Research Article Rice Photosynthetic Productivity and PSII Photochemistry under Nonflooded Irrigation

Transcription

1 Hinwi Pulishing Corportion e Sientifi Worl Journl, Artile ID , 14 pges Reserh Artile Rie Photosyntheti Proutivity n PSII Photohemistry uner Nonflooe Irrigtion Hiing He, 1 Ru Yng, 1 Bio Ji, 1 Lin Chen, 2 Hu Fn, 1 Jing Cui, 1 Dong Yng, 1 Menglong Li, 1 n Fu-Yu M 1 1 Agriulturl College, Shihezi University/Key Lortory of Osis Eology Agriulture of Xinjing Bingtun, Shihezi, Xinjing , Chin 2 Agriulturl Drought Reserh Institute of Tinye Group Compny, XinJing , Chin Corresponene shoul e resse to Fu-Yu M; mfy gr@163.om Reeive 24 Novemer 2013; Aepte 18 Jnury 2014; Pulishe 5 Mrh 2014 Aemi Eitors: P. Prolin n R. Srkr Copyright 2014 Hiing He et l. This is n open ess rtile istriute uner the Cretive Commons Attriution Liense, whih permits unrestrite use, istriution, n reproution in ny meium, provie the originl work is properly ite. Nonflooe irrigtion is n importnt wter-sving rie ultivtion tehnology, ut little is known on its photosyntheti mehnism. The ims of this work were to investigte photosyntheti hrteristis of rie uring grin filling stge uner three nonflooe irrigtion tretments: furrow irrigtion with plsti mulhing (), furrow irrigtion with nonmulhing (), n rip irrigtion with plsti mulhing (). Compre with the onventionl flooing (CF) tretment, those grown in the nonflooe irrigtion tretments showe lower net photosyntheti rte (P N ), lower mximum quntum yiel (F V /F m ), n lower effetive quntum yiel of PSII photohemistry (Φ PSII ). An the poor photosyntheti hrteristis in the nonflooe irrigtion tretments were minly ttriute to the low totl nitrogen ontent (TNC). Uner non-flooe irrigtion, the P N, F V /F m,nφ PSII signifintly erese with reution in the soil wter potentil, ut these prmeters were rpily reovere in the n tretments when supplementry irrigtion ws pplie. Moreover, The tretment lwys h higher photosyntheti proutivity thn the n tretments. Grin yiel, mtter trnslotion, n ry mtter post-nthesis (DMPA) were the highest in the CF tretment, followe y the,, n tretments in turn. In onlusion, inresing nitrogen ontent in lef of rie plnts oul e key ftor to improve photosyntheti pity in nonflooe irrigtion. 1. Introution To meet the inresing emn for rie from the wor s growing popultion, rie proution must inrese y 60% y 2025 oring to urrent projetions [1]. However, shortge of wter resoures is lrey prolem for griulture [2]. Therefore, wter shortges re expete to limit rie proution, whih requires lrge mount of wter. In reent yers, vrious wter-sving ultivtions for rie proution hve een teste. Rie is grown uner nonflooe irrigtion with equte inputs n supplementry irrigtion t times uring the growth perio when rinfll is insuffiient. Rie grown in this wy shows high wter use effiieny n grin yiel [3 7]. These tehnologies provie importnt theoretil referene vlues for oping with potentil wter efiit n the emns for stple foo. Grin yiel formtion minly epens on photosyntheti proution uring the grin-filling stge [8, 9]. Therefore, photosynthesis uring the grin-filling stge is n importnt physiologil ftor ffeting iomss n grin yiel [10]. Theflgleves,theseonnthirlevesfromthetop of the plnt re onsiere to e funtionl leves uring grin filling [11]. Therefore, stuies on the photosyntheti hrteristis of flg leves uring the grin-filling stge help us unerstn their physiologil sttus n the grin proution potentil of the plnt [11]. Wter stress is the most importnt limiting ftor ffeting plnt growth n rop proution worlwie. Previous stuies reporte tht the photosyntheti rte of the flg leves eline quikly when grin-filling stge ws sujete to nonflooe onitions [12, 13] n tht grin yiel ws ffete y wter efiit stress [14, 15]. However, stuies on photosyntheti

2 2 The Sientifi Worl Journl mehnisms of rie in nonflooe onition hve generlly pplie only short-term wter regultion of wter supply, for exmple, growing rie uner nonflooe ultivtion uring the grin-filling stge, while pplying flooing onitions uring other stges of growth [12, 13, 16]. There hve een reltively few stuies on the photosynthesis of rie flg leves uring the grin-filling stge tht hve use plnts grown uner nonflooe ultivtion for the whole growth perio. It is very interesting to know photosyntheti hrteristis n photosyntheti proution pity uring the grinfilling stge uner long-term nonflooe ultivtion. Suh reserh will lso ontriute to n unerstning of the rie grin yiel proution potentil uner long-term nonflooe ultivtion. Light energy is riving ftor of photosynthesis. Light energy sore y hlorophyll moleules in lef n e lost from photosynthesis (photohemistry), het loss, n hlorophyll fluoresene [17]. The proesses of photohemistry, hlorophyll fluoresene, n het loss iretly ompete for exittion energy [18]. Therefore, hlorophyll fluoresene, espeilly for the PSII system, n e very powerful tool to stuy photosyntheti performne, the egree of wter stress or photoinhiition, n photoprotetive mehnisms [17 19]. Uner ioti stress, the photosyntheti rte is signifintly reue [12], n the requirement for photosyntheti eletrons lso ereses so tht surplus rint energy must e egre in lterntive wys [20]. To llevite or voi mging the plnt s photosyntheti pprtus, exessive energy n e issipte y het emission (nonphotohemil quenhing); this mehnism protets the photosyntheti pprtus n helps to resist photoinhiition [21]. Photoinhiition ours when there is lrge surplus of rint energy n/or nonphotohemil quenhing is insuffiient to issipte exess energy [22]. To te, there hs een little systemti reserh on the photosyntheti ttriutes (light energy sorption, proportion of energy istriute to the photosyntheti pprtus, photoprotetion, n pttion mehnisms) of rie grown uner long-term nonflooe irrigtion. In rie, photosynthesis is ffete y nonflooe ultivtion onitions. The photosyntheti pity is signifintly improve in the mulhing ultivtion thn in the re ln ultivtion [7]. It is likely tht ifferent nonflooe ultivtion methos will ffet photosyntheti performne, photoprotetion, n pttion mehnisms, ultimtely ffeting yiel. Therefore, in this stuy, we ultivte rie using three ifferent nonflooe ultivtion methos n nlyze vrious photosyntheti prmeters. The ojetives of this stuy re (1) to hrterize photosynthesis, photoprotetion, n pttion mehnism of flg leves uring grin-filling uner long-term nonflooe irrigtion mngement n (2) to evlute the photosyntheti proution potentil uner ifferent ultivtion onitions. 2. Mterils n Methos 2.1. Plnt Mteril n Experiment Design. Fiel experiments using the rie (Oryz stiv L.) ultivr Ninggeng28 were onute in 2011 n 2012 t the Agriulturl Drought Reserh Tle 1: Soil hrteristis of the fiel experiments onute in Shihezi in 2011 n Vlues re the men ± stnr error (SE); the SE ws lulte ross five replites in oth yers n verge for the nonflooe irrigtion n onventionl flooing sites. Prmeter Cly (%) 23 ± ± 0.98 Silt (%) 38 ± ± 1.43 Sn (%) 43 ± ± 2.26 ph 7.51 ± ± 0.18 Olsen-P (mg kg 1 ) ± ± 1.33 Orgni mtter (mg kg 1 ) ± ± 1.11 Alkline-N (mg kg 1 ) ± ± 1.65 Aville potssium (mg kg 1 ) ± ± Soil sturtion volume moisture ontent (%) ± ± 0.25 Institute of the TinYe Group Compny ( N, E), Xinjing Provine, Chin. The verge temperture, evportion, n preipittion of the experimentl sites were C, mm, n mm, respetively, uring the rie growing seson (My to Otoer) in oth yers (Figures 1(), 1(), n1()). The vlue of photosynthetilly tive rition uring experimentl time (10:30 12:30) ws μmol photon m 2 s 1 in oth yers. The soil properties of the experimentl sites were similr n its hemil n physil properties liste in Tle 1. The nonflooe irrigtion tretments (,, n tretments) were sown y rtifiil hn iling t epth of 3 m on April 18 in 2011 n April 23 in 2012, n then irrigte t rte of 450 m 3 h 1 on the next y fter sowing to ensure norml germintion euse of the ry iretseee system use in this stuy. No further irrigtion ws supplie until the thir lef emerge. The three nonflooe irrigtion tretments were rrnge in ompletely rnomize esign with three replites (Figure 2()). The size of eh plot ws 5.5m 10 m. Wterproof memrnes were urie to epth of 60 m elow the soil surfe etween jent plots in the nonflooe irrigtion tretments to prevent wter exhnge. All plots were overe y plsti film efore sowing. Two rip tpes (emitter ishrge rte, 3.20 L h 1 ; emitter sping, 0.30 m) were li uner the plsti film for the tretment. Flexile hoses with 2 m imeter were lote on oth sies of the plsti film to supply wter in the n tretments (Figure 2()). In the n tretments, 20 m high ms were onstrute n overe with plsti film to minimize wter surfe runoff. Holes were opene on the memrne surfe whentheriewssown.theplntingensityws45.71 hills m 2 with m row-sping onfigurtion. The plnt sping within the hills ws 10 m (Figure 2). The plnting ensity were minly se on the results of preliminry stuy out iretly seee rie

3 The Sientifi Worl Journl Temperture ( C) Evportion (mm) My June July Aug. Sept. Ot. Month () My June July Aug. Sept. Ot. Month () Preipittion (mm) My June July Aug. Sept. Ot. Month () Figure 1: Averge temperture (), evportion (), n preipittion () uring the rie growing perio in Shihezi in 2011 n Eh tum point represents the men of month. uner rip irrigtion with full mehniztion in reent yers. Bsi seeling numers per hill were six plnts in oth yers. The wter regimes were pplie from the 3-lef stge to mturity. Forty to sixty millimeter of wter ws pplie when the soil wter potentil in the 0 20 m soil lyer of the nrrow rows (Figure 2()) roppe to 30 KP, s monitore y tensiometer (Wtermrk, Irrometer Compny, Riversie, CA). This soil wter potentil threshol ws estlishe se on the results of preliminry fiel investigtion in The soil wter potentil t the 20 m epth osionlly roppe to 40 KP uring the rie growing perio. To rete the re-soil tretment (i.e., the tretment), the plsti films were remove t the 3-lef stge. The hyrologil onitions uring the t quisition perio re shown in Figure 3. When the threshol vlues for supplementry irrigtion were rehe, supplementry irrigtion ws immeitely pplie. In prtiulr, plnts grown in nonflooe irrigtion tretments were irrigte fter quiring gs exhnge n hlorophyll fluoresene prmeters uring the t quisition perio. The CF ultivtion tretment ws set s CK; the plnting ensity of the CF tretment ws 40 hills m 2 (10 m 25 m) with five plnts per hill. The sees were sown on the nursery trys on the sme y when the nonflooe irrigtions were sown, n then twenty-one-yol seelings from the nursery trys were trnsplnte. A wter epth of 5 10 m ws ontinuously mintine in the CF tretment from trnsplnting to mturity. The sites of the CF tretment were out 150 m wy from the nonflooe

4 4 The Sientifi Worl Journl Min irrigtion line Plot with 54 m 2 Plots of ifferent irrigtion moels with ultivr Apply fertilizer pprtus Rie row Drip tpes Flexile hose Brnh irrigtion line Comintion of vlve n flow meter () Film with (160 m) Rie hill Plsti film Drip tpes Wie row sping (30 m) Nrrow row sping (10 m) Distne etween the two films (45 m) Wtermrk (instrument of monitoring soil wter potentil) () Figure 2: Experiment lyout () n sketh mp of plnting moe () uner nonflooe irrigtion tretments in Shihezi in oth yers. irrigtion plots n the soil physiohemil property ws onsistent with nonflooing irrigtion tretments in oth yers(theflooingtretmentwssetinthreesmllpoolsuilt in 2010, n the flooing plots were not previously tritionl py;thereoftheehsmllpoolwslsothesmewith the plot of nonflooing irrigtion tretments). Fertilizers pplie were 270 kg N per hetre s ure, 100 kg K 2 O per hetre s potssium hlorie, 90 kg P 2 O 5 per hetre s lium superphosphte, n 30 kg zin sulfte per hetre, of whih 10% N, ll K 2 O, ll P 2 O 5,nllZnwere pplie s sl fertilizer; the rest of N ws pplie in four splitpplitions:20%tthethreeleflesstge,35%t tillering, 35% t pnile initition, n 10% t flowering Mesurement of Dry Mtter Prenthesis (DMPrA), Dry Mtter Postnthesis (DMPA), Lef Are Inex t Flowering (LAI mx ), Mtter Trnslotion, n Grin Yiel. To mesure DMPrA, DMPA, n (LAI mx ) (green lef re t flowering), 0.50 m 2 plntsmplesweretkenfromehplottthe flowering perio (August 2 in 2011 n August 4 in 2012) n the mture stge (Septemer 13 in 2011 n Septemer 12 in 2012) in the two yers. The smples were seprte into stem, lef, n pnile when present. The lef re ws mesure with LI-3100 lef re meter (LI-COR In., Linoln, NE,USA). Then smples were rie in n oven t 75 Cfor72hntheweightsofstem,lef,npnilewere mesure. The ry mtter t the flowering perio ws efine

5 The Sientifi Worl Journl Dys fter nthesis () Dys fter nthesis () Soil wter potentil (kp) Soil wter potentil (kp) () () Figure 3: Soil wter potentil t 0 20 m soil lyer uner nonflooe irrigtion tretments from the 16th y fter nthesis to the 19th y fter nthesis in Shihezi in 2011 () n 2012 (). Vertil rs represent SE of the men; the SE ws lulte ross three replites for eh yer. s DMPrA. DMPA ws lulte s follows: ry mtter t mturity ry mtter t nthesis. Mtter trnslotion = ry weight of stems n sheths t nthesis ry weight of stems n sheths t mturity. The prmeter of mtter trnslotion ws mesure euse the stems n sheths re onsiere s importnt energy storge orgns n the mtter trnslotion rte will ffet grin yiel formtion [8, 9]. At mturity (Septemer 15, 2011 n Septemer 14, 2012), 8 m 2 plnts in eh plot were hrveste to lulte grin yiel. Grin weight is expresse t 14% moisture ontent Mesurement of Chlorophyll Content. Fresh flg lef tissue (0.1 g) ws extrte in 10 ml of 80% (v/v) etone uner rk n sele onitions for 48 h. The sorne (OD vlues) of the solution ws mesure with 722S visile spetrophotometer (Shnghi Thir instrument Ftory, Shnghi, Chin) t 647 nm n 664 nm. In se of highly elevte titers (optil ensity [OD] vlues > 0.8), the extrte solution ws further ilute in 80% (v/v) etone to give OD vlues of etween 0.1 n 0.8. The hlorophyll ontent ws lulte s esrie y Porr [23], s follows: Chl (mg L 1 )=[12.25 OD OD 647 ] ilution rtio. Chl (mg L 1 )=[20.31 OD OD 664 ] ilution rtio. Chl ( + ) (mg L 1 )=[17.76 OD OD 664 ] ilution rtio. Chl / = Chl /Chl. Finlly, Chl (mg g 1 FW) = Chl (mg L 1 ) 0.01 L/0.1 g FW (fresh weight) Mesurement of Totl Nitrogen Content (TNC) n Nitrogen Content per Lef Are (NLA) of Flg Leves. To mesure totl nitrogen ontent, flg leves were hrveste on the 16th y fter nthesis in The TNC of the rie tissues ws etermine using the miro-kjelhl metho [24]. The mount of nitrogen per lef re (NLA) ws lulte y iviing TNC y the speifi lef weight. The speifi lef weight of the flg lef ws efine s flg lef weight per unit re Mesurement of Root Ativity. The root tivity ws etermine on the 20th y fter nthesis in 2012 using the triphenyltetrzolium hlorie (TTC) metho [25]. Fresh n young roots from the 0 20 m soil lyer (whih ontine pprox. 85% of the root system; t not presente) were wshe n ut t 2 m from the root tips. Then, pproximtely 0.30 g fresh root tissue ws ple into test tue with 5 ml of 0.40% (w/v) TTC n 5 ml phosphte uffer (0.06 mol L 1,pH=7).Tueswereinutet37 Cin wterthfor3h,nthen2mlof1moll 1 sulfuri i ws e to eh tue to stop the retion. The roots were then pike out n groun in pestle with 3-4 ml of ethyl ette n little qurtz sn. The liqui phse ws remove into test tue n the pestle ws wshe 2-3 times with smll volume of ethyl ette. The sorne (OD vlues) of the extrtnts ws reore t 485 nm with 722S visile spetrophotometer (Shnghi Thir instrument Ftory, Shnghi, Chin).

6 6 The Sientifi Worl Journl Tle 2: Anlysis-of-vrine (F-vlues) for hlorophyll (Chl), net photosyntheti rte (P N ), stomtl onutne (g s ), interellulr CO 2 onentrtion (C i ), mximl quntum yiel of PSII photohemistry (F V /F m ), PSII mximum effiieny (F V /F m ), effetive quntum yiel of PSII photohemistry (Φ PSII ), n nonphotohemil quenhing (NPQ) etween/mong yers n tretments. Soure of vrition f DMPA Yiel Chl P N g s C i F V /F m F V /F m Φ PSII NPQ Cultivtion moe Yer ns 3.78 ns 2.27 ns 4.25 ns 0.03 ns 0.26 ns 2.28 ns 2.65 ns 0.89 ns 0.07 ns C Y ns 2.41 ns 1.05 ns 0.32 ns 0.57 ns 0.47 ns 2.94 ns ns 0.08 ns Signifine ifferene t P < Signifine ifferene t P < ns Nonsignifint ifferenes Mesurement of Net Photosyntheti Rte (P N ), Stomtl Conutne (g s ),InterellulrCO 2 Conentrtion (C i ),n Trnspirtion Rte (E). Five iniviul flg leves in vivo were smple n lele for eh plot to quire gs exhnge prmeters n hl fluoresene ross tretments n yers. Gs exhnge prmeters were mesure with photosynthesis system (Li-6400, LI-COR Biosienes, Linoln, NE, USA) t 10:30 12:30 h from the 16th y fter nthesis to the 19th y fter nthesis uner 1200 μmol photon m 2 s 1 light intensity. The light ws provie y re/lue LED light soure system in oth yers. The gs exhnge prmeters inluing P N (μmol m 2 s 1 ), g s (mol m 2 s 1 ), C i (μmol mol 1 ), n E (mmol m 2 s 1 )werequire.the tmospheri CO 2 onentrtion, ir temperture, n reltive ir humiity were μmol mol 1,26 28 C, n %, respetively, uring the t quisition perio of oth stuy yers Mesurement of Chlorophyll Fluoresene Anlysis. Chl fluoresene ws synhronously mesure with gs exhnge t 10:30 12:30 h y portle sturtion pulse fluorometer (PAM-2100, Wlz GmH, Effeltrih, Germny), equippe with 2030-B lef lip holer, whih n monitor PAR n lef temperture simultneously. The leves were ontinuously illuminte t 1200 μmol m 2 s 1 tini light with 5 minutes to mesure the stey-stte fluoresene yiel (F s ), then the mximl fluoresene level (F m ) in the lightpte leves were reore fter 0.80-s sturting pulse (8000 μmol m 2 s 1 ). Menwhile, mximl fluoresene yiel of rk-pte stte (F m ) n minimum fluoresene yiel of rk-pte stte (F o ) were mesure t prewn, eing lso with the lele flg leves (Note tht lef tempertures monitore y 2030-B lef lip holer were C t this time ross oth yers). F o ws etermine uner illumintion with fr-re light (<1 μmol m 2 s 1 ), n then 0.80-s sturting pulse (8000 μmol m 2 s 1 )wssupplie to etermine F m. The minimum fluoresene yiel in lightpte stte (F o ) ws lulte s F o = F o /[(F V /F m )+ (F o /F m )] [26]. The potentil mximum effiieny of PSII ws estimte s F V /F m = (F m F o )/F m.thepsiimximum effiieny ws estimte s F V /F m =(F m F o )/F m [27]. The tul PSII effiieny of PSII ws estimte s Φ PSII = (F m F s )/F m [27]. Nonphotohemil quenhing ws estimte s NPQ =(F m F m )/F m [28]. The photohemil quenhing oeffiient whih lso represents the frtion of open PSII retion enters ws estimte s q p = (F m F s )/(F m F o ) [29] Sttistil Anlysis. Dt were nlyze using the generlize liner moel (GLM) proeure (SPSS16.0, SPSS In., Chigo, USA). The effets of the vrious ftors inlue ultivtion moe, yer, n intertions of ultivtion moe yer were ssesse y nlysis of vrine. Mens were ompre y Fisher s lest-signifint-ifferene test t the 5% proility level. Also, two-tile t-test ws use to ompre with the ifferene of gs exhnge n hlorophyll fluoresene prmeters gs exhnge n etween 16th y fter nthesis n 19th y fter nthesis. 3. Results 3.1. Anlysis-of-Vrine of Tretments. As shown in Tle 2, the DMPA, grin yiel, Chl, P N, g s, C i, F V /F m, F V /F m, Φ PSII, n NPQ were ffete signifintly y the ifferent ultivtion moes (P < 0.001). However, there were no signifint ifferenes etween the two yers for ll prmeters (E, q P, n DMPrA not present). There ws signifint intertion effet etween the ultivtion moe n yer for F V /F m (P< 0.05), ut not for ny of the other prmeters. Therefore, t from two stuy yers were verge for further nlyses DMPrA, DMPA, LAI mx,mttertrnslotion,ngrin Yiel. In plnts grown uner nonflooe irrigtion, the DMPrA ws slightly higher n the DMPA ws signifintly lower thn tht of plnts in the CF tretment (P < 0.05; Tle 3). The tretment h the highest lef re inex t flowering stge, followe y the tretment, the tretment, n then the CF tretment (Tle 3). The mtter trnslotion ws in the orer of CF > > > tretments (Tle 3). As Tle 3 showe, the grin yiel ws out 8500 kg h 1 inthecftretmentnrngefrom 2100 kg h 1 to 5800 kg h 1 in the nonflooe irrigtion tretments. The grin yiel ws signifintly higher in the tretmentthninthentretments(p < 0.05; Tle 3) Chnges in Chlorophyll Content, Root Ativity, TNC, n NLA. The Chl ( + ) n Chl / vlues etermine on the 4 ys of mesurement (from the 16th y fter nthesis to the 19th y fter nthesis) were verge for the sme tretment, euse no signifint ifferenes were oserve mong the ifferent ys of the t quisition perio (t of nlysis-of-vrine not present). The results showe tht the Chl ( + ) onentrtion in the CF tretment (ontrol)

7 The Sientifi Worl Journl 7 Tle 3: The ry mtter prenthesis (DMPrA), ry mtter postnthesis (DMPA), mtter trnslotion, grin yiel, lef re inex t flowering stge (LAI mx ), root tivity, totl nitrogen ontent (TNC), n nitrogen ontent per lef re (NLA) of ultivr Ninggeng28 (Oryz stiv L.) uner ifferent tretments in Shihezi. DMPrA DMPA Mtter trnslotion Yiel Root tivity TNC NLA kg h 1 kg h 1 kg h 1 kg h 1 LAI mx μgg 1 FW h 1 μgg 1 μgm 2 CF ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.08 Vlues re the men ± SE; the SE ws lulte ross three replites for eh yer n verge for the 2 yers. Vlues within olumns followe y ifferent lowerse letters re signifintly ifferent t P < 0.05 oring to lest-signifint-ifferene test.

