REVIEW Improvement in Rice Grain Quality by Deep-flood Irrigation and its Underlying Mechanisms

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1 JARQ 1 (), (17) REVIEW Improvement in Rice Grin Qulity by Deep-flood Irrigtion nd its Underlying Mechnisms Mshiro CHIBA 1 *, Tomio TERAO, Hjime WATANABE 3, Osmu MATSUMURA nd Yoshihiko TAKAHASHI 3 1 Lowlnd Crops Reserch Division, Western Region Agriculturl Reserch Center, NARO (Fukuym, Hiroshim 71-1, Jpn) Hokuriku Reserch Center, Centrl Region Agriculturl Reserch Center, NARO (Joetsu, Niigt , Jpn) 3 Grdute School of Science nd Technology, Niigt University (Niigt, Niigt 9-11, Jpn) Abstrct The incresed occurrence of chlky rice grins s result of globl wrming is becoming serious problem. The ppliction of deep-flood irrigtion (DFI) to wter depth of 1 cm from the ctive tillering stge to the mximum tillering stge suppresses the occurrence of chlky grins under both high nd norml temperture conditions without decresing yields. The mechnism by which DFI reduces chlky grins ws nlyzed reltive to crbohydrte supply s crbohydrte deficiencies hve been proposed s cuse of chlky grins. DFI suppresses the occurrence of chlky grins due to the incresed supply of crbohydrtes to the pnicles. In pddy fields where wter depth of 1 cm is not possible, such s in pddy fields with low levees or low wter supplies, the combined use of moderte DFI t wter depth of 1 cm with deep plnting cn be substituted to produce high-qulity rice. DFI did not dmge root ctivity t the ripening stge, even in soils with low redox potentil. Although the DFI tretment slightly decresed the penetrtion resistnce of the soil, the bering cpcity ws not ffected t the time of combine hrvest. Discipline: Crop production Additionl key words: chlky grins, deep plnting, high temperture ripening, sink-source Introduction Globl wrming hs cused increses in the verge ir temperture (ICPP 13), nd higher summer ir tempertures my dmge the production of crops grown in summer, including rice (Oryz stiv L.). High ir tempertures t the flowering stge of rice my cuse sterility by inhibiting nther dehiscence (Mtsui 9), thus cusing reduction in grin yield. Grin weight hs lso been reported to decrese under high tempertures t the ripening stge (Morit et l. ); moreover, high tempertures lso dmge rice grin qulity, with high temperture ripening reportedly cusing chlky grins (Resurreccion et l. 1977). Chlky grins hve white opque portion in which crbohydrtes hve not fully ccumulted (Tshiro & Wrdlw 1991). When the verge temperture over dys fter heding exceeds C, the occurrence of chlky grins increses (Kondo et l. ). Furthermore, high tempertures tht occur from 1 to 1 dys fter heding led to n increse of crcked grins (Ngt ). Deep-flood irrigtion (DFI) is cultivtion method tht uses deep wter to irrigte pddy field. DFI cn be clssified into two mjor types ccording to the timing of ppliction nd its objectives. The first type is the use of DFI t the reproductive stge to protect pollen formtion from cold dmge. Low tempertures tht occur from the spikelet differentition stge to the young microspore stge (tetrd stge nd erly microspore stge) cuse serious yield losses due to pollen formtion filure (Stke et l. 197). During these stges, young pnicles re still present t the bottom of the stem nd my be covered by wter t temperture higher thn tht of the ir during cool summer if the wter is deep enough (Stke et l. 19). Therefore, DFI is n effective method of preventing yield losses cused by poor pollen formtion during cool summers. The second type is the use of DFI t the vegettive stge, which is currently ttrcting gret del of ttention, such s in Aichi Prefecture (Aichi Agriculturl Reserch *Corresponding uthor: e-mil gdi@ffrc.go.jp Received Februry 1; ccepted 9 June 1. 17

