Effect of Low Light Intensity on Longevity of Flowering on Bedding Plants Targeted for Indoor Use

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1 JARQ 5 (), 79 (7) Effect of Wek Light on Flower Longevity on Bedding Plnts Effect of Low Light Intensity on Longevity of Flowering on Bedding Plnts Trgeted for Indoor Use Ttsuo OKAZAWA, nd Tkki NISHIJIMA, * Tokyo Metropolitn Agriculture nd Forestry Reserch Center (Tchikw, Tokyo 9-, Jpn) Grdute School of Life nd Environmentl Sciences, Tsuku University (Tsuku, Irki 5-577, Jpn) Institute of Vegetle nd Floriculture Science, NARO (Tsuku, Irki 5-5, Jpn) Astrct The dptility of nine edding plnts to low light intensity ws evluted for their indoor use. Bsed on the durtion of flowering under indoor low light intensity [, lx,. µmol m s photosynthetic photon flux density (PPFD)], the plnts dptility ws clssified into three groups. In group, the effect of low light intensity ws uncler due to short flowering longevity irrespective of light intensity; this group included Helinthus. Group included species not dptle to indoor low light intensity, under which the durtion of flowering indoors ws less thn three weeks; this group included Petuni Slvi, nd Veren. Group included species dptle to indoor conditions, under which the durtion of flowering ws longer thn three weeks; this group included Cthrnthus, Imptiens, Tgetes, Toreni nd Zinni. The effect of low light intensity on shoot growth did not pper s reduction in plnt width, ut did pper in plnt height nd length of the longest lterl stem. The lef color of most species ws drkened y low light intensity. Even Cthrnthus, Toreni nd Zinni, which showed the highest dptility to low light intensity, could not mintin sufficient ornmentl qulity under. µmol m s PPFD. The durtion of flowering ecme longer s light intensity incresed, lthough the response differed mong species. In Toreni nd Zinni, the durtion of flowering ws extended under,5 lx (. µmol m s PPFD), indicting tht longterm use ws possile under right indoor conditions, including t such loctions s windowsills nd showcses. Discipline: Horticulture Additionl key words: flower dimeter, indoor environment, numer of flowers, wek light Introduction Bedding plnts re minly used to improve the lndscpe qulity t pulic fcilities, such s prk nd streets, s well s in privte grdens. Although the production of edding plnts ccounts for only 5% of Jpn s totl domestic flower production, edding plnts re key item in suurn horticulture s their compctness enles intensive production on smll frms (MAFF ). However, due to the decresing trend in grdening, lower sles ttriuted to n economic slump, nd more people intending to live in n prtment uilding rther thn detched house, the consumption of edding plnts in Jpn decresed y more thn % in s compred to (MAFF ). In order to stop this decrese, we developed new culture system to fcilitte the indoor use of edding plnts. This system uses n orgnic culture medium ( mixture of coconut coir nd pet moss) wrpped with discrded school uniform mteril, which hs net ppernce nd cn e discrded s urnle grge fter use (Okzw et l. ). In this system, indoor low light intensity is clerly the min limiting fctor for plnt longevity. In such potted flowers s Cyclmen nd Delphinium, low light intensity (. µmol m s PPFD nd 7. µmol m s PPFD, respectively) reduced plnt longevity due to decresing light intensity (Komgt et l., Tnse et l. 5). In Cyclmen, the decrese in longevity ppered s lower flower numer nd reduced depth of flower color. Under low light intensity, Ficus enjmin, n ornmentl folige plnt, exhiited fded lef color nd *Corresponding uthor: e-mil tkki@ffrc.go.jp Received 9 July ; ccepted August. 79

