detected at the forth day and reached its peak at the sixth day after the cut carnation flower was cultured under controlled conditions of 27 ℃ with a 14 h photoperiod of 15000 lx provided by fluorescent lamps. The change of calmodulin content positively correlated with the increased' content of ACC, the activity of ACC synthase and ethylene production. The calmodulin contents in petals of the detached flower treated with GA, silver thiosulfate (STS) and aminooxyacetic acid (AOA) were lower than those in control flower petals before they withered, ethylene releasing was reduced and their senescence was delayed too. Ca2+ stimulated ethylene releasing in carnation flower petals, but chlorobenzene (CPZ), an antagonist of calmodulin, inhibited its releasing. It seemed that calmodulin was involved in the regulation of senescence of carnation flower.     

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.     

Characteristics of the inhibitory action of 1,1-dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) on ethylene production in carnation (Dianthus caryophyllus L.) flowers

1,1-Dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS)inhibited ethylene productionin carnation flowers during natural senescence, butdid not inhibit the ethyleneproduction induced by exogenous ethylene in carnationflowers, by indole-3-acetic acid (IAA) in mungbean hypocotylsegments and by wounding in winter squashmesocarp tissue. These findings suggested that DPSSdoes not directly inhibit ethylene biosynthesis fromL-methionine to ethylenevia S-adenosyl-L-methionine and1-aminocyclopropane-1-carboxylate. During naturalsenescence of carnation flowers, abscisic acid (ABA)was accumulated in the pistil and petals 2 days beforethe onset of ethylene production in the flower, andthe ABA content remained elevated until the onset ofethylene production. Application of exogenousABA to cut flowers from the cut stem end caused arapid increase in the ABA content in flower tissuesand promoted ethylene production in the flowers. These results were in agreement with the previousproposal that ABA plays a crucial role in theinduction of ethylene production during natural senescence incarnation flowers. DPSS preventedthe accumulation of ABA in both the pistil and petals,suggesting that DPSS exerted its inhibitory action onethylene production in naturally-senescing carnationflowers through the effect on the ABA-related process.     

Sites of ethylene production in the pollinated and unpollinated senescing carnation (Dianthus caryophyllus) inflorescence

Production of endogenous ethylene from the styles, ovary and petals of pollinated and unpollinated flowers of Dianthus caryophyllus L. was measured. The rate of ethylene production of cut, unpollinated flowers aged in water at 18°C was low until the onset of petal wilting, when a rapid surge of ethylene occurred in all tissues. The flower ethylene production was evolved mostly from the styles and petals. The bases of petals from unpollinated, senescing flowers evolved ethylene faster and sometimes earlier than the upper parts. Treatment of cut flowers with propylene, an ethylene analogue, accelerated wilting of flower petals and promoted endogenous ethylene production in all flower tissues. Pollination of intact flowers also promoted endogenous ethylene production and caused accelerated petal wilting within 2–3 days from pollination. Although the data are consistent with the hypothesis that ethylene forms a link between pollination of the style and petal wilting, in the unpollinated flower the style and petals can evolve a surge of ethylene independently of each other, about the time when the petals irreversibly wilt. The results are discussed in relation to the role of ethylene in flower senescence.     

Role of ethylene in acceleration of flower senescence by filament wounding in Portulaca hybrid

Factors accelerating flower senescence of Portulaca hybrid were investigated. Self‐and cross‐pollination, emasculation and removing of pistil significantly accelerated senescence. However, wounding of filaments was much more effective in accelerating flower senescence. Senescence was further accelerated by an increase in the number of wounded filaments, and ethylene production was also accelerated by wounding of filaments. Treatment with 0.1 µl 1⁻¹ ethylene for 1 h significantly accelerated flower senescence, and the senescence of both the intact and filament‐wounded flowers was markedly delayed by exposure to norbornadiene (NBD), an inhibitor of ethylene action. The sensitivity to ethylene increased significantly within 1 h after wounding of filaments, but ethylene production did not. These results suggest that acceleration of flower senescence by wounding of filaments is caused by an increase in the sensitivity to ethylene and the subsequent production of ethylene.     

Correlative changes in sucrose uptake, ATPase activity and membrane fluidity in carnation petals during senescence

Apparent sucrose uptake. ATPase activity and membrane fluidity changes were studied during the development and senescence of carnation flowers ( Dianthus caryophyllus L., cv. Cerise Royallette). Typical changes associated with senescence of a cut flower, such as respiration, ethylene production and fresh weight, were measured. Concomitant with a rise in respiration and ethylene production and a decline in fresh weight, a sharp decrease in apparent sucrose uptake was observed. Sucrose uptake was pH dependent (pH optimum, 5.5) and influenced by membrane integrity. Apparently, the activity of ATPase is related to sucrose uptake, because similar changes occurred during flower development. In addition, the activity of ATPase was well correlated with membrane fluidity.
It is suggested that sucrose uptake is controlled by ATPase activity, which in turn is modulated by membrane lipid fluidity. The decline in membrane fluidity associated with senescence leads to a corresponding reduction in ATPase activity and sucrose uptake. Further evidence supporting this view comes from experiments in which senescence was enhanced by 1-aminocyclopropane-l-carboxylic acid. It shortened the time to decline in fresh weight, rise in respiration and ethylene production. In parallel, reduction in membrane fluidity, ATPase activity and sucrose uptake were observed.     

The role of ethylene in the senescence of carnation flowers,a review

The senescence of flower petals is a highly regulated developmental process which requires active gene expression and protein synthesis. The biochemical changes associated with petal senescence in carnation flowers include an increase in hydrolytic enzymes, degradation of macro-molecules, increased respiratory activity and a climacteric-like increase in ethylene production. It is clear that the gaseous phytohormone ethylene plays a critical role in the regulation and coordination of senescence processes. Many reviews on physiology and mode of action of ethylene are available. Molecular cloning led to the isolation of genes involved in ethylene biosynthesis and action. This review describes the current status of the studies on regulation of ethylene biosynthesis and ethylene response in carnation flowers. An overview is given of studies on senescence-related gene expression and possibilities to improve postharvest longevity by genetic engineering.     

Ethylene production and β-cyanoalanine synthase activity in carnation flowers

The relationship between ethylene production and the CN^--assimilating enzyme -cyanoalanine synthase (CAS; EC 4.4.1.9) was examined in the carnation (Dianthus caryophyllus L.) flower. In petals from cut flowers aged naturally or treated with ethylene to accelerate senescence the several hundred-fold increase in ethylene production which occurred during irreversible wilting was accompanied by a one- to twofold increase in CAS activity. The basal parts of the petal, which produced the most ethylene, had the highest CAS activity. Studies of flower parts (styles, ovaries, receptacles, petals) showed that the styles had a high level of CAS together with the ethylene-forming enzyme (EFE) system for converting 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. The close association between CAS and EFE found in styles could also be observed in detached petals after induction by ACC or ethylene. Treatment of the cut flowers with cycloheximide reduced synthesis of CAS and EFE. The data indicate that CAS and ethylene production are associated, and are discussed in relation to the hypothesis that CN^- is formed during the conversion of ACC to ethylene.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglyoine - CAS -cyanoalanine synthase - CHI cycloheximide - EFE ethylene-forming enzyme