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1 Journl of Agronomy, 215. ISSN ns net 215 Asin Network for Scientific Informtion Asin Network for Scientific Informtion RESEARCH ARTICLE OPEN ACCESS DOI:.3923/j.215. Synergistic Effects of Ethephon nd Gierellic Acid on the Growth of Rice Seedlings Grown under Field nd Environmentlly Controlled Conditions 1 H. Wtne, 1 Y. Adchi nd 2 M. Sigus 1 Fculty of Agriculture, Niigt University, Ikrshi, Niigt, , Jpn 2 Reserch Center for Advnced Agrotechnology nd Biotechnology, Toyohshi University of Technology, Toyohshi, Aichi, , Jpn A R T I C L E I N F O Article History: Received: Accepted: Corresponding Author: H. Wtne, Fculty of Agriculture, Niigt University, Ikrshi, Niigt, , Jpn A B S T R A C T Improving erly seedling growth is crucil for direct-seeding rice cultivtion. In this study, field nd lortory experiments were conducted to determine the effects of Plnt Growth Regultors (PGRs) such s gierellic cid (GA 3 ) nd ethephon (ET) on the erly growth of direct-seeded rice. Seeds were treted with the PGRs nd pre-germinted t 3 C in the drk. For the field experiment, two Flooding Depth (FD) regimes were estlished during the growth period: cm (drined condition) nd 2 cm (flooded condition). Tretment of seeds with ET or GA 3 lone promoted the growth of seedling orgns compred to tht of the control t oth the FDs in some cses. However, comined ppliction of ET nd GA 3 (ET+GA 3 ) synergisticlly improved the growth of different seedling orgns t oth the FDs in most cses with slight exception: the coleoptile nd mesocotyl plus coleoptile (mesocotyl+coleoptile) length were not different cross the PGR tretments under drined condition. Further, the growth of the second node tiller ws stimulted y the ppliction of ET lone under drined conditions. The lortory experiment reveled tht ET+GA 3 incresed the growth rte of mesocotyl+coleoptile nd tht of the first lef. These results suggest tht the comined ppliction of ET nd GA 3 might e useful for improving the growth performnce of rice seedlings in the direct seeding method. Key words: Coleoptile, direct seeding, ethephon, gierellin, mesocotyl, rice, seedling INTRODUCTION Direct seeding involves plnting of seeds without prepre for seeded nd rising seedlings. This method is highly economicl thn trnsplnting system, since it reduces lor. For direct seeding of rice, ensuring erly seedling growth, including seedling emergence nd vigor, is crucil. Tretment of seeds with Plnt Growth Regultors (PGRs) is known to improve erly seedling growth. Plnt growth regultors such s gierellin, ethylene nd scisic cid re known to promote the elongtion of rice seedling orgns (Suge, 1974; Rskin nd Kende, 1983; Tkhshi nd Kufmn, 1983, 1992; Furukw et l., 1997; Wtne nd Tkhshi, 1997; Wtne et l., 21). Suge (1974) indicted tht comined ppliction of ethylene nd GA 1, nturlly ctive gierellin in rice plnts, synergisticlly stimulted the growth of coleoptiles nd the first lef in rice. Furukw et l. (1997) suggested tht the synergistic ctions of ethylene nd gierellins on lef elongtion were ttriuted to the incresing responsiveness to nd turnover of GA 1 y ethylene ppliction. Previously, we showed tht the comined ppliction of ethephon (ET) nd gierellic cid (GA 3 ) improved the erly growth of rice cultivted t different growth tempertures nd flooding depths (Wtne et l., 27). However, our previous study nd other relevnt studies on PGRs (Suge, 1974; Furukw et l., 1997) were conducted in growth chmers; therefore, nlyzing the effects of PGRs in field trils is necessry for their prcticl ppliction gronomiclly. Elongtion of seedling orgns, including mesocotyl, coleoptile nd the first lef, ply importnt roles in the etter emergence nd estlishment of seedlings otined using the direct seeding method (Wtne et l., 26, 27; 1

