Gas Exchange of Flower Buds and Water Transport Capacity of the Peduncle of Two Cut Roses during Vase Life

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1 Gs Exchnge of Flower Buds nd Wter Trnsport Cpcity of the Peduncle of Two Cut Roses during Vse Life W. Grf 1,, W.B. Herppich 2, S. Huyskens-Keil 3 nd H. Grüneerg 1 1 Section of Floriculture, Institute of Horticulturl Science, Humoldt-Universität zu Berlin, Germny 2 Deprtment for Horticulturl Engineering, Leiniz-Institute for Agriculturl Engineering, Potsdm-Bornim, Germny 3 Section of Qulity Dynmics nd Posthrvest Physiology, Institute of Horticulturl Science, Humoldt-Universität zu Berlin, Germny Keywords: posthrvest, trnspirtion, respirtion, hydrulic conductivity Astrct Cut rose (Ros hyrid L.) cultivrs lrgely differ in their vse life nd entneck resistnces. The most importnt fctor determining these fetures is the posthrvest wter sttus mngement of plnts, especilly under drought stress. Structure nd function of the peduncle is crucil for the ent neck susceptiility. In ddition, ll nutrients, crohydrtes, plnt hormones nd, of course, the wter essentil for flower development must pss through this prt of the stem. The cut rose cultivrs Akitio, typiclly with short vse life, nd Red Gint with long vse life were investigted. To quntify the wter trnsport cpcity of the peduncle, the ctul hydrulic conductivity of unstressed rose stems ws mesured destructively in summer nd winter. Furthermore, whole vse life gs exchnge of flower uds ws investigted from My 2006 to My Dry mtter relted flower ud trnspirtion ws lwys significntly higher in Red Gint (n=8) thn in Akito (n=10). Throughout ll studies the hydrulic conductivity ws higher in Red Gint. However, differences were only significnt in winter. It cn e ssumed tht the generlly etter posthrvest wter mngement of Red Gint plnts my e relted to higher trnsport cpcity. In ddition, Red Gint roses cn chieve long vse life despite of their high respirtion rtes. INTRODUCTION The vse life of cut roses is lrgely determined y the posthrvest wter regime. Prticulrly, the inhiition of continuous wter supply in the peduncle tissue leds to ending of the flower (ent-neck), s descried y Burdett (1970). The cultivr Akito hs low resistnce to posthrvest drought stress (Grf et l., 2006). Plnts of this cultivr re normlly chrcterised y short vse life (Hendriks et l., 2006; Grf et l., 2007) wheres those of Red Gint hve long vse life (Grf et l., 2007). After turgor loss the mechnicl strength of the peduncle ecomes the mjor determining fctor (Zieslin et l., 1978). This prmeter ws shown to e significntly higher in roses of Red Gint thn in Akito (Grf et l., 2006, 2007). The optiml mngement of the posthrvest wter sttus, especilly under drought stress conditions, is generlly more importnt in cultivrs with low mechnicl strength thn in those with strong peduncle. Plnts normlly exhiit tight stomtl control of lef wter losses. However, rose petls do not hve stomt (Stus nd Frncis, 1971; Myk nd Hlevy, 1974; vn Doorn, 1997), hence, lcking ny physiologicl control of wter losses (Drlington nd Dixon, 1991). So, petl trnspirtion is only governed y the wter vpour pressure deficit etween lef nd ir ( w). As shown y Crpenter nd Rsmussen (1974) lef trnspirtion ws responsile for 75% of the totl wter losses of well-wtered cut Forever Yours roses. Only 20% of grlu-erlin@we.de Proc. IX th Int l Symp. on Posthrvest Qulity of Ornmentl Plnts Eds.: C.-O. Ottosen et l. Act Hort. 847, ISHS

