Physiological response of cut rose flowers to cold storage

The effects of low temperature storage on the physiology of cut rose flowers ( Rosa hybridaL. cv. Mercedes) were studied. Extension of cold storage or increase in temperature (from 3 to 8°C) was accompanied by shortening of vase life and advancement of petal senescence, as reflected in an advance in the timing of the rise in ethylene production and an increase in membrane permeability (ion leakage). Although storage at a relative humidity (RH) of 65% reduced petal water content by 20% in comparison with flowers stored at 95% RH, it did not shorten vase life. The progression of petal senescence was measured during storage at 3°C and during aging at 22°C. Both ethylene production rates and membrane microviscosity measured by fluorescence depolarization increased with time at 3°C and at 22°C, but more slowly at 3°C. At 3°C membrane permeability measured by ion leakage did not increase. Following cold storage the rate of ethylene production in the petals was increased by up to eight times the rate in unstored flowers. Silver thiosulphate extended the vase life of both stored and fresh flowers equally by 2 days, but did not increase the life of stored flowers to that of treated fresh flowers. It is concluded that the primary effect of cold storage on roses is to slow down senescence and that the continued slow senescence leads to shorter vase life. The possible occurrence of sequential processes during senescence and the effects of temperature on these processes is discussed.     

Acceleration of membrane senescence in cut carnation flowers by treatment with ethylene

The lipid microviscosity of microsomal membranes from senescing cut carnation (Dianthus caryophyllus L. cv. White Sim) flowers rises with advancing senescence. The increase in membrane microviscosity is initiated within 3 to 4 days of cutting the flowers and coincides temporally with petal-inrolling denoting the climacteric-like rise in ethylene production. Treatment of young cut flowers with aminoethoxyvinylglycine prevented the appearance of petal-inrolling and delayed the rise in membrane microviscosity until day 9 after cutting. When freshly cut flowers or aminoethoxyvinylglycine-treated flowers were exposed to exogenous ethylene (1 microliter per liter), the microviscosity of microsomal membranes rose sharply within 24 hours, and inrolling of petals was clearly evident. Thus, treatment with ethylene accelerates membrane rigidification. Silver thiosulphate, a potent anti-ethylene agent, delayed the rise in microsomal membrane microviscosity even when the flowers were exposed to exogenous ethylene. Membrane rigidification in both naturally senescing and ethylene-treated flowers was accompanied by an increased sterol:phospholipid ratio reflecting the selective loss of membrane phospholipid that accompanies senescence. The results collectively indicate that the climacteric-like surge in ethylene production during senescence of carnation flowers facilitates physical changes in membrane lipids that presumably lead to loss of membrane function.     

Physiological Responses of Cut Rose Flowers to Exposure to Low Temperature: Changes in Membrane Permeability and Ethylene Production

Senescence of cut rose flowers (Rosa hybrida L. cv. Mercedes)at 22 °C occurred earlier in flowers previously held at2 °C for 10 d or 17 d than in freshly cut flowers. Thisadvanced senescence was observed as an earlier increase in bothethylene production rate and membrane permeability. The risein ethylene production preceded the rise in the level of ionleakage from petals, and this in turn preceded visible symptomsof petal death. Applied ethylene stimulated ion leakage andinhibitors of ethylene synthesis and action (amino-oxyaceticacid and silver thiosulphate respectively) inhibited the normalincrease in ion leakage. The maximum rate of ethylene productionof 22 °C increased markedly in petals of flowers previouslyheld at 2 °C, up to nine times the level in fresh flowers.We conclude that during exposure of rose flowers to 2 °C,in addition to senescence, processes were induced which ledto stimulated ethylene production after transferral to 22 °C.Ethylene apparently caused the subsequent advance in membranepermeability and senescence. Key words: Rose flower, Low temperature, Senescence     

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 site of 1-aminocyclopropane-1-carboxylic acid synthesis in senescing carnation petals

To study the cause of the uneven production of ethylene by upper and basal portions of detached petals of carnation ( Dianthus caryophyllus L. cv. White Sim), the petals were divided and exposed to ethylene (30 μl 1^-1 for 16 h). The treatment induced rapid wilting and autocatalytic ethylene production in the basal portion similar to that induced in entire petals. In contrast to the response in entire petals and the basal portions, the upper portions responded to ethylene by delayed wilting and much lower ethylene production. Aminocyclopropane carboxylic acid (ACC)-synthase activity in the basal portion of the petals was 38 to 400 times that in the upper portion. In untreated detached petal pieces from senescing carnation flowers, ethylene production by the upper portion declined after 6 h while the basal portion was still producing ethylene at a steady rate 18 h later. Application of ACC to the upper portion of senescing petals increased their ethylene production. α-Aminooxyacetic acid (0.5 m M ), reduced the ethylene production of the senescing basal portion more than that of the upper portion. Endogenous ACC content in basal portions of senescing carnation petals was 3 to 4 times higher than in the upper parts. When detached senescing petals were divided immediately after detaching, the endogenous ACC levels in upper portions remained steady or declined during 24 h after division, while in the basal portions the ACC level rose steadily as in the intact petals. There was no change in the conjugated ACC in either portion after 24 h. Benzyladenine (BA) applied as a pretreatment to entire preclimacteric petals greatly reduced the development of ACC-synthase activity of the basal portion, but had little effect on the activity in the upper portion of the petal. In both portions, however, BA effectively reduced the conversion of ACC to ethylene.     

