Petal Abscission Research Articles

PYL9 is involved in the regulation of ABA signaling during tomato fruit ripening.

Abscisic acid (ABA) regulates fruit ripening, yet little is known about the exact roles of ABA receptors in fruit. In this study, we reveal the role of SlPYL9, a tomato pyrabactin resistance (PYR)/pyrobactin resistance-like (PYL)/regulatory component of ABA receptors (RCAR) protein, as a positive regulator of ABA signaling and fruit ripening. SlPYL9 inhibits protein phosphatase-type 2C (PP2C2/6) in an ABA dose-dependent way, and it interacts physically with SlPP2C2/3/4/5 in an ABA-dependent manner. Expression of SlPYL9 was observed in the seeds, flowers, and fruits. Overexpression and suppression of SlPYL9 induced a variety of phenotypes via altered expression of ABA signaling genes (SlPP2C1/2/9, SlSnRK2.8, SlABF2), thereby affecting expression of ripening-related genes involved in ethylene release and cell wall modification. SlPYL9-OE/RNAi plants showed a typical ABA hyper-/hypo-sensitive phenotype in terms of seed germination, primary root growth, and response to drought. Fruit ripening was significantly accelerated in SlPYL9-OE by 5–7 d as a result of increased endogenous ABA accumulation and advanced release of ethylene compared with the wild-type. In the SlPYL9-RNAi lines, fruit ripening was delayed, mesocarp thickness was enhanced, and petal abscission was delayed compared with the wild-type, resulting in conical/oblong and gourd-shaped fruits. These results suggest that SlPYL9 is involved in ABA signaling, thereby playing a role in the regulation of flower abscission and fruit ripening in tomato.

Petal abscission in roses is associated with the activation of a truncated version of the animal PDCD4 homologue, RbPCD1

Abscission is a developmental process that leads to shedding of organs not needed by the plant. Apart from wall hydrolysis, the cells of the abscission zone (AZ) are also believed to undergo programmed cell death (PCD). We show that ethylene-induced petal abscission in Rosa bourboniana is accompanied with the activation of RbPCD1 (PROGRAMMED CELL DEATH LIKE 1) encoding a protein of 78 amino acids. Its expression increases during natural and ethylene-induced petal abscission. Its transcription in most tissues is up-regulated by ethylene. RbPCD1 shows similarity to the N-terminal domain of animal PDCD4 (PROGRAMMED CELL DEATH PROTEIN 4) proteins that are activated during apoptosis and function as transcriptional and translational repressors. RbPCD1 resides in the nucleus and cytoplasm and acts as a transcriptional repressor. Constitutive expression of RbPCD1 in transgenic Arabidopsis is seedling lethal. Heat-induced expression of RbPCD1 under the soybean heat-shock promoter affects leaf function, inflorescence development, silique formation, seed yield and reduces survival. Nuclear localization of RbPCD1 is necessary for manifestation of its effects. RbPCD1 may be necessary to mediate some of the ethylene-induced changes during abscission and senescence in specific tissues.

Rosa hybrida RhERF1 and RhERF4 mediate ethylene- and auxin-regulated petal abscission by influencing pectin degradation.

The timing of plant organ abscission is modulated by the balance of two hormones, ethylene and auxin, while the mechanism of organ shedding depends on the loss of middle lamella pectin in the abscission zone (AZ). However, the mechanisms involved in sensing the balance of auxin and ethylene and that affect pectin degradation during abscission are not well understood. In this study, we identified two members of the APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor family in rose (Rosa hybrida), RhERF1 and RhERF4 which play a role in petal abscission. The expression of RhERF1 and RhERF4 was influenced by ethylene and auxin, respectively. Reduced expression of RhERF1 or RhERF4 was observed to accelerate petal abscission. Global expression analysis and real-time PCR assays revealed that RhERF1 and RhERF4 modulate the expression of genes encoding pectin-metabolizing enzymes. A reduction in the abundance of pectin epitopes was detected in the AZs of RhERF1 and RhERF4-silenced plants by immunofluorescence microscopy analysis. In addition, RhERF1 and RhERF4 were shown to bind to the promoter of the pectin-metabolizing gene β-GALACTOSIDASE 1 (RhBGLA1), and reduced expression of RhBGLA1 delayed petal abscission. We conclude that during petal abscission, RhERF1 and RhERF4 integrate and coordinate ethylene and auxin signals to modulate pectin metabolism, in part by regulating the expression of RhBGLA1.