2 M. Chib et l. Center 1), Toyook City, Hyogo Prefecture (Toyook City Government), nd Shig Prefecture (Toritsuk et l. 13). DFI pplied t the tillering stge cn control the growth of rice plnts by suppressing the formtion of lteemerging wek tillers (Furuy et l. 1991, Ohe et l. 1). Wek tillers become inferior stems or eventully die before heding, nd suppression of wek tillers hs been shown to improve the sink-source blnce (Furuy et l. 1991, Miur et l. 1, Ohe et l. 1). Such improvements could reduce the occurrence chlky grins s poor ccumultion of crbohydrtes cused by low source bility to sink is probbly mjor cuse of chlky grins. In this study, we introduce precise nd prcticl DFI cultivtion method for the production of high-qulity rice, nd ssess the potentil mechnisms by which DFI suppresses the occurrence of chlky grins. 1. Wter mngement by deep-flood irrigtion Fig. 1 shows n exmple of wter mngement regimes in Niigt, Jpn tht use DFI nd conventionl wter irrigtion (CWI) (Chib et l. 9, Chib et l. 11b). Rice seedlings were trnsplnted in the middle of My under both wter mngement regimes. The fertiliztion conditions were s follows: bsl dressing of 3 g m - nd top dressing t er formtion stge of g m - in both experiments. Under both CWI nd DFI, the wter depth in the pddy field ws mintined t pproximtely cm from seedling trnsplnttion to rooting. After rooting, the wter depth ws mintined t low level until midseson dringe under the CWI regime. Intermittent irrigtion ws subsequently conducted until the end of August. At the beginning of September, the wter in the pddy field ws drined to prepre for the hrvest. However, the wter depth in the DFI regime ws incresed to 1 cm t the ctive tilling stge nd mintined t tht depth until the mximum tillering stge (Fig., Chib et l. 9). After the mximum tillering stge, midseson dringe ws conducted, followed by intermittent irrigtion performed in similr mnner to tht for the CWI regime.. Effect of deep-flood irrigtion on the growth nd yield of rice Fig. 3 shows chnges in the number of stems under CWI nd DFI (Chib et l. 9). Under CWI, the number CWI cm Low wter Midseson cm dringe Inter-irrigtion Dringe My June July August September DFI DFI tretment 1 cm Htsuboshi nd Ssnishiki cm Low wter Midseson cm dringe Inter-irrigtion Dringe My June July August September Moderte DFI Moderte DFI tretment 1 cm cm My June Midseson dringe Htsuboshi nd Ssnishiki Inter-irrigtion Dringe July August September Htsuboshi Fig. 1. Schemtic digrms of wter mngement regimes by conventionl wter irrigtion (CWI), deep-flood irrigtion (DFI) t wter depth of 1 cm (from to 9) nd moderte DFI t wter depth of 1 cm (from to 9). The rrows indicte the ripening period. Tringles indicte the trnsplnting time. 1 JARQ 1 () 17

3 Improvement in Rice Qulity by DFI nd its Underlying Mechnisms of stems incresed until the mximum tillering stge, but decresed therefter. This chnge in the number of stems is typicl for rice plnts grown using conventionl cultivtion in Jpn. However, chnges in the number of stems under DFI ws different from tht under CWI. The DFI tretment completely suppressed the formtion of new tillers, none of the emerged tillers died, nd lmost ll of the tillers tht emerged prior to DFI tretment produced pnicles. Therefore, fewer pnicles of n inferior stem, such s secondry tillers or primry tillers from higher node, were observed under DFI thn under CWI. This suppression of tillering nd concomitnt increse in the percentge of productive stems re consistent with the results from other studies (Furuy et l. 1991, Miur et l. 1, Ohe et l. 1). Decresing the bsl dressing nd deeper plcement of the top dressing hve reportedly been effective in incresing the percentge of productive stems (Tnk 1971). However, chnges in the number of stems re inconsistent. The number of stems under DFI ws estblished in the erly stge nd my not chnge until hrvesting, while tht for deeper top dressing, prticulrly with no bsl dressing, my grdully increse until heding (Tnk 1971). This difference my hve cused the difference in tillering pttern (i.e., less emergence of high-order tillers in the lte stge under DFI versus lte emergence but better development until ripening for the deeper top dressing tretment). The combined use of DFI nd deeper plcement of top dressing ws not implemented. However, it would be interesting to determine the effect of incresing the percentge of productive stems nd the consequent better development of stems nd pnicles. The totl grin yield under DFI ws similr to tht under CWI, lthough the yield components were different (Tble 1, Chib et l. 9). DFI significntly decresed the number of pnicles by 1.9 to 19.% due to the suppression of tillering, wheres it significntly incresed the number of grins per pnicle by.1 to 1.%. Thus, the number of grins per pnicle ppered to increse s compenstion for the decresed number of pnicles. Given the incresed number of grins, the number of grins per unit re under DFI ws only slightly reduced or equivlent to tht under CWI. Moreover, the 1-grin weight incresed by. to.7% under DFI; therefore, the totl yield under DFI ws not lower thn tht under CWI. DFI is wter mngement process tht suppresses the increse in stems to improve grin qulity. DFI hd no negtive effects on yield under the nitrogen pplictions used in this study. However, DFI ppers to not be useful for obtining high yields becuse the decresed number of stems/pnicles cn limit the yield. 3. Effect of deep-flood irrigtion on the qulity of rice grins We lso exmined the effect of DFI on the percent occurrence of chlky grins under mbient conditions s well s under high-temperture tretment, by covering the open top of the chmber just before heding occurred. A field mesuring 1. m squre ws surrounded by plstic film t height of 1. m in n open-top chmber (Chib nd Tero 1). The verge temperture in the dytime ws pproximtely.9 C higher in this tretment. DFI decresed the occurrence of chlky grins not only under mbient conditions (rice grown outside of the open-top chmber) but lso under high-temperture conditions. Therefore, DFI decresed the percent occurrence of chlky grins in ll cultivrs, even t high tempertures (Fig. ). These results show tht DFI cn reduce the occurrence of chlky grins under wide rnge of temperture conditions. 7 7 Number of stems (m-)-) Number of stems(m Fig.. View of the CWI nd DFI tretments t Hokuriku Reserch Center. Left to right: DFI nd CWI. Abbrevitions re the sme s in Fig DFI DFI Dys fter plnting Dys fter plnting Fig. 3. Chnges in the stem number of rice plnts under DFI nd CWI. 19

4 M. Chib et l. Cultivr Wter mngement Tble 1. Effect of DFI tretment on the yield nd yield components. Grin yield Number of pnicles Number of grins per pnicle Ripening percentge 1-grin weight Number of grins per re (g m -) (m - ) (%) (g) (1 m - ) Htsuboshi CWI DFI Sshishiki CWI DFI CWI DFI Wter mngement ns * ** ns * ns Cultivr ns *** *** ns *** *** Wter mngement Cultivr ns ns ns ns ns ns *, ** nd *** indicte significnce t P<.,.1 nd.1, respectively. "ns" indictes not significnt. The dt represent the verges of 3 yers in Htsuboshi nd nd yers in Ssnishiki. Chlky grins in DFI (%) 1 1 Ambient High-tempetture tretment Ssnishiki Htsuboshi Ssnishiki Htsuboshi 1 1 Chlky grins in CWI (%) Fig.. Effect of DFI on the occurrence of chlky grins. Brown rice smples of more thn 1. mm in thickness were investigted with n ES-1 rice inspector (Shizuok Seiki Co., Ltd., Shizuok, Jpn). Chlky