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1 Advnces in Environmentl Biology, 5(10): , 2011 ISSN This is refereed journl nd ll rticles re professionlly screened nd reviewed ORIGINAL ARTICLE The Study of Dry Mtter Remobiliztion in Rice Cultivrs due to Plnting Density Vritions 1 Shhrm Lck, 1 Mndn Bymni nd 2 Mehrn Mombeni 1 Deprtment of Agronomy Science nd Reserch Brnch Islmic Azd University (IAU), Khuzestn, Irn. 2 Deprtment of Agronomy,Rmhormoz Brnch, Islmic Azd University, Rmhormoz, Irn. Shhrm Lck, Mndn Bymni nd Mehrn Mombeni: The Study of Dry Mtter Remobiliztion in Rice Cultivrs due to Plnting Density Vritions. ABSTRACT In order to investigte the effect of plnting density on remobiliztion of ccumulted dry mtter of three rice cultivrs in north-estern region of Khouzestn Province(south-west of Irn), this reserch ws conducted s split plot using Rndomized Complete Block Design (RCBD) with three replictions in the 2010 cropping seson in the reserch field of Khuzestn Agriculturl Reserch nd Nturl Resources Center(Shvoor griculturl reserch sttion).in this study, plnting density in three levels (30*30, 25*25 nd 20*20 cm 2 ) ws regrded s the min fctor in the min plots nd rice cultivrs (Hmr, RedAbrbou nd Gherdeh Rmhormoz) were regrded s the secondry fctors in the sub plots.results indicted tht plnting density significntly ffected grin yield,the number of fertile tillers, the hrvest index, dry mtter remobiliztion of flg lef, ll leves, stem nd totl remobiliztion nd current photosynthesis. The highest nd lowest grin yields were respectively observed in densities of 20*20 nd 30*30cm 2. The difference between cultivrs ws significnt for ll the bovementioned ttributes. Red Anbrbou cultivr with n verge of 5369 kgh -1 hd the highest grin yield.theinterction effect of densities nd differences ofcultivrs ws significnt on ll ttributes. The highest grin yield belonged to Gherdeh Rmhormoz cultivr with n verge of 5936 kgh -1 in 20*20 cm 2 density nd the lowest yield ws seen for Hmr cultivr in 30*30cm 2 density. Among the cultivrs, the highest nd lowest rtesof dry mtter remobiliztion occurred for Red Anbrboucultivr in 20*20 cm 2 density nd Hmr cultivr in 30*30 cm 2 densityrespectively. Considering the higher yield of Red Anbrboucultivr in 25*25 nd 30*30 cm 2 densities, this cultivr must be selected for cropping in the Khouzestn province. Furthermore, becuse cropping history nd bckground, semi dwrf nd high compressibility of Gherdeh Rmhormoz cultivr, its replnting in the north-estern of Khouzestn province is recommended. Key words: Rice, Plnting density, Grin yield, Remobiliztion nd Current photosynthesis. Introduction Rice is specificlly importnt s the second strtegic crop (fter whet) in Irn nd the whole world. Although the globl cropping re of rice is less thn whet but their productionsre roughly equl. Interntionl importnce of rice is so considerble tht the United Ntions dubbed the 2004 yer s the rice yer; such nming ws unprecedented for ny crop. Rice (Oryz stiv L.) is one of the most importnt crops in Irn. It is the lrgest crop in terms of re nd production in north of Irn[1].World rice production must increse by pproximtely 1% nnully to meet the growing demnd for food tht will result from popultion growth nd economic development [2]. A number of reserchers hve reported tht mintennce of the criticl level of rice plnt popultion in field is necessry to mximize grin yield. Corrseponding Author The effects of plnt density on grin dimension were lso identified during different pnicle development stges[27,28,29,30]. The reson for such low yield is minly ssocited with culturl technologies. Among culturl technology pplictions,the best plnting spce is the importnt one[3]. When the plnt density exceeds n optimum level, competition mong plnts for light bove ground or for nutrients below the ground becomes severe, consequently the plnt growth slows down nd the grin yield decreses [4]. Hossin et l.,[5] reported tht in densely populted rice fields the inter-specific competition between the plnts is high in which sometimes results in grdul shding nd lodging nd thus fvor the incresed production of strw insted of grin. Therefore, it is necessry to determine the optimum plnt spcing nd the number of seedlingsper hill for high yield [4]. Miller et l.,[6] Shhrm Lck, Deprtment of Agronomy Science nd Reserch Brnch Islmic Azd University Irn. E-mil: Sh.lck@ Khuzestn.srbiu.c.ir

2 stted tht like other crops, determining the desirble density hs been lwys tken into ccount by rice reserchers nd producers s limiting fctor. The effects of seedling distnce nd plnting pttern on the yield were minly studied in rice-rich Asin countries whilethe impct of plnt density in direct nd non-flooding cropping methods ws mostly investigted in non-asin rice-producing countries. Due to the vriety of nursery nd cropping techniques, extremely diverse nd even contrdictory results hve been presented by reserchers. Nonetheless, most results re suggestive of the fct tht poor reltionship is normlly observed between finl plnt density nd grin yield; the min reson is compensting the effect of yield components. Plnting pttern selection through reducing or incresing the distnce between nd in the rows cuses decline or increse in plnt density per re unit.omidi[7] pplied source restriction nd different plnting density on commercil long-durtion corn hybrids nd sserted tht dry mtter remobiliztion rte of crop s eril orgns (lef, stem nd husk) plys crucil role in grin filling of corn hybrids. He stted tht their contributions to dry mtter remobiliztion in grin filling re different nd stem plys more importnt role in this regrd. A lowdensity plnting lso might increse rice yield by the slow erly growth nd increse crop growth rte during the two weeks just before heding. This is closely relted to yield potentil [8]. Arun Geethnd Thiyrjn[9] reported tht the compounds ccumulted in eril orgns ply n importnt role in grin filling when the crop is influenced by environmentl fctors in different growth stges.chturredind Rm[10] stted tht rice ccumultes greet dels of crbohydrtes in different segments prticulrly in stem, nd the fct tht these mtters undertke importnt prt when the crop encounters environmentl tensions during different growth stges. Thmsebi Srvestni nd Pirdshti [11] nd Mostfvi Rdnd Thmsebi Srvestni [12]showed tht dry mtter remobiliztion plys n importnt role in rice grin filling nd eril orgns contribution ws different in terms of remobiliztion of ccumulted ssimiltes to the grin; stems nd leves respectively possessed more significnt effects. Different rice cultivrs behve differently regrding dry mtter remobiliztion ffected by vrint environmentl conditions. Hving studied dry mtter ccumultion before pollintion nd its mobiliztion to grin during grin filling in five Indic nd three Jponic cultivrs in two consecutive yers, Ntnos nd Koutroubbs[13] reported tht the mount of mobilized mtters is influenced by the cultivrs chrcteristics. Yoshid [14] stted tht the ccumultions in orgns cn be trnsferred to the grins vi the remobiliztion process during the grin production stge when photosynthesis is not ble to provide ll sink requirements.thmsebi Srvestni nd pirdshti 3339 [15] reported tht dry mtter remobiliztion of shoot (stem+ flg lef + other leves) hd n importnt effect on grin dry mtter ccumultion. Results of studies showed tht remobiliztion of reserves to grin is criticl for grin yield, if the plnts re subjected to different tretments such s wter stress during the grin filling stge [16].Mesbhet l.,[17] fter studying the reltionship between yield nd yield components of 17 rice cultivrs concluded tht grin yield hd significntly positive correltion with the number of grins per pnicle,the number of filled grins per pnicle nd the 1000grin weight. Besides,the number of grins per pnicle nd the number of filled grins per pnicle were two mjor fctors ffecting grin yield. The current reserch is intended to ssess the effects of plnting density on grin nd biologicl yields nd lso dry mtter remobiliztion in different rice cultivrs. Furthermore, this study ims to determine the contribution of remobiliztion process in the finl vlue of grin weight. Mterils nd Methods This reserch ws conducted in the 2010 cropping seson in the reserch field of KhouzestnAgriculturl Reserches nd Nturl Resources (ltitude 31 o 20'N, longitude 48 o 41'E nd ltitude 22.). In terms of climte, this region fetures very wrm, dry nd long summers nd moderte winters. The study ws split-plot experiment, using Rndomized Complete Block Design (RCBD) with three replictions. Three plnting dtes including 5 th My(D 1 ), 25 th My(D 2 ) nd 14 th