Differential and reciprocal regulation of ethylene pathway genes regulates petal abscission in fragrant and non-fragrant roses

The fragrant rose, Rosa bourboniana, is highly sensitive to ethylene and shows rapid petal abscission (within 16–18 h) while the non-fragrant hybrid rose, R. hybrida, shows delayed abscission (50–52 h) due to reduced ethylene sensitivity. To understand the molecular basis governing these differences, all components of the ethylene pathway (biosynthesis/ receptor/signalling) were studied for expression during abscission. Transcript accumulation of most ethylene biosynthesis genes (ACS/ACO families) increased rapidly in petal abscission zones of R. bourboniana within 4–8 h of ethylene treatment. The expression of most receptor and signalling genes encoding CTRs, EIN2 and EIN3/EIL homologues also followed similar kinetics. Under natural field conditions where abscission takes longer, there was a temporal delay in transcript accumulation of most ethylene pathway genes while some biosynthesis genes (showing reduced ethylene sensitivity) were more strongly up-regulated by abscission cues. In contrast, in R. hybrida where even ethylene-induced abscission is considerably delayed, transcript accumulation of most ethylene biosynthesis and signalling genes was, surprisingly, reduced by ethylene and showed an opposite regulation compared to R. bourboniana. The results suggest that differential and reciprocal regulation of ethylene pathway is one of the major reasons for differences in petal abscission and vase-life between Rosa bourboniana and R. hybrida.

A novel tomato F-box protein, SlEBF3, is involved in tuning ethylene signaling during plant development and climacteric fruit ripening.

Ethylene is instrumental to climacteric fruit ripening and EIN3 BINDING F-BOX (EBF) proteins have been assigned a central role in mediating ethylene responses by regulating EIN3/EIL degradation in Arabidopsis. However, the role and mode of action of tomato EBFs in ethylene-dependent processes like fruit ripening remains unclear. Two novel EBF genes, SlEBF3 and SlEBF4, were identified in the tomato genome, and SlEBF3 displayed a ripening-associated expression pattern suggesting its potential involvement in controlling ethylene response during fruit ripening. SlEBF3 downregulated tomato lines failed to show obvious ripening-related phenotypes likely due to functional redundancy among SlEBF family members. By contrast, SlEBF3 overexpression lines exhibited pleiotropic ethylene-related alterations, including inhibition of fruit ripening, attenuated triple-response and delayed petal abscission. Yeast-two-hybrid system and bimolecular fluorescence complementation approaches indicated that SlEBF3 interacts with all known tomato SlEIL proteins and, consistently, total SlEIL protein levels were decreased in SlEBF3 overexpression fruits, supporting the idea that the reduced ethylene sensitivity and defects in fruit ripening are due to the SlEBF3-mediated degradation of EIL proteins. Moreover, SlEBF3 expression is regulated by EIL1 via a feedback loop, which supposes its role in tuning ethylene signaling and responses. Overall, the study reveals the role of a novel EBF tomato gene in climacteric ripening, thus providing a new target for modulating fleshy fruit ripening.

Influence of genotype, floral stage, and water stress on floral nectar yield and composition of mānuka (Leptospermum scoparium).