2 T. Okzw et. l ccelerted internode elongtion (Chen et l. 5). However, there is no informtion out the longevity of edding plnts under indoor low light intensity conditions, lthough the effect of light intensity on edding plnts growing in n open field nd greenhouse hs een reported (Niu et l., Cerny et l., Moccldi & Runkle 7). Light intensity lso differs significntly depending on the indoor loction, such s windowsill or ck of the room. According to Jpnese Industril Stndrds (JIS Z 9, JIS Hndook ()), the pproprite illumintion level is 5 lx (. µmol m s PPFD) for conference room nd 75 lx (. µmol m s PPFD) for n office. For households, reding nd hndicrft require illumintions of 5 lx nd lx (. µmol m s PPFD), respectively. Thus, different light intensities ccording to light instlltion loctions give us different plnt growth responses. In fct, potted crntions plced under 9. µmolm s PPFD exhiit severe lef yellowing nd lef deth, with lost esthetic vlue; however, higher light intensity (5. nd 7. µmolm s PPFD) improves the qulity of such plnts (Komgt et l. 5). In the present study, we investigted the effect of indoor low light intensity on the growth nd flowering of edding plnts, nd screened species suitle for indoor use. We lso investigted the effects of different light intensities on screened species y simulting vrious indoor loctions. Bsed on the results, the pproprite indoor mngement of those species is discussed. Mterils nd Methods. Plnt mteril nd growth conditions Tle lists the nine species of edding plnts used in experiment. These species re identified y genus nme in the following text, tle nd figures. Three species (i.e., Cthrnthus, Toreni, Zinni) tht showed high dptility for indoor conditions in experiment were used in experiment. Seeds were sown in -cell plug try filled with commercil medium (TM-; Tkii Seed. Co., Ltd., Kngw, Jpn). Plnts were grown using the cloth continer culture system (Okzw et l. ). In rief, the cloth continer ws sewn into flt nd squre envelop mesuring cm per side using discrded school uniform (Tomo Co., Ltd., Okym, Jpn). This envelope ws filled with lightweight orgnic culture medium, -ml mixture of coco pet (Coco-yuki; DIA Co., Ltd., Kngw, Jpn) nd pet moss (Min River; Oji Forest & Products Co., Ltd., Tokyo, Jpn, : in volume). For sl fertilizer, g N, 7 g P O 5 nd g K O were dded per L of medium. A seedling ws trnsplnted to continer when - leves opened, nd then to glsshouse under nturl sunlight. The ventiltion nd heting tempertures were 5 C nd C, respectively.. Light tretment As soon s ll plnts within n experimentl plot ore n open flower, they were trnsferred to n incutor simulting indoor light conditions (hereinfter referred to s indoor tretment ). In experiment, which ws conducted to screen species highly tolernt to low light intensity, plnts were illuminted y fluorescent lmps (FHFEX-N-HN; Pnsonic Co., Ltd., Tokyo, Jpn) for h/dy from 5: to 7: in experiment. Light intensity t the plnt top level ws, lx [photosynthetic photon flux density (PPFD) of. µmol m s ], one of the indoor light levels recommended y the JIS Z 9 illumintion stndrd mentioned ove. Species Tle. Bedding plnts used in this study. Cultivr Strt of tretment Cthrnthus roseus Titn Rose Aug Helinthus nnus Kontsu 7 Sep Imptiens wllerin Super Elphin XP Rose 7 My Petuni hyrid Rondo Rose Aug Slvi splendens Red Hot Slly My Tgetes ptul Sfri Yellow 5 Aug Toreni fournieri Kui Rose My Veren hyrid Osession White My Zinni elegns Z. ngustifoli Profusion Yellow Aug All experiments were conducted in. JARQ 5 () 7

3 Effect of Wek Light on Flower Longevity on Bedding Plnts Temperture ws mintined t C. Control plnts were grown in the greenhouse s descried ove (hereinfter referred to s greenhouse tretment ). The tretment ws conducted for four weeks. The plnt width, plnt height, length of the longest lef, length of the longest lterl stem, numer of opened flowers (flower numer), nd flower dimeter were mesured every week. The color of the lrgest lef ws mesured using chlorophyll meter (SPAD-5; Konic Minolt Co., Ltd., Tokyo, Jpn). Ech plnt ws mesured three times, nd the verge ws used s n individul dtum. We used plnts per experimentl plot. In experiment, plnts were sujected to the sme tretment