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.     

Reversible inhibition of ethylene action and interruption of petal senescence in carnation flowers by norbornadiene

The inhibitory effects of the cyclic olefin 2,5-norbornadiene (NBD) on ethylene action were tested in carnation (Dianthus caryophyllus L. cv White Sim) flowers. Treatment of flowers at anthesis with ethylene in the presence of 500 microliters per liter NBD increased the concentration of ethylene required to elicit a response (petal senescence), indicating that NBD behaves as a competitive inhibitor of ethylene action. Transfer of flowers producing autocatalytic ethylene and exhibiting evidence of senescence (petal in-rolling) to an atmosphere of NBD resulted in a rapid reduction in ethylene production, petal 1-aminocyclopropane-1-carboxylic acid synthase activity, 1-aminocyclopropane-1-carboxylic acid content, and ethylene forming enzyme activity. Removal of NBD resulted in recovery of ethylene biosynthesis. These results support the autocatalytic regulation of ethylene production during the climacteric stage of petal senescence and suggest that continued perception of ethylene is required for maintenance of ethylene biosynthesis. The inhibition of ethylene action by NBD after the flowers had reached the climacteric peak was associated with interruption of petal senescence as evidenced by reversal of senescence symptoms. This result is in contrast to the widely held belief that the rate of petal senescence is fixed and irreversible once petals enter into the ethylene climacteric.     

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.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AIB -amino-isobutyric acid - AOA amino oxyacetic acid - AVG aminoathoxyvinyl glycine - DACP diazocyclopentadiene - EFE ethylene forming enzyme - MACC malonyl 1-aminocyclopropane-1-carboxylic acid - MTA 5-methylthio-adenosine - NBD 2,5 norbornadiene - ppb parts per billion - SAM S-adenosyl-methionine - STS silver thiosulphate     

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.     

Effect of oxygen concentration on the senescence and energy metabolism of cut carnation flowers

The effect of O₂ concentration on energy metabolism and senescence has been studied in cut flowers of Dianthus caryophyllus L. cv. Scania. As compared to the control (21% O₂), 5% O₂ delays flower senescence as well as decay of nucleotide level and AEC (adenylate energy charge). An atmosphere of 100% O₂ accelerates senescence as well as the decrease of nucleotide level and AEC. While anoxia brings about a faster decrease of ATP and AEC than of total nucleotides, hyperoxia brings about a faster decrease in adenyl nucleotides than in ATP and AEC values. Petal oxygen uptake is over 90% of the maximal value under 4% O₂ and saturates at 10% O₂. The development of senescence is dicussed as a two phase process (first phase-progressive and second phase-catastrophic) triggered by the action of hyperoxia, first on the system for energy utilization and later on the system for energy production, the degradation of which seems to be linked with increase in membrane permeability and withering.     

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     

Daffodil flowers delay senescence in cut Iris flowers

Visible symptoms of tepal senescence in cut Iris x hollandica (cv. Blue Magic) flowers were delayed by placing one cut daffodil flower (Narcissus pseudonarcissus, cv. Carlton) in the same vase. Addition of mucilage, exuded by daffodil stems, to the vase water had the same effect as the flowering daffodil stem. The active compound in the mucilage was identified as narciclasine (using LC/MS, GC/MS, 1H and 13C-NMR, and comparison with an authentic sample of narciclasine). The delay of senescence, either by mucilage or purified narciclasine, was correlated with a delayed increase in protease activity, and with a considerable reduction of maximum protease activity. Narciclasine did not affect in vitro protease activity, but is known to inhibit protein synthesis at the ribosomal level. Its effects on senescence and protease activity were similar to those of cycloheximide (CHX), another inhibitor of protein synthesis, but the effective narciclasine concentration was about 100 times lower than that of CHX. It is concluded that the delay of Iris tepal senescence by daffodil stems is due to narciclasine in daffodil mucilage, which apparently inhibits the synthesis of proteins involved in senescence.     

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。     

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.     

Ethanol reduces sensitivity to ethylene and delays petal senescence in cut Tweedia caerulea flowers

Tweedia caerulea flowers are sensitive to ethylene and the closing of the flowers, a characteristic of senescence, is accelerated by exposure to ethylene. T. caerulea flowers were continuously treated with ethanol at concentrations of 0, 2, 4, 6, 8, 10 or 12 %, and treatment levels at 4 % and above showed delayed closing. Ethanol accelerated climacteric increase in ethylene production from flowers. Although ethylene production was higher in gynoecium than in petals, ethanol treatment accelerated ethylene production by both organs. Exposure to ethylene increased autocatalytic ethylene production, and production was further accelerated by ethanol treatment. When flowers treated with ethanol were exposed to ethylene, senescence was delayed compared to that for untreated flowers, suggesting that ethanol reduces the sensitivity of flowers to ethylene. These results indicate that treatment with ethanol delays petal senescence in cut T. caerulea flowers, possibly through reduced sensitivity to ethylene.     