Changes in the Physical State of Membrane Lipids during Senescence of Rose Petals

Changes in the physical state of microsomal membrane lipids during senescence of rose flower petals (Rosa hyb. L. cv Mercedes) were measured by x-ray diffraction analysis. During senescence of cut flowers held at 22°C, lipid in the ordered, gel phase appeared in the otherwise disordered, liquid-crystalline phase lipids of the membranes. This was due to an increase in the phase transition temperature of the lipids. The proportion of gel phase in the membrane lipids of 2-day-old flowers was estimated as about 20% at 22°C. Ethylene may be responsible, at least in part, for the increase in lipid transition temperature during senescence since aminooxyacetic acid and silver thiosulfate inhibited the rise in transition temperature. When flowers were stored at 3°C for 10 to 17 days and then transferrd to 22°C, gel phase lipid appeared in membranes earlier than in freshly cut flowers. This advanced senescence was the result of aging at 3°C, indicated by increases in membrane lipid transition temperature and ethylene production rate during the time at 3°C. It is concluded that changes in the physical state of membrane lipids are an integral part of senescence of rose petals, that they are caused, at least in part, by ethylene action and that they are responsible, at least in part, for the increase in membrane permeability which precedes flower death.     

Role of ethylene in the senescence of isolated hibiscus petals

Senescence of petals isolated from flowers of Hibiscus rosa-sinensis L. (cv Pink Versicolor) was associated with increased ethylene production. Exposure to ethylene (10 microliters per liter) accelerated the onset of senescence, as indicated by petal in-rolling, and stimulated ethylene production. Senescence was also hastened by basal application of 1-aminocyclopropane-1-carboxylic acid (ACC). Aminooxyacetic acid, an inhibitor of ethylene biosynthesis, effectively inhibited ethylene production by petals and delayed petal in-rolling. In marked contrast to these results with mature petals, immature petals isolated from flowers the day before flower opening did not respond to ethylene in terms of an increase in ethylene production or petal in-rolling. Furthermore, treatment with silver thiosulfate the day before flower opening effectively prevented petal senescence, while silver thiosulfate treatment on the morning of flower opening was ineffective. Application of ACC to both immature and mature petals greatly stimulated ethylene production indicating the presence of an active ethylene-forming enzyme in both tissues. Immature petals contained less free ACC than mature, presenescent petals and appeared to possess a more active system for converting ACC into its conjugated form. Thus, while the nature of the lack of responsiveness of immature petals to ethylene is unknown, ethylene production in hibiscus petals appears to be regulated by the control over ACC availability.     

Evidence for the involvement of gibberellins in developmental phenomena associated with carnation flower senescence

The application of 10^–4 M GA₃ to preclimacteric carnation flowers delayed senescence, climateric ethylene production reduced the rate of loss in fresh weight of intact flowers and the decrease in moisture content of the petals. The loss in flower fresh weight commenced prior to the ethylene climacteric. The increased membrane permeability which was observed when intact, control flowers were half opened, was delayed by GA₃ application. This effect was only significant when GA₃ was applied to young flowers. In addition to slowing down the loss in fresh mass, GA₃ inhibited ethylene production by the style and stigma. The increase in ovary dry weight and chlorophyll content and the associated decrease in petal dry weight was slowed down by GA₃ but not arrested, this despite reduced ethylene production by the ovary. It is proposed that a decline in endogenous gibberellin may be a correlative event associated with the onset of the senescence process in carnation flowers.Abbreviations GA₃ gibberellic acid - STS silver thiosulphate     

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.     