s in experiment, lthough under different light intensities of 5 lx (. µmol m s PPFD),, lx (. µmol m s PPFD), nd,5 lx (. µmol m s PPFD). These light intensities were set ccording to JIS Z 9, which recommends light intensities for interior spces. Thus, the pproprite illumintion level is 5 lx for conference room,, lx for typicl office, nd,5 lx for displys in supermrkets. The tretment ws conducted for six weeks. The numer of opened flowers were mesured every week.. Sttisticl nlysis Dt were nlysed sed on Tukey s multiple rnge tests. Results. Screening of edding plnts highly tolernt to indoor conditions In the greenhouse tretment, ll species tested exhiited norml flowering (Fig. ). The plnts flowered vigorously throughout the tretment lthough tretment ws suspended when the numer of flowers under indoor tretment reched zero. In contrst, the indoor tretment ffected flowering differently mong species. In Helinthus, which ers only one cpitulum, oth the durtion of flowering (defined s the period during which the plnt hd opened flowers) nd flower dimeter did not differ significntly etween indoor nd greenhouse tretments (Fig. ). The durtion of flowering ws less thn three weeks for Petuni, Slvi nd Veren receiving indoor tretment. Veren exhiited very short flowering durtion of only two weeks. In Petuni, the flower dimeter decresed y 9.5% in indoor tretment compred with tht in greenhouse tretment fter two weeks of tretment. In contrst, Cthrnthus, Imptiens, Tgetes, Toreni nd Zinni flowered for more thn three weeks with the indoor tretment. Low light intensity egn to reduce the flower dimeter fter one week of tretment in Cthrnthus nd Zinni, nd fter two weeks of tretment in Imptiens, Tgetes nd Toreni. After three weeks of indoor tretment, the decrese in flower dimeter compred with tht in greenhouse tretment ws reltively smll in Tgetes nd Toreni (i.e., nonsignificnt nd.% decrese, respectively), while it ws.9%,.% nd.9% in Cthrnthus, Imptiens nd Zinni, respectively. Indoor tretment reduced the plnt width in Petuni, Veren nd Zinni compred with greenhouse tretment, wheres indoor tretment cused no significnt effect on Cthrnthus, Imptiens, Slvi, Tgetes nd Toreni (Tle nd Fig. ). Indoor tretment reduced oth the plnt height nd length of the longest lterl stem in most species tested. In contrst, indoor tretment incresed the SPAD vlue (index of reltive chlorophyll content), except for Veren nd Zinni. The length of the lrgest lef length ws lmost the sme etween indoor nd greenhouse tretments, except in Imptiens, which hd significntly greter lef length with indoor tretment. When the effect of indoor tretment ws chrcterized sed on the chnges during tretment, the plnt height incresed slightly in Cthrnthus, Veren nd Zinni, wheres it incresed remrkly y.7% in Imptiens nd y.% in Toreni (dt not shown). Lef color ws slightly fded in Tgetes nd Veren, unchnged in Cthrnthus, Petuni, Slvi, Toreni nd Zinni, nd drkened in Helinthus (dt not shown).. Effects of vrious light intensities (simulting indoor conditions) on growth nd flowering Flowering response to different light intensities simulting vrious indoor conditions ws investigted for species highly tolernt to low light intensity, specificlly Cthrnthus, Toreni nd Zinni (Figs. nd ). In Cthrnthus, the durtion of flowering ecme longer s light intensity incresed: three weeks under. µmol m s PPFD, four weeks under. µmol m s PPFD, nd five weeks under. µmol m s PPFD. Toreni showed distinct response to different light intensities fter two weeks of tretment. Higher light intensity resulted in lrger flower numer. The lrge difference in the numer of flowers, which ws seen in Cthrnthus nd Zinni etween. µmol m s nd. µmol m s PPFD, ws not detected in Toreni;. µmol m s PPFD light did not reduce the flower numer to zero even fter five weeks. However, the flower numer ecme zero fter six weeks of tretment, irrespective of the light conditions exmined. Zinni showed reduced flower numer under.

