Regulation of ABA levels in senescing petals of rose flowers

During the vase life of a rose flower, changes in the levels of abscisic acid (ABA) were observed: a decrease during the first 3 days, followed by a steady state at a low level, and finally a sharp increase in late senescence. Feeding [2-¹⁴C]ABA to isolated petals showed that metabolism was very active despite the age of the flower, oxidation processes increased with age, whereas conjugation decreased but the level of nonmetabolized ABA remained stable. When the isolated petal was subjected to water stress, whatever its age, the ABA level increased. Hydrolysis of ABA-GE was not involved in this phenomenon. Thus, ABA synthesis occurred in the isolated petal; it could be directly correlated to the decrease in water potential. However, the ABA increase in isolated petals was limited. Moreover, on the rose tree, increases in ABA levels were not correlated to water potential changes. ABA levels seemed, therefore, mainly regulated by changes in import from leaves and other parts of the flower.     

外源ABA、NO和H2O2对葱莲花瓣及叶片表皮气孔开闭的影响

以葱莲(Zephyranthes candida)为材料,研究不同浓度外源脱落酸、硝普钠(sodium nitroprusside,SNP)及过氧化氢对花瓣和叶片表皮气孔开闭的影响,以期为三者在切花保鲜中的应用提供新的依据。实验结果表明,10~1000 μmol/L脱落酸和硝普钠均能不同程度地引起花瓣和叶片表皮气孔关闭,且花瓣气孔较叶片气孔有更高的敏感性。过氧化氢对叶片表皮气孔开闭的影响大于对花瓣气孔的影响,花瓣表皮的气孔孔径仅在1000 μmol/L处理时变化显著。这说明在外源信号物质延缓切花衰老的过程中,花瓣表皮气孔的运动也可能起到了一定的作用。适当外源信号物质处理能诱导花瓣表皮气孔关闭,从而使花瓣的蒸腾作用减小,维持植物体内水势,延缓切花衰老。     

外源ABA、NO和H2O2对葱莲花瓣及叶片表皮气孔开闭的影响

以葱莲（Zephyranthes candida）为材料,研究不同浓度外源脱落酸、硝普钠（sodium nitroprusside,SNP）及过氧化氢对花瓣和叶片表皮气孔开闭的影响,以期为三者在切花保鲜中的应用提供新的依据。实验结果表明,10～1000μmol/L脱落酸和硝普钠均能不同程度地引起花瓣和叶片表皮气孔关闭,且花瓣气孔较叶片气孔有更高的敏感性。过氧化氢对叶片表皮气孔开闭的影响大于对花瓣气孔的影响,花瓣表皮的气孔孔径仅在1000μmol/L处理时变化显著。这说明在外源信号物质延缓切花衰老的过程中,花瓣表皮气孔的运动也可能起到了一定的作用。适当外源信号物质处理能诱导花瓣表皮气孔关闭,从而使花瓣的蒸腾作用减小,维持植物体内水势,延缓切花衰老。     

Determination of subcellular concentrations of soluble carbohydrates in rose petals during opening by nonaqueous fractionation method combined with infiltration–centrifugation method

Petal growth associated with flower opening depends on cell expansion. To understand the role of soluble carbohydrates in petal cell expansion during flower opening, changes in soluble carbohydrate concentrations in vacuole, cytoplasm and apoplast of petal cells during flower opening in rose (Rosa hybrida L.) were investigated. We determined the subcellular distribution of soluble carbohydrates by combining nonaqueous fractionation method and infiltration–centrifugation method. During petal growth, fructose and glucose rapidly accumulated in the vacuole, reaching a maximum when petals almost reflected. Transmission electron microscopy showed that the volume of vacuole and air space drastically increased with petal growth. Carbohydrate concentration was calculated for each compartment of the petal cells and in petals that almost reflected, glucose and fructose concentrations increased to higher than 100 mM in the vacuole. Osmotic pressure increased in apoplast and symplast during flower opening, and this increase was mainly attributed to increases in fructose and glucose concentrations. No large difference in osmotic pressure due to soluble carbohydrates was observed between the apoplast and symplast before flower opening, but total osmotic pressure was much higher in the symplast than in the apoplast, a difference that was partially attributed to inorganic ions. An increase in osmotic pressure due to the continued accumulation of glucose and fructose in the symplast may facilitate water influx into cells, contributing to cell expansion associated with flower opening under conditions where osmotic pressure is higher in the symplast than in the apoplast.     