2 the wter loss origintes from the flowers, while 5% rises from the stems. Under drought stress conditions these proportions will chnge to higher contriution of flowers ecuse fter drought-induced closure of lef stomt flower trnspirtion is the min source of wter losses (vn Doorn, 1997). Cut flowers often experience posthrvest drought stress during trnsporttion from the grower to the consumer. During this time cut flowers need wter for rehydrtion nd flower expnsion (Berkholst, 1980). Furthermore, excessive flower wter loss normlly results in cvittion which in turn leds to emolism in the wter conducting system lrgely limiting wter flow from the min plnt xis to the distl region of peduncle (Drlington nd Dixon, 1991). So, tissue drought stress in the peduncle my e common. High flower trnspirtion rtes demnd high wter supply cpcity. Cultivrs with low wter uptke ility show pronounced tendency for erly flower wilting (Zieslin, 1978). The ctul hydrulic conductnce is mesure of the ctul trnsport cpcity of the xylem system. As shown y Drlington nd Dixon (1991) the lowest hydrulic conductnce is generlly found in the picl peduncle, irrespective of the cultivrs investigted ( Roylity nd Smnth ). In ddition, humidity conditions during growth (i.e. vrying or constnt ir humidity) did not influence this effect. During continuous dehydrtion, plnts of Akito showed pronounced lower ctul hydrulic conductivity thn roses of Milv (Grf et l., 2006). Grf et l. (2006) lso found high correltion etween the decrese in wter potentil (Ψ) nd tht in hydrulic conductnce. However, further dt especilly out the hydrulic conductnce in rose peduncles re lcking. In cut roses, rtes of flower development nd ging re closely correlted with the rte of respirtion (Reid, 2003) nd this rte closely depends on temperture. Reid (2003) found tht pistils nd stmens exhiit the highest respirtion (pproximtely 300 ml CO 2 kg -1 h -1 ). Respirtion rtes of petls re in the rnge of the verge vlue of the entire cut rose stem (c 200 ml CO 2 kg -1 h -1,), while leves nd stems were lower (175 ml CO 2 kg -1 h -1 nd 100 ml CO 2 kg -1 h -1, respectively) (Reid, 2003). Therefore, it cn concluded tht respirtion of cut roses were highest in flowers. According to Bhttchrjee nd Phl (1999) cut rose cultivrs with short vse life show high respirtion rtes compred to cultivrs with long vse life; nd the respirtion rte is highly cultivr specific. Bord et l. (2005) generlly confirmed tht roses with short vse life hve high respirtion rte ut lso found high respirtion rtes in some cultivrs with long vse life. Bord et l. (2005) concluded tht these roses must hve rpid depletion of their energy reserves nd in generlly tht the linking respirtion to vse life cn depend gretly on the cultivr. MATERIALS AND METHODS Plnts of the cut rose cultivrs (Ros hyrid) Akito nd Red Gint were grown in greenhouse t the Institute of Horticulturl Sciences (Humoldt-Universität zu Berlin, Germny). Heting temperture ws set to 18 C while ertion temperture ws 23 C. Reltive ir humidity ws in the rnge of 50 to 90% with lrge vritions during the dy. Nturl light ws supplemented with high pressure sodium lmps to yield minimum photosynthetic photon flux density (PPFD) of 140 µmol m -2 s -1 for 18 h dily nd yer round. Plnts were utomticlly trickle irrigted with nutrient solution in n open system. Cultivted with the Jpnese system (ending down the lind or redundnt stlks to increse lef re for photosynthesis), 8.6 plnts/m 2 were cultivted in doule rows in 7 L pots in commercil pet-coir sed sustrte (Stender AG, Lucku, Germny) on tles. Roses were hrvested t the flower development stge 2, modified fter Grszynsk et l. (1989). After hrvest stems were plced in Chrysl professionl 2 (Pokon & Chrysl Interntionl B.V., Nrden, the Netherlnds) solution (2%) nd stored over night in cooling chmer t 1 to 4 C nd 80-90% rf. Mesurements of the ctul hydrulic conductivity were done following Durkin (1979, ) nd vn Dorn et l. (1989) on the upper third of the peduncle using pproximtely 12 cm long stem segments of roses hrvested the dy efore nd stored in 302

3 drkness t 2-4 C over night. The flowers were cut with new rzor lde 1-2 cm elow the flower ud. The sl cuts were done 2 cm elow the first or second lef elow the flower. Cutting the segments nd fitting them into silicone tues were done under wter to prevent ir entrnce into the vessels. After 5 min-pre flush with 0.1 mol KCl-solution (Millipore-wter, degssed throw 6 min stirring under vcuum) with pressure of 0.01 MP, the pure degssed wter pssed through the segments t the sme pressure s collected in glss tues filled with filter pper nd the mount ws mesured y weighting the filled tues on n electronic lnce (Anlytic AC 210 P, Srtorius, Goettingen, Germny). According to Drlington nd Dixon (1991) ctul hydrulic conductivity ws clculted from the mount of wter, the segment length, pplied pressure nd time s K h. [m 4 s -1 MP -1 ] = mount of wter [m 3 ] * segment length [m] time [s] * pressure [MP] These investigtions were crried out in Jnury nd July 2007 with 30 flowers of ech cultivr. From 17 My 2006 to 4. June 2007 gs exchnge mesurements were performed with stems of Akito (n=10, 5 in winter, 5 in summer) nd Red Gint (n=8, 4 in winter, 4 in summer). The time from 21 Septemer to 20 Mrch ws denoted s winter nd the period from 21 Mrch to 20 Septemer s summer. For the mesurements n open, fully climte-controlled Wlz Mini-Cuvette System (Heinz Wlz GmH, Effeltrich, Germny) with two mesuring chmers ttched to GK 022 peltiersystems. CO 2 nd H 2 O gs exchnge ws determined with differentil infrred Gs Anlystor (Binos 4, Leyoldt- Hereus, Hnu, Germny). The flowers were hermeticlly seled into the chmers. The stem se ws plced in glss ottle filled with Chrysl professionl 2 solution. Light ws provided y hlogen spot lmps. PPFD ws mesured with Li-Cor LI 190 S Quntum Sensor (LI-COR Inc., Lincoln, USA). Dry mss sed net CO 2 exchnge (J CO2 ), trnspirtion (J H2O ), conductnce for wter vpour (g H2O ) nd w (von Willert et l., 1995) were clculted following the equtions of von Cmmerer und Frquhr (1981). End of the experiment ws determined y the rek down of respirtion (J CO2 =0). Dt were nlysed y nlysis of vrince (ANOVA) nd mens were compred y Duncn s multiple rnge test (p=0.05) using WinSTAT (R. Fitch Softwre, Stufen, Germny). RESULTS AND DISCUSSION The yerly mens of stomtl conductnce were significntly lower in Akito thn in Red Gint. Sesonl differences etween stomtl conductnces of the two cultivrs (Fig. 1) could not e found. Furthermore, in summer, there ws no difference etween men g H2O of the cultivrs. The yerly mens of trnspirtion of Akito tended to e higher thn tht of Red Gint flowers (Fig. 2) though difference ws not significnt. Flower trnspirtion of Red Gint roses ws significntly lower during summer thn in the winter period. One explntion for the higher trnspirtion in winter grown roses cn e weker petl structure resulting from lower tempertures nd higher men ir humidity. Moe nd Kristoffersen (1969) found lrger nd hstte epidermis cells in petls from Ros Bccr plnts grown under low tempertures (12 C) compred to those cultivted under high tempertures (27 C). In the present experiments, temperture differences were less thn those reported y Moe nd Kristoffersen (1969) ecuse the heting temperture of 18 C lrgely reduced the effect of low tempertures. Lef trnspirtion ws promoted y weker tissue structure including more nd igger dysfunctionl stomt in roses grown in very humidity ir compred to plnts grown t low humidity (Torre et l., 2003). However, in contrst to leves, the higher wter losses of flower heds in winter cnnot result from dysfunctionl stomt s in leves (Torre et l., 2003) simply ecuse there were no stomt on petls (Stus nd Frncis, 1971; Myk nd Hlevy, 1974; vn Doorn, 1997). On the other hnd, the development of generlly weker epiderml nd tissue structure during growth t high reltive humidity ir s found for leves (Torre et 303

4 l., 2003) my lso e vlid in flowers. More investigtions on this topic re needed to close this lck of knowledge. The flower respirtion ws significntly higher in Red Gint plnts thn in Akito nd differed etween the sesons (Fig. 3). Temperture differences in posthrvest my e n explntion for the different respirtion rtes in summer nd winter in Akito (Reid, 2003) ut could not explin the differences in Red Gint roses ecuse respirtion ws higher in winter thn in summer. For Red Gint generl higher gs exchnge my e n explntion resulting from different ntomicl properties induced y climtic conditions, e.g. temperture nd ir humidity, which effects oth respirtion nd trnspirtion. Another explntion my e the potentilly higher mount of crohydrte reserves in this cultivr nd/or etter photosynthetic efficiency (Bord et l., 2005). Hydrulic conductivity in the upper third peduncle differed significntly etween cultivrs nd growth climte conditions (Fig. 4). The only time tht no cultivr differences were found ws July. In Red Gint, hydrulic conductivity ppered to e relted to trnspirtion rte. On the other hnd, in Akito the tendentiously higher trnspirtion rte in winter ws ssocited with higher hydrulic conductivity ut the stomtl conductnce ws similr in winter nd summer. In contrst to Drlington nd Dixon (1991) significnt differences etween cultivrs nd climte conditions were found. One reson for this discrepncy cn e lrger difference etween the vse life nd the posthrvest physiology of Akito nd Red Gint thn etween Roylity nd Smnth. CONCLUSIONS Bsed on results with Akito nd Red Gint, we suggest tht wter loss of rose flower is n importnt fctor determining the vse life nd is dependent on cultivr. Growth climte induced differences etween rose flower wter losses during summer nd winter were found. Higher trnspirtion rtes in winter were compensted y higher hydrulic conductnce. The high respirtion in this cultivr must e compensted y lrger energy resources in the whole stem or etter photosynthetic efficiency of the leves in posthrvest. More specific investigtions on the petl ntomy of rose plnts grown under different climte conditions re necessry. Additionlly, investigtions on gs exchnge nd the hydrulic conductivity of leves, stems nd petls of cut rose cultivrs with nd without dehydrtion stress re needed. A etter understnding of the function of the flower s potentil lek in the whole system of cut rose will e helpful to optimize prend posthrvest mngement. Additionlly, comprehensive knowledge of flower physiology cn fcilitte reeding for cultivrs with etter posthrvest wter mngement nd stress tolernce. ACKNOWLEDGEMENTS We thnk the Hns-Böckler-Foundtion for the scholrship to Wolfgng Grf, nd mny compnies for mteril sponsoring: The rose nursery W. Kordes, Söhne Klein Offenseth- Sprrieshoop, Germny nd Rosen Tntu, Uetersen, Germny for the rose plnts nd licences, the rootstock nursery Lodder, Dülmen, Germny for the rootstocks, Hermnn Meyer, Rellingen, Germny for the pots, Stender AG, Lucku, Germny for the sustrte nd Brun GmH, Lemgo, Germny for the Chrysl fresh flower food. Literture Cited Berkholst, C.E.M De wterhuishouding vn fgesneden rozen. Bedrijfsontwikkeling 11: Bhttchrjee, S.K. nd Phl, M Posthrvest life, qulity nd respirtion rte of rose cultivrs. Ahrshtr Agriculturl University 24: Bord, A.M., Nell, T.A. nd Clrk, D.G The reltionship etween florl frgrnce nd vse-life of cut roses. Act Hort. 689: Burdett, A.N The cuse of ent neck in cut roses. J. Amer. Soc. Hort. Sci. 304

5 95(4): Crpenter, W.J. nd Rsmussen, H.P The role of flower nd leves in cut flower wter uptke. Sci. Hort. 2: Drlington, A.B. nd Dixon, M.A The hydrulic rchitecture of roses (Ros hyrid). Cn. J. Bot. 69: Durkin, D.J Some chrcteristics of wter flow through isolted rose stem segments. J. Amer. Soc. Hort. Sci. 104: Durkin, D.J Effect of millipore filtrtion, citric cid, nd sucrose on peduncle wter potentil of cut rose flowers. J. Am. Soc. Hort. Sci. 104: Grf, W., Herppich, W.B., Huyskens-Keil, S. nd Grüneerg, H Cell wll chemistry nd mechnicl strength of the peduncle of cut roses. Proceedings of the Cell Wll Mcromolecules nd Rection Wood (CEMARE) Workshop. Potsdm, 26 th 28 st Septemer. Grf, W., Huyskens-Keil, S., Herppich, W.B. nd Grüneerg, H Impct of wter sttus, iochemicl nd mechnicl product properties on ent neck occurrence in cut roses. Proceedings of the Fifth plnt Biomechnics Conference. Stockholm, August 28 Septemer : Grf, W., Schmid, O., Grüneerg, H., Hendriks, L. nd Huyskens-Keil, S Hydrulische Leitfähigkeit und Wsserpotenzil von Schnittrosensorten. Proceedings of the 43. Annul Meeting of the Germn Society of Horticulturl Science. Potsdm, Ferury:233. Goszynsk, D.M., Michlczuk, B. nd Rudnicki, R.M The effect of florl preservtive enriched with clcium nitrte on keeping qulity of cut Soni roses. Act Hort. 261: Hendriks, L., Spinrov, S., Hss-Tschirschke, I., Schmidt, O. nd Keim, E Grntiert schöne Schnittrosen uf dem Prüfstnd. Gärtnerörse 106(6): Mrtin, J.T. nd Juniper, B.E The cuticules of plnts. Edwrd Arnold, London. Myk, S. nd Hlevy, A.H The ction of kinetin in improving the wter lnce nd delying senescence processes of cut rose flowers. Physiol. Plnt. 32: Moe, R. nd Kristoffersen, T The effect of temperture nd light on growth nd flowering of Ros Bccr in greenhouses. Act Hort. 14: Reid, M Effects of temperture. p In: A. Roerts, T. Deener nd S. Gudin (eds.), Encyclopedi of Rose Science, Vol. 2, Elsevier, Amsterdm. Stus, J.M. nd Frncis, M.J.O Electron microscopicl studies of rose petl cells during flower mturtion. Plnt Medic 20: Torre, S., Field, T., Gislerød, H.R. nd Moe, R Lef ntomy nd stomt morphology of greenhouse roses grown t moderte or high ir humidity. J. Am. Soc. Hort. Sci. 128: vn Doorn, W.G Wter reltions of cut flowers. Hort. Rev. 18:1-85. vn Doorn, W.G., Schurer, K. nd de Witte, Y Role of endogenous cteri in vsculr lockge of cut rose flowers. J. Plnt Physiol. 134: Von Cmmerer, S. nd Frquhr, G.D Some reltionships etween the iochemistry of photosynthesis nd the gs exchnge of leves. Plnt 153: von Willert, D.J., Mtyssek, R. nd Herppich, W Experimentelle Pflnzenökologie. Thieme, Stuttgrt, New York. Zieslin, N., Kohl, H.C., Kofrnek, A.M. nd Hlevy, A.H Chnges in the Wter Sttus of Cut Roses nd its Reltionship to Bent-neck Pheonomenon. J. Amer. Soc. Hort. Sci. 103:

6 Figurese gh2o (mmol kg -1 s -1 ) 'Akito' Summer hlf (n = 5) 'Akito' Winter hlf (n = 5) Summer (n = 4) Cultivr/ Time Winter (n = 4) 'Akito' Yer round (n = 10) Yer round (n = 8) Fig. 1. Men vlues of stomtl conductnce from flowers t the intct stems of Akito nd Red Gint over the whole vse life, relted to dry mss from My 2006 till June 2007 in reltion from winter to summer. Different letters ( ) on the SD rs indicte significnt differences (p<0.05). J-H2O (mmol kg -1 s -1 ] 'Akito' Summer hlf (n = 5) 'Akito' Winter hlf (n = 5) Summer (n = 4) Cultivr/ Time Winter (n = 4) 'Akito' Yer round (n = 10) Yer round (n = 8) Fig. 2. Men vlues of trnspirtion from flowers t the intct stems of Akito nd Red Gint over the whole vse life, relted to dry mss from My 2006 till June 2007 in reltion from winter to summer. Different letters ( ) on the SD rs indicte significnt differences (p<0.05). 306

7 J-CO2 [µmol kg -1 s-1] 'Akito' Summer hlf (n = 5) 'Akito' Winter hlf (n = 5) Summer (n = 4) Cultivr/ Time Winter (n = 4) 'Akito' Yer round (n = 10) Yer round (n = 8) Fig. 3. Men vlues of respirtion from flowers t the intct stems of Akito nd Red Gint over the whole vse life, relted to dry mss from My 2006 till June 2007 in reltion from winter to summer. Different letters ( ) on the SD rs indicte significnt differences (p<0.05). ktul hydrulic conductivity [m4 s-1 MP -1 E -9 ] 'Akito' Jn 'Akito' Jul Jn c Jul 'Akito' yer men yer men Cultivr/ Time Fig. 4. Men vlues of ctul hydrulic conductivity in the upper third peduncle prt of Akito nd Red Gint in Jnury nd July 2007 (n=30) in reltion from winter to summer. Different letters ( c) on the SD rs indicte significnt differences (p<0.05). 307

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