8 8 The Sientifi Worl Journl Chl ( + ) (mg g 1 FW) Chl / CF Tretment CF Tretment Chl (A + B) Chl A/B () () Figure 4: Chl ontent of ultivr Ninggeng28 (Oryz stiv L.) uner CF,,, n tretments t the grin-filling stge, respetively, in Shihezi. The CF inites onventionl flooing, n the,, n re plsti film mulhing with rip irrigtion, plsti film mulhing with furrow irrigtion, n no mulhing with furrow irrigtion, respetively. Vertil rs represent SE of the men; the SE ws lulte ross five replites for eh yer n verge for the 2 yers. Vlues of ifferent tretments followe y the sme letter inite no signifint ifferenes (P < 0.05) oring to lest-signifint-ifferene test. ws 5.01 mg g 1 FW, whih ws 53.10% higher thn in the tretment, 69.12% higher thn in the tretment, n 73.31% higher thn in the tretment (Figure 4()). No signifint ifferenes were oserve in Chl / mong the four tretments (P > 0.05; Figure 4()). At the grin-filling stge, the root tivity in the CF tretment ws the highest, whih ws signifintly inrese y 21.93% ompre with the tretment, y 38.39% ompre with the tretment, n y 50.64% ompre with the tretment (P < 0.05; Tle 3). The highest TNC n NLA vlues for the flg leves were in the CF tretment, followeythetretment,thenthetretment,n then the tretment. Signifint ifferenes in the TNC n NLA prmeters existe mong the four tretments (P < 0.05; Tle 3) Anlysis of Lef Gs Exhnge. Plnts in the tretment h higher P N thn i plnts in the n tretments from the 16th y fter nthesis to the 19th y fter nthesis. However, the P N of plnts in the,, n tretments ws lwys signifintly lower thn tht of plnts in the CF tretment uring the t quisition perio (Figure 5()). The P N in the CF tretment remine reltively stle from the 16th y fter nthesis to the 19th y fter nthesis (Figure 5()). In ontrst, plnts grown in the nonflooe irrigtion tretments showe eresing P N sthesoilwterpotentilerese,withminimump N vlues on the 18th y fter nthesis (Figure 5()), whih thesoilwterpotentilontheyreheitslowestvlues ross tretments n yers (from 28 KP to KP) (Figures 3() n 3()). After tht, the P N rose on the 19th y fter nthesis, when the soil wter potentil h rehe 3 n 5.40 KP s result of supplementry irrigtion in the n tretments, respetively. No signifint ifferene were oserve for the prmeter etween the 16th y fter nthesis n the 19th y fter nthesis in the n tretments, ut signifint ifferene existe in the tretment (two-tile t-test. For the tretment: f =5,t = 1.08, P = 0.31; for the tretment: f = 5, t = 1.38, P = 0.20; for the tretment: f = 5, t = 4.31, P = 0.01), initing tht the P N oul ompletely reover fter supplementry irrigtion in the n tretments. The trens in g s n E vlues were similr to those oserve for P N ross soil wter potentil n ultivtion moes. Their vlues were signifintly lower uner the nonflooe irrigtion tretments thn uner the CF tretment (P < 0.05). Menwhile, oth g s n E prmeters grully erese sthesoilwterpotentilereseuntilthe18thyfter nthesis in the nonflooe irrigtion tretments, n then reovere on the 19th y fter nthesis, fter supplementry irrigtion, in the n tretments ompre with the 16th y fter nthesis (two-tile t-test; P > 0.05 for the n tretments; P < 0.05 for the tretment. Dt of nlysis-of-vrine not present). The vrition in C i ws smll mong the ifferent tretments, ut higher C i vlues were oserve in the nonflooe irrigtion tretments thn in the CF tretment uring the entire mesurement perio (Figure 5()).

9 The Sientifi Worl Journl P N (μmol (CO 2 )m 2 s 1 ) E (mmol (H 2 O) m 2 s 1 ) 2 0 Dys fter nthesis () Dys fter nthesis () 0 CF CF () () g s (mol (H 2 O) m 2 s 1 ) C i (μmol (CO 2 )mol 1 ) Dys fter nthesis () Dys fer nthesis () 0 CF CF () () Figure 5: The P N (), E (), g s (), n C i () of ultivr Ninggeng28 (Oryz stiv L.)uner ifferent tretments from the 16th y fter nthesis to the 19th y fter nthesis in Shihezi. The CF inites onventionl flooing, n the,, n re plsti film mulhing with rip irrigtion, plsti film mulhing with furrow irrigtion, n no mulhing with furrow irrigtion, respetively. Vertil rs represent SE of the men, the SE ws lulte ross five replites for eh yer n verge for the 2 yers. Vlues of eh mesurement te followe y the sme letter inite no signifint ifferenes (P < 0.05) oring to lest-signifint-ifferene test.

10 10 The Sientifi Worl Journl 3.5. Anlysis of Chlorophyll Fluoresene. The vlues of F V /F m, F V /F m, q p,nφ PSII in the nonflooe irrigtion tretments were signifintly lower thn their respetive vlues in the CF tretment from the 16th y fter nthesis to the 19th y fter nthesis (P < 0.05; Figures6(), 6(), 6(e), n 6(f)). During the four ys, oth NPQ n Fo vlues in the nonflooe irrigtion tretments were signifintly higher thn in the CF tretment (P < 0.05; Figures 6() n 6()). For the CF tretment, ll fluoresene prmeters were reltively stle. However, for the nonflooe irrigtion tretments, vlues of the F V /F m, F V /F m, q p,nφ PSII erese with eresing soil wter potentil until the 18th y fter nthesis, n then ompletely reovere fter supplementry irrigtion on the 19th y fter nthesis in the n tretments. These results were supporte y two-tile t-test, whih showe no signifint ifferenes etween the 16th y fter nthesis n the 19th y fter nthesis in the n tretments (P > 0.05 inthentretments;p < 0.05 in the tretment. Dt of nlysis-of-vrine not present). Uner nonflooe irrigtion, F V /F m, F V /F m, q p,nφ PSII were lwys signifintly higher in the tretment thn in the n tretments uring t oservtion perio (P < 0.05; Figure 6). The F o n NPQ vlues were signifintly higher uner the nonflooe irrigtion tretments thn uner the CF tretment, n grully inrese s the wter potentil erese until the 18th y fter nthesis. Then, oth F o n NPQ vlues sustntilly erese on the 19th y fter nthesis euse of supplementry irrigtion (Figures 6() n 6()). 4. Disussion Dry mtter umultion is ritil ftor in grin yiel formtion. The ovegroun iomss efore nthesis my ontriute 20 40% to the finl rop yiel [30], n the rest of the mtter tht ontriute to grin yiel is erive from photosynthesis uring the grin-filling stge [8, 9]. In our stuy, there were no signifint ifferenes in the DMPrA mong tretments. However, the mtter trnslotion in the n tretments ws signifintly lower thn tht in the CF n tretments (P < 0.05; Tle 3). The low trnslotion effiieny my hve een insuffiient to hieve high grin yiel in the n tretments [9]. For thetretment,themttertrnslotionwsonlyslightly reue ompre with the CF tretment. Therefore, we infer thttheeresegrinyieloulminlyepenonthe photosyntheti pity uring the grin-filling stge in the tretment (Figure 5()) nlsoereltetothery mtter trnslotion effiieny t the prenthesis stge in the n tretments (Figure 5(); Tle 3). Moreover, signifintly higher popultion struture (LAI mx ) ws oserve in nonflooe irrigtion tretments thn in the CF tretment (P < 0.05; Tle 3). We n speulte tht the high LAI mx negtively ffete iomss umultion n yiel formtion uner nonflooe irrigtion. There re two min resons for this speultion: first, onsierle proportion of the rop ws invli tillers (nonproutive tillers), espeilly in the n tretments (t not shown). The umulte ssimiltes re rrely trnsferre from invli tillers to effetive pniles, n this lrge proportion of reunnt mtter n energy is gretly wste in poorly performing tillers. Thus, grin yiel formtion oul e limite y inequte mteril supply [31]. Seon, the onsumption of photosynthte woul inrese euse the respirtion rte of C 3 plnts inreses lmost proportionlly to the inrese in LAI [32]. Finlly, rop filure oul lso e relevnt to the poor popultion struture. The P N in the tretment ws signifintly lower thn tht in the CF tretment. This result ws supporte y previous stuies [7]. Plnts in the tretments with plsti mulh ( n tretments) showe lower P N thn those in the CF tretment, whih iffers from the result foun y Zhng et l. [7]. In the nonflooe irrigtion tretments, Chl ( + ) showe signifint elines ