Pollination-Induced Ethylene in Carnation (Role of Pollen Tube Growth and Sexual Compatibility)

The pollen-pistil interactions that result in the stimulation of ethylene production and petal senescence in carnation (Dianthus caryophyllus L.) flowers were investigated. Pollination of White Sim flowers with Starlight pollen elicited an increase in ethylene production by styles, leading to increased petal ethylene and premature petal senescence. In contrast, pollination with 87-29G pollen led to an early increase in ethylene production, but this was not sustained, and did not lead to petal senescence. Both Starlight and 87-29G pollen germinated on White Sim stigmas and their tubes grew at similar rates, penetrating the length of the style. Crosses between Starlight and White Sim led to the production of viable seeds, whereas 87-29G pollen was infertile on White Sim flowers. Pollination of other carnations with 87-29G elicited ethylene production and petal senescence and led to the production of viable seeds. These results suggest that physical growth of pollen tubes is insufficient to elicit a sustained increase in ethylene production or to lead to the production of signals necessary for elicitation of petal ethylene production and senescence. Rather, the cell-cell recognition reactions leading to sexual compatibility in Dianthus appear to play a role in this interorgan signaling after pollination.     

Regulation of Senescence in Carnation (Dianthus caryophyllus) by Ethylene: Mode of Action

Carnation (Dianthus caryophyllus) flowers were exposed to 2 μl/l ethylene and examined at intervals to determine the time course of wilting, decrease in water uptake, and increase in ionic leakage in response to ethylene. A rapid decrease in water uptake was observed about 4 hours after initiating treatment with ethylene. This was followed by wilting (in-rolling of petals) about 2 hours later. Carbon dioxide inhibited the decline in water uptake and wilting and this is typical of most ethylene-induced responses. Ethylene did not affect closure of stomates. Ethylene enhanced ionic leakage, as measured by efflux of ³⁶Cl from the vacuole. This was judged to coincide with the decrease in water uptake. Gassing flowers with propylene initiated autocatalytic ethylene production within 2.4 hours. Since the increase in ethylene production by carnations preceded the increase in ionic leakage and the decline in water uptake by several hours, it is apparent that the change in ionic leakage does not lead to the initial increase in ethylene production as reported (Hanson and Kende 1975 Plant Physiol 55:663-669) in morning glory but may explain the autocatalytic phase of ethylene production.     

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.     

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.     

Comparison between Ultraviolet Irradiation and Ethylene Effects on Senescence Parameters in Carnation Flowers

The effects of ethylene and ultraviolet (UV) irradiation on parameters of senescence in carnation (Dianthus caryophyllus L. cv White Sim) flowers were characterized and compared.

UV irradiation (λ_max = 254 nanometers), at fluences above 18 kilojoules per square meter, induced petal in-rolling, similar to that which occurred during natural senescence or after ethylene treatment. Increase in the UV dose from 36 to 54 kilojoules per square meter increased the rate of in-rolling to a maximum. Petal in-rolling was accompanied by increased electrolyte leakage, whether it occurred during natural senescence or was induced by UV irradiation or ethylene.

Sucrose uptake by cells, membrane ATPase activity, and membrane lipid fluidity all decreased after UV treatment. These parameters were shown earlier to decline during natural or ethylene-induced senescence.

UV irradiation induced ethylene production by the petals only during the period of irradiation. However, silver thiosulfate treatment, which blocks ethylene action, showed that the irradiation effects were not due to the ethylene evolved.

On the basis of the above results, we concluded that both ethylene and UV irradiation promote a sequence of reactions in the tissue similar to those of natural senescence. However, UV irradiation initiates a reaction which is independent of that which ethylene initiates.

     

Interrelationship between Abscisic Acid and Ethylene in the Control of Senescence Processes in Carnation Flowers

The involvement of abscisic acid (ABA) in senescence of carnationflowers, in the presence of silver ions (which inhibit ethyleneaction), and aminoethoxyvinylglycine (AVG) (an inhibitor ofethylene synthesis) was studied. ABA stimulated senescence asseen by advancement of ethylene surge, and time to the developmentof in-rolling of petal margins. ABA also increased the sensitivityof the flowers to ethylene. Silver ions did not affect the timeor extent of the ethylene surge, but prevented the appearanceof visual senescence symptoms, and lowered the sensitivity toethylene. AVG delayed the ethylene surge and lowered the maximumrate of ethylene production. Also, AVG delayed the developmentof visible senscence. In the presence of silver ions, ABA advanced the ethylene surgebut senescence symptoms did not develop. The effect of ABA onthe parameters measured was prevented by AVG. Thus it is suggestedthat ABA exerts its effect on senescence via ethylene. The possibleinvolvement of an ABA-ethylene sequence as a mediator of waterstress-promoted senescence is discussed.     