2 J. Agron., 215 Ogiwr nd Tershim, 21; Mori et l., 212); however, investigtions on the growth kinetics of these orgns treted with ET nd GA 3 re still lcking. This study imed to investigte the effects of single nd comined ppliction of ET nd GA 3 on the erly growth of seedling orgns of rice cultivted t different flooding depths under field conditions. Further, the growth-promoting effects of ET nd GA 3 on rice seedlings were ssessed under environmentlly controlled conditions. MATERIALS AND METHODS Generl procedure: A rice (Oryz stiv L.) Jponic cultivr Hitomeore ws used in the study. The seeds were treted with PGRs s descried previously (Wtne et l., 27). Briefly, the seeds were sterilized with thiurm nd enomyl solution for 24 h ccording to instructions, immersed in wter for 24 h nd then soked in the test solution for 48 h. Ethephon (2-chloroethylphosphonic cid; Ishihr Sngyo Kish, Ltd., Osk, Jpn) ws used s n ethylene-producing compound (Artec, 1996) nd GA 3 (Sigm Chemicl Co., MO, USA) ws used for gierellin. The components of the test solution were s follows: (1) wter (control), (2) 5 mg LG 1 ethephon (ET), (3) mg LG 1 GA 3 nd (4) 5 mg LG 1 ET+ mg LG 1 GA 3 (ET+GA 3 ). After the seeds were treted with the PGRs, they were immersed in wter for 48 h to remove ny excess test solution. Seed steriliztion nd tretments were performed t 15 C. The imied seeds were germinted in wter mintined t 3 C in the drk. Field experiments: In 24, field tril ws conducted t the Field Science Center of Tohoku University, Miygi Prefecture, Jpn (38 44 N, E; ltitude, 22 m). This re hs non-llophnic volcnic sh soil (Andisol nd Alic Pchic Mellnudnd). Nitrogen, potssium nd phosphorus were pplied s chemicl fertilizers t the rtes of 8 g mg 2. The fertilizers were pplied to the pddy, 7 dys efore seeding. Metl flmes (3 l 3 w 15 h cm) were uried in the soil nd then the pddy within the flme ws divided into 4 prts for the PGR tretments y using thin plstic pltes. The size of ech tretment plot ws.225 mg 2 (15 15 cm). On My 11, 25 uniformly germinted seeds were sown in ech tretment plot t depth of 1. cm. After seeding, two flooding depth regimes were estlished throughout the growth period: cm (drined conditions) nd 2 cm (flooded conditions). The seedlings were grown for 3 dys. After the seedlings were smpled, the plnt length nd orgn lengths were mesured. The numers of tillers on the second node (the second node tiller) were counted nd their lengths were mesured using ruler. The emergence of tillers suggests tht their tips hd emerged from the sutending lef (second lef) sheth of the mother stem. The length of the tillers included the lef lde nd lef sheth. Lortory experiment: The rice cultivr, method of PGR tretments nd preprtion of seeds were the sme s descried ove. The lortory experiment ws performed s descried previously (Wtne et l., 27) unless otherwise stted. The PGR-treted nd germinted seeds were sown t seeding depth of 1. cm in seedling pots with smll comprtments contining fertilized grnulted soils (Kureh Chemicl Co., Ltd., Tokyo, Jpn). Twenty one uniformly germinted seeds were used for ech tretment. The seeds were grown t 2 C with 12 h light nd drk photoperiod. Fluorescent lmps were used to supply photosynthetic photon flux of 12 µ mol mg 2 secg 1. The flooding depth ws 2 cm. The seedlings were smpled t 22 Dys After Seeding (DAS) nd the plnt length nd the length of ech orgn were mesured. Experimentl design nd sttisticl nlysis: A rndomized complete lock design with four replictes ws used. Dt is presented s Men±Stndrd Error (SE) nd were nlyzed using nlysis of vrince (ANOVA). Pirwise multiple comprison ws performed using Tukey test t the 5% significnce level. Sttisticl nlysis ws performed using JMP for Windows, version 4.. (SAS Institute, Cry, NC, USA). Temperture ( C) RESULTS AND DISCUSSION Field experiment Air temperture condition: The ir temperture during the experimentl period is shown in Fig. 1. The temperture ws higher thn the verge temperture in My during sowing nd continued to increse up to the seedling emergence stge. Therefter, the temperture grdully egn to reduce nd ws only slightly higher thn the verge temperture until the end of June. Stimulting effects of ET nd GA 3 on shoot elongtion: The PGR tretments significntly ffected the morphologicl prmeters of seedlings grown under oth drined nd flooded conditions (Fig. 2). Under drined conditions, tretment with ET or GA 3 lone, did not ffect the growth of seedling orgns such s the mesocotyl, coleoptile, mesocotyl+coleoptile nd Averge yer 24 My Month June Fig. 1: Air temperture conditions during the experimentl period 2