Combined Effects of Abscisic Acid and Sucrose on Growth and Senescence of Rose Flowers

The effects of sucrose and abscisic acid (ABA) and their interaction on development and senescence of petals were studied with leafless roses cultivar Super Star. Sucrose and ABA had opposing effects on the cut flowers. Sucrose retarded and ABA promoted processes associated with senescence: wilting, increase in pH, “blueing” and decrease in protein content of petals. These opposing effects are mutually antagonized when both chemicals are applied. ABA applied to flowers cut at the bud stage, promoted the rate of petal growth (but not their final size), increased respiration and caused a decrease in sucrose and an increase in level of reducing sugars. It is suggested that one way by which ABA accelerates senescence of cut roses is by promoting petal growth and respiration, thus decreasing the carbohydrate level in the petals and triggering the chain of metabolic processes leading to aging.     

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     

Microviscosity of plasmalemmas in rose petals as affected by age and environmental factors

The microviscosity of the plasmalemma of protoplasts isolated from rose (Rosa hyb. cv. Golden Wave) petals was measured by fluorescence depolarization. The plasmalemma's microviscosity was found to increase in petals which were allowed to age on cut flowers or after isolation as well as in isolated protoplasts aged in an aqueous medium. Increasing the temperature of the cut flowers or the isolated protoplasts enhanced the increase of the microviscosity of the protoplast plasmalemma. The mole ratio of free sterol to phospholipid was greater in protoplasts isolated from old flowers or in protoplasts aged after isolation than in protoplasts isolated from younger flowers. Microviscosity was greatest when protoplasts were aged at pH 4.4 and in the presence of Ca²⁺. Artificial alterations of the sterol to phospholipid ratio in the protoplasts, induced by treatment with liposomes, caused similar changes in their measured microviscosity.

These findings strongly suggest that the increase in the petal plasmalemma microviscosity with age is associated with an increase in the sterol to phospholipid ratio which results, at least partially, from the activity of endogenous phospholipases.

     

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.     

Changes in abscisic acid and phenols during flower development in two diverse species of rose

Changes in endogenous abscisic acid (ABA) and phenols were determined in petals of two diverse species of rose, viz., Rosa damascena Mill and Rosa bourboniana Desport during flower development. A progressive increase in free ABA was observed during flower development till full bloom in both the species with higher content of free ABA in Rosa damascena. While bound ABA level increased in Rosa damascena till stage 6, in Rosa bourboniana it continued to increase till full bloom. Acidic phenols increased slowly in both the species till stage 4, but sharply afterwards and no significant differences were noticed during full bloom period. Bound phenols content was higher in Rosa damascena during full bloom period. The significance of these changes in relation to flowering in the two diverse species of rose is discussed.     

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.     

Possible involvement of abscisic acid in senescence of daylily petals

Daylily flowers (Hemerocallis hybrid, cv. Stella d'Oro) senesce and die autonomously over a 24 h period after opening. Investigations were performed to determine some of the mechanisms that lead to death of the petals. The flowers are insensitive to ethylene, but exogenous ABA prematurely upregulates events that occur during natural senescence, such as loss or differential membrane permeability, increases in lipid peroxidation and the induction of proteinase and RNase activities. Furthermore, the same patterns of proteinase and RNase activities appearing on activity gels during natural senescence are induced prematurely by ABA. The mRNA profile from ABA-treated, prematurely senescing petals visualized by differential display shows a high degree of similarity to the mRNA profile of naturally senescing petals 18 h later. In addition, endogenous ABA increases before flower opening and continues to increase during petal senescence. An osmotic stress by sorbitol increases endogenous levels of ABA and upregulates the same parameters of senescence as those occurring during natural senescence and after application of ABA. The mRNA profile from sorbitol-treated, prematurely senescing petals, but somewhat less similarity to mRNA from ABA-treated petals. The possibility is discussed that ABA is a constituent of the signal transduction chain leading to programmed cell death of daylily petals.     

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.     

The involvement of tonoplast proton pumps and Na+(K+)/H+ exchangers in the change of petal color during flower opening of Morning Glory, Ipomoea tricolor cv. Heavenly Blue

The petal color of morning glory, Ipomoea tricolor cv. Heavenly Blue, changes from purplish red to blue during flower opening. This color change is caused by an unusual increase in vacuolar pH from 6.6 to 7.7 in the colored adaxial and abaxial cells. To clarify the mechanism underlying the alkalization of epidermal vacuoles in the open petals, we focused on vacuolar H+-ATPase (V-ATPase), H+-pyrophosphatase (V-PPase) and an isoform of Na+/H+ exchanger (NHX1). We isolated red and blue protoplasts from the petals in bud and fully open flower, respectively, and purified vacuolar membranes. The membranes contained V-ATPase, V-PPase and NHX1, which were immunochemically detected, with relatively high transport activity. NHX1 could be detected only in the vacuolar membranes prepared from flower petals and its protein level was the highest in the colored petal epidermis of the open flower. These results suggest that the increase of vacuolar pH in the petals during flower opening is due to active transport of Na+ and/or K+ from the cytosol into vacuoles through a sodium- or potassium-driven Na+(K+)/H+ exchanger NXH1 and that V-PPase and V-ATPase may prevent the over-alkalization. This systematic ion transport maintains the weakly alkaline vacuolar pH, producing the sky-blue petals.     

The Abscission of Rose Petals

Petal abscission was studied in twelve hybrid tea rose (Rosahybrida L.) cultivars. At about 20 °C the time to petalabscission in uncut stems in greenhouses was the same as incut stems placed in water in the greenhouse or in a climate-controlledroom. The time between petal unfolding and abscission dependedon the cultivar, and varied between 12 and 35 d. The time topetal abscission of the cultivars was inversely correlated withtheir flower diameter at full bloom (linear regression, r² =0·82). In the cultivars with a relatively large flowerdiameter (10-18 cm) the petals fell without visible desiccationsymptoms, whereas in the group with a small diameter the petalswere partially or fully desiccated when shed. Fertilization occurred in some flowers of a few cultivars studied.In cultivars with a relatively large flower diameter (Papa Meilland,Cocktail, Dr. Verhage, Tineke) it had no effect on the timeto abscission in Motrea, Europa, and Carolien roses, which bearsmall flowers, the petals fell after fertilization, whereasin unfertilized flowers of the latter group of cultivars anabscission zone just above the uppermost node became activeand all parts above this node (pedicel and flower) turned brownand desiccated, though remained attached for more than a month. It is concluded that in the cultivars investigated: (a) thetime to petal abscission was inversely related to their flowerdiameter, (b) abscised petals were more desiccated in cultivarsin which the time to abscission was longer, (c) fertilizationhad little effect on the time to abscission in most cultivars,whereas the absence of fertilization prevented petal abscissionin a number of the small-diameter cultivars where it was replacedby flower abscission, and (d) cutting and placement in waterat 20 °C did not affect the time to abscission.Copyright1995, 1999 Academic Press Abscission, fertilization, flowers, petals, Rosa hybrida L., rose, water stress, carbohydrate stress     

青霉素和比久对月季切花保鲜效应的研究

切花保鲜的关键技术是降低水分的散失和防止营养亏缺。以月季为材料,采用室内瓶插的方法研究 了青霉素和比久对切花保鲜的效应。结果表明:含不同浓度青霉素和比久B9的保鲜剂均能延长月季切花的 瓶插寿命,增加切花鲜重,增大花径,提高花瓣过氧化物酶(POD)的活性,改善切花体内水分状况,维持花瓣膜 结构的相对稳定。青霉素处理对提高月季切花保鲜品质的效果好于B9。     

The influence of light quality on rose flower senescence: involvement of abscisic acid

The aim of this work was to study the impact of light applied during preharvest culture on the subsequent senescence of cut rose flower and to analyse the possible involvement of abscisic acid (ABA). The longevity of cut rose flowers was longer when rose plants were previously grown under high pressure sodium lamps than under metal halide lamps. A change in light source did not lead to a change in leaf ABA content but significantly affected the petal ABA content. The relationship between ABA level and flower longevity, previously reported for differences of genetic origin, was again observed for culture-induced differences: the higher the ABA level at harvest, the shorter the vase-life observed.