grins included the totl of milky white grins, white belly grins nd bsl immture grins. The results represent n verge of 3 yers in Htsuboshi nd nd yers in Ssnishiki. The percentges of chlky grins under DFI re equl to those under CWI long the dotted line.. Mechnism of high-qulity rice production under deep-flood irrigtion Chlky grins re primrily cused by the insufficient development of strch grins in the endosperm cells (Tshiro & Ebt 197). Assimilted crbohydrtes re necessry to fill the strch grins so tht gps do not occur. Crbohydrte shortges cuse gps in the grins, which led to chlky grins. There re two mjor sources of crbohydrtes for the pnicle: crbohydrtes tht ccumulte in the stem prior to heding, nd crbohydrtes produced by photosynthesis in the leves fter heding hs occurred. The crbohydrtes ccumulted in the stem were estimted using the mount of nonstructurl crbohydrte (NSC) s n indictor, wheres the crbohydrtes produced by photosynthesis in the leves were estimted using the lef re nd nitrogen content of the lef blde s indictors. These indictors were used to elucidte the mechnisms by which DFI suppresses the occurrence of chlky grins (Chib et l. 11). First, we nlyzed these indictors in ll types of stems on hill under mbient nd high temperture conditions. The DFI tretment incresed ll three indictors nd decresed the percentge of chlky grins under the mbient nd high-temperture tretments (Fig., Chib et l. 11). These results suggested tht both crbohydrte sources (i.e., ccumulted in stems nd newly ssimilted) were incresed by the DFI tretment over the entire hill regrdless of temperture conditions. This increse in the crbohydrte supply fully filled the endosperm, which inhibited the occurrence of chlky grins. We suggest tht this is the principl mechnism by which DFI produces high-qulity rice. The DFI tretment chnged the composition of the stems, nd the rtio of superior stems tht hve good ripening chrcteristics ws incresed due to the decresed 11 JARQ 1 () 17

5 Improvement in Rice Qulity by DFI nd its Underlying Mechnisms Ambient Percentge of chlky grin (%) 1 1 A B C Htsuboshi CWI Htsuboshi DFI CWI DFI High temperture tretment Percentge of chlky grin (%) Stem NSC per grin (mg/grin) Lef nitrogen per grin (μg/grin) Lef re per grin (cm /grin) Fig.. Reltionship between the source bility to the pnicle nd the chlky grin percentge for the entire hill. A: Stem NSC t the full heding stge, B: Nitrogen in the lef blde t the full heding stge, C: Lef re t the middle ripening stge. The dt represent n verge of yers. number of inferior stems (Chib et l. 9). The DFI tretment lso decresed the occurrence of chlky grins (Fig. ). However, it is not cler whether the improved grin qulity ws cused by improvement in the superior stem rtio or improvement in the source bility to both superior nd inferior stems. Therefore, we nlyzed the crbohydrte source to the pnicle by seprting the superior stem (min stem) nd inferior stems (highest primry tiller nd secondry tiller) obtined under mbient conditions (Fig., Chib et l. 13). In this cse, little or no secondry tillers were present under DFI; therefore, these dt were omitted. When compring the effect of DFI in both the min stem nd highest primry tiller; we found tht the source ctivity per grin ws incresed, nd the occurrence of chlky grins decresed under the DFI tretment (Fig., Chib et l. 13). This result shows tht both superior nd inferior stems incresed the source bility per grin under DFI. Therefore, DFI reduced the occurrence of chlky grins by incresing the source bility of ech stem (even in the inferior stems). When compred with CWI, however, contrdictory phenomenon ws observed, prticulrly in Htsuboshi. Although the inferior stems hd poor source bility