The development of Botrytis cinerea on cut flowers of carnation

Enclosing carnation blooms in polythene increased rotting associated with naturally occurring Botrytis infections and accelerated the rate of conidia development when flowers were artificially inoculated before being stored at 1·7 °C. Petal infections were observed 16 and 48 h after inoculation and incubation at 18·3 and 1·7 °C respectively. The products of exosmosis from petals kept at 18·3 °C for 7 days stimulated germination of B. cinerea conidia. Slight pectic enzyme activity was detected in a liquid medium, derived from carnation petals, after incubating B. cinerea cultures at 18·3 °C for 6 days. Although cultures of Botrytis evolved virtually no ethylene, the surge of ethylene produced by uncontaminated ageing flowers occurred sooner after inoculation. A spray containing 1·2% a.i. of 2-aminobutane controlled rotting but damaged flowers.     

Cytokinins in cut carnation flowers. II. Relationship between endogenous ethylene and cytokinin levels in the petals

Tentative identification using HPLC and RIA techniques indicated the presence of zeatin-O-glucoside, zeatin, ribosylzeatin, dihydrozeatin, iso-pentenyladenine and iso-pentenyladenosine in the petals of carnation flowers. Dihydrozeatin is apparently responsible for most of the biological activity. Within the petals most activity was detected in the basal parts which also senesced much slower than the upper parts of the petals. Treatment with AOA extended petal longevity and reduced ethylene production. This was associated with higher cytokinin-like activity in the basal parts of the petals.These higher levels of cytokinins were not observed in the petals of ACC treated flowers or in the detached control flowers. It is suggested that cytokinin transport and/or metabolism may play an important role in regulating ethylene production in cut carnations.     

Regulation of membrane phospholipid catabolism in senescing carnation flowers

Evidence has been obtained for the involvement of μ M levels of Ca²⁺ in phospholipid catabolism during petal senescence by following the breakdown of [U-¹⁴C]-phosphatidylcholine by microsomal membranes from cut carnation ( Dianthus caryophyllus L. cv. White-sim) flowers. Phospholipid degradation was mediated by three membrane-associated lipases, viz. phospholipase D (EC 3.1.4.4), phosphatidic acid phosphatase (EC 3.1.3.4) and lipolytic acyl hydrolase. The activities of phospholipase D and phosphatidic acid phosphatase were stimulated by 30 and 100%, respectively, in the presence of 40 μ M free Ca²⁺, and the Ca²⁺-stimulation of phosphatidic acid phosphatase was calmodulin-dependent. When L-3-phosphatidyl-[2-³H]-inositol and L-3-phosphatidyl-[N-methyl-³H]-choline were used as substrates, inositol and choline accounted for 95 and 99%, respectively, of the water-soluble radiolabelled products. This suggests a predominance of phospholipase D activity over phospholipase C activity in these membranes.
Breakdown of membrane phospholipids in senescing carnations is known to be accelerated by treatment of young flowers with ethylene. To determine whether this involves a specific turnover of phosphatidylinositol as observed in animal systems in response to certain agonists, young flowers pre-labelled with ³²PO^3-₄ were treated with 10 ppm ethylene. All phospholipids incorporated the label, but no enhanced turnover of phosphatidylinositol was observed. Inositol 1,4,5-triphosphate did not release Ca²⁺ from preloaded microsomal vesicles at concentrations known to be effective in animal systems (i.e. < 5 μ M ) although release of Ca²⁺ was observed when a higher (20 μ M ) concentration was used.     

Cytokinins in cut carnation flowers: I. The complex in ovaries

Tentative identification of the cytokinins present in extracts of Dianthus caryophyllus ovaries using High Performance Liquid Chromatography and Radioimmunoassay techniques, revealed the presence of trans-ribosylzeatin, trans-zeatin, dihydrozeatin and N⁶ (²-isopentenyl)adenine. In addition slow moving compounds (paper chromatography) which could be hydrolysed by -glucosidase were also detected. After hydrolysis the active compounds co-chromatographed with zeatin and ribosylzeatin.     

月季切花衰老过程中多胺与膜脂过氧化的关系

以月季切花为材料,研究了月季切花瓶插过程中多胺含量的变化,外源多胺处理对月季药花体内多胺含量的影响以及多胺与膜脂过氧化的关系。结果表明,月季切花瓶插衰老过程中腐胺在前2d略有增加,亚精胺和精胺均呈下降趋势;外源亚精胺和精胺处理均能增加切花体内多胺含量,并能延缓切花衰老和改善切花品质;且亚精胺和精胺处理降低了MDA含量的积累和膜相对透性的上升趋势。     

Senescence of cut carnation flowers: Ovary development and CO2 fixation

In the presence of ethylene, which enhances carnation flower senescence, carbohydrates contribute to ovary growth not only from the stem and calyx but also from the petals. With silver thiosulphate and ethanol treatments which delay flower senescence, the petals remain the active sink and ovary development is suppressed. Ethylene stimulated chloroplast development in the ovary wall. However, the calyx plus stem of all treatments showed the greater photosynthetic ability and transported a major portion of the synthesised products to the ovary.