Pollination-Induced Corolla Wilting in Petunia hybrida Rapid Transfer through the Style of a Wilting-Inducing Substance

Pollination or wounding of the stigma of Petunia hybrida flowers led to the generation of a wilting factor and its transfer to the corolla within 4 hours. This was concluded from the effects of time course removal of whole styles. In this 4-hour period, pollen tubes traversed only a fraction of the total distance to the ovaries. Both pollination and wounding of the stigma immediately resulted in an increase of ethylene evolution. Accelerated wilting, however, occured only when treated styles remained connected with the ovaries, and not when they were detached and left in the flower. A wilting factor was found in eluates collected from the ovarian end of the styles, only in the case of previous pollination or wounding. In such eluates, the level of the ethylene precursor 1-amino-cyclopropane-1-carboxylic acid was below detection.

These observations suggest a material nature of the wilting factor in Petunia flowers, which rapidly passes through the style to the corolla, but which is different from 1-aminocyclopropane-1-carboxylic acid.

     

The Effects of Inhibitors of Polyamine and Ethylene Biosynthesis on Senescence, Ethylene Production and Polyamine Levels in Cut Carnation Flowers

The role of polyamine metabolism in the regulation of senescenceand ethylene evolution was examined in cut carnations. Endogenousconcentrations of spermine and spermidine did not change asflowers aged, but putrescine, their immediate biosynthetic precursor,increased dramatically and paralleled a sharp rise in ethylene.When D-arginine, difluoromethylarginine and methylglyoxal bis(guanylhydrazone)were used to inhibit specific steps in polyamine synthesis,ethylene production and the onset of senescence were promoted.In contrast, inhibition of ethylene by aminooxyacetic acid increasedthe level of spermine, presumably by increasing the availabilityof aminopropyl groups derived from S-adenosylmethionine (SAM)and required for the synthesis of polyamines from putrescine.These results suggest that the ethylene and polyamine biosyntheticpathways compete for SAM during senescence of carnation flowers. (Received September 1, 1983; Accepted January 7, 1984)     

Role of Ethylene in Senescence of Petals--Morphological and Taxonomical Relationships

Petal senescence in mature flowers was studied in 93 speciesfrom 22 families. The initial symptom of senescence was eitherwilting or abscission, but in some species the time span betweenwilting and abscission was very short. There was no apparent relationship between corolla form (choripetalousor sympetalous), ovary position (inferior or superior with respectto the corolla) and type of senescence (initial wilting or initialabscission). In monocots no initial abscission was found, whilein dicots the difference between the wilting type and the abscissiontype was generally at the family level. With respect to petalsenescence, sensitivity to exogenous ethylene (C₂H₄) was alsorelated to the family level. Except for a few families (all tested Campanulaceae, Caryophyllaceaeand Malvaceae, and most Orchidaceae), most of the flowers investigatedthat showed initial wilting were not sensitive to exogenousethylene, e.g. all tested Compositae, Iridaceae, and Liliaceae.Most of the flowers showing initial abscission were sensitiveto exogenous ethylene (Geraniaceae, Labiatae, Ranunculaceae,Rosaceae, Scrophulariaceae). Experiments with silver thiosulphate (STS) confirmed the effectsof exogenous ethylene, both in flowers showing initial wiltingand in flowers showing initial abscission. The data indicate,therefore, that ethylene is involved in the natural senescenceof only a minority of the wilting type of flowers and in a majority(if not all) of the abscising type of flowers. Key words: Abscission, ethylene, senescence, silver thiosulphate     

The Role of Ethylene in Interorgan Signaling during Flower Senescence

The roles of 1-aminocyclopropane-1-carboxylic acid (ACC) and ethylene in interorgan signaling during senescence in orchid (Cymbidium) flowers were investigated. Following application of radiolabeled ACC to the stigma or the rostellum (modified lobe of the stigma), radiolabeled ethylene is produced by all flower parts. In intact flowers as well as in excised central columns, stigma- or rostellum-applied ACC or [alpha]-aminoisobutyric acid were largely immobile. Local treatment of the central column of previously aminoethoxyvinylglycine-treated flowers with either ethylene or 2-chloroethylphosphonic acid (ethephon) rapidly induced emission of ethylene from the petals, showing that ethylene is readily translocated within the flower. Creation of alternative outlets (incisions) in the labellum or the central column significantly delayed the occurrence of senescence symptoms in ACC-treated flowers. The results do not confirm the presumed role of ACC as a signal in interorgan communication during flower senescence. In these flowers, ethylene produced in the stigmatic region following pollination or emasculation serves as a mobile factor responsible for senescence symptoms observed in other flower parts.     

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.     

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.     

Pollination-Induced Expression of Ethylene Biosynthetic Genes at Transcription Level in Orchid Flowers

The authors investigated pollination-induced ethylene production and expression patterns of genes encoding 1-aminocyclopropane-l-carboxylate (ACC) synthase and ACC oxidase in orchid flowers (Doritaenopsis hybrida Hort. ). Following pollination both ACC synthase and ACC oxidase mRNAs were detected in the different organs of flowers, and the patterns of both ACC synthase and ACC oxidase mRNA accumulation were similar, mRNA accumulation of ACC synthase mRNA was more organ-specific than that of ACC oxidase mRNA. However, ACC oxidase mRNAs were much more abundant than ACC synthase mRNAs in the flower organs.     

Mitochondrial Changes in Harvested Carnation Flowers (Dianthus caryophyllus L.) during Senescence

Harvested carnation (Dianthus caryophyllus L.) flowers wereplaced in either a preservative solution or deionized waterand monitored through senescence during which time flower freshweight was measured as well as production of ethylene and CO₂.Flower fresh weight, ethylene, and CO₂ levels increased as theflowers aged, but fresh weight and CO₂ levels fell once flowersbegan to senesce regardless of holding solution. Preservative-treatedflowers senesced at a slower rate than deionized water-treatedflowers. The amount of ADP phosphorylated to ATP per oxygenatom consumed, using mitochondria isolated from petal tissueprovided with either succinate or malate as substrates, wasfound to increase as flowers senesced and then to decrease inthe later stages of senescence. Respiratory control ratios withsuccinate as the substrate did not change appreciably untilthe final stages of senescence white respiratory control valuesusing malate showed greater variation but no consistent patternrelative to the progress of senescence. Cyanide-resistant respirationwas noted with isolated mitochondria oxidizing either substrate,but no correlation between cyanide-resistant respiration andsenescence could be found. (Received July 10, 1984; Accepted April 16, 1985)     

ABA和乙烯在草莓采后成熟衰老中的作用

随着草莓果实采后成熟衰老,ABA和乙烯生成迅速增长,乙烯累积与果实的变质腐烂程度呈正相关。ABA处理能增高纤维素酶活性和呼吸,而GA有抑制作用。ABA能促进乙烯、ACC生成,对MACC则无影响。GA_3抑制乙烯、ACC生成,促进MACC积累。CO_2对草莓有良好保鲜效果,并有效地抑制ABA和乙烯生成,低温下效果更为显著。     

Isozymes of Superoxide Dismutase in Mitochondria and Peroxisomes Isolated from Petals of Carnation (Dianthus caryophyllus) during Senescence

The balance between reactions involving free radicals and processes which ameliorate their effect plays an important role in the regulation of plant senescence. In this study a method was developed to isolate peroxisomes and mitochondria from carnation (Dianthus caryophyllus L. cv Ember) petals. Based on electron microscopy and marker enzyme levels, the proportion of peroxisomes to mitochondria increases during senescence. The superoxide dismutase (SOD) content of these fractions was examined. Mitochondria and peroxisomes were shown to contain two electrophoretically distinct SODs, a manganese-, and an ironcontaining SOD. The Mn- and Fe-SOD were found to have relative molecular weights of 75,000 and 48,000 and isoelectric points of 4.85 and 5.00, respectively. The presence of a Fe-SOD in mitochondria and peroxisomes is unique because this enzyme is usually located in chloroplasts. The activity of these two isoenzymes decreased during senescence in mitochondria but remained high in peroxisomes from senescent tissue. It is suggested that peroxisomes play a particular role in the process of senescence.     

Effects of Previous Pollination and Stylar Ethylene on Pollen Tube Growth in Petunia hybrida Styles

The effect of ethylene on the growth rate of pollen tubes in styles of Petunia hybrida was examined. Apart from its strong inhibition of pollination-induced ethylene synthesis, aminoethoxyvinylglycine, placed on the stigma, did not impede tube growth. The inhibitors of the action of ethylene, silver thiosulfate and 2,5-norbornadiene, were similarly ineffective. Application of the ethylene precursor, 1-amino-cyclopropane-1-carboxylic acid, onto the stigma at different intervals prior to pollination evoked synthesis of ethylene, but was without effect on tube growth. However, prepollination (by 24 hours) with Nicotiana tabacum pollen, significantly enhanced tube growth of Petunia pollen. This enhancement was not counteracted by the pretreatment of stigmas with aminoethoxy-vinylglycine. It is concluded that the ethylene associated with pollination is without effect on pollen tube growth in the style, but that other pollination-induced factors may lead to an acceleration of growth.     

Pollination-Induced Transcriptome and Phylogenetic Analysis in Cymbidium tortisepalum (Orchidaceae)

Russian Journal of Plant Physiology - Orchids comprise a group of ecologically and evolutionarily significant plants, and the Orchidaceae is one of the most abundant angiosperm families. Yet little...     

Inhibitory Effect of Coronamic Acid Derivatives on Senescence in Cut Carnation Flowers

(+)-(1R,2S)-Allocoronamic acid, (?)-(1S,2R)-allocoronamic acid, and their racemate showed an inhibitory effect on senesence in cut carnation flowers. This antisenescent activity was based on the inhibition of endogenous ethylene formation catalyzed by an ethylene-forming enzyme.