3 J. Agron., 215 Tretment Fig. 2(-): Comprison of growth prmeters of control nd plnt growth regultor-treted seedlings grown under different flooding regimes in the field, () Drined condition nd () Flooded condition. Mens±SE (n = 4) for ech tretment re shown. Different letters indicte significnt differences y Tukey test t the 5% significnce level, ns: Not significnt. Comprisons vlid within the sme flooding regimes 3

4 J. Agron., 215 Emergence (%) Control ET GA 3 ET+GA 3 Tretment Fig. 3: Effects of plnt growth regultors on the percent emergence of second node tillers under drined conditions. Mens±SE (n = 4) for ech tretment re shown. Different letters indicte significnt differences y Tukey test t the 5% significnce level Length (mm) Control Flooded Drined ET GA 3 ns ET+GA 3 Control Tretment ET GA 3 ET+GA 3 Fig. 4: Effects of plnt growth regultors on the length of the second node tillers. Mens±SE (n = 4) for ech tretment re shown. Different letters indicte significnt differences y Tukey test t the 5% significnce level, ns: Not significnt. Comprisons vlid within the sme flooding regimes the first nd second leves (Fig. 2). However, ET+GA 3 tretment significntly elongted the mesocotyl nd improved the growth of the first nd second leves nd plnt length. Under flooded conditions, comined tretment with ET nd GA 3 produced the most prominent effect on seedling growth. However, the responses of seedling orgns to ech PGR tretment under flooded condition were slightly different from those of seedlings grown under drined conditions. Under flooded condition, GA 3 lone lso significntly improved the growth of mesocotyl, coleoptiles, mesocotyl+coleoptile nd the first nd second leves compred to those in the control (Fig. 2); these effects were slightly improved fter tretment with ET+GA 3. Ymuchi nd Bisws (1997) lso suggested tht the growth of seedling orgns differed etween flooded nd drined conditions. Thus, even under field conditions, the synergistic effects of ET nd GA 3 on seedlings growth were noted; however, coleoptile nd mesocotyl+coleoptile growth under drined conditions were slightly different from those otined in the previously reported growth chmer experiments (Wtne et l., 27). Ethephon ffected the growth of the second node tiller: Tiller numer cn significntly contriute to the yield potentil; however, informtion on the hormonl regultion of tillering is scrce (Hnd, 1993; Krili nd Mohptr, 27). Hence, the effects of PGR on tiller numer were determined using the different flooding regimes. Since, the second node tillers were not noted under flooded conditions, the percent emergence of tillers under drined conditions ws recorded (Fig. 3). The ET nd ET+GA 3 tretments significntly incresed the percent emergence of second tillers thn those noted in control nd GA tretment lone (Fig. 3). The lengths of the tillers were not significntly different cross the PGR tretments under flooded conditions; however, ET nd ET+GA 3 tretments significntly incresed the tiller length under drined condition compred to those noted in control nd GA 3 tretments under drined conditions (Fig. 4). Further, under drined condition the tiller length ws not different fter tretment with ET nd ET+GA (Fig. 4). These results suggested tht ET promoted tillering ut not synergisticlly with GA under drined conditions. Tillering is known to e ffected y environmentl fctors such s nutrient supply, plnt spcing nd flooding depth (Hnd, 1993; Yoshid, 1981); it is dversely ffected with