Background and AimsFloral nectar can be variable in composition, influencing pollinator behaviour and the composition of honey derived from it. The non-peroxide antibacterial activity of mānuka (Leptospermum scoparium, Myrtaceae) honey results from the chemical conversion of the triose sugar dihydroxyacetone (DHA), after DHA accumulates for an unknown reason in the nectar. This study examined variation in nectar DHA, glucose, fructose and sucrose content with floral stage of development, between mānuka genotypes with differing flower morphology, and in response to water stress.MethodsSix mānuka genotypes were grown without nectar-feeding insects. Stages of flower development were defined, nectar was harvested and its composition was compared between stages and genotypes, and with floral morphology. Water stress was imposed and its effect on nectar composition was examined.Key ResultsNectar was present from soon after flower opening until the end of petal abscission, with the quantity of accumulated nectar sugars rising, then stabilizing or falling, indicating nectar secretion followed by reabsorption in some genotypes. The quantity of DHA, the ratio of DHA to other nectar sugars and the fructose to glucose ratio also varied with stage of development, indicating differences in rates of production and reabsorption between nectar components. Nectar composition and yield per flower also differed between genotypes, although neither was positively related to nectary area or stomatal density. Drying soil had no effect on nectar composition or yield, but variation in nectar yield was correlated with temperature prior to nectar sampling.ConclusionsMānuka nectar yield and composition are strongly influenced by plant genotype, flower age and the environment. There were clear stoichiometric relationships between glucose, fructose and sucrose per flower, but DHA per flower was only weakly correlated with the amount of other sugars, suggesting that accumulation of the triose sugar is indirectly coupled to secretion of the larger sugars by the nectary parenchyma.

Post-translational maturation of IDA, a peptide signal controlling floral organ abscission in Arabidopsis

ABSTRACTThe abscission of sepals, petals and stamens in Arabidopsis flowers is controlled by a peptide signal called IDA (Inflorescence Deficient in Abscission). IDA belongs to the large group of small post-translationally modified signaling peptides that are synthesized as larger precursors and require proteolytic processing and specific side chain modifications for signal biogenesis. Using tissue-specific expression of proteinase inhibitors as a novel approach for loss-of-function analysis, we recently identified the peptidases responsible for IDA maturation within the large family of subtilisin-like proteinases (subtilases; SBTs). Further biochemical and physiological assays identified three SBTs (AtSBT5.2, AtSBT4.12, AtSBT4.13) that cleave the IDA precursor to generate the N-terminus of the mature peptide. The C-terminal processing enzyme(s) remain(s) to be identified. While proline hydroxylation was suggested as additional post-translational modification required for IDA maturation, hydroxylated and non-hydroxylated IDA peptides were found to be equally active in bioassays for abscission.

Changes in postharvest physio-biochemical characterustics and antioxidant enzymes activity of cut alsteroemeria aurantiaca flower as affected by cycloheximide, coconut water and 6-benzyladenine

Early leaf yellowing in cut alstroemeria ( Alstroemeria aurantiaca ) flowers before flower development and petal abscission is an important limiting postharvest quality and vase life factors. Early leaf senescence reduces postharvest longevity of cut flowers and promotes petal's wilting. A study was made to evaluate the response of cut alstroemeria flowers at varying concentrations of cycloheximide (CHI) (50, 100 and 200 mg l -1 ), coconut water (5, 10 and 20%) and 6-benzyladenine (BA) (50, 100 and 200 mg l -1 ). CHI, coconut water and BA extended the vase life at all concentrations compared to the control, but coconut water at 5% concentration (with 17.39 days) was the most effective treatment. Control cut flowers showed the least vase life (10.76 days). Ethylene production in cut flowers promoted flower senescence. All concentrations of CHI, coconut water and BA delayed ethylene production compared to the control. Treatment of cut flowers with coconut water at concentration of 5% maintained the highest fresh weight of flowers and increased the content of water uptake. The chlorophyll degradation was significantly reduced by the application of CHI, coconut water and BA. The maximum content of membrane's lipid peroxidation and antioxidant enzymes activity (super oxide dismutase and peroxidase) was obtained in control cut flowers. Thus, 5% fresh coconut water has the potential to be applied as vase solution (preservative medium) due to prolongs of cut alstroemeria flowers.

Transcriptome Profiling of Petal Abscission Zone and Functional Analysis of an Aux/IAA Family Gene RhIAA16 Involved in Petal Shedding in Rose

Roses are one of the most important cut flowers among ornamental plants. Rose flower longevity is largely dependent on the timing of petal shedding occurrence. To understand the molecular mechanism underlying petal abscission in rose, we performed transcriptome profiling of the petal abscission zone during petal shedding using Illumina technology. We identified a total of 2592 differentially transcribed genes (DTGs) during rose petal shedding. Gene ontology term enrichment and pathway analysis revealed that major biochemical pathways the DTGs were involved in included ethylene biosynthesis, starch degradation, superpathway of cytosolic glycolysis, pyruvate dehydrogenase and TCA cycle, photorespiration and the lactose degradation III pathway. This suggests that alterations in carbon metabolism are an important part of rose petal abscission. Among these DTGs, approximately 150 genes putatively encoding transcription factors were identified in rose abscission zone. These included zinc finger, WRKY, ERF, and Aux/IAA gene families, suggesting that petal abscission involves complex transcriptional reprogramming. Approximately 108 DTGs were related to hormone pathways, of which auxin and ethylene related DTGs were the largest groups including 52 and 41 genes, respectively. These also included 12 DTGs related to gibberellin and 6 DTGs in jasmonic acid pathway. Surprisingly, no DTGs involved in the biosynthesis/signaling of abscisic acid, cytokinin, brassinosteroid, and salicylic acid pathways were detected. Moreover, among DTGs related to auxin, we identified an Aux/IAA gene RhIAA16 that was up-regulated in response to petal shedding. Down-regulation of RhIAA16 by virus-induced gene silencing in rose promoted petal abscission, suggesting that RhIAA16 plays an important role in rose petal abscission.

Effects of 1-methylcyclopropene on flower senescence and petal abscission in Dianthus caryophyllus L.

In carnations, senescence initially occurs by inrolling and wilting of petals due to reduced turgidity; this is associated with autocatalytic ethylene synthesis in petals. However, whether petal abscission occurs during flower senescence or is induced by petal wilting is unknown. Here, we investigated this process by determining differences in cellular morphology at the abscission zone and measuring petal turgidity and breakstrength during development in carnations. DcACS1 and DcACO1 played roles in autocatalytic ethylene production in carnations, and changes in these genes correlated with changes in ethylene biosynthesis. DcACS1 and DcACO1 transcripts were upregulated by treatment with ethylene and downregulated by treatment with 1-methylcyclopropene (1-MCP). Longitudinal sections of flowers at the initial fully opened stage showed anatomically distinct cell layers in the petal-receptacle boundaries, similar to the abscission zone in Arabidopsis, suggesting that petal abscission could occur during flower senescence in Dianthus caryophyllus. Petal breakstrength was relatively low in turgid petals, but increased with loss of turgidity. Moreover, 1-MCP effectively delayed the loss of petal turgidity, and differences in petal breakstrength were unclear after senescence was initiated in wild-type and ethylene-treated flowers. Thus, although petal breakstrength decreased following ethylene treatment, petals did not abscise, even after complete wilting of the flowers.

Pollination increases ethylene production in Lilium hybrida cv. Brindisi flowers but does not affect the time to tepal senescence or tepal abscission

In many species, pollination induces a rapid increase in ethylene production, which induces early petal senescence, petal abscission, or flower closure. Cross-pollination in Lilium hybrida cv. Brindisi resulted in a small increase in flower ethylene production. In intact plants and in isolated flowers, pollination had no effect on the time to tepal senescence or tepal abscission. When applied to closed buds of unpollinated flowers, exogenous ethylene slightly hastened the time to tepal senescence and abscission. However, exogenous ethylene had no effect when the flowers had just opened, i.e. at the time of pollination. Experiments with silver thiosulphate, which blocks the ethylene receptor, indicated that endogenous ethylene had a slight effect on the regulation of tepal senescence and tepal abscission, although only at the time the tepals were still inside buds and not in open flowers. Low ethylene-sensitivity after anthesis therefore explains why pollination had no effect on the processes studied.