June(D 3 )were considered s the min plots nd the subplots consisted of three rice cultivrs including Hmr(V 1 ), Red-Anbrbou(V 2 ) nd Gherdeh Rmhormoz(V 3 ).Nitrogen fertilizer consisting of 90 kgh -1 ure ws consumed t three times s follows; 40 percents t the time of trnsplnting to the min plot, 30 percent t the beginning of stem elongtion, nd the rest 30 percent t the beginning of thereproductivity stge. After trnsferring to the min plot, the seedlings were plnted in hills 25*25 cm prt; five seedlings were plnted in ech hill. The irrigtion opertion in ll plots ws implemented directly nd seprtely in order to reduce the negtive effects of wter temperture. Smpling ws done once every four dys from the beginning of pollintion until the grin mturity stge with the intention of investigting the supplying sources of dry mtter including current photosynthesis. Therte of remobiliztion nd current photosynthesis were evluted vi the following formuls [18]: Dry mtter remobiliztion rte = Dry weight of vegettive orgns t the pollintion stge dry weight of vegettive orgns t the mturity stge Current photosynthesis Rte =Grin yield Dry mtter remobiliztion rte

3 In order to determine the grin yield, 25 hills (equivlent to 1 m 2 of hrvesting surfce) were selected in ech plot, nd fter seprting the pnicles, the vilble filled grins were seprted from ll pnicles nd were plced in the oven t the temperture of 73 o C for 48 hours. Dt vrinces were nlyzed using the MINITAB nd MSTAT C softwres nd the verges were compred vi the Duncn s multiple rnge test. Results nd Discussions Grin Yield: Density effect on grin yield ws significnt (Tble 1). As density incresed, grin yield lso went up. The densities 20*20 nd 30*30 cm 2 with verges of 5434 nd 4724 kgh -1 possessed the highest nd lowest grin yields respectively (Tble 2).In low densities, ll crops bsorb more light thnks to hving lrger spce round them; they photosynthesize more perfectly nd grow better thn the closer crops [19]. Generlly, the frmers believe tht greter density cn enhnce the yield. High plnt density leds to increse in the pnicle number per re unit s well s grin weight reduction in ech pnicle. Accordingly, incresing plnt density ffects ll yield components [20]. The cultivrs lso exhibited significnt difference in terms of yield; Red Anbrbound Hmr cultivrs with verges of grin yield 5396 nd 4624 kgh -1 respectively ssumed the highest nd lowest grin yields (Tble 2). This different cn minly rise from the genotype, the morphologicl nd physiologicl differences of cultivrs, nd benefitting from inputs s well s environmentl fctors nd relted processes to the grin yield. The highest grin yield belonged to Gherdeh Rmhormoz cultivr in 20*20 cm 2 density with n verge of 5936 kgh -1. Number of Fertile Tillers: The number of fertile tillers showed significnt difference in different densities.thenumber of fertile tillers incresed s the distnce between plnts incresed. The highest nd lowest numbers of fertile tillers were respectively observed in 20*20 nd 30*30 cm 2 densities. As density increses, vegettive growth decreses in ech hill is restricted becuse of the reduction in free spce for crop development nd lso diminishing rdition nd nutrients s well s exceeding competition nd green re propgtion nd consequently the number of fertile tillers declines in ech plnt. However, in lower densities becuse of less competition between plnts, vegettive growth still proceeds nd results in delyed flowering besides n increse in tillers 3340 number. Thus, density reduction from two spects decresesthe number of tillers per re unit: first, insufficient crop per re unit, nd second, mortlity of some tillers due to inter-plnt competition nd restriction of environmentl supplies nd ltogether crop inbility to support produced tillers; while density lowering brings bout enhncement of crop s tillering cpcity. This fct implies tht in low density,the min portion of produced dry mtter in ech hill is llocted to vegettive orgns. On the contrry, vegettive growth is limited in high density nd more dry mtter is mobilized towrd the vegettive orgns due to further competition between crops. Different cultivrs hd significnt difference in terms of the number of fertile tillers; the highest number belonged to Hmr nd RedAnbrboucultivrs nd the lowest vlue ws observed in Gherdeh Rmhormoz (Tbles 1 nd 2). Tillers number reduction vries bsed on cultivrs. Normlly, the tillers in cultivrs producing lrger number of tillers die more rpidly nd frequently owing to intense inter-plnt competition. As result, lrger number of tillers in vegettive stge s potentil nd finl gent for determining the number of pnicles - is regrded one of the most principl fctors for chieving higher yield becuse the finl yield is completely ffected by the number of tillers,the number of grins per pnicle nd their weight per re unit. The results re in ccordnce with reports of Yoshid[14].The highest nd lowest numbers of tillers respectively belonged to Hmr cultivr in 20*20 cm 2 density nd Gherdeh Rmhormoz cultivr in 30*30 cm 2 (Tble 3). These results cn be ttributed to the genetic difference of cultivrs in terms of benefitting from growth fctors especilly the mounts of dry mtter ccumultion vilble in crop tissue nd light bsorbtion. Hrvest Index: The effect of density on the hrvest index ws significnt (Tble 1). The highest nd lowest hrvest indecieswere respectively obtined for densities 30*30 nd 20*20 cm 2 (Tble 2).High vlues of the hrvest index show tht the hrvest index improves s the plnting distnce between cultivrs increses. The cultivrs hd significnt difference in terms of the hrvest index, s the highest nd lowest hrvest index vlues belonged to Gherdeh Rmhormoz nd Hmr cultivrs respectively (Tble 2). High hrvest index vlue of Gherdeh Rmhormoz cultivr cn be ttributed to crop s geometricl structure improvement, better light penetrtion into cnopy, reduction in respirtion rte nd finlly, increse in dry mtter ccumultion cpcity per re unit.yoshid [21] reported tht negtive correltion between plnt height nd the hrvest index. He lso indicted tht tll cultivrs usully hve lower hrvest index.lrger vlue of the hrvest index in

4 Gherdeh Rmhormoz cultivr cn be justified by its greter fertility rte, the number of grins per pnicle nd the higher cpcity of dry mtter ccumultion besides more rpid crop growth rte in the flowering stge. The results confirm the ccurcy of reports by Chng nd Vergr [22]climing tht rice hrvest index hs negtive correltion with biologicl yield. Dry Mtter Remobiliztion nd Dry Mtter Remobiliztion of Flg Lef : Density hd significnt effect on dry mtter remobiliztion of flg lef; 20*20 cm 2 density behved better thn two otherdensities. In ddition, ricecultivrs showed significnt difference in this regrd s Gherdeh Rmhormoz nd Red Anbrboucultivrs fetured the highest nd lowest rtes of flg lef dry mtter remobiliztion respectively (Tbles 1 nd 2). The greter rte of dry mtter remobiliztion in Gherdeh Rmhormoz cultivr compred to other ones cn be explined by the better development nd propgtion of lef surfce re. The lowest nd highestrtes of flg lef dry mtter remobiliztion respectively belonged to Gherdeh Rmhormoz cultivr in 20*20 cm 2 density ( g/plnt) nd Red Anbrbou cultivr in 30*30 cm 2 density (0.6167g/plnt) (Tble 3).Flg lef plys n importnt role in dry mtter remobiliztion to the grin becuse it is the lst lef to be formed nd emerged. The results of current reserch ffirmed the reports by ThmsebiSrvestni nd Pirdshti [11]. Flg lef of RedAnbrbou cultivr served s physiologicl source in this experiment s the mount of dry mtter vilble in its flg lef ws greter thn tht of othercultivrs. The reson cn be ttributed to the lower cceptnce cpcity of this cultivr compred to Hmr nd Gherdeh Rmhormozcultivrs; consequently less remobiliztion occurred in this cultivr. Dry Mtter Remobiliztion from other Leves(except for flg lef): Plnting density significntly influenced dry mtter remobiliztion fromother leves (except for flg lef). The highest density ccounted for the lrgest dry mtter remobiliztion from other leves. Results showed tht different orgns do not hve the sme contribution to the dry mtter supply; these results were in greement with those obtined in other reserches. Mend Ohir[23] reported tht lef orgns re the min source of dry mtter remobiliztion to grin while sheth nd stems bring less contribution in this regrd. Rice cultivrs lso exhibited significnt difference in terms of the rte of remobiliztion from other leves s the gretest vlues were respectively observed in RedAnbrbound Hmr cultivrs; the lowest rte belonged to Gherdeh Rmhormoz cultivr (Tbles nd 2). Hmr nd Red Anbrboucultivrs possess lrger leves s result of being tller stem thn Gherdeh Rmhormoz cultivr; they llocte lrger mounts to photosynthesis products remobiliztion compred to Gherdeh Rmhormoz cultivr. Thmsebi Srvestni nd Pirdshti [11] proved tht dry mtter remobiliztion from eril orgns plys n essentil role in dry mtter ccumultion of rice grin, nd mong the eril orgns, lef plys the most essentil role for dry mtter remobiliztion. The highest nd lowest rte of dry mtter remobiliztion respectively belonged to Red Anbrboucultivr in 30*30 cm 2 density nd Gherdeh Rmhormoz cultivr in 30*30 cm 2 density (Tble 3). Stem Dry Mtter Remobiliztion: Plnting density significntly ffected stem dry mtter remobiliztion. 30*30cm 2 density ssumed the highest rte of stem dry mtter remobiliztion (Tbles 1 nd 2).The highest remobiliztion rte ws obtined for Red Anbrbou cultivr with n verge of g/plnt. The highest nd lowest rtes of stem dry mtter remobiliztion belonged to Red Anbrbou cultivr in 20*20 cm 2 density nd Hmr cultivr in 20*20 cm 2 cultivr respectively (Tble 3).Remobiliztion constitutes mjor portion of dry mtter supply for rice grin. Stem plys more significnt role compred to other orgns for this purpose. Hving compred tll locl cultivrs with dwrf ones, Souzet l.,[24] concluded tht tll cultivr hd greter remobiliztion mount thn the dwrf. In the cses of not needing the remobiliztion of ccumulted mtters, the crop stores the crbohydrtes lredy used for energy consumption during remobiliztion process in different orgns including stem. Dry mtter remobiliztion hd considerble effect on rice grin filling. Aeril orgns behve differently in terms of ccumulted ssimiltes remobiliztion to the grin; stem nd leves respectively plys more significnt roles. Ghosh nd Singh [25]showed tht stem brings more contribution to dry mtter remobiliztion compred to other eril orgns, nd eril orgns behve differently in terms of dry mtter remobiliztion in different genotypes nd environmentl conditions. Totl Dry Mtter Remobiliztion nd Current Photosynthesis nd Totl Dry Mtter Remobiliztion: Plnting density hd significnt effect on totl dry mtter remobiliztion. The highest remobiliztion rte belongedto 20*20cm 2 density (Tbles 1 nd 2). The difference between rice cultivrs ws significnt in terms of totl remobiliztion s the highest vlue ws obtined for RedAnbrbou with n verge of g/plnt (Tble 2).

5 The higher vlue of totl remobiliztion in RedAnbrbou cultivr cn be explined by fetures such s higherstem nd pnicle length nd lower number of tillers. This difference is relted to difference of cultivrs in the process of dry mtter remobiliztion to different orgns. The findings were in lignment with reports by Thmsebi Srvestni nd Pirdshti [11]. The interction effects of density nd cultivr were significnt in terms of totl dry mtter remobiliztion; the highest remobiliztion rte ws chieved for Red Anbrbou cultivr nd 20*20 cm 2 density (Tbles 1 nd 3). Current Photosynthesis: Plnting density significntly ffected current photosynthesis rte; the highest nd lowest current photosynthesis rtes respectively occurred in 30*30 nd 20*20 cm 2 densities (Tbles 1 nd 2). Among ll, Gherdeh Rmhormoz cultivr ssumed the highestrte of current photosynthesis (with n verge of 1.62 grms per plnt). Also, the highest rte of current photosynthesis ws obtined for Gherdeh Rmhormoz cultivr in 30*30 cm 2 density (Tble 3).Theimprovement of current photosynthesis forgherdeh Rmhormoz cultivr cn be ssocited with high vlues of the hrvest index nd the 1000grinweight. Yet, it cn be lso sid tht high current photosynthesis results from lrge demnd of sink for receiving photosynthetic products which led to yield improvement through incresing the hrvest index nd the 1000grin weight. The results ffirmed the report by Kfi et l.,[26] stting tht yield improves vi incresing the grin number nd the fct tht growing grins consume extr bsorbed mtters. The dry mtter remobiliztion is limited when the photosynthetic products re sufficient for grin filling. Photosynthesis role in grin weight cn 3342 be regrded s selective mechnism becuse metbolic energy is consumed during the remobiliztion process in both the ccumultion nd re-movement stges. Tking into ccount tht energy consumption is lower in the process of current ssimiltes mobiliztion to the grin the efficiency of current photosynthesis products mobiliztion to grins will be higher. Conclusions: The results showed thtthe highest nd lowest grin yields respectively belonged to 20*20 nd 30*30 cm 2 densities. Red Anbrboucultivr fetured the highest grin yield with n verge of 5369 kgh - 1 while Hmr cultivr ssumed the lowestgrin yield. Thehighest nd lowestgrin yield were respectively chieved for Gherdeh Rmhormoz cultivr in 20*20 cm 2 density (5936 kgh -1 ) nd Hmr cultivr in 30*30 cm 2 density. Among ll cultivrs, the highest nd lowest rtesof dry mtter remobiliztion were observed for Red Anbrbouin 20*20 cm 2 density nd Hmr in 30*30 cm 2 density respectively. The results of this reserch ffirm the fct tht density lters growth nd development pttern ffecting crbohydrtes production nd their distribution. Generlly, if desirble plnt density is reduced, ctully the vilble potentil will not be perfectly benefitted. On the other hnd, incresing the density beyond the desirble limit will be followed by extreme competition to chieve crbohydrtes resulting in considerble reduction of llyield components nd finlly,grin yield declined. It must be lso noted tht the suitble density is not the one in which the best growth nd highest production of single plnt is chieved but is the density which brings bout the best grin production per hectre. Tble 1: Anlysis of vrince of yield nd yield components nd dry mtter remobiliztion. S.O.V Repliction Density (D) E Cultivr(C) D C Eb CV% df Grin Yield * *: significnt in 1% probbility level : significnt in 1% probbility level 5 Number of Fertile Tillers Hrvest Index * * * Men Squre Flg Lef * * Dry Mtter Remobiliztion Totl All Stem Remobilizti Leves on * Current Photosynthes is * *

6 3343 ns: non-significnt Tble 2: Men comprison of grin yield nd yield components. Tretment Plnting density D 1 D 2 D 3 Cultivr Grin Yield (Kg h -1 ) b Number of Fertile Tillers Hrves t Index (%) Flg Lef All Leves (g/plnt ) c b b 4724 b c c b b Dry Mtter Remobiliztion Stem (g/pln t) Totl Remobiliztion Current Photosynthesis b b b b C b b b c c b C b b b C b b b b b * verges of ny test column hving t lest one letter in common lcks sttisticl difference bsed on Duncn s multiple rnge test in 1% probbility level. * In ech column which two verges hve letters in common, there is no difference bsed on Duncn s multiple rnge test in 1% probbility level. D1= 30*30 cm 2, D2: 25*25 cm 2, nd D3= 20*20 cm 2 V 1= Hmr Cultivr, V 2= RedAnbrbou Cultivr, nd V3= Gherdeh Rmhormoz Cultivr Tble 3: Men comprison of interction effects of plnting density nd cultivr on the studied ttributes in different tretments. Dry Mtter Remobiliztion Tretment Grin Number Hrvest All Totl Current Flg Lef Stem Yield of Fertile Index Leves Remobiliztion Photosynthesis (kgh -1 ) Tillers (%) D1V bcd c cd b f e de D1V bc b c bc cd cde D1V b b bc d b b D2V cde c cde cd ef f e D2V b b b e d b b 1.108cd D2V ef d b e d d b D3V f c c de d e f cde D3V b b b e c b c D3V de d b e b c * verges of ny test column hving t lest one letter in common lcks sttisticl difference bsed on Duncn s multiple rnge test in 1% probbility level. * In ech column which two verges hve letters in common, there is no difference bsed on Duncn s multiple rnge test in 1% probbility level. D1= 30*30 cm 2, D2: 25*25 cm 2, nd D3= 20*20 cm 2 V 1= Hmr Cultivr, V 2= RedAnbrbou Cultivr, nd V3= Gherdeh RmhormozCultivr References 1. Htmi, H., Effect of trnsplnting dte, plnting density nd fertiliztion on rice yield. MS Thesis. Tehrn Azd University, Science nd Reserch Brnch, Irn, pp: Horie, T., T. Shiriw, nd K. Hom Cn yields of lowlnd rice resumes the increses tht they showed in the 1980? Proceedings of the 4th Interntionl Crop Science. Congress Brisbne, Austrli. 3. Brri, T.D., H. Pirdshti, M. Nsiri, A. Gznchin, nd S. Hoseini, Determintion of morphologicl chrcteristics ffected by different gronomicl tretments in rice (IR promising line). Asin Journl of Plnt Science, 6(1): Hsnuzzmn, M., M.L. Rhmn, T.S. Roy, J.U. Ahmed, nd A.S.M. Zober, Plnt chrcters, yield components nd yield of lte trnsplnted Amn Rice s Affected by plnt spcing nd number of seedling per hill. Advnces in Biologicl Res., 3(5-6): Hossin, M.S., A.A. Mmun, M.N. RiktBsk nd M.K. Anm Effects of cultivr nd spcing on weed infesttion nd performnce of trnsplnted Amn rice in Bngldesh. Pkistn J. Agron, 2(3):

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