incresing wter depth in pddy fields (Hnd, 1993). In this study, the second node tiller numer ws not incresed fter tretment with ET nd ET+GA 3 under flooded conditions; this suggested tht the growth-promoting effect of ET on tillering ws eliminted y flooding. This finding ws consistent with tht of Sekiy (1951), who indicted tht the growth of the second tillering primordium nd tillering ud were remrkly influenced y wter depth nd tht their growth ws the est t wter depth of cm. ET hs een used to increse tillering nd prevent lodging in mny cerel crops, including mize, whet nd rley (Cox nd Andrde, 1988; Cox nd Otis, 1989; Foster et l., 1991). However, the growth-promoting effect of ET on tillering in rice hs not yet een investigted. To our knowledge, this is the first report suggesting tht ET promotes tiller growth in rice. Further studies re wrrnted to elucidte the mechnisms underlying the effect of ET on tiller growth in rice. 4

5 J. Agron., 215 Length (mm) Length (mm) () Mesocotyl+coleoptile Control ET GA3 ET+GA ns () First lef 3 Fig. 5(-): Differences in the growth of orgns etween the plnt growth regultors-treted nd control plnts, () Mesocotyl+coleoptile nd () First lef. Mens±SE (n = 4) for ech tretment re shown. The seedlings were grown in growth chmer t 2 C. Different letters indicte significnt differences y Tukey test t the 5% significnce level, ns: Not significnt Lortory experiments: The length of coleoptile plus mesocotyl nd the first lef re importnt fctors tht determine successful emergence nd estlishment of seedlings (Andrews et l., 1997; Hoshikw, 1993; Ries nd Hofmnn, 1995; Aliu et l., 211). Since, the finl length of seedling orgns were different cross the PGR tretments (Fig. 2) nd ET+GA 3 improved the emergence nd estlishment of seedlings in the field experiments, the growth kinetics of seedling orgns treted with PGRs were nlyzed (Fig. 5). The mesocotyl+coleoptile length ws not different etween the control nd treted seedlings t 2 DAS; however, their length significntly incresed fter tretment with PGRs from 4 DAS. ET+GA 3 hd the most significnt effect on mesocotyl+coleoptile lengths from 4- DAS. The finl length of mesocotyl+coleoptile fter tretment with ET+GA 3, incresed pproximtely y 18% compred with the other tretments. Further, the elongtion rtes of c DAS (dy) c c mesocotyl+coleoptile were the highest fter tretment with ET+GA 3 (Fig. 5). The synergistic effects of ET nd GA 3 were lso noted for the growth of the first lef (Fig. 5). ET+GA 3 significntly incresed the first lef length compred to those of the other tretments t 6 DAS. The growth of the first lef fter tretment with ET+GA 3 ws noted only until 12 DAS. In other tretments, the first lef continued to grow even fter 14 DAS. The finl length of the first lef fter tretment with ET+GA 3 ws incresed round y 24% thn those of the other tretments. Nonetheless, the highest growth rte of the first lef, s well s tht of the coleoptile+mesocotyl nd the longest first lef length were noted fter tretment with ET+GA 3. These results suggested tht the elongtion rte nd speed of mesocotyl+coleoptile nd first lef in ET+GA 3 contriute to erly seeding growth nd vigor. CONCLUSION Our results showed the synergistic effects of ET nd GA 3 on the growth of rice seedlings in the field experiment. In the future, we intend to perform experiments to determine the effects of ET+GA 3 on the lter growth stges of rice seedlings, s well s on the grin yield nd rice qulity. To our knowledge, this is the first study showing tht ET incresed the growth of the second node tiller under drined conditions. The findings of this study might form the sis to determine the mechnism of how ET promotes tiller growth nd fcilitte the use of ET in rice production. REFERENCES Aliu, S., Y. Sito, H. Shiwchi nd K. Irie, 211. Reltionship etween coleoptile nd mesocotyl elongtion of uplnd rice (Oryz stiv L.) seedlings under sumergence nd soil-snd culture. Afr. J. Agric. Res., 6: Andrews, M., A. Dougls, A.V. Jones, C.E. Milurn, D. Porter nd B.A. McKenzie, Emergence of temperte psture grses from different sowing depths: Importnce of seed weight, coleoptiele plus mesocotyl length nd shoot strength. Ann. Applied Biol., 13: Artec, R.N., Historicl Aspects nd Fundmentl Terms nd Concepts. In: Plnt Growth Sustnces: Principles nd Applictions, Artec, R.N. (Ed.). Chpmn nd Hll, New York, USA., ISBN-13: , pp: Cox, W.J. nd H.F. Andrde, Growth, yield nd yield components of mize s influenced y ethephon. Crop Sci., 28: Cox, W.J. nd D.J. Otis, Growth nd yield of winter whet s influenced y chlormequt chloride nd ethephon. Agron. J., 81: Foster, K.R., D.M. Reid nd J.S. Tylor, Tillering nd yield responses to ethephon in three rley cultivrs. Crop Sci., 31:

6 J. Agron., 215 Furukw, K., Y.Y. Yng, I. Hond, T. Yngisw, A. Skuri, N. Tkhshi nd Y. Kmiy, Effects of ethylene nd gierellins on the elongtion of rice seedlings (Oryz stiv L.). Biosci. Biotech. Biochem., 61: Hnd, K., Tillers. In: Science of the Rice Plnt. Volume 1: Morphology, Mtsuo, K. nd K. Hoshikw (Eds.). Food nd Agriculture Policy Reserch Center, Tokyo, Jpn, pp: Hoshikw, K., Morphology nd Development of Vegettive Orgns. In: Science of the Rice Plnt. Volume 1: Morphology, Mtsuo, K. nd K. Hoshikw (Eds.). Food nd Agriculture Policy Reserch Center, Tokyo, Jpn, pp: Krili, E. nd P.B. Mohptr, 27. Hormonl regultion of tiller dynmics in differentilly-tillering rice cultivrs. Plnt Growth Regul., 53: Mori, S., H. Fujimoto, S. Wtne, G. Ishiok, A. Oke, M. Kmei nd M. Ymuchi, 212. Physiologicl performnce of iron-coted primed rice seeds under sumerged conditions nd the stimultion of coleoptile elongtion in primed rice seeds under noxi. Soil Sci. Plnt Nutr., 58: Ogiwr, H. nd K. Tershim, 21. A vrietl difference in coleoptile growth is correlted with seedling estlishment of direct Seeded rice in sumerged field under low-temperture conditions. Plnt Prod. Sci., 4: Rskin, I. nd H. Kende, Regultion of growth in rice seedlings. J. Plnt Growth Regul., 2: Ries, R.E. nd L. Hofmnn, Grss seedling morphology when plnted t different depths. J. Rnge Mnge., 48: Sekiy, F., Studies on the tillering primordium nd tillering ud in rice seedlings: 1. The influence of wter depth on the development of tillering primordium nd tillering ud. Jpn. J. Crop Sci., 2: Suge, H., Synergistic ction of ethylene with gierellins in the growth of rice seedlings. Proc. Crop Sci. Soc. Jpn., 43: Tkhshi, K. nd P.B. Kufmn, Growth regultion of rice seedlings. Proc. Plnt Growth Regul. Soc. Am., : Tkhshi, K. nd P.B. Kufmn, Regultion of internodes elongtion of rice seedlings y plnt growth regultors. Jpn. J. Crop Sci., 61: Wtne, H. nd K. Tkhshi, Effects of plnt growth regultors on the ppernce of MC type rice seedlings. Jpn. J. Crop Sci., 66: Wtne, H., K. Tkhshi nd M. Sigus, 21. Morphologicl nd ntomicl effects of scisic cid (ABA) nd fluridone (FLU) on the growth of rice mesocotyls. Plnt Growth Regul., 34: Wtne, H., M. Sigus nd S. Morit, 26. Identifiction of Csprin nds in the mesocotyl nd lower internodes of rice (Oryz stiv L.) seedlings using fluorescence microscopy. Plnt Prod. Sci., 9: Wtne, H., S. Hse nd M. Sigus, 27. Effects of the comined ppliction of ethephon nd gierellin on growth of rice (Oryz stiv L.) seedlings. Plnt Prod. Sci., : Ymuchi, M. nd J.K. Bisws, Rice cultivr difference in seedling estlishment in ooded soil. Plnt nd Soil, 189: Yoshid, S., Tillering. In: Fundmentls of Rice Crop Science, Yoshid, S. (Ed.). Interntionl Rice Reserch Institute, Los Bños, Philppine, ISBN-13: , pp:

H. Randall Smith; Ph.D. Agronomy and Wayne Porter: Ph.D. Horticulture Mississippi State University Extension Service

H. Randall Smith; Ph.D. Agronomy and Wayne Porter: Ph.D. Horticulture Mississippi State University Extension Service Effect of SumGrow on growth, development nd yield of Irish pottoes (Solnum tuerosum) t the Beumont Reserch Sttion (Mississippi Stte University) during 217 H. Rndll Smith; Ph.D. Agronomy nd yne Porter: