Effects of 1,1-dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) on carnation flower longevity

The effects of a novel preservative for cut carnation flowers, 1,1-dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS), were investigated. DPSS extended the vase life of cut carnation flowers not only by continuous treatment but pulse treatment as well. This inhibition of senescence by DPSS appeared to depend on that of ethylene production in carnation flowers. DPSS provided no protection from the action of ethylene nor did it inhibit 1-aminocyclopropane-1-carboxylic acid (ACC) synthase. It did inhibit ACC-dependent ethylene production in carnation petal discs, suggesting possible potential for inhibiting ACC oxidase.     

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.     

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.     

Changes in 1-aminocyclopropane-1-carboxylic-acid content of cut carnation flowers in relation to their senescence

The rise in ethylene production accompanying the respiration climacteric and senescence of cut carnation flowers (Dianthus caryophyllus L. cv. White Sim) was associated with a 30-fold increase in the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in the petals (initial content 0.3 nmol/g fresh weight). Pretreatment of the flowers with silver thiosulfate (STS) retarded flower senescence and prevented the increase in ACC concentration in the petals. An increase in ACC in the remaining flower parts, which appeared to precede the increase in the petals, was only partially prevented by the STS pretreatment. Addition of aminoxyacetic acid (2 mM) to the solution in which the flowers were kept completely inhibited accumulation of ACC in all flower parts.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AOA -aminoxyacetic acid - STS silver thiosulfate complex     

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.     

Comparison of mRNA levels of three ethylene receptors in senescing flowers of carnation (Dianthus caryophyllus L.)

Three ethylene receptor genes, DC-ERS1, DC-ERS2 and DC-ETR1, were previously identified in carnation (Dianthus caryophyllus L.). Here, the presence of mRNAs for respective genes in flower tissues and their changes during flower senescence are investigated by Northern blot analysis. DC-ERS2 and DC-ETR1 mRNAs were present in considerable amounts in petals, ovaries and styles of the flower at the full-opening stage. In the petals the level of DC-ERS2 mRNA showed a decreasing trend toward the late stage of flower senescence, whereas it increased slightly in ovaries and was unchanged in styles throughout the senescence period. However, DC-ETR1 mRNA showed no or little changes in any of the tissues during senescence. Exogenously applied ethylene did not affect the levels of DC-ERS2 and DC-ETR1 mRNAs in petals. Ethylene production in the flowers was blocked by treatment with 1,1-dimethyl-4-(phenylsulphonyl)semicarbazide (DPSS), but the mRNA levels for DC-ERS2 and DC-ETR1 decreased in the petals. DC-ERS1 mRNA was not detected in any cases. These results indicate that DC-ERS2 and DC-ETR1 are ethylene receptor genes responsible for ethylene perception and that their expression is regulated in a tissue-specific manner and independently of ethylene in carnation flowers during senescence.     

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.     

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     

The role of abscisic acid (ABA) in ethylene insensitive Gladiolus (Gladiolus grandiflora Hort.) flower senescence

Gladiolus flowers are ethylene insensitive and the signals that start catabolic changes during senescence of gladiolus flower are largely not known. Therefore, experiments were performed to understand the role of abscisic acid (ABA) in ethylene insensitive floral senescence in gladiolus (Gladiolus grandiflora Hort.). It was observed that ABA accumulation increased in attached petals of gladiolus flowers as they senesced. Exogenous application of ABA in vase solution accelerated senescence process in the flowers due to change in various senescence indicators such as enhanced membrane leakage, reduced water uptake, reduced fresh weight and ultimately vase life. Enhancement of in vivo ABA level in petals by creating osmotic stress also upregulates the same parameters of flower senescence as those occurring during natural senescence and also akin to exogenous application of ABA. Attempts to increase vase life of flowers by application of putative ABA biosynthesis inhibitor fluridone in vase solution to counteract ABA effect were unsuccessful. In contrast, ABA action was mitigated by application of GA₃ in holding solution along with ABA which is basically an antagonist of ABA action. The present study provides valuable insights into the role of ABA as a hormonal trigger in ethylene insensitive senescence process and therefore would be helpful for dissecting the complex mechanism underlying ABA-regulated senescence process in gladiolus.     

1,1-Dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) does not inhibit the in vitro activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and ACC synthase obtained from senescing carnation Dianthus caryophyllus L.) petals

The effects of 1,1-dimethyl-4-(phenylsulfonyl)semicarbazide (DPSS) on the in vitro activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and ACC synthase isolated from senescing carnation petals were investigated. In contrast to a previous proposal, DPSS at 1 mM did not inhibit the in vitro activity of ACC oxidase. It was confirmed that DPSS does not inhibit ACC synthase activity. DPSS probably does not exert its inhibitory action on ethylene production by a direct action on ACC oxidase and ACC synthase, but by some unknown action.     

Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability

Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers ( Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post-harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψ_w), and turgor (ψ_p), that preceded the rise in ABA and ethylene. As senescence progressed, ψ_w continued to decline, but ψ_p returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time-scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric-like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.     

Endogenous levels of abscisic acid in aging carnation flower parts

Aging carnation flower parts were used to determine whether or not any correlation existed between the concentration of abscisic acid (ABA) and a predisposition of the tissue for ethylene synthesis. Levels of ABA were measured using an enzyme-linked immunosorbent assay (ELISA) following purification steps including prepacked silica gel columns. Increased ABA levels paralleled the increase of ethylene and the onset of irreversible wilting in the carnation petals. Neither the green tissue nor the receptacle showed any sign of wilting with the remainder of the flower parts, but increased ABA was detected in both tissues subsequent to, or coincident with, the ethylene climacteric peak in the senescing petals. An increase of ABA in both the styles and the ovary was detected in the preclimacteric flower, and did not appear to be triggered by the production of ethylene. Increased ABA in the gynoecium also did not result in the onset of ethylene production in the preclimacteric flower.     

Ethylene biosynthetic genes are differentially expressed during carnation (Dianthus caryophyllus L.) flower senescence

Ethylene production and expression patterns of an 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (CARAO1) and of two ACC synthase (EC 4.4.1.14) genes (CARACC3 and CARAS1) were studied in floral organs of cut carnation flowers (Dianthus caryophyllus L.) cv. White Sim. During the vase life and after treatment of fresh flowers with ethylene, production of ethylene and expression of ethylene biosynthetic genes first started in the ovary followed by the styles and the petals. ACC oxidase was expressed in all the floral organs whereas, during the vase life, tissue-specific expression of the two ACC synthase genes was observed. After treatment with a high ethylene concentration, tissue specificity of the two ACC synthase genes was lost and only a temporal difference in expression remained. In styles, poor correlation between ethylene production and ACC synthase (CARAS1) gene expression was observed suggesting that either activity is regulated at the translational level or that the CARAS1 gene product requires an additional factor for activity.Isolated petals showed no increase in ethylene production and expression of ethylene biosynthetic genes when excised from the flower before the increase in petal ethylene production (before day 7); showed rapid cessation of ethylene production and gene expression when excised during the early phase of petal ethylene production (day 7) and showed a pattern of ethylene production and gene expression similar to the pattern observed in the attached petals when isolated at day 8. The interorgan regulation of gene expression and ethylene as a signal molecule in flower senescence are discussed.     

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.     

Correlative Changes in Phytohormones in Relation to Senescence Processes in Rose Petals

A comparative study of the level of abscisic acid (ABA) and cytokinin and of ethylene production by rose (Rosa sp.) petals of the short-lived cultivar Golden Wave (Dr. Verhage) and the long-lived cultivar Lovita was conducted. In both cultivars, the level of ABA increased as the flowers aged; it was higher in Golden Wave in all developmental stages tested. Ethylene production by cut flowers of the two cuitivars remained low for a short time concomitant with development and then increased sharply. The rise in ethylene production occurred after 3 and 4 days in Golden Wave and Lovita, respectively. Cytokinin level increased as the flower started to open and then decreased to a low level. The significance of these changes in relation to maturation and senescence of rose petals is discussed.     

Role of cytokinins in carnation flower senescence

Stem and leaf tissues of carnation (Dianthus caryophyllus) plants appear to contain a natural antisenescence factor since removal of most of these tissues from cut carnation flowers hastened their senescence. However, kinetin (5-10 μg/ml) significantly delayed senescence of flowers with stem and leaf tissues removed. In addition, the life span of cut flowers with intact (30-cm) stems was increased with kinetin treatment. Peak ethylene production by presenescent flowers was reduced 55% or more with kinetin treatment and was delayed by 1 day. Kinetin-treated flowers were less responsive to applied ethylene (100 μl/l for 3 hours) than untreated flowers. Possible natural roles of cytokinins in carnation flower senescence are discussed.     

Effects of Ethylene and Sucrose on Translocation of Dry Matter and 14C-Sucrose in the Cut Flower of the Glasshouse Carnation (Dianthus caryophyllus) During Senescence

The translocation and distribution of dry matter were studiedin the floral and vegetative parts of the cut carnation duringsenescence. The change in dry weights of the tissues and theamount of radioactivity recovered from them after feeding with¹⁴C-sucrose were measured. Treatments with ethylene and sucrosewere used to alter the rate of senescence of the flowers. Sucrosemoved through the stem relatively unchanged but was rapidlyinverted and metabolized in the petals. During natural ageing,¹⁴C moved from the stem to the flower and the movement was enhancedby exogenous sucrose, which also reduced the loss of dry matterin the petals and promoted their growth. Treatment with ethylenecaused petals to wilt and lose dry weight, and ovaries to enlargeand increase in dry weight. The distribution of radioactivityin flowers fed with 14C-sucrose before and after ethylene treatmentsupported the observation that dry matter was translocated betweenthe flower parts. The results indicate that a change in thesource-ink relationships of the flower parts contributes tothe factors that determine the rate of flower senescence.     

Transient Water Stress in Carnation Flowers: Effect of Amino-oxyacetic Acid

A short and temporary water stress imposed on cut carnationflowers (Dianthus caryophyllus L., cv. White Sim) flowers advancedsenescence symptoms, including ethylene production and wilting.Pretreatment with amino-oxyacetic acid (AOA) resulted in anincrease of the resistance of the flowers to water stress: waterloss during stress was reduced, recovery was more rapid andwilting was delayed. Water stress accelerated the decrease inlevel of membrane phospholipids, but pretreatment with AOA counteractedthis effect. Since the content of membrane sterols was not affectedby the treatments, the mole ratio of sterol to phospholipidincreased in water-stressed flower petals but not in stressedflowers pretreated with AOA. Membrane permeability and fluiditywere also adversely affected by water stress and AOA: waterstress alone resulted in an increase in permeability and a decreasein fluidity, but in AOA-pretreated stressed flower petals theseparameters were similar to those of nonstressed control flowerpetals. On the basis of these results two main conclusions can be drawn:(a) Water stress induces alterations in the physical and compositionalproperties of carnation petal membranes, (b) Pretreatment ofthe flowers with AOA influences petal membrane traits, mostprobably via modifications in phospholipid turnover, in a waywhich counteracts the effects of water stress. Key words: Amino-oxyacetic acid, Water stress, Carnation flowers