4 T. Okzw et. l Flower numer Helinthus Flower dimeter (cm) Flower numer (Indoor tretment) Flower numer (Greenhouse tretment) Flower dimeter (Indoor tretment) Flower dimeter (Greenhouse tretment) Flower numer 7 9 Petuni Slvi 5 Flower dimeter (cm) Flower numer Veren 5 5 Cthrnthus Flower dimeter (cm) Flower numer Imptiens * Tgetes * * Flower dimeter (cm) Flower numer Toreni Weeks of tretment Zinni * Weeksoftretment Flower dimeter (cm) Fig.. Effect of low light intensity on flower numer nd dimeter. Verticl rs represent ± SE., *, nd indicte t-test evlution of non-significnt nd significnt differences t P =.5,. nd., respectively, from the control plnts grown in greenhouse. Helinthus ore only one flower in oth indoor nd greenhouse tretments. JARQ 5 () 7

ngustifoli Growing condition Plnt width (cm) Plnt height (cm) Length of the longest lterl stem (cm) Length of the lrgest lef length (cm) Lef color (SPAD) greenhouse. y.7. 7.9.7 indoor 5.5 5.5.. 9.

5 Effect of Wek Light on Flower Longevity on Bedding Plnts Tle. Effect of indoor low light intensity on the growth of edding plnts. Species Cthrnthus roseus Helinthus nnus Imptiens wllerin Petuni hyrid Slvi splendens Tgetes ptul Toreni fournieri Veren hyrid Zinni elegns Z. ngustifoli Growing condition Plnt width (cm) Plnt height (cm) Length of the longest lterl stem (cm) Length of the lrgest lef length (cm) Lef color (SPAD) greenhouse. y indoor t-test x * greenhouse.7 7. Z 9. indoor t-test greenhouse indoor t-test greenhouse indoor t-test * * greenhouse indoor t-test greenhouse indoor t-test greenhouse indoor t-test greenhouse indoor t-test greenhouse indoor t-test * x, * nd indicte t-test evlution of non-significnt nd significnt differences t P =.5 nd P =., respectively. y Dt were collected fter three weeks of tretment, except for Helinthus nnus nd Veren hyrid, which were mesured fter one nd two weeks of tretment, respectively, when the flower numer reched zero. Vlues show the men (n = ). z : no dt. G I G I Imptiens Slvi Fig.. Effect of low light intensity on plnt shpe in Imptiens nd Slvi. These photogrphs were tken three weeks (Imptiens) nd two weeks (Slvi) fter light tretment. G: greenhouse tretment (control), I: indoor tretment. Scle rs indicte cm. µmol m s PPFD nd reched ner zero fter six weeks of tretment. Weker light intensity t. µmol m s PPFD lso reduced the numer of flowers within two weeks of tretment. The plnts hd no flowers fter three weeks of tretment. In contrst, the numer of flowers incresed continuously during tretment under. µmol m s PPFD. Discussion As edding plnts re not ssumed to e used indoors, their propgtion is usully trgeted for outdoor use. On the other hnd, the dptility to indoor conditions hs een evluted in indoor plnts. For

6 T. Okzw et. l Flower numer Flower numer Flower numer 5 Cthrnthus Toreni Zinni.μmol m - s - PPFD. μmol m - s - PPFD. μmol m - s - PPFD Fig.. Effect of light intensity on flower numer. Dt represents the men ± SE (n = ). The sme letters indicte non-significnt differences mong the tretments t P vlue <.5 y Tukey s test. exmple, in potted cyclmen (Komgt et l. ) nd Dieffenchi (Conover & Poole 9), the minimum illumintion level necessry to mintin sufficient qulity ws, lx (=. µmol m s PPFD) nd µmol m s PPFD, respectively. In the present study, we intended to identify edding plnts highly tolernt to indoor low light intensity. According to questionnire survey (MPS Jpn ), most consumers requested cut flower longevity s long s one week. Given this result, the sufficient longevity for our cloth continer system ws set s three weeks ecuse we felt tht consumers would nturlly expect much longer longevity for intct plnts thn cut flowers. Bsed on the durtion of flowering under indoor low light intensity (. µmol m s PPFD), the dptility of edding plnts to indoor conditions ws clssified into three groups (Fig. ). 