compred with the superior stems except for the lef re in secondry tillers in Htsuboshi, which should theoreticlly produce low-qulity grins, the percentge of chlky grins in the inferior stems ws smller thn tht for the superior stems. This could be explined by the percentge of secondry rchis grins tht usully hve lower grin qulity thn tht of primry rchis grins (Yoshino et l. 7). The secondry rchis grin percentge in the highest primry tiller ws lower thn tht of the min stem; it ws much lower in the secondry tillers, which consequently incresed the grin qulity (Chib et l. 13, dt were omitted). The effect of DFI to increse the source bility counters the effect of incresing secondry rchis grins becuse the increse in grin qulity under DFI occurred even when the secondry rchis grins incresed (Fig., Chib et l. 13).. Improvements vi deep-flood irrigtion High levees in pddy fields re necessry to mintin wter depth of 1 cm under DFI. Furthermore, lrge initil input of wter is necessry to increse the wter level to 1 cm, lthough the totl wter requirements throughout the seson for DFI re not much higher thn those for CWI (Arit et l. ). Consequently, DFI is not possible in ll pddy fields. We therefore suggest modified version of DFI in fields where wter depth of 1 cm is not possible. The control of rice plnt growth by DFI decreses with decresing wter depth. For exmple, the percentge of 111

6 M. Chib et l. Htsuboshi Percentdes of chlky grin (%) A B C Min stem in CWI Min stem in DFI Highest primry tiller in CWI Highest primry tiller in DFI Secondry tiller in CWI Percentdes of chlky grin (%) Stem NSC per grin (mg/grin) Lef nitrogen per grin (μg/grin) Lef re per grin (cm /grin)) Fig.. Reltionship between the source bility to the pnicle nd the chlky grin percentge s determined by the superior nd inferior stems smpled under mbient conditions. A: Stem NSC t the full heding stge, B: nitrogen in the lef blde t the full heding stge, nd C: lef re t the middle ripening stge. The dt represent n verge of yers. productive tillers ws lower when the wter depth ws less thn 1 cm (Fig. 7). At wter depth of 1 cm, the percentge of productive tillers ws 1% in Htsuboshi nd nerly 1% in. Similr results were obtined for wter depths s low s 1 cm; therefore, reduction in wter depth to 1 cm might be sufficient for DFI, lthough 1 cm my still be difficult depth to mintin. At wter depth of pproximtely 1 cm, the percentge of productive tillers ws decresed to pproximtely 9% in Htsuboshi nd less thn % in. Deep plnting is nother method of suppressing tiller emergence (Ito et l. 197, Sito 199). Although deep plnting is not recommended in certin prefectures (Deprtment of Agriculture, Forestry nd Fisheries, Niigt Prefecturl Government, ; Deprtment of Agriculture, Forestry nd Fisheries, Shimne Prefecturl Government, 1), only smll reductions in yield were observed when the plnting depth ws within the djustble rnge of trnsplnting mchine (usully cm) (Chib et l. 11b). Accordingly, the combined use of moderte DFI (t wter depth of 1 cm) nd djustment of the deepest plnting depth using mchine plnting might provide n lterntive to DFI t 1 cm (Chib et l. 11b). We implemented moderte DFI t wter depth of 1 cm t the rooting stge nd drined the pddy t the mximum tillering stge (Fig. 1). This moderte DFI ws combined with deep plnting ( cm) nd norml-depth plnting (3 cm). Becuse we mnully trnsplnted the mid-sized seedlings but not the young seedlings plnted by mchine, the depth of deep plnting in this experiment ws cm, nd thus lrger thn the mximum depth of common trnsplnting mchine ( cm). The moderte DFI tretment nd deep plnting individully suppressed increses in the number of stems, lthough the effect ws weker thn tht under the DFI tretment t 1 cm (Fig., Chib et l. 11b). However, the combined use of moderte DFI tretment nd deep plnting showed greter suppression of the number of stems (Fig. ), which consequently decresed the number of pnicles nd incresed the grins per pnicle (Tble, Chib et l. 11b). Therefore, the combintion of moderte DFI nd deep plnting hd n dditive effect on increses in pnicle weight s compred with ech seprte effect. As decreses in the number of pnicles re compensted for by increses in the number of grins per pnicle, the number of grins per unit re ws unffected by either wter mngement or plnting depth. Therefore, moderte DFI nd deep plnting did not chnge the grin yield t our pplied nitrogen level. However, deep plnting slightly delyed initil growth (Fig. ), which might limit the yield, 11 JARQ 1 () 17

7 Improvement in Rice Qulity by DFI nd its Underlying Mechnisms Percentge of productive stem (%) Wter depth (cm) Htsuboshi Number of stems m - CWI + Norml plnting DFI + Norml plnting Moderte DFI + Norml plnting CWI + Deep plnting Moderte DFI + Deep plnting DFI Moderte DFI Dys fter plnting Fig. 7. Effect of the irrigtion wter depth on the vilbility of stems (%) tht cn ber pnicles. The error brs represent the stndrd error. Fig.. Effect of the wter mngement regime nd plnting depth on chnges in the number of stems during the growth stges. Cultivr Tble. Effect of moderte DFI tretment nd deep plnting on the yield nd yield components. Wter mngement Plnting depth Grin yield Number of pnicles Number of grins per pnicle Ripening percentge 1-grin weight Number of grins per re (g m - ) (m - ) (%) (g) (1 m - ) Htsuboshi CWI Norml Deep Moderte DFI Norml Deep CWI Norml Deep Moderte DFI Norml Deep Plnting depth ns * *** ns ns ns Wter mngement ns * *** ns ns ns Cultivr ns * *** ** *** ** Plnting depth Cultivr ns ns ns ns ns ns Plnting depth Wter mngement ns ns ns ns ns ns Wter mngement Cultivr ns ns ns ns ns ns *, ** nd *** indicte significnce t P<.,.1 nd.1, respectively. ns indictes not significnt. The dt represent the verges of yers. nd erlier trnsplnting could provide method of obtining sufficient pnicles if retrded growth poses problem. Fig. 9 shows the effect of these lterntive methods on the percentge of chlky grins (Chib et l. 11b). Moderte DFI nd deep plnting individully reduced the occurrence of chlky grins, lthough the reduction ws less thn tht under DFI. The suppression of chlky grins in the combined use of moderte DFI nd deep plnting 113

8 M. Chib et l. tretment ws lrger thn tht in either individul tretment nd comprble to tht under DFI in certin cses. We therefore recommend the combined use of moderte DFI nd deep plnting s cultivtion method in pddy fields where DFI cnnot be introduced due to the levee height.. Effect of deep flood irrigtion on root ctivity nd the bering cpcity of soil Rice frmers might wonder whether DFI will cuse the soil to become too highly reduced s DFI hs been shown to decrese the soil redox potentil (Chib et l. 11b, Furuy et l. 1991). A low redox potentil in soil is known to cuse serious dmge to rice plnt roots. Therefore, we investigted the effect of DFI on root ctivity by mesuring the rte of bleeding from newly cut sections of stems on hill s puttive index of root ctivity (Morit 1999). At the full heding stge, significnt differences in the bleeding rte were not observed between the DFI nd CWI tretments (Fig. 1, Chib et l. 11b). At the middle ripening stge, the bleeding rte under DFI ws not reduced compred to tht under CWI nd ws even higher under certin conditions. Although the soil redox potentil ws lowered under DFI, decreses in the bleeding rte were not observed, which likely indicted no decrese in root ctivity. Therefore, DFI likely does not dmge the rice plnt roots, even