postharvest characteristics of cut flowers and techniques for … · 2018-12-27 · techniques for...

AGri-Bioscience Monographs, Vol. 8, No. 1, pp. 1–22 (2018) www.terrapub.co.jp/onlinemonographs/agbm/

Received on February 8, 2016Accepted on

November 9, 2016Online published on

December 28, 2018

Keywords• dahlia• ethylene• Eustoma grandiflorum• gentian• phytohormone• pollination• sugars

© 2018 TERRAPUB, Tokyo. All rights reserved.doi:10.5047/agbm.2018.00801.0001

decreased ornamental value judged by human subjectsin Oriental-Trumpet hybrid cut l i ly (Lilium)(Mochizuki-Kawai et al. 2012) and tulip (Tulipagesneriana) flowers (Mochizuki-Kawai et al. 2014).

To improve the vase life of cut flowers, clarifyingthe factors inducing their senescence will be impor-tant. The best known and most important factor is eth-ylene, a phytohormone that induces senescence of flow-ers, maturation of fruit and abscission of leaves. Theethylene biosynthesis pathway is methionine Æ S-adenosylmethionine (SAM) Æ 1-aminocyclopropane-1-carboxylic acid (ACC) Æ ethylene. Since the me-thyl group is reutilized for methionine through the Yangcycle, ethylene is biosynthesized continuously. Con-sequently, a rapid and remarkable increase in ethyleneis induced at flower senescence. Moreover, the amountof ethylene increases autocatalytically because ethyl-ene production is accelerated by treatment with exog-enous ethylene (Veen 1979). ACC synthase and ACCoxidase are important in regulation of ethylene bio-synthesis. In the ethylene response, ethylene binds toreceptors, activating the ethylene signal transduction

AbstractLong vase life of cut flowers is valued highly by consumers. In addition, a sales systemguaranteeing the vase life of cut flowers is becoming common among retailers and vol-ume sellers. Therefore, postharvest techniques to extend the vase life have been increas-ingly required over decades. This review summarizes the factors affecting vase life anddescribes effective treatments for extending vase life, mainly for Eustoma (Eustomagrandiflorum), gentian (Gentiana) and dahlia (Dahlia) flowers. In cut Eustoma flowers,several treatments using sugars and/or ethylene inhibitors to improve vase life have beendeveloped. Factors shortening the vase life due to pollination have also been clarified.Gentiana scabra is highly sensitive to ethylene, but gentians show species variation ofsensitivity to ethylene. Vase life of G. scabra and its hybrids is extended by treatmentwith ethylene inhibitors. A spray treatment with a cytokinin, 6-benzylaminopurine (BA),improves the vase life of cut dahlia flowers, although their vase life is still short. Theseresults should contribute to supplying consumers with cut flowers that keep their qualityfor long periods.

Postharvest Characteristics of Cut Flowers andTechniques for Extending Vase Life, with a Focuson Eustoma, Gentiana and Dahlia

Hiroko Shimizu-Yumoto

Institute of Vegetable and Floriculture Science,National Agriculture and Food Research Organization (NARO),2-1 Fujimoto, Tsukuba 305-0852, Japane-mail: [email protected]

1. Introduction

Long vase life is desirable for consumers when theybuy cut flowers. To encourage the purchase of cut flow-ers for home ornamental use, a sales system guaran-teeing the vase life of cut flowers started with volumesellers in England (http://www.jelfa.net/project/vaselife/foreign%20interview.html), which led to aremarkable increase in sales of cut flowers, and sincethen, this system has spread to France, Germany, theNetherlands and Japan. Research on extending the vaselife of cut flowers is becoming increasingly important.

The vase life of cut flowers is the interval duringwhich their ornamental value is maintained. The orna-mental value is lost when petals wilt, abscise or be-come discolored. If cut flower stems are an inflores-cence such as a cyme, the number of wilting flowers isan important determinant of the vase life of the entirestem. In horticultural studies, vase life of cut flowerstems is determined based on the research. Recent stud-ies clarified that physiological senescence of cut flow-ers, such as discoloration of petals or stem bending

2 H. Shimizu-Yumoto / AGri-Biosci. Monogr. 8: 1–22, 2018

doi:10.5047/agbm.2018.00801.0001 © 2018 TERRAPUB, Tokyo. All rights reserved.

pathway, and finally, petals wilt or abscise. Ethylenereceptors downregulate the signal transduction path-way in the absence of ethylene. When ethylene bindsreceptors, downregulation by receptors is triggered, andthe signal transduction pathway is activated (Hua andMeyerowitz 1998).

Some flowers in which senescence is accelerated byethylene are categorized as having high sensitivity toethylene (Woltering and van Doorn 1988), such as car-nation (Dianthus caryophyllus) and Consolida ajacis.In general, these flowers produce remarkable levels ofethylene during senescence, suggesting that ethyleneis related to flower senescence. In addition, chemicalsthat inhibit ethylene biosynthesis or ethylene action areusually effective in extending vase life.

In flowers highly sensitive to ethylene, such as car-nation, pollination accelerates flower senescence (Burgand Dijikman 1967; Whitehead et al. 1984; Larsen etal. 1995). Ethylene is also related to flower senescenceinduced by pollination. For example, ethylene produc-tion increases in styles of carnation after pollination,and subsequently increases in petals and wilted petals(Larsen et al. 1995). Vase life is two to three weeks inunpollinated Phalaenopsis flowers, but is only two daysafter pollination (Porat et al. 1994). This observationindicates that pollination seriously deteriorates thevalue of cut flowers. In Digitalis purpurea, corollaabscission is accelerated proportionally with the de-gree of pollination (Stead and Moore 1979). In Petu-nia, the maximum wilting rate of flowers is inducedby more than 800 viable pollen grains; that is, about 1/5 of the stigmatic surface must be covered with activepollen after cross- or self-pollination (Gilissen 1977).In geranium (Pelargonium ¥ hortorum), petal abscis-sion accelerates with an increase in the number of pol-linated stigmatic lobes, and ethylene production bypistils also increases (Hilioti et al. 2000). Thus, theamount of pollen on the stigma surface affects the se-nescence of flowers. In Nicotiana tabacum, growth ofpollen tubes and patterns of ethylene production byflowers are different when N. repanda, N. rustica, N.trigonophylla and Petunia hybrida are used as pollenparents (De Martinis et al. 2002). In N. tabacum, thestylar transmitting tissue, which is the pathway forpollen tube growth, becomes highly disorganized whenmany pollen tubes reach the bottom half of the style,and ethylene accelerates this disorganization (Wang etal. 1996). These findings suggest that ethylene affectspollen tube growth. To delay flower senescence inducedby pollination, treatment with ethylene inhibitors iseffective (Ichimura and Goto 2000). Methods to pre-vent pollination are also available during transporta-tion of cut flowers and in breeding programs.

Ethylene inhibitors can inhibit ethylene synthesis orethylene action. Aminoethoxyvinyl glycine (AVG) andaminooxyacetic acid (AOA) inhibit ACC synthase.AVG extends vase life in carnation and C. ajacis (Uda

1996). These compounds are inhibitors of pyridoxalphosphate-requiring enzymes, which play a major rolein the metabolism of amino acids (Schneider et al.2000). Recent research revealed that AVG inhibitsauxin biosynthesis independently of ethylene inArabidopsis seedlings (Soeno et al. 2010). An inhibi-tor of ACC oxidase activity is a-aminoisobutyric acid(AIB), which extends the vase life of cut carnationflowers (Onozaki et al. 1998). Silver thiosulfate com-plex (STS) and 1-methylcyclopropene (1-MCP) aretypical ethylene action inhibitors. Silver suppresses theethylene response (Beyer 1976), but the cations of sil-ver in silver nitrate solution do not easily move inplants. Veen and van de Geijn (1978) found that STScould be made by mixing silver nitrate with sodiumthiosulfate at a ratio ranging from 1:4 to 1:16. STS ismobile in plants and inhibits ethylene action. In addi-tion, STS inhibits autocatalytic production of ethylenein carnation flowers (Veen 1979). STS is effective ininhibiting ethylene action and extending vase life ofmany flowers such as carnation and C. ajacis(Woltering and van Doorn 1988). Nowadays, STS isused as a preservative to extend the vase life of cutflowers worldwide. 1-MCP inhibits ethylene action bybinding ethylene receptors irreversibly (Serek et al.1995; Sisler et al. 1996). In fruits, 1-MCP is very ef-fective in delaying ripening (Fan et al. 1999). How-ever, in flowers such as Campanula carpatica ,Schlumbergera truncata, and sweet pea (Lathyrusodoratus), the effect of 1-MCP in delaying senescenceis similar to or less effective than STS (Serek and Sisler2001; Ichimura et al. 2002).

In contrast, other cut flowers such as chrysanthemum(Chrysanthemum morifolium) and gladiolus (Gladi-olus) do not show accelerated senescence after ethyl-ene treatment. These types of flowers are categorizedas having low sensitivity to ethylene (Woltering andvan Doorn 1988). High levels of ethylene are not de-tected from these flowers during senescence, and eth-ylene inhibitors are not effective in extending their vaselife. Therefore, ethylene is not important in inducingsenescence in these flowers, and the key factors in-volved instead of ethylene are unclear. Recently,cytokinins, another category of phytohormone, havebeen used to treat cut flowers in which senescence isnot affected by ethylene. A cytokinin was first identi-fied as a compound accelerating cell division, and af-terward was shown to be involved in various physi-ological events such as breaking of apical dominanceand distribution of nutrient elements. Treatment withthe synthetic cytokinins BA or thidiazuron improvesthe vase life of cut anemone (Anemone coronaria), tu-lip (Tulipa spp.) and Dutch iris (Iris ¥ hollandica) flow-ers (Meir et al. 2007; Macnish et al. 2010; van Doornet al. 2011). Cytokinins are also effective in extendingthe vase life of cut carnations and Eustoma flowers,whose senescence is regulated by ethylene (Eisinger

H. Shimizu-Yumoto / AGri-Biosci. Monogr. 8: 1–22, 2018 3


1977; Kelly et al. 1985; van Staden and Joughin 1988;Huang and Chen 2002; Meir et al. 2007). These obser-vations suggest that cytokinin affects a pathway of petalsenescence that is common to both ethylene depend-ent and ethylene independent flowers. Leaf yellowingis known to be delayed with cytokinin treatment (Rich-mond and Lang 1957; Gan and Amasino 1995). Thecytokinin kinetin causes 14C-labeled alanine to be ac-cumulated in treated leaves of Vicia faba (Mothes andEngelbrecht 1963). Cytokinin also induces expressionof the mRNA encoding cell wall invertase, an impor-tant enzyme involved in supplying carbohydrates tosink cells in tissue of Chenopodium rubrum plants(Ehneß and Roitsch 1997). In tobacco (N. tabacum)leaves, high activity of extracellular invertase is im-portant to delay leaf senescence caused by cytokinin(Balibrea Lara et al. 2004).

Other phytohormones, auxin and abscisic acid(ABA), are also used to improve the quality of horti-cultural crops. Auxin is related to many aspects of plantgrowth and development. Application of syntheticauxins to trees reduces fruit drop of apples (Maluspumila) (Marini et al. 1993) and oranges (Citrus spp.)(Zur and Goren 1977), abscission of rose buds (Halevyand Kofranek 1976) and drop of flower bracts inBougainvillea (Chang and Chen 2001). In addition, thecombined application of the auxin 1-naphthaleneaceticacid (NAA) and AVG is even more effective in reduc-ing apple fruit drop before harvest (Yuan and Carbaugh2007). When ABA, involved in stomatal closure, isadded to sucrose solution, it reduces leaf damage inroses (Markhart and Harper 1995; Pompodakis andJoyce 2003), and the vase life of leaves in Geraldtonwaxflower (Chamelaucium uncinatum) is extended bycontinuous treatment with ABA (Joyce and Jones1992). ABA increases uptake of carbohydrates in im-mature fruits of peach (Kobashi et al. 1999) and invacuoles isolated from immature apples (Yamaki andAsakura 1991).

Application of metabolic sugars such as glucose,fructose and sucrose to cut flowers extends the vaselife of many flowers (Halevy and Mayak 1981; Halevyand Kofranek 1984; Ichimura and Korenaga 1998).Sugars play important roles as respiration substratesor compounds regulating osmotic pressure. Moreover,treatment with sugars decreases sensitivity to ethyl-ene (Mayak and Dilley 1976; Ichimura et al. 2000) anddelays the increase in ethylene production during se-nescence (Dilley and Carpenter 1975; Ichimura andSuto 1999). Flower bud opening (Mor et al. 1984;Koyama and Uda 1994) and pigmentation of petals byanthocyanins (Maekawa and Nakamura 1978; Ichimuraand Korenaga 1998; Ichimura and Hiraya 1999) arepromoted by sugars. Anthocyanins are very importantcompounds for the red, purple and pink coloration ofpetals. Sugars are used as substrates for production ofanthocyanin glycosides but also upregulate expression

of genes involved in anthocyanin synthesis (Tsukayaet al. 1991; Kawabata et al. 1999). For these reasons,sugar treatment is very effective in improving the qual-ity of cut flowers that have many flowering buds, suchas Eustoma or Gypsophila paniculata, and cut flowersharvested at the bud stage, such as roses (Rosa). Tre-halose, a sugar found in yeast and other fungi, extendsthe vase life of cut tulip flowers, by reducing the hy-draulic conductance and decreasing the cell elongationrate of tepals (Iwaya-Inoue and Tanaka 2001; Wada etal. 2005), and gladiolus flowers, by enhancing wateruptake into petal tissues (Otsubo and Iwaya-Inoue2000).

As ethylene inhibitors, sugars and phytohormonescan be effective, so it is necessary to understand thepostharvest characteristics of cut flowers. We clarifiedpostharvest characteristics and developed techniquesextending the vase life of cut flowers of Eustoma, gen-tian and dahlia. In Japan, most cut Eustoma flowerstems are produced from summer to autumn. Cut gen-tian flowers are also produced during summer and au-tumn. Production of cut dahlia flowers has been in sum-mer, but because of their short vase life, productionhas shifted to late autumn. Quality deterioration is se-rious because these flowers are distributed and sold inseasons with high temperatures.

This monograph summarizes the factors affectingvase life of cut Eustoma, gentian and dahlia flowersand describes treatments that extend their vase life.

2. Postharvest characteristics of cut Eustoma flow-ers and techniques for extending their vase life

Eustoma grandiflorum is categorized as an annualbelonging to the Gentianaceae. Its area of origin is fromthe United States to northern Mexico. Eustoma wasintroduced to Japan about 80 years ago (Ohkawa et al.1991), and many cultivars with various colors, flowersizes and shapes of petals have been developed. WildEustoma is single-flowered, but double-floweredculivars were developed in the late 1980s. Large anddouble-flowered cultivars with fringed petals havebecome popular. There have been some problems, suchas development of rosette plants when seedlings aregrown at high temperature, and blasting of floral budsduring winter because of low sunlight intensity (Ushioand Fukuta 2010). Recently, these problems have beensolved by various techniques, enabling almost year-round production. Market sales in 2008 were 13.2 bil-lion yen, ranking 5th out of 20 kinds of cut flowersproduced domestically in the Japanese market.

Cut Eustoma flowers are sensitive to ethylene andthe ‘Auska-no-nami’ cultivar produces ethylene dur-ing senescence (Ichimura et al. 1998). Moreover, pol-lination induces ethylene production by pistils and ac-celerates flower senescence (Ichimura and Goto 2000).These observations indicate that ethylene is involved



in flower senescence in Eustoma. In this chapter, fac-tors affecting senescence of cut Eustoma flowers andtreatments extending their vase life are described. Vaselife of cut Eustoma flowers was defined as the intervalfrom the start of examination to when petals wilted.Vase life of cut Eustoma flower stems was determinedas the interval from treatment when certain number offlowers had opened with erect pedicels.

2-1. Factors responsible for cultivar variation invase life of unpollinated Eustoma flowers

There is cultivar variation in the vase life of Eustomaflowers (Motozu and Makihara 2001). The involvementof ethylene in cultivar variation in unpollinated flow-ers has been examined in detail (Shimizu-Yumoto andIchimura 2009b).

The factors responsible for cultivar variation in thevase life of unpollinated flowers were clarified by in-vestigating vase life, ethylene production, and sensi-tivity to ethylene using emasculated flowers of sixEustoma cultivars (Shimizu-Yumoto and Ichimura2009b). Cultivar variations in vase life of unpollinatedflowers ranges from 9.8 to 18.5 days (Table 1). A cli-macteric-like increase in ethylene production was de-tected in all tested Eustoma cultivars during flowersenescence (Fig. 1). Cultivars with short vase life pro-duced climacteric-like ethylene earlier than cultivarswith long vase life, except for ‘Asuka-no-nami’.Cultivars which produced a large amount of ethylenedid not always show short vase life. Therefore, ethyl-ene production presumably is not primarily responsi-

ble for cultivar variation in the vase life of unpollinatedEustoma flowers.

Sensitivity to ethylene in the same six cultivars wasexamined to clarify the factors responsible for cultivarvariation in the vase life of unpollinated flowers.Unpollinated flowers were treated with 10 mL L-1 eth-ylene for 24 h at 0, 1, and 2 days after harvest. In threecultivars, ethylene treatment did not accelerate flowersenescence at 0 days after harvest, but flower senes-cence in five cultivars was accelerated by ethylenetreatment 1 or 2 days after harvest. In only one cultivar,‘Asuka-no-nami’, was vase life not shortened by eth-ylene treatment (Table 2).

We also estimated the sensitivity to ethylene accord-ing to the degree of reduction in flower diameter after

Table 1. Vase life of cut unpollinated flowers of six Eustomacultivars.

Values are means of 8 replications ±S.E.zVase life was defined as the time from harvest to when pet-als wilted.Modified from Shimizu-Yumoto and Ichimura (2009b).

Fig. 1. Changes in ethylene production by unpollinated flowers in six Eustoma cultivars. Each plot represents the mean ofthree or four replications + S.E. Modified from Shimizu-Yumoto and Ichimura (2009b).



ethylene treatment (Shimizu-Yumoto and Ichimura2009b; Fig. 2). If the relative flower diameter was lessthan 100, the diameter of ethylene-treated flowers wasless than that of control flowers. That is to say, flowersenescence was accelerated by ethylene treatment.

Relative flower diameter was either temporarily orcontinuously reduced by ethylene treatment in sixcultivars. In ‘Azuma-no-sakura’ and ‘Maite Sky’, rela-tive flower diameter was reduced more rapidly by eth-ylene treatment at 1 or 2 days after harvest than at 0days. In ‘Azuma-no-murasaki’, relative flower diam-eter had decreased at 1 day, then slightly increased fol-lowed by a rapid decrease following ethylene treatment.These three cultivars were categorized as short vaselife cultivars (Table 1). On the other hand, in ‘Asuka-no-sazanami’ and ‘New Small Lady’, relative flowerdiameter did not decline markedly. Relative flower di-ameter of ‘Asuka-no-nami’ declined to 46 to 66% ofthe control at 1 day after ethylene treatment, but thenincreased to about 100% of the control. This resultsuggests that sensitivity to ethylene is lower in ‘Asuka-no-nami’ than in the other cultivars. These threecultivars, ‘Asuka-no-nami’, ‘Asuka-no-sazanami’ and‘New Small Lady’, were categorized as long vase lifecultivars (Table 1). Therefore, sensitivity to ethylene,which is indicated by a reduction in flower diameter,might be one of the factors involved in cultivar varia-tion in the vase life of cut unpollinated Eustoma flow-ers.

2-2. Factors related to senescence induced bypollination in cut Eustoma flowers

2-2A. Cultivar variation in distance from stigma toanther

When petals were removed from Eustoma flowers,

it was observed that there was cultivar variation in thedistance from stigma to anther. We hypothesized thata cultivar with a short distance from stigma to antherundergoes self-pollination easily. Therefore, distancefrom stigma to anther, ratio of flower pollination, andvase life were investigated in 13 cultivars of Eustoma(Shimizu and Ichimura 2002).

Distance between stigma and anther in emasculatedflowers of 13 cultivars of Eustoma ranged from 0.1 to4.0 mm (Table 3). Rate of pollinated flowers was from0 to 90% (Table 3). There was a negative correlation(r = –0.86, significant at 0.1% level) between distancefrom stigma to anther and rate of pollinated flowers.This result suggests that self-pollination was inducedeasily in flowers with a short distance between stigmaand anther.

However, there was no clear relationship betweendistance from stigma to anther and vase life (r = 0.27,not significant at 5% level) or between rate of polli-nated flowers and vase life (r = –0.50, not significantat 5% level). From these results, we hypothesized thatthe amount of pollen on the stigma affects senescenceof cut Eustoma flowers because the pollinated area ofthe stigmatic surface was very small in naturally polli-nated flowers.

2-2B. Pollinated area of the stigmatic surfaceTo test our hypothesis, the influence of pollinated

area of the stigmatic surface on vase life of cut Eustomaflowers was examined (Shimizu-Yumoto and Ichimura2006). Emasculated flowers of six cultivars were leftunpollinated or pollinated to cover whole area or 1/8of the area of the stigmatic surface when the stigmasmatured. In six cultivars, flowers with whole area or1/8 of the area pollinated senesced faster thanunpollinated flowers (Table 4). In three cultivars,

Table 2. Vase life of cut unpollinated flowers of six Eustoma cultivars with or without ethylene treatment.

Values are means of 5 replications ±S.E.zVase life was defined as the interval from harvest to when petals wilted.yUnpollinated flowers were treated with 10 mL L-1 ethylene for 24 h at 0, 1, and 2 days after harvest.xns, *, ** indicate non-significant and significant at P < 0.05 or 0.01, respectively, compared to controls of each cultivar (byDunnett test).wNT: not tested.Modified from Shimizu-Yumoto and Ichimura (2009b).



Fig. 2. Changes in relative flower diameter after ethylene treatment of unpollinated flowers in six Eustoma cultivars. Eachplot represents the mean of five replications + S.E. Unpollinated flowers were treated with 10 mL L-1 ethylene for 24 h.Modified from Shimizu-Yumoto and Ichimura (2009b).

‘Asuka-no-kozakura’, ‘Asuka-no-nami’, and ‘MaiteSky’, flowers pollinated over the whole area wiltedsignificantly earlier than flowers pollinated over 1/8of the area (Table 4). The other three cultivars alsotended to have shorter vase life in flowers pollinatedover the whole stigma than in flowers pollinated onlyover 1/8 of the area. These results suggest that theamount of pollen on the stigma affects flower senes-cence in cut Eustoma flowers.

We next investigated the ethylene production of flow-ers with different pollination treatments using ‘Asuka-no-nami’. In flowers pollinated over the whole area ofthe stigma, ethylene was produced rapidly, largely at 1

day after pollination. Flowers pollinated over 1/8 ofthe area produced very low amounts of ethylene thefirst 2 days. After that, the ethylene level increasedgradually, and reached a peak on day 5. Unpollinatedflowers produced ethylene at a lower level than polli-nated flowers, and a climacteric increase in ethylenewas detected on day 7. This confirmed that ethylene isrelated to flower senescence induced by pollination inEustoma (Ichimura and Goto 2000). Our results indi-cated that a larger pollinated area increased the rate ofethylene production by Eustoma flowers.

To test whether growth of pollen tubes differs de-pending on pollinated area, pollen tube growth in styles



with stigmas taken from ‘Asuka-no-nami’ flowers 1,2, and 3 days after pollination whole area or 1/8 of thearea was observed microscopically under incident ul-traviolet illumination. At 1 and 2 days after pollina-tion, many more pollen tubes reached the base of thestyles in the flowers with pollen covering the stigmasthan in 1/8-pollinated flowers. These results suggestthat growth of pollen tubes in the style was faster whenthe pollinated area increased.

In conclusion, a large pollinated area of the stigmaticsurface induces early ethylene production and short-ens vase life in cut Eustoma flowers. Therefore,cultivars with a short distance from stigma to anthermay easily be pollinated, especially during transporta-

tion. Conversely, development of cultivars with a longdistance from stigma to anther is expected to lead toimprovement of vase life in Eustoma.

2-3. Postharvest techniques for extending vase lifeof cut Eustoma flower stems

2-3A. AVG and NAA treatment of cut Eustomaflower stems

The senescence of cut Eustoma flowers is acceler-ated by ethylene (Ichimura et al. 1998). Therefore, theeffect of ethylene action inhibitors STS and 1-MCPhave been examined to extend vase life of cut Eustomaflowers (Shimamura and Okabayashi 1997; Ichimura

Vase lifez (days)Pollination Asuka-no-kozakura Asuka-no-nami Asuka-no-shizuku Azuma-no-kasumi Maite Sky New Small Lady

Unpollinated 7.3 ay 5.3 a 8.0 a 7.9 a 5.4 a 8.8 a1/8 area 4.8 b 3.8 b 4.1 b 4.0 b 3.5 b 4.6 bWhole area 2.6 c 2.5 c 3.1 b 3.1 b 1.9 c 3.3 b

Significancex

Cultivar P = 0.0002Pollination P < 0.0001Cultivar ¥ Pollination P = 0.1764

Table 4. Effect of pollinated area on vase life of six Eustoma cultivars after pollination.

Values are means of 8 replications.zVase life was defined as the time from pollination to when petals wilted.yValues with different letters are significant at P < 0.05 by Tukey-Kramer test.xTwo-way ANOVA.Modified from Shimizu-Yumoto and Ichimura (2006).

Table 3. The influence of distance from stigma to anther and rate of pollinated flowers on vase life of 13 cultivars of cutEustoma flowers.

Values are means of 10 flowers ±S.E.zVase life was defined as the time from harvest to when petals wilted.yThe distance from stigma to anther was measured every 2 days and is expressed as the mean of the minimum lengths.Modified from Shimizu and Ichimura (2002).



et al. 1998; Cho et al. 2001; Shimizu and Ichimura2005). In contrast, the effects of ethylene synthesisinhibitors such as AVG have not yet been explored. Inapple fruit, combined application of the auxin NAAand AVG is even more effective in reducing fruit dropbefore harvest (Yuan and Carbaugh 2007). We treatedcut Eustoma ‘Umi-Honoka’ flower stems with 5 mMNAA, 1 mM AVG, or a combined solution for 23 h(Shimizu-Yumoto and Ichimura 2010). Afterward, cutflower stems were individually transferred to distilledwater and kept at 23∞C. The vase life of cut flowerstems was longer following AVG treatment than in thecontrol, and the combined treatment with AVG andNAA extended the vase life much more than the othertreatments (Table 5). NAA treatment did not extendvase life, but treatments containing NAA increased thefresh weight of flower stems compared to the control.AVG plus NAA treatment greatly extended the flow-ering period when more than four flowers had opened.Based on these results, AVG is effective in extendingthe vase life of cut Eustoma flower stems, and addi-tion of NAA increases its efficacy.

2-3B. Combination treatment of STS and sucrosefor cut Eustoma flower stems

STS is commonly used by growers to improve thevase life of carnation and C. ajacis. In cut Eustomaflower stems, STS treatment extends vase life(Shimamura and Okabayashi 1997; Ichimura et al.1998). In contrast, Cho et al. (2001) reported that STStreatment does not significantly extend vase life of cutEustoma flower stems left in ethylene-free air. Treat-ment with sucrose extends vase life of Eustoma flowerstems, such as treatment with 5 to 10% sucrose for 24h (Halevy and Kofranek 1984), with 2% sucrose con-tinuously (Ichimura and Korenaga 1998), or with 6%sucrose for 24 or 48 h (Cho et al. 2001). A combinedtreatment with 4% sucrose and 50 mg L-1 BA for 24 hincreases vase life of Eustoma flower stems (Huangand Chen 2002). The Eustoma flower stem is a cymeinflorescence, which has branches with flowers or buds.Therefore, promotion of bud opening is also impor-tant in extending vase life. Continuous treatment with2% sucrose improves bud opening and anthocyaninconcentration of petals in cut Eustoma flower stems(Ichimura and Korenaga 1998). This may be becausesugars induce expression of genes involved in anthocy-anin biosynthesis in Eustoma (Kawabata et al. 1999).

The effects of treatments with STS, sucrose, and acombination of the two on quality of cut Eustomaflower stems were examined (Shimizu and Ichimura2005). Cut Eustoma ‘Asuka-no-nami’ flower stemswere treated with 0.2 mM STS, 4% sucrose, or 0.2 mMSTS combined with 4% sucrose for 20 h. Afterward,the flower stems were individually transferred to dis-tilled water and kept at 23∞C. STS treatment extendedthe vase life and increased the rate of bud opening

above the control. STS + sucrose and sucrose aloneextended vase life and increased the rate of bud open-ing more effectively than STS alone (Table 6). Wilt-ing of the leaves was delayed by all treatments overthe control. There was no visible damage to leaves inany treatment. ‘Asuka-no-nami’ is a cultivar withpicotee petals rimmed with violet. The anthocyaninconcentration in the violet parts of petals was higherin flowers treated with sucrose or STS + sucrose thanwith STS alone or the control (Table 7). Petals of flow-ers treated with sucrose and STS + sucrose showedhigher concentrations of sucrose, glucose, and totalsugar than those treated with STS alone or the control(Table 7). These results suggest that treatment with0.2 mM STS + 4% sucrose for 20 h improvedpostharvest quality of cut Eustoma flower stems moreeffectively than 0.2 mM STS alone.

2-3C. Sugar treatments for cut Eustoma flower stems2-3C.1. Sugar application and leaf damage

In cut Eustoma flowers, 10% sucrose treatment for

Treatment Vase lifez (days)

Control 5.6 ay

NAA 7.1 aAVG 12.8 bNAA + AVG 16.1 cSignificancex

NAA **AVG ***NAA ¥ AVG NS

Table 5. The effect of 5 mM NAA, 1 mM AVG and theircombination on vase life of cut ‘Umi-Honoka’ Eustomaflower stems.

Values are means of 8 replications.NS, not significant; **, *** indicate significance at P < 0.01,0.001, respectively.zVase life of cut flower stems was determined as the intervalfrom treatment to when the number of open flowers witherect pedicels was less than 3.yMeans with different letters within a column are signifi-cantly different among treatments by Tukey-Kramer’s mul-tiple range test at P < 0.05.xTwo-way ANOVA.Treatment solutions were supplemented with 0.5 mL L-1 ofLegend MK antimicrobial compound (Rohmand Haas Japan,Tokyo, Japan), which contains 11.3 g L-1 5-chloro-2-methyl-4-isothiazolin-3-one and 3.9 g L-1 2-methyl-4-isothiazolin-3-one as active ingredients. The antimicrobial compoundsolution was used as the control.Reprinted with permission from Postharv. Biol. Technol., 56,Shimizu-Yumoto H, Ichimura K. Combination pulse treat-ment of 1-naphthaleneacetic acid andaminoethoxyvinylglycine greatly improves postharvest lifein cut Eustoma flowers, 104–107, 2010. Copyright 2010Elsevier.



24 h was more effective in extending vase life of cutflower stems and promoting bud opening than 2.5%sucrose for 24 h (Halevy and Kofranek 1984), but treat-ment with a high concentration of sucrose sometimesdamages leaves (Shimizu-Yumoto and Ichimura 2007).

Similar symptoms have been reported in roses(Markhart and Harper 1995) and Tweedia caerulea(Hiraya et al. 2002) treated with sucrose. In roses,plasmolyzed palisade parenchyma cells are observedin sucrose-treated leaves (Markhart and Harper 1995),and damage is induced in leaves with a high transpira-tion rate (Torre and Fjeld 2001); the extent of leaf dam-age increases at higher concentrations of sucrose(Markhart and Harper 1995). Doi et al. (2000) reportedthat relative humidity influences the transpiration rateof cut roses.

In Eustoma, the mesophyll near the veins of dam-aged leaves becomes water-soaked and eventually de-hydrates (Shimizu-Yumoto 2009; Fig. 3). Palisade tis-sues of the damaged leaf area are compressed whenobserved microscopically. In addition, the sucrose con-

centration is higher in leaves treated with 4% sucrosethan when treated with distilled water. These resultssuggest that an increase in sucrose level in leaves mayinduce dehydration of mesophyll cells.

To clarify the sucrose concentration and other con-ditions inducing leaf damage, cut ‘Mira Coral’ flowerstems were treated with distilled water (0%), 2% or4% sucrose at 23∞C, and at a relative humidity of 53%,71% or 86% in the dark for 24 h (Shimizu-Yumoto andIchimura 2007). The percentage of leaf damage was100% at 53% relative humidity with 4% sucrose, and50% at 71% relative humidity with 4% sucrose, butleaf damage did not occur in the other treatments (Ta-ble 8). The total uptake of treatment solution washigher at the lowest relative humidity at every sucroseconcentration, but total sucrose uptake was greater with4% sucrose than with 2% of sucrose at all relativehumidities. The vase life was affected more by sucroseconcentration than by relative humidity, and 4% su-crose extended the vase life at all relative humiditiescompared to 2% sucrose. These results indicate that

Treatment Vase life (days) Rate of bud openingx (%)Cut flower stemz Leavesy

Control 4.8 aw 5.0 a 32STS 8.1 b 7.5 b 61Sucrose 11.3 c 7.9 b 94Sucrose + STS 11.9 c 8.6 b 94

Table 6. Effects of treatments with distilled water (control), 0.2 mM STS, 4% sucrose and 4% sucrose + 0.2 mM STS for 20h on vase life and bud opening in cut ‘Asuka-no-nami’ flower stems.

Values are means of 8 replications.Solutions containing sucrose were added to 200 mg L-1 8-hydroxyquinoline sulfate as an antimicrobial compound.zVase life of cut flower stems was determined as the interval from treatment to when the number of open flowers with erectpedicels was less than 2.yVase life of leaves was defined as the number of days when more than half of the leaves lost turgor.xNumber of buds opening during vase life of cut flower stems/number of buds at harvest ¥ 100.wValues with different letters are significant at P < 0.05 by Fisher’s PLSD test.From Shimizu-Yumoto (2009).

Treatment Anthocyanin concentration Sugar concentration (mg g FW-1)

(OD 530 nm g FW-1) Sucrose Glucose Fructose Total

Control 3.8 az 1.2 a 1.5 a 0.4 a 3.1 aSTS 3.8 a 1.5 a 1.5 a 0.4 a 3.4 aSucrose 6.9 b 7.0 b 9.9 b 0.2 a 17.1 bSTS + sucrose 7.3 b 8.6 b 12.0 b 0.4 a 20.9 b

Table 7. Effects of treatments with distilled water (control), 0.2 mM STS, 4% sucrose and 4% sucrose + 0.2 mM STS for 20h on anthocyanin and sugar concentrations in petals of flowers at anthesis in cut ‘Asuka-no-nami’ flower stems.

Values are means of 4 replications. Bud length at harvest was 4.4 ± 0.1 cm.Solutions containing sucrose included 200 mg L-1 8-hydroxyquinoline sulfate as an antimicrobial compound.zValues with different letters are significant at P < 0.05 by Fisher’s PLSD test.Modified from Shimizu and Ichimura (2005).



both low relative humidity and high sucrose concen-tration increase the risk of leaf damage because lowhumidity accelerates solution uptake and thus increasesthe amount of sucrose in leaves. When cut Eustomaflower stems are treated with high concentrations ofsucrose, high relative humidity reduces the risk of leafdamage and enables uptake of enough sucrose to ex-tend the vase life.

Another technique can reduce the uptake of sucrosefrom solutions by cut Eustoma flower stems. Cut ‘MiraCoral’ flower stems were treated with 10 mM (+) ABA[(+)-2-cis,4-trans-abscisic acid], 4% sucrose, and acombination, and held at 23∞C and 66% relative hu-midity for 21 h. The percentage of leaf damage was

50% in 4% sucrose (Shimizu-Yumoto and Ichimura2009a; Table 9). In contrast, treatment with 4% su-crose + ABA did not lead to leaf damage. These re-sults indicate that ABA is effective in reducing leafdamage induced by a high concentration of sucrose,even at low relative humidity. The amount of solutiontaken up was lower in 4% sucrose + ABA than in 4%sucrose alone (Table 9). ABA acts directly on stomatalclosure, which induces a decrease in transpiration andthus a decrease in water uptake. Therefore, the reduc-tion of leaf damage by applying ABA with the sucrosesolution could be attributable to a decrease in uptakeof the solution used for treatment. Vase life of cutflower stems was longer in treatments with sucrose and

Fig. 3. Photographs showing leaf injury caused by 4% sucrose treatment in cut Eustoma flower stems. I: ‘Asuka-no-kozakura’,II: ‘Asuka-no-yosooi’, III: ‘Tsukushi-no-yuki’. From Shimizu-Yumoto (2009).



sucrose + ABA than in the control (Table 9). Wiltingof the leaves was delayed with ABA or sucrose + ABA,but not with sucrose alone (Table 9). Based on theseresults, treatment with sucrose + ABA is effective inimproving the quality of cut Eustoma flower stems.

To clarify the role of ABA in the reduction of leafdamage induced by sucrose treatment, distribution ofcarbon was investigated using 13C-labeled sucrose

(Shimizu-Yumoto et al. 2010). Cut ‘Mahoroba PinkFlash’ Eustoma flower stems were treated with 4%sucrose with or without 10 mM (+) ABA. 12C-sucrose(normal sucrose) and 13C-labeled sucrose were used tomake solutions. Flower stems were kept at 23∞C and56% relative humidity for 24 h. After 24 h, they weretransferred to distilled water and 0, 2 and 5 days later,the stems were divided into leaves, stems, open flow-

Table 8. Effect of relative humidity and sucrose concentration on solution absorption and rate of leaf damage in cut ‘MiraCoral’ Eustoma flower stems.

Values are means ±S.E. of 6 replications.zNumber of flower stems which had at least one injured leaf out of 6 flower stems ¥ 100.yTwo-way ANOVA.Modified from Shimizu-Yumoto and Ichimura (2007).

Treatment Solution absorption Rate of leaf damagez Vase life (days)(g g FW 21 h -1) (%) Cut flower stemy Leavesx

Control 0.75 aw 0 8.4 a 6.9 aABA 0.36 b 0 8.8 ab 10.1 bSucrose 0.71 a 50 10.4 bc 7.0 aSucrose + ABA 0.41 b 0 11.9 c 13.4 c

-1

Table 9. Effects of treatments with distilled water (control), 4% sucrose, 10 mM (+) ABA and 4% sucrose + 10 mM (+) ABAfor 21 h on the solution absorption, rate of leaf damage, and vase life in cut ‘Mira Coral’ Eustoma flower stems.

Values are means of 10 replications.Solutions containing sucrose were added to 0.5 mL L-1 Legend MK (Rohm and Haas Japan K.K., Tokyo, Japan (active ingre-dients: 11.3 g L-1 5-chloro-2-methyl-4-isothiazolin-3-one and 3.9 g L-1 2-methyl-4-isothiazolin-3-one) as an antimicrobialcompound.zNumber of flower stems that had at least one damaged leaf out of 10 flower stems ¥ 100.yVase life of cut flower stems was determined as the interval from treatment to when the number of open flowers with erectpedicels was less than 5.xVase life of leaves was defined as the number of days when more than half of the leaves lost turgor.wValues with different letters are significant at P < 0.05 by Tukey-Kramer test.Reprinted with permission from J. Hort. Sci. Biotech., 84, Shimizu-Yumoto H, Ichimura K. Abscisic acid, in combinationwith sucrose, is effective as a pulse treatment to suppress leaf damage and extend foliage vase-life in cut Eustoma flowers,107–111, 2009. Copyright 2009 Taylor & Francis.



ers, and flower buds, which were dried. Total carboncontent and atom% 13C of each part of the stems wasanalyzed by an infrared mass spectrometer coupled toan elemental analyzer, and the exogenous carbon de-rived from the applied sucrose was calculated.

The uptake of the treatment solution was less in thesucrose + ABA treatment than in the sucrose treatment,and no leaf damage was detected in sucrose + ABA,but all cut flowers had leaf damage in the sucrose treat-ment. In the sucrose treatment, 40% of the exogenouscarbon was in leaves at 0 days after treatment. In con-trast, only 15% was in the leaves in the sucrose + ABAtreatment. At 0 days, the amount of exogenous carbon(in mg gFW-1) in leaves was much higher in the su-crose treatment than in sucrose + ABA (Fig. 4). How-ever, there were no differences in the amount of exog-enous carbon of open flowers and flower buds betweenthe sucrose and sucrose + ABA treatments (Fig. 4).These results mean that the more of the solution ab-sorbed by the cut flower stems, the more sucrose isaccumulated in the leaves rather than in the open flow-ers and flower buds. ABA apparently reduced accu-mulation of applied sucrose in the leaves, thus avoid-ing leaf damage in the sucrose + ABA treatment.

On day 2 after treatment, the amount of carbon (in

Fig. 4. Changes in amount of exogenous carbon derived from sucrose applied to leaves (A), stems (B), open flowers (C) andflower buds (D) after a 24 h treatment with 4% (w/v) sucrose alone (open circles) or with 4% sucrose plus 10 mM ABA (filledcircles) in cut Eustoma ‘Mahoroba Pink Flush’ flower stems. The two treatment solutions contained 0.5 mL L-1 Legend MK asa biocide. Each plot represents the mean of three replications ±S.E. Values followed by ns, *, **, or *** were nonsignificantor significant at P < 0.05, 0.01, or 0.001, respectively based on t-test. Reprinted with permission from J. Hort. Sci. Biotech.,85, Shimizu-Yumoto H, Kondo M, Sanoh Y, Ohsumi A, Ichimura K. Effect of abscisic acid on the distribution of exogenouscarbon derived from sucrose applied to cut Eustoma flowers, 83–87, 2010. Copyright 2010 Taylor & Francis.

mg gFW-1) from applied sucrose increased in openflowers and flower buds, but decreased in leaves andstems in sucrose and sucrose + ABA treatments (Fig.4). These results suggest that carbon from the appliedsucrose was translocated from leaves and stems to openflowers and flower buds. The amount of carbon fromapplied sucrose was lower in open flowers and flowerbuds in the sucrose + ABA treatment than in the su-crose treatment on days 2 and 5 (Fig. 4). However,there was no significant difference in total carbon ofopen flowers and flower buds between the sucrose andsucrose + ABA treatments on day 5. Therefore, we in-ferred that endogenous carbohydrates were alsotranslocated to open flowers and flower buds, and thattranslocation of endogenous carbohydrates might bepromoted by ABA, which contributed to extension ofvase life of cut Eustoma flower stems treated with su-crose + ABA.2-3C.2. Continuous sugar treatment from harvest toretailer

It takes a few days for cut flowers to be transportedfrom growers to markets. Handling during transport isimportant because the mode of transportation and thetemperature affect the vase life of cut flowers (Doi etal. 1999). Cut flowers are transported by either a wet



3. Postharvest characteristics of cut gentian flow-ers and techniques for extending their vase life

There are many Gentiana species in the world.Gentiana triflora grows naturally in the north and G.scabra in the south of Japan. Cultivars of cut gentianflowers are usually developed from G. triflora, G.scabra and their hybrids in Japan. Many cultivars de-rived from G. triflora have characters of petals thatare not reflective at anthesis and a flowering season oflate July to August. In cultivars derived from G. scabra,the petals generally are reflective at anthesis, and theflowering season is late September to October. Hybridcultivars show intermediate characteristics between G.triflora and G. scabra. The gentian flower stem is acyme inflorescence, which has short branches withflowers or buds.

or dry method. No water is supplied to cut flowersduring dry transportation. In contrast, wet transportsupplies water, usually containing antimicrobial com-pounds, to cut flowers. Wet transport is becoming popu-lar in Japan for cut flowers, including Eustoma, rose,and G. paniculata. This method maintains the visiblefreshness of cut flowers better than dry transport.

The effects of combining various treatments with wetor dry transport on postharvest quality of cut Eustoma‘Mira Marine’ flower stems have been explored undersimulated conditions; treatments with 0.2 mM STS, 4%sucrose, and 10 mM ABA for 24 h and 1% sucrose dur-ing wet transport for 24 h extended vase life of cutflower stems, delayed wilting of the leaves and pro-moted bud opening (Shimizu-Yumoto 2009).

We also developed another approach to supply sug-ars to cut Eustoma flower stems during distribution.Cut Eustoma ‘Umi-Honoka’ flower stems were treatedwith tap water or commercial preservative containingabout 0.5% sugar and antibacterial compounds in thebackyard of a grower for 1 day (average temperature:10.4∞C), and then transported wet or dry to a flowermarket for 1 day (average temperature: 7.1∞C). Dur-ing wet transport, cut flower stems were continuouslytreated with a commercial preservative containingabout 0.5% sugar. After transport, the flower stemswere placed in a solution containing antibacterial com-pounds or commercial preservative (about 0.8% sugarplus antibacterial compounds) for 3 days at 23∞C (re-tailer simulation). After that, they were transferred todistilled water or a solution containing antibacterialcompounds for 14 days at 23∞C (consumer simulation).Continuous sugar treatments extended vase life, al-though treatment with antibacterial compounds at theconsumer step was necessary (Table 10). We confirmedthat sugars even at low concentration were effective inpractice if supplied continuously from harvest to re-tailer.

Table 10. Effects of continuous sugar treatment on vase life in cut ‘Umi-Honoka’ flower stems.

Values are means ±S.E. of 10 replications.zVase life of cut flower stems was determined as the interval from beginning of consumer treatment to when more than half offlowers wilted.y0.5 mL L-1 KATHON CG (Rohm and Haas Japan K.K., Tokyo, Japan, active ingredients: 11.3 g L-1 5-chloro-2-methyl-4-isothiazolin-3-one and 3.9 g L-1 2-methyl-4-isothiazolin-3-one) as an antimicrobial compound.xSugar solution was used in form of commercially available products which contain sugars and antibacterial components.wValues with different letters are significant at P < 0.05 by Tukey-Kramer test.

Table 11. Effect of ethylene exposure on vase life after har-vest of Gentiana scabra ‘Shinbisei’ flowers.

Values are means ±S.E. of 10 replications.The flowers were harvested at anthesis, and then, they weretreated with ethylene for 24 h.zVase life was determined as the the time elapsed from theend of the ethylene treatment to the time of petal wilting.Reprinted with permission from Postharv. Biol. Technol., 63,Shimizu-Yumoto H, Ichimura K. Effects of ethylene, polli-nation, and ethylene inhibitor treatments on flower senes-cence of gentians, 111–115, 2012. Copyright 2012 Elsevier.



Cut gentian flower stems are produced from sum-mer to autumn. The production area of cut gentian flow-ers is mainly the northern cool region in the summer,but the consumption areas, such as Tokyo or Osaka,are hotter than the production area. Therefore, properhandling after harvest is important to maintain the qual-ity of the cut flower stems. This chapter describespostharvest characteristics of cut gentian flowers andtreatments that extend the vase life. Vase life of cutgentian flowers was defined as the interval from thestart of examination to when petals wilted.

3-1. Postharvest characteristics of gentian flow-ers

There has been little research on gentian flowers.Eason et al. (2007) reported that sensitivity to ethyl-ene is low in G. triflora ‘Showtime Starlet’ flowers.

Other gentian species, such as G. dahurica, G.kochiana, and G. sino-ornata, also have low sensitiv-ity to ethylene (van Doorn 2001).

To clarify the sensitivity of G. scabra ‘Shinbisei’flowers to ethylene, they were treated with 0.5, 2, 5,or 10 mL L-1 ethylene for 24 h (Shimizu-Yumoto andIchimura 2012). Flower senescence was accelerated byconcentrations higher than 0.5 mL L-1 ethylene (Table11). This observation suggests that ‘Shinbisei’ flow-ers are highly sensitive to ethylene and that there isspecies variation in sensitivity to ethylene. Shishidoet al. (2011) also reported that sensitivity to ethyleneis higher in cultivars derived from G. scabra, G. triflora¥ G. scabra and G. triflora (in that order) when treatedwith 10 mL L-1 ethylene for 48 h.

In gentian ‘Shinbisei’ flowers, self-pollination short-ened the vase life, which was about half that ofunpollinated flowers. Ethylene production by whole

Fig. 5. Changes in ethylene production from whole flowers (A), petals (B), gynoecium (C), and stamen (D) of unpollinated(open circles) and pollinated (filled circles) flowers of G. scabra ‘Shinbisei’. Each plot represents the mean of three replica-tions ±S.E. Values followed by ns, * and ** were nonsignificant or significant at P < 0.05, or 0.01, respectively, for unpollinatedand pollinated flowers based on t-test. Reprinted with permission from Postharv. Biol. Technol., 63, Shimizu-Yumoto H,Ichimura K. Effects of ethylene, pollination, and ethylene inhibitor treatments on flower senescence of gentians, 111–115,2012. Copyright 2012 Elsevier.



Fig. 6. Effect of 1-MCP on wilting of cut G. scabra ‘Yuki-hotaru’ (A), G. triflora ‘Koharu’ (B) and their hybrid, ‘Aoi-kaze’(C) flower stems. Open circles indicate the control, and filled circles indicate 1-MCP treatment. It took 2 days from harvest toarrive at our laboratory. After transport, the top flower and several lateral flowers had opened. The cut flower stems wererecut to 58 cm, and colorless buds were removed. The node numbers of cut flower stems were about 4 or 5 in ‘Yuki-hotaru’and ‘Aoi-kaze’, and about 7 or 8 in ‘Koharu’. Each plot represents the mean of eight or ten replications (‘Yuki-hotaru’ and‘Aoi-kaze’, n = 8, ‘Koharu’, n = 10). Reprinted with permission from Postharv. Biol. Technol., 63, Shimizu-Yumoto H,Ichimura K. Effects of ethylene, pollination, and ethylene inhibitor treatments on flower senescence of gentians, 111–115,2012. Copyright 2012 Elsevier.



flowers and gynoecium increased at 1 day after polli-nation (Fig. 5). Based on these results, a rapid increasein ethylene from the gynoecium is related to acceler-ated flower senescence induced by pollination in gen-tian ‘Shinbisei’. In G. triflora ‘Showtime Starlet’ flow-ers, cross-pollination by gentian ‘Lovely Ashiro’ short-ens the vase life, and ethylene inhibitors prevent thesenescence induced by pollination (Eason et al. 2007).

In gentian ‘Shinbisei’ flowers, neither the ethyleneaction inhibitors STS and 1-MCP nor the ethylene pro-duction inhibitor AIB extended the vase life beyondthe controls. Only AVG, an ethylene production inhibi-tor, significantly extended vase life. In G. triflora‘Showtime Starlet’, AOA, another ethylene productioninhibitor, also extends the vase life of unpollinatedflowers (Eason et al. 2007). AVG and AOA are notspecific inhibitors of ACC synthase. They inhibit ac-tivity of pyridoxal phosphate (Yang and Hoffman1984), an important co-enzyme related to amino acidmetabolism (Schneider et al. 2000) and the auxinbiosynthetic pathway (Soeno et al. 2010). In addition,AVG is reported to reduce protein biosynthesis (Saltveit2005). Therefore, it is possible that AVG treatmentdelayed senescence of G. scabra flowers not only byinhibiting ethylene biosynthesis, but also by affectingother metabolic pathways.

3-2. Postharvest treatments for extending the vaselife of cut gentian flower stems

Treatment with 3% sucrose and 0.5 mM STS for 24h extends the vase life of cut G. triflora ‘Akita Blue’flower stems (Zhang and Leung 2001). Treatment with10 mM gibberellic acid or 5% sucrose for 24 h extendsthe vase life of cut G. triflora ‘Late Blue’ flower stems(Eason et al. 2004).

Cut ‘Koharu’, ‘Aoi-kaze’ and ‘Yuki-hotaru’ flowerstems, respectively derived from G. triflora, G. triflora¥ G. scabra, and G. scabra, were treated for 24 h with2 mL L-1 1-MCP, an ethylene action inhibitor; the per-centage of wilting flowers per stem increased moreslowly for ‘Yuki-hotaru’ and ‘Aoi-kaze’ flower stemscompared to that for ‘Koharu’ (Shimizu-Yumoto andIchimura 2012; Fig. 6). These results indicate that 1-MCP delays flower senescence of cut gentian flowerstems, and that its effectiveness varies among species.Shishido et al. (2011) reported that 0.2 mM STS wasmore effective in extending the vase life of gentianflower stems derived from G. scabra than those de-rived from G. triflora ¥ G. scabra, and was not effec-tive on cultivars derived from G. triflora. The ethyl-ene action inhibitors STS and 1-MCP did not delaysenescence of gentian ‘Shinbisei’ flowers harvested atanthesis (Shimizu-Yumoto and Ichimura 2012). Be-cause cut gentian flower stems have many flowers atdifferent stages of development, some flowers mightbe pollinated. Treatment with AOA or 1-MCP mark-

edly delays senescence of gentian flowers pollinated24 h earlier (Eason et al. 2007). Therefore, the effectof 1-MCP on cut gentian flower stems may have beendue to delaying senescence of flowers that had beenpollinated.

Taken together, this suggests that the level of sensi-tivity to ethylene differs depending on species. Incultivars derived from G. triflora, sensitivity of flowersenescence to ethylene is low, and ethylene inhibitorsare less effective in extending vase life. Treatment withsucrose or gibberellic acid is effective, but there iscultivar variation in the effects of these treatments(Eason et al. 2004). On the other hand, sensitivity offlower senescence to ethylene is high and ethylene in-hibitors are effective in extending the vase life in cutgentian flower stems derived from G. scabra. In bothtypes of gentian flowers, pollination shortens the vaselife. Gentian flowers can be pollinated easily and natu-rally by insects in the field, because the flower stemsused for cutting are usually grown in open fields inJapan. Therefore, covering the plants with insect-proofnets is effective in preventing field pollination.

4. Postharvest characteristics of cut Dahlia flow-ers and techniques for extending their vase life

Dahlia (Dahlia ¥ hybrida) is a bulbous plant in theAsteraceae; its flower is a capitulum inflorescence,which is composed of many florets. The place of ori-gin is Central and South America. In 1789, the dahliawas introduced to Europe, and double-floweredcultivars were developed in 1808. After that, cultivarswith various flower shapes, such as cactus type andball type, were developed. Dahlia was introduced fromEurope to Japan around 1842. Cut flower cultivars suchas ‘Shukuhai’ were released starting in the 1930s, butproduction of cut dahlia flowers decreased from the1980s. Around 2005, attractive cultivars such as‘Kokucho’, developed by breeders, became popular asornamentals for weddings, and their production on arevenue basis has increased about 4.5 times in the pastfive years. Through protected cultivation, productionof cut dahlia flowers shifted from summer to late au-tumn, winter and spring. Although their vase life isshort (about five to seven days), demand for gift andhome use of cut dahlia flowers has increased. There-fore, improvement of postharvest quality is necessaryto expand the demand.

This chapter describes the postharvest characteris-tics of cut dahlia flowers and treatments to extend theirvase life. Vase life of dahlia florets was defined as theinterval from start of examination to when petals wiltedor discolored, and the vase life of cut dahlia flowerswas defined as the interval from start of examinationto when several petals had abscised or two-thirds ofthe petals of whole flowers had wilted or discolored.



4-1. Postharvest characteristics of cut dahlia flow-ers with a focus on ethylene

Woltering and van Doorn (1988) and van Doorn(2001) classified sensitivity of flower senescence toethylene into five categories by degree of accelerationof flower senescence when exposed to 3 mL L-1 ethyl-ene for 24 h. Based on these categories, dahlia ‘KarmaThalia’ flowers are insensitive to ethylene becauseflower senescence is not accelerated by 1 mL L-1 eth-ylene for 16 h (Dole et al. 2009). On the other hand,the length of exposure to ethylene is important for eth-ylene responsiveness in some flowers. In Campanulamedium, the vase life of flowers is not shortened byexposure to ethylene for 16 h, whereas it was short-ened by exposure for 48 h (Kato et al. 2002). The sen-sitivity of carnation to ethylene is evaluated by con-tinuous exposure to ethylene, which has clarified thatthere are marked variations in sensitivity to ethyleneamong strains (Onozaki et al. 2004, 2008). Senescenceof dahlia ‘Kokucho’ flowers was accelerated by con-tinuous exposure to 2 or 10 mL L-1 ethylene (Shimizu-Yumoto and Ichimura 2013). Uptake of 1 or 10 mL L-

1 2-chloroethylphosphonic acid (CEPA), which releasesethylene in the plant, also accelerated senescence ofcut dahlia flowers. These results suggest that dahlia‘Kokucho’ flowers are sensitive to ethylene.

Cut flowers with high sensitivity to ethylene usuallyproduce ethylene during senescence, and ethylene in-hibitors delay flower senescence. Therefore, ethyleneproduction by ray petals, ovaries, calyxes and recepta-cles was measured for 9 days after harvest of cut‘Kokucho’ flowers at anthesis. In ray petals, ovariesand receptacles, ethylene production at harvest washigh and then decreased up to 5 days. No significantdifferences in ethylene production were detected at 5

to 7 days in these flower parts. Senescence symptomsappeared at 8 days, which was when the first row offlorets wilted. The calyxes produced very little ethyl-ene during the experimental period.

Treatment with 0.2 mM STS for 24 h did not extendthe vase life compared to the control in cut dahlia‘Kokucho’ flowers. In dahlia ‘Karma Thalia’, flowersenescence is not delayed by treatment with 0.2 mMSTS for 16 h (Dole et al. 2009). Treatment with 0.1 to1.6 mM STS for 1 h does not extend the vase life ofcut dahlia ‘Kin-Sen’ flowers (Uda 1996). Taken to-gether, these findings indicate that ethylene is not veryimportant for senescence of cut dahlia flowers, al-though they show sensitivity to ethylene.

4-2. Postharvest techniques for extending the vaselife of cut dahlia flowers

4-2A. Treatment of cut dahlia flowers with the cyto-kinin BA

The effects of the synthetic cytokinin BA on vaselife of cut dahlia flowers were investigated (Shimizu-Yumoto and Ichimura 2013). The method of BA appli-cation was also studied because direct application ofBA to petals is more effective in extending vase lifethan application by immersing the base of cut rosestems into a solution (Mayak and Halevy 1970) andcut flower stems of Grevillea ‘Sylvia’ (Setyadjit et al.2004). In carnation studies using 14C-labeled BA, itappeared that only a small percentage of radioactivitymoves from the petals into the remainder of the flow-ers (van Staden and Joughin 1988), and most of thelabeled BA and its metabolites remain localized in thestem, from which labeled BA is supplied (Kelly et al.1985).

Ray petals of each floret were dipped into BA solu-

Table 12. Effects of 6-benzylaminopurine (BA) on vase life after treatment of dahlia ‘Kokucho’ florets.

Values are means ±S.E. of 15 replications.The flowers were harvested at the stage when the first row of petals from outside had opened.Five florets in the first row from each of three flowers were used, for a total of 15 florets for each treatment.zVase life of a floret was defined as the time from treatment to when the petals wilted or discolored.yValues followed by ns were not significantly different and values followed by ** were significantly different from the controlat P < 0.01 by Dunnett’s test.Reprinted with permission from Postharv. Biol. Technol., 86, Shimizu-Yumoto H, Ichimura K. Postharvest characteristics ofcut dahlia flowers with a focus on ethylene and effectiveness of 6-benzylaminopurine treatments in extending vase life, 479–486, 2013. Copyright 2013 Elsevier.



tion for 5 seconds, and then florets were transferred todistilled water (dip treatment), and allowed to absorbBA solution continuously (absorption treatment). Diptreatment with 50, 100, or 500 mM BA delayed senes-cence of dahlia ‘Kokucho’ florets, but immersion in100 mM BA did not (Table 12). To clarify the influ-ence of BA on ethylene sensitivity, dahlia floretspretreated with 1-MCP or BA were allowed to absorbdistilled water or CEPA to test whether ethylene hasany effect on petal senescence. Treatment with 1-MCPdelayed senescence of florets held in both solutionscompared with the control. However, BA dipping wasmore effective in extending the vase life than 1-MCPwhen the florets were held in either distilled water orCEPA solution. This result suggests that BA may beeffective in suppressing not only ethylene sensitivitybut also other factors promoting petal senescence.

In cut ‘Kokucho’ dahlia flowers, BA was applieddirectly to petals by spraying because the diameter ofa whole dahlia ‘Kokucho’ flower is about 15 to 20 cm.Spray treatment with 50, 100 and 500 mM BA extendedthe vase life beyond the controls. In contrast, immer-sion of the base of stems in 50, 100 or 500 mM BA didnot extend the vase life. The vase life of flowers ofother dahlia cultivars, ‘Kamakura’ or ‘Mitchan’, wasextended by about 1.8 or 2.6 days by BA spray treat-ments over controls. Tsujimoto et al. (2014) reportedthat vase life of 27 cultivars of dahlia flowers is ex-tended by 0.6 to 2.8 days by BA spray compared tocontrols. Based on these results, direct application ofBA is effective in improving the quality of cut dahliaflowers.

4-2B. Improvement of BA treatment methods forextending the vase life of cut dahlia flowers

Continuous sugars treatment extends the vase life ofcut dahlia flowers (Lukaszewska 1986; Dole et al.

2009). Therefore, combined treatments of BA spray-ing and sugar solutions were investigated in cut dahlia‘Kamakura’ and ‘Mitchan’ flowers. Cut dahlia flowerswere sprayed with BA solutions in commercial pro-duction or left unsprayed. Afterward, the base of theirstems was placed in a solution of 1% glucose and anti-bacterial compounds or in distilled water. The vase lifeof cut ‘Kamakura’ or ‘Mitchan’ flowers was extendedby 4 or 5 days by a combination treatment of BA sprayand sugar solution over that of the control with neitherBA spray nor sugar.

However, stems of half of the ‘Kamakura’ and all ofthe ‘Mitchan’ flowers bent after a combination of BAspray and being placed in distilled water. Followingthese observations, the size of the nozzle of the sprayvessel was changed. In dahlia cultivar ‘Mitchan’, thestem of only one flower bent; this flower was sprayedwith BA using a spray vessel with a large nozzle. Byusing a spray vessel with a small nozzle, the dropletsof BA solution dried sooner; the vase life was about 4days longer than that of flowers without BA spray.

To test the effectiveness of BA spray by growers, acommercial product containing BA was sprayed on cut‘Kamakura’ and ‘Aya-pea’ flowers at the growers, andthe next day, the flowers were transferred to a marketwhile allowing them to absorb commercial preserva-tive containing sugar for one day. After arrival at themarket, the flowers were placed in commercial pre-servative containing sugar. The vase life of bothcultivars was about 2 days longer by using the BA sprayat the growers.

We also examined the effects of respraying with BAat retailers on the vase life of dahlia cultivars sprayedwith BA at the growers. Cut ‘Kokucho’, ‘Nessho’,‘Mitchan’ and ‘Port Light Pair Beauty’ flowers weresprayed with commercial product containing BA at thegrowers, and on the next day, they were transferred to

Values are means ±S.E. of 6 replications.Cut flowers were sprayed with BA, then transferred from growers to our institute while absorbed in preservative solutioncontaining sugar. After arrival, the cut flowers were resprayed with BA, absorbed in sugar, or both as a simulation of retailertreatments.zVase life of cut flowers was defined as the time from treatment to when several petals had abscised, or two-thirds of the petalsof whole flowers had wilted or discolored.yValues with different letters are significant at P < 0.05 by Fisher’s PLSD test.x0.5 mL L-1 KATHON CG (Rohm and Haas Japan K.K., Tokyo, Japan, active ingredients: 11.3 g L-1 5-chloro-2-methyl-4-isothiazolin-3-one and 3.9 g L-1 2-methyl-4-isothiazolin-3-one).

Table 13. Effects of combination treatment with BA spray and glucose solution at retailer on vase life of four cultivars of cutdahlia flowers.



our laboratory in a sugar solution that they were al-lowed to absorb for 1 day. After arrival at our labora-tory, cut flower stems were sprayed with commercialproduct containing BA again, or left unsprayed, andthen placed in sugar solution or distilled water. Re-spraying BA plus immersion of the cut stems in thesugar solution extended the vase life of cut ‘Kokucho’,‘Mitchan’ and ‘Nessho’ flowers more than other treat-ments (Table 13). In ‘Port Light Pair Beauty’, the vaselife of cut flowers treated by respraying with BA plusimmersion in sugar solution was similar to that of cutflowers treated by immersion in sugar solution only.Tsujimoto et al. (2016) reported that spraying with BA2 to 3 times is effective in extending the vase life ofcut ‘Kokucho’ and ‘Kamakura’ flowers.

Taken together with these results, combining a BAspray with immersion in sugar solution is very effec-tive in extending vase life, and respraying BA at theretailer as well as at the growers is important in ensur-ing cut dahlia flowers have a long vase life for con-sumers.

5. Concluding remarks

For Eustoma, gentian and dahlia flowers, postharvestcharacteristics affecting vase life and techniques forextension of vase life have been summarized. In cutEustoma flowers, sensitivity to ethylene is probablyrelated to cultivar variation in vase life of cutunpollinated flowers. The distance between stigma andanther and the pollinated area of the stigmatic surfaceare factors affecting the shortened vase life inducedby pollination. Sugars and ethylene inhibitors extendthe vase life of cut Eustoma flowers, and methods ofavoiding sugar-induced leaf damage have also beendeveloped. In gentian, there is species variation in sen-sitivity of flower senescence to ethylene, and wiltingof flowers is delayed by treatment with ethylene in-hibitors in cultivars derived from G. scabra and G.triflora ¥ G. scabra. In cut dahlia flowers, spray treat-ment with the cytokinin BA improves vase life, and acombination treatment of BA spray with sugar solu-tion is more effective in extending vase life than theindividual treatments. New products preserving orna-mental plants by addition of phytohormones such ascytokinins or gibberellic acid have been developed.These products are used for bulb plants, such as dahlia.If the mechanisms behind the delay of senescence bycytokinins can be better understood, more effectiveproducts will be developed. This research will lead toa supply of cut flowers with longer vase life for con-sumers.

AcknowledgmentsThis work was partially supported by A Scheme to Revi-

talize Agriculture and Fisheries in Disaster Area ThroughDeploying Highly Advanced Technology and by the Research

and Development Projects for Application in Promoting NewPolicy of Agriculture, Forestry and Fisheries in Japan. I amgrateful to growers for providing cut flowers, and to Dr.Ichimura for many suggestions on my research.

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