ASYMMETRIC LEAVES1 regulates abscission zone placement in Arabidopsis flowers.

BackgroundThe sepals, petals and stamens of Arabidopsis flowers detach via abscission zones formed at their boundaries with the underlying receptacle. The ASYMMETRIC LEAVES1 (AS1) MYB transcription factor plays a critical role in setting boundaries between newly formed leaf primordia and the shoot meristem. By repressing expression of a set of KNOTTED1-LIKE HOMEODOMAIN (KNOX) genes from developing leaf primordia, AS1 and its partner ASYMMETRIC LEAVES2 allow the patterning and differentiation of leaves to proceed. Here we show a unique role for AS1 in establishing the positions of the sepal and petal abscission zones in Arabidopsis flowers.ResultsIn as1 mutant flowers, the sepal abscission zones are displaced into inverted V-shaped positions, leaving behind triangular stubs of tissue when the organs abscise. Movement of the petal abscission zones is also apparent. Abscission of the medial sepals is delayed in as1 flowers; loss of chlorophyll in the senescing sepals contrasts with proximal zones that remain green. AS1 has previously been shown to restrict expression of the KNOX gene, BREVIPEDICELLUS (BP), from the sepals. We show here that loss of BP activity in as1 flowers is sufficient to restore the positions of the sepal and petal abscission zones, the sepal-receptacle boundary of the medial sepals and the timing of their abscission.ConclusionsOur results indicate that AS1 activity is critical for the proper placement of the floral organ abscission zones, and influences the timing of organ shedding.

Increase in DNA fragmentation and the role of ethylene and reactive oxygen species in petal senescence of Osmanthus fragrans

In sweet osmanthus (Osmanthus fragrans Lour.) flowers, petal browning, partial abscission and wilting are the visible symptoms of senescence, 4–5 days after flowering, which seriously affect its ornamental and economic value. In the present study, DNA fragmentation was used as a marker to investigate the role of ethylene and reactive oxygen species (ROS) in flower senescence of O. fragrans ‘Liuye Jingui’. In intact plants, nuclear shrinkage and DNA fragmentation occurred at the late full flowering stage when senescence symptoms became visible. This coincided with a rapid increase in ethylene production, ROS generation and lipid peroxidation. To further determine the role of ethylene and ROS in flower senescence, cut flowers were treated with ethephon, silver thiosulphate (STS), hydrogen peroxide (H2O2), and vitamin C (Vc). The vase life of cut flowers was significantly prolonged by 0.2mM STS and 2.5mM Vc treatments, but reduced by 0.03% H2O2 and 500mgL−1 ethephon treatments, compared to distilled water. The percentage of DNA fragmentation was dramatically increased by ethephon but reduced by STS treatment throughout vase life. In contrast, the dramatic increase of DNA fragmentation in the H2O2 treated samples was only observed at day three, and clear petal abscission and rapid petal wilting occurred only with ethephon. Compared with the distinguishable nuclei and complete vacuoles in both STS treatment and distilled water, ethephon treatment caused substantial damage to large central vacuoles and other organelles, and many petal cells twisted out of shape due to a loss of cytoplasm, resulting in rapid petal wilting. Thus, it is concluded that ethylene plays an important role in flower senescence of sweet osmanthus, enhancing DNA fragmentation, damaging cellular structure, and leading to petal abscission and wilting. In addition, ROS is also involved in the regulation of late DNA degradation and lipid peroxidation.