under conditions with low redox potentil. Another issue with implementing DFI is the possibility tht DFI might reduce the soil bering cpcity t hrvest becuse the soil moisture level might still be high. Therefore, we mesured the penetrtion resistnce in the pddy fields under CWI, DFI nd moderte DFI t hrvest. The penetrtion resistnce under the DFI tretment ws slightly less thn tht under the CWI tretment, lthough the differences were not significnt (Fig. 11, Chib et l. 11b). The penetrtion resistnce under ll wter mngement regimes ws higher thn 3. kg cm - the stndrd soil bering cpcity required for combine hrvesting (Ministry of Agriculture, Forestry nd Fisheries 13). This experiment ws conducted in experimentl pddy fields contining hevy b b Fig. 1. Effect of the wter mngement regime on the bleeding rte from the cutting section of tillers. The sme letter indictes no significnt differences between the sme cultivr nd stge by Tukey's test (P<.). The error brs represent the stndrd error. b b Percentege of chlky grin (%) 1 Ambient High-temperture tretment Penetrtion resistnce (kg/cm ) CWI + Norml plnting DFI + Norml plnting CWI + Deep plnting Moderte DFI + Norml plnting Moderte DFI + Deep plnting CWI + Norml plnting DFI + Norml plnting CWI + Deep plnting Moderte DFI + Norml plnting Moderte DFI + Deep plnting Htsuboshi Fig. 9. Effect of the wter mngement regime nd plnting depth on the percentge of chlky grins. The verge mbient temperture over dys fter heding ws. C t Htsuboshi nd.1 C t.the error brs represent the stndrd error. Fig. 11. Effect of the wter mngement regime on the penetrtion resistnce in pddy field t hrvest. The penetrtion resistnce t depth of -1 cm ws investigted using cone penetrometer DIK1 (Diki Rik Kogyo Co., Ltd., Sitm, Jpn) nd verged. The line t 3 kg cm - represents the minimum resistnce for mchine hrvesting. The error brs represent the stndrd error. 11 JARQ 1 () 17

9 Improvement in Rice Qulity by DFI nd its Underlying Mechnisms cly soil. Even if this hevy cly presented poor dringe, the soil bering cpcity ws still sufficient. Therefore, no problems should be seen with respect to root ctivity nd field bering cpcity from the implementtion of DFI, except in fields with exceptionlly poor dringe. References Aichi Agriculturl Reserch Center (1) Technicl mnul of deep nd permnent irrigtion method for rice by the V-furrow no-till direct seeding. [In Jpnese]. fukmizu.pdf Arit, H. et l. () Suitble pddy field system for deep ponding cultivtion of rice. Study bsed on survey of frmers nd lnd improvement districts in deep ponding wter mngement implementtion re. Trns of JSIDRE,, 1-131[In Jpnese nd English summry]. Chib, M. et l. (9) Improvement of grin qulity nd yield by deep-flood irrigtion. Jpn. J. Crop Sci., 7, - [In Jpnese nd English summry]. Chib, M. et l. (11) Mechnism of high qulity rice production in deep-flood irrigtion. Jpn. J. Crop Sci.,, 13- [In Jpnese nd English summry]. Chib, M et l. (11b) Effect of deep plnting nd deep-flood irrigtion on the yield nd qulity of rice. Jpn. J. Crop Sci.,, 31-3 [In Jpnese nd English summry]. Chib, M. et l. (13) Deep-flood irrigtion suppresses the occurrence of chlky grins through high source bility, in spite of the high percentge of secondry rchis grins. Jpn. J. Crop Sci.,, 3-3 [In Jpnese nd English summry]. Chib, M. & Tero, T. (1) Open-top chmbers with solr-heted ir introduction tunnels for the high-temperture tretment of pddy fields. Plnt Prod. Sci., 17, 1-1. Deprtment of Agriculture, Forestry nd Fisheries, Niigt Prefecturl Government () Guideline for cultivtion of rice: Mngement of pddy field. kizyun/pdf/119 hondenknri.pdf [In Jpnese]. Deprtment of Agriculture, Forestry nd Fisheries, Shimne Prefecturl Government (1) Guideline for cultivtion of rice, whet, brley nd soyben: Rice cultivtion, II Cultivtion techniques, Preprtion in pddy field nd trnsplnting. nougyo_tech/kenyui/sisin_mnyuru/ine-sisin/ine-sisin. dt/7.3.pdf [In Jpnese]. Furuy et l. (1991) Effects of wter mngement t middle growing stge on growth nd yield of rice: Emphsis on deep wter irrigtion. Bull. Hokuriku Ntl. Agric. Exp. Stn., 33, 9-3 [In Jpnese]. ICPP (13) Climte chnge 13: The physicl science bsis. www. climtechnge13. org/ imges/ report/ WG1AR_ALL_FINAL.pdf Ito, S., et l. (197) Plnting depth of trnsplnting cultivtion using young rice seedling. Tohoku. Agric. Res., 11, -7 [In Jpnese]. Kondo, M. et l. () Effects of ir temperture during ripening nd grin protein contents on grin chlkiness in rice. Jpn. J. Crop Sci., 7 (Extr ), 1-1 [In Jpnese]. Mtsui, T. (9) Floret sterility induced by high tempertures t the flowering stge in rice (Oryz stiv L.). Jpn. J. Crop Sci., 7, [In Jpnese nd English summry]. Ministry of Agriculture, Forestry nd Fisheries (13) Formultion nd hndling of introduction pln of the specific high-performnce griculturl mchine. guide_line.pdf Miur, C et l. (1) Difference of the reserved non-structurlcrbohydrte by tillering control of rice. Tohoku Agric. Res.,, - [In Jpnese]. Morit, S. (1999) How to mesure nd how to evlute bleeding sp rte. Root Res.,, [In Jpnese]. Morit, S. et l. () Effect of high temperture on ripening in rice plnts: Comprison of the effects of high night tempertures nd high dy tempertures (crop physiology nd cell biology). Jpn. J. Crop Sci. 71, 1-19 [In Jpnese nd English summry]. Ngt, K. et l. () Effect of ir temperture during the erly grin-filling stge on grin fissuring in rice. Jpn. J. Crop Sci., 73, 33-3 [In Jpnese nd English summry]. Ohe, M. et l. (1) Effects of deep-flooding irrigtion on growth, cnopy structure nd pnicle weight yield under different plnting ptterns in rice. Plnt Prod. Sci., 13, Resurreccion, A. P. et l. (1977) Effect of temperture during ripening on grin qulity of rice. Soil Sci. Plnt Nutri., 3, Sito, Y. (199) Growth of infnt seedling with reltion to trnsplnting depth. Hokuriku Crop Sci., 9, -3 [In Jpnese]. Stke, T. et l. (197) Mle Sterility Cused by Cooling Tretment t the Young Microspore Stge in Rice Plnts. XXVII. Effect of wter temperture nd nitrogen ppliction before the criticl stge on the sterility induced by cooling t the criticl stge. Jpn, J. Crop Sci.,, -1. Stke, T. et l. (19) Mle sterility cused by cooling tretment t the young microspore stge in rice plnts. XXVIII. Prevention of cool injury with the newly devised wter mngement prctices: Effects of the temperture nd depth of wter before the criticl stge. Jpn. J. Crop Sci., 7, 3-1. Tnk, M. (1971) Studies on the deep lyer plcement of top-dressing fertilizer in rice production. Aomoriken nogyo shikenjo sougo gyoseki (Synthetic chievements of Aomori griculturl experimentl sttion), 3, 1-39 [In Jpnese]. Tshiro, T & Ebt, M. (197) Studies on white-belly rice kernel: IV. Opque rice endosperm viewed with scnning 11

10 M. Chib et l. electron microscope. Proc. Crop Sci. Soc. Jpn,, -1 [In Jpnese nd English summry]. Tshiro, T. & Wrdlw, I.F. (1991) The effect of high temperture on kernel dimensions nd the type nd occurrence of kernel dmge in rice. Aust. J. Agric. Res.,, -9. Toritsuk S. et l. (13). Improvement of the rice grin qulity in by deep flood-irrigtion t the tillering stge long with the combintion of fish production. [In Jpnese]. Toyook City Government. Agriculturl prctices to foster storks. frming/guide.html [In Jpnese]. Yoshino, Y. et l. (7) The effect of top dressing t er formtion stge on brown rice on the qulity nd crude protein content of brown rice. Chib Agric. Res. Cent.,, 9-1 [In Jpnese nd English summry]. 11 JARQ 1 () 17