5 Weeks of tretments In group, the effect of low light intensity is uncler given the short flower longevity irrespective of light intensity. This group includes Helinthus, which hs only one cpitulum. Group includes species not dptle to indoor low light intensity. In this group, the durtion of flowering under indoor conditions ws less thn three weeks. This group includes Petuni, Slvi nd Veren. Group includes species dptle to indoor conditions. In this group, the durtion of flowering ws longer thn three weeks. This group includes Cthrnthus, Imptiens, Tgetes, Toreni nd Zinni. These findings clerly show tht the minimum light intensity to confer sufficient qulity mintennce vries mong species. Menwhile, Imptiens nd Petuni re quntittive longdy plnts, while Slvi, Tgetes, Toreni nd Zinni re quntittive short-dy plnts, nd Ctrnthus nd Helinthus re dy-neutrl plnts (Editoril Committee of Mnul for Flowering Regultion 995). In this study, the illumintion period ws fixed to hours. Thus, whether the length of dy in indoor tretment ffected the flowering of long- or short-dy plnts cnnot e ruled out. In order to otin sufficient qulity for indoor use, plnts require not only light intensity t the light compenstion point (Eugene et l. 975) ut lso extr light to produce photosynthtes to mintin continuous flowering. The plnts clssified in group descried ove grew nd flowered well under the low light intensity, wheres those in group grew very slowly with poor flowering (Fig., dt not shown for vegettive growth). Thus, species highly dptle to low light intensity my hve not only low light compenstion point ut lso low lighting requirement to otin continuous flowering. Fust et l. (5) reported tht the photosynthetic dily light integrl (DLI) enling sufficient growth ws lower in Begoni nd Imptiens, nd higher in Cthrnthus, Petuni, Tgetes nd Zinni when tested in nturl sunlight with shding mterils, where light intensity ws much higher thn tht employed in our indoor conditions. Our results coincided with their results with respect to Imptiens nd Petuni. However, Cthrnthus, Tgetes nd Zinni were highly dptle to indoor conditions (Fig. ). These results suggest tht the effect of high light intensities on plnt growth nd flowering does not necessrily correlte with dptility to low light intensity. Low light intensity is one of the mjor fctors reducing plnt qulity. For exmple, the flower dimeter of potted crntions ws significntly smller t 9. nd 5. µmol m s PPFD thn t 7. µmol m s PPFD (Komgt et l. 5). A reduction in flower size ws JARQ 5 () 7

7 Effect of Wek Light on Flower Longevity on Bedding Plnts lso oserved in the present study, lthough it vried mong species (Fig. ); for exmple, Tgetes nd Toreni showed reltively smll reduction in flower size. A reduction in flower size is clerly n dptive response to low light intensity, which enles preferentil distriution of photosynthtes to photosynthetic orgns (leves) rther thn flowers. Therefore, it ws ssumed tht the smll reduction in flower dimeter possily indictes low light compenstion point nd/or smll demnd for photosynthtes to produce sufficient size of flower. Menwhile, shoot growth ws gretly reduced y low light intensity (Tle ). It should e noted tht low light intensity preferentilly retrds upright growth, which did not pper s reduction in plnt width ut insted s greter height nd length of the plnt s longest lterl stem. Another chrcteristic effect of low light intensity on shoots ws drk lef color, which is common dptive response to low light intensity (Di Benedetto & Grci, 99). Cthrnthus, Toreni nd Zinni ll showed high dptility to low light intensity, ut only Toreni showed continuous flowering under n extremely low light intensity (5 lx,. µmol m s PPFD), which is necessry for conference room. However, it ws difficult to otin flowers of sufficient ornmentl qulity. Bsed on these results, we concluded tht no species tested cn mintin sufficient ornmentl qulity under. µmol m s PPFD. In contrst, under. nd. μmol m s PPFD, the durtion of flowering lsted more thn three weeks in these three species. Thus, sid species re suitle under light conditions used for such detiled work s design nd component ssemly (JIS Z 9, i.e.,. μmol m s PPFD) or for displys in supermrkets nd such shops s fshion outlets (i.e.,. μmol m s PPFD). In ddition, PPFD t the window without direct sunlight is out, lx (. μmol m s PPFD) (Kjikw ). In Toreni, no extension of flowering durtion ws oserved t. compred with. μmol m s PPFD. However, even fter six weeks of indoor conditions under. μmol m s PPFD, Toreni plnts continued forming nd growing new flower uds. Bsed on these results, flowering in Toreni my occur intermittently under low light intensities. Therefore, Toreni cn e grown for long period under light intensity greter thn.μmol m s PPFD, provided tht intermittent flowering is tolerted. In Zinni, the flower numer continuously incresed under. µmol m s PPFD, thus suggesting tht this light intensity is comprle to outdoor conditions in terms of flowering. In conclusion, severl species of edding plnts such s Cthrnthus, Toreni nd Zinni re ville for indoor use. Our results showed tht light righter thn tht for typicl office (. μmol m s ) ws required for indoor use, wheres the rightness of conference room (. μmol m s ) ws insufficient. The effect of higher light intensity otined ner window is yet to e elucidted, s we re witing more species for nlyses. References Cerny, T. A. et l. () Influence of photoselective films nd growing seson on stem growth nd flowering of six plnt species. J. Amer. Soc. Hort. Sci.,, -9. Chen, J. et l. (5) Response of tropicl folige plnts to interior low light conditions. Act Hort., 9, 5-5. Conover, C. A. & Poole, R. T. (9) Influence of light nd fertilizer level nd fertilizer sources on folige plnts mintined under interior environments for one yer. J. Amer. Soc. Hort. Sci.,, Di Benedetto, A. H. & Grci, A. F. (99) Adption of ornmentl roids to their indoor light environments. I. Spectrl nd ntomicl chrcteristics. J. Hort. Sci., 7, 79-. Editoril Committee of Mnul for Flowering Regultion (995) Mnul for flowering regultion in nnul nd iennil plnts, Ishizue Co. Ltd., Chi, -7 [In Jpnese]. Eugene, G. K. et l. (975) Cron dioxide compenstion points of flowering plnts. Plnt Physiol., 5, 9-. Fust, J. E. et l. (5) The effect of dily light integrl on edding plnt growth nd flowering. HortScience,, 5-9. Kjikw, A. () Revegettion, Nougyogijyututikei Kki- Hen (Agric. Tech. Sys.),, 59-5 [In Jpnese]. Komgt. T. et l. () Effect of interior ir temperture nd light intensity on qulittive mintennce of potted Cyclmen percicum Mill. Bull. Hort. Res. Inst. Irki Agric. Ctr.,, - [In Jpnese with English summry]. Komgt. T. et l. (5) Effect of interior light intensity on qulittive mintennce of potted crntion. Bull. Hort. Res. Inst. Irki Agric. Ctr.,, 5- [In Jpnese with English summry]. MAFF () MAFF sttistics report, Ministry of Agriculture, Forestry nd Fisheries. MAFF () MAFF sttistics report, Ministry of Agriculture, Forestry nd Fisheries. Moccldi, L. A. & Runkle, E. S. (7) Modeling the effects of temperture nd photosynthetic dily light integrl on growth nd flowering of Slvi splendens nd Tgetes ptul. J. Amer. Soc. Hort. Sci.,, -. MPS Jpn () Hn to knkyo niknsuru cyous. Florl Mrketing Co., Ltd., Tokyo, Jpn, [In Jpnese]. 5

8 T. Okzw et. l Niu, G. et l. () Dy nd night tempertures, dily light integrl, nd CO enrichment ffect growth nd flower development of pnsy (Viol wittrockin). J. Amer. Soc. Hort. Sci. 5, -. Okzw, T. et l. () Growth nd flowering of edding plnts cultivted using cloth continer nd orgnic medi. Hort. Res. (Jpn), 5, 9- [In Jpnese with English summry]. Tnse. K. et l. (5) Effects of light intensity on flower life of potted Delphinium plnts. J. Jpn. Soc. Hort. Sci. 7, JARQ 5 () 7

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