Ethylene as a Postharvest “Evil” and its Remedies in some Horticultural Crops

Postharvest is an agricultural operation starting from the time of harvesting till the commodity reaches to the ultimate user/consumer. The postharvest life of horticultural produces is different from other produces in having shortest shelf life. In some horticultural crops which we call climacteric, there is an increase rate of respiration mainly due to a very high synthesis of the ripening hormone (ethylene), which has both beneficial and detrimental (“evil”) effects depending on the type of commodity. The effect of ethylene is accumulative so continuous exposure to a low concentration of ethylene throughout marketing can cause significant harm. In climacteric fruits exogenous C2H4 caused the peel and flesh to ripen out of phase, with the flesh ripening faster than the peel. In a study of cut flowers, exposure to ethylene at 100 μl l-1 reduced vase life by about 30%. In order to minimize this evil effect different vase solutions have been investigated. STS (silver thiosulfate) and 1-MCP (1-methylcyclopropene) can effectively protect flowers against exogenous ethylene. Pre-treatment of plants with 1 μl l-1 1- MCP for 2 h completely inhibited ethylene-induced petal abscission. Applications of Silver thiosulphate (STS) and 1-MCP have a great role to withstand the impact of ethylene. Thus they give relief for those concerned with horticultural crops which are sensitive to ethylene action. However more researches have to be done about the level and time of application of these chemicals and a new chemical against ethylene should be investigated.

Defense enzyme activities and biochemical variations of Pelargonium zonale in response to nanosilver application and dark storage

Pelargonium petal abscission and ethylene-induced leaf senescence are major problems that reduce the longevity of plants. This study was carried out to determine the poststorage influence of nanosilver (NS) particle (0, 20, 40, 60, and 80 mg L-1) application during dark storage period on chlorophyll and carotenoid pigments, malondialdehyde (MDA) content, leaf protein and ethylene concentration, petal abscission, membrane stability index (MSI), and enzyme activity including ascorbate peroxidase (APX), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and \BETA-glucosidase (\BETA-GLU) in two Pelargonium pot plants of the cultivars Flowerfairy and Foxi. Enhanced photosynthetic pigment contents were recorded in leaves of both NS-treated cultivars when compared to the control. In both cultivars, MDA content decreased significantly with the increase of NS concentration up to 60 mg L-1, and then a rapid increase followed at 80 mg L-1. NS treatments markedly decreased petal abscission compared to the control. Enzymes activities were affected differently by various NS concentrations. The highest APX activity was observed at 40 mg L-1 NS concentration, but specific activities of SOD and POD increased to a maximum level at 60 mg L-1 in both cultivars. CAT activity was pronounced at 20 mg L-1 and 40 mg L-1 NS treatments in Flowerfairy and Foxi, respectively. Both under control conditions and at the highest NS concentration, \BETA-GLU showed lower activity than other NS levels. It was suggested for the first time that NS extended petal longevity and improved defense enzyme activities of Pelargonium pot plants under dark storage conditions.

Spray treatment with silver nanoparticles plus thidiazuron increases anti-oxidant enzyme activities and reduces petal and leaf abscission in four cultivars of geranium (Pelargonium zonale) during storage in the dark

SummaryLeaf senescence and petal abscission in flowering plants such as Pelargonium occur in the dark during commercial transportation. Both affect plant quality and the commercial viability of the plant. In this experiment, we investigated the effects of 60 mg l 1 silver nanoparticles (SNP) in combination with 75 µM thidiazuron (TDZ) on selected physiological and biochemical characteristics of four cultivars of Pelargonium zonale (‘Foxi’, ‘Flowerfairy’, ‘Bluewonder’, and ‘Anthony’) incubated in the dark.The concentrations of photosynthetic pigments and proteins were measured, and petal abscission and anti-oxidant enzyme activities were analysed under the treatments applied. Following exposure to SNP plus TDZ, the extent of lipid peroxidation as well as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities changed, together with changes in the isozyme patterns of POD and SOD. SNP plus TDZ significantly decreased the incidence of petal abscission and leaf senescence compared to untreated control plants. Photosynthetic pigment concentrations increased in the SNP plus TDZ–treated plants, especially in ‘Anthony’ and ‘Foxi’. A significant reduction in lipid peroxidation was recorded in ‘Bluewonder’ and in ‘Flowerfairy’ flowers following SNP plus TDZ treatment, compared to the untreated controls. APX activities increased in all cultivars, except ‘Foxi’, following SNP plus TDZ treatment compared to the respective untreated control plants. Furthermore, increases in both POD and CAT activities were observed following treatment with SNP plus TDZ. The increases in CAT and SOD activities were most pronounced in ‘Anthony’ and ‘Flowerfairy’, relative to untreated control plants. These results demonstrate that co-treatment with SNP plus TDZ could be an effective strategy to retard post-harvest senescence in sensitive geranium cultivars such as ‘Flowerfairy ‘and ‘Bluewonder’.

Postharvest characteristics of cut dahlia flowers with a focus on ethylene and effectiveness of 6-benzylaminopurine treatments in extending vase life

With the aim of extending vase life of cut dahlia flowers, we investigated the postharvest characteristics of the flowers. Our focus was on the role of ethylene on senescence and on treatments that have extended vase life of other flowers. Continuous exposure to ethylene at 2 or 10μLL−1 significantly accelerated petal abscission in cut flowers. Flowers continuously immersed in 1 or 10μLL−1 2-chloroethylphosphonic acid (CEPA) solution wilted earlier than those treated with distilled water (DW) or 0.15gL−1 citric acid. Ethylene production from the ovary and ray petal was relatively high (4.5 and 0.9nLg−1freshweighth−1, respectively) at harvest, but decreased gradually over 5 days. No remarkable increase in ethylene production was observed during senescence. Silver thiosulfate complex (STS), an inhibitor of ethylene action, did not extend the vase life of cut flowers, although a high silver concentration was detected in flower organs. In contrast, pulse treatment with 1-methylcyclopropene (1-MCP) and dip treatment with 6-benzylaminopurine (BA) extended the vase life of florets, and BA was more effective than 1-MCP when the flowers were held in both DW and CEPA. BA spray treatment extended vase life of cut ‘Kokucho,’ ‘Kamakura’ and ‘Michan’ flowers. These results suggest that dahlia flower senescence is partially regulated by ethylene, and BA is more effective in delaying the senescence of cut dahlia flowers than ethylene action inhibitors.

Morphological and molecular characterization of ethylene binding inhibition in carnations

Ethylene perception by ethylene receptors can be suppressed by ethylene antagonists, such as 1-methylcyclopropene (1-MCP). 1-MCP binds to ethylene receptors blocking ethylene binding, and thereby represses ethylene responses, including flower senescence and petal abscission. Despite its antagonistic propensity, plants treated with 1-MCP often regain sensitivity to ethylene, suggesting that ethylene receptors are synthesized de novo post-treatment. To investigate this observation, we determined the relationship between the mRNA levels of ethylene biosynthesis and ethylene receptor genes and the degree of ethylene sensitivity of carnation flowers after ethylene and 1-MCP treatments. Flowers treated with a single application of 1-MCP lost the inhibitory effect in ethylene production after 7d of the treatment. In contrast, multiple treatments with 1-MCP completely suppressed several ethylene biosynthesis genes and ethylene production throughout the experiment. Multiple 1-MCP treatments increased vase life by almost three-fold relative to control flowers. Eventually ethylene-independent browning and desiccation on the edges of petals contributed to loss of vase life. We observed that the transcript levels of the ethylene receptor genes, DcETR1 and DcERS1, decreased with flower development, but increased at the onset of floral senescence. Our results suggest that ethylene receptors are continually synthesized during later stages of floral development. While ethylene responsiveness is temporarily blocked by 1-MCP treatment, we predict that new receptors synthesized days after 1-MCP treatment can bind ethylene. This leads to the observed recovery of ethylene sensitivity in the flowers. In addition, we predict that the degradation of ethylene receptors that is stimulated by ethylene binding is prevented by successive treatments with 1-MCP prior to recovery of ethylene sensitivity. This study improves our understanding about the uses and effectiveness of 1-MCP and will facilitate the development and improvement of postharvest treatments for multiple crops.

Differential expression of several xyloglucan endotransglucosylase/hydrolase genes regulates flower opening and petal abscission in roses

Flower opening is a process that requires movement of petals from a closed position to a horizontal open position, while petal abscission requires cell-wall disassembly. Both processes are controlled by ethylene and require cell-wall modification at the junction (abscission zone) of the petal and thalamus to facilitate the movement or separ- ationofpetals.Inthepresentstudy,afamilyofxyloglucanendotransglucosylase/hydrolase(XTH)geneswasstudiedto understand their role in petal abscission in flowers of Rosa bourboniana (ethylene sensitive, early abscising) and Rosa hybrida(lessethylenesensitive,lateabscising).TranscriptomesequencingofpetalabscissionzonecDNAwasperformed atdifferenttimepoints(ethylenetreatedanduntreated)andscreenedforXTHgenes.ThestudyidentifiedninenewXTH genes that showed differential changes in gene expression during flower opening and abscission. Of these, RbXTH3, RbXTH5, RbXTH6 and RbXTH12 were rapidly induced by ethylene within 1-4 h of ethylene treatment, corresponding to the period of flower opening. These genes also showed an early up-regulation during flower opening under ethylene-untreated (field abscission) conditions, indicating a possible role in anthesis and petal movement during flower opening. Other genes such as RbXTH4 and RbXTH9 were up-regulated later at 8-12 h after ethylene treatment and at 24-36 h under natural abscission conditions, indicating a possible role in abscission. Treatment with a higher ethylenedose(15 m LL 21 ethylene)acceleratedabscission,leadingtohighersteady-statelevelsofXTHgenetranscripts atanearliertimepointcomparedwith0.5 m LL 21 ethylene.Incontrast,transcriptaccumulationofmostoftheXTHswas considerablydelayedin thelate-abscising rose,R.hybrida, inkeeping with the slowerfloweropeningand delayedpetal abscission. The results suggest coordinated action of different XTHs in cell-wall modification of xyloglucan moieties during flower opening as well as cell separation during abscission.

β-Cyclodextrin-based nanosponges improve 1-MCP efficacy in extending the postharvest quality of cut flowers

Investigations of the effect of the β-cyclodextrin-based nanosponge-1-methylcyclopropene (1-MCP) complex (β-CD-NS complex) on six ethylene-sensitive cut flowers were performed. Anemone coronaria L. multicolor, Ranunculus asiaticus L. ‘Minou Abrown’, Helianthus annuus L. ‘Sunrich Orange’, Rosa hybrida L. ‘Jupiter’, Paeonia lactiflora L. ‘Sarah Bernhardt’, and Papaver nudicaule L. multicolor underwent four different treatments: a vase placement in a suspension of β-CD-NS complex (0.25μLL−1), exposure to gaseous 1-MCP (0.25μLL−1) for 6h, exposure to exogenous ethylene (1±0.2μLL−1) for 24h, and placement in tap water.β-Cyclodextrin-based nanosponges proved to enhance 1-MCP efficacy in all the tested species. According to the species, senescence symptoms were decreased or delayed. Anemone and poppy had a longer esthetic flower quality and vase life, and a reduced petal abscission. In ranunculus, β-CD-NS complex improved longevity. In sunflower, it also maintained longer chlorophyll leaf content and cut flower ornamental value. Peony opened more slowly and rose maintained its ornamental quality longer than 1-MCP treated flowers. This study opens possibilities for commercial use of the β-CD-NS complex in the floriculture industry.