The Involvement of Water Stress and Ethylene in Senescence of Cut Carnation Flowers

Exposing cut carnation (Dianthus caryophyllus, cv. White Sim)to short term (12 h) water stress resulted in a marked increasein the water saturation deficit (WSD) of the petals. Full recoveryoccurred upon transfer of the flowers to water in humid conditions(r.h. 85%). However, an increase in aminocyclopropane carboxylicacid (ACC) content occurred immediately upon stress. An associatedrise in ethylene production following transfer to humid conditionswas observed earlier than in the control. Exogenous ethylene,applied alone or in combination with water stress, increasedthe WSD of the petals. Continuous treatment of cut flowers with amino-oxyacetic acid(AOA), a known inhibitor of ACC synthesis, suppressed ethyleneproduction, delayed the rise in WSD which accompanied developmentand senescence and hence delayed wilting. Similar results wereobtained with short term (2 h) treatment with AOA prior to stressingthe flowers. Short term AOA treatment partially inhibited therise in WSD during the stress period. On the basis of our findings, in particular that no rise inethylene production occurred during water stress, it is suggestedthat the effect of water stress is not directly mediated byethylene. The possible modulatory effect of water stress andAOA on certain characteristics of the petal cell membrane isdiscussed.     

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.     

Involvement of ethylene in the disease caused by Botrytis cinerea on rose and carnation flowers and the possibility of control*

Ethylene production by flowers, petals and leaves of rose was correlated with severity of grey mould. However, when the host became completely macerated, ethylene production diminished. Ethylene production by Botrytis cinerea grown on autoclaved flowers which were supplemented with methionine was negligible. Methionine spray, incubation with ethylene, or precooling of flowers at 4°C increased disease incidence considerably. Ethylene also induced susceptibility of carnation flowers to attack by B. cinerea. On the other hand, sprays of silver thiosulphate (STS) aminooxyacetic acid (AOA) and aminoethoxyvinylglycine (AVG) decreased disease severity in rose petals and leaves inoculated with mycelial plugs or conidia. Treatment of cut rose flowers with STS (by dipping) or AOA (by spraying) significantly decreased disease incidence during subsequent incubation at 20 and 10°C. This suggests a treatment for reducing grey mould damage in flowers transported overseas.     

Role of Aminocyclopropane-1-carboxylic Acid (ACC) in Control of Ethylene Production in Fresh and Cold-stored Rose Flowers

The relationships between ethylene production, aminocyclopropane-1-carboxylicacid (ACC) content and ethylene-forming-enzyme (EFE) activityduring ageing and cold storage of rose flower petals (Rose hybridaL. cv. Gabriella) were investigated. During flower ageing at20 °C there was a climacteric rise in petal ethylene production,a parallel increase in ACC content, but a continuous decreasein EFE activity. Applied ACC increased petal ethylene productionc. 200-fold. During cold storage of flowers at 1 °C therewere parallel increases in petal ethylene production and ACCcontent, to levels greater than those reached in fresh flowersheld at 20 °C. EFE activity decreased during storage. Immediatelyafter cold-stored flowers were transferred to 20 °C ethyleneproduction and ACC levels were c. four times greater than infreshly cut flowers. These levels increased to maximum valuesof two to four times the maximum values reached during ageingof fresh, unstored, flowers. It was concluded that in rose petalsethylene synthesis is probably regulated by ACC levels and thatcold storage stimulates ethylene synthesis because it increasesthe levels of ACC in the petals. Key words: Rose flower, senescence, ethylene     

Effect of cycloheximide on some physiological changes associated with senescence of detached flowers of Iris germanica L.

Silverthiosulphate which is a potent inhibitor of ethylene action was found to be ineffective in delaying senescence of detached flowers of Iris germanica whereas cycloheximide, a protein synthesis inhibitor, effectively delayed the senescence of these flowers and extended the longevity to 6 days. However, this treatment resulted in suppression of bud opening. When cycloheximide treatment was given at progressive intervals it became less effective in inhibiting bud opening and delaying senescence. Cycloheximide treatment maintained a higher protein content in the perianth tissue of flowers compared to untreated flowers.     

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.     

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.     

Intracellular energy depletion triggers programmed cell death during petal senescence in tulip

Programmed cell death (PCD) in petals provides a model system to study the molecular aspects of organ senescence. In this study, the very early triggering signal for PCD during the senescence process from young green buds to 14-d-old petals of Tulipa gesneriana was determined. The opening and closing movement of petals of intact plants increased for the first 3 d and then gradually decreased. DNA degradation and cytochrome c (Cyt c) release were clearly observed in 6-d-old flowers. Oxidative stress or ethylene production can be excluded as the early signal for petal PCD. In contrast, ATP was dramatically depleted after the first day of flower opening. Sucrose supplementation to cut flowers maintained their ATP levels and the movement ability for a longer time than in those kept in water. The onset of DNA degradation, Cyt c release, and petal senescence was also delayed by sucrose supplementation to cut flowers. These results suggest that intracellular energy depletion, rather than oxidative stress or ethylene production, may be the very early signal to trigger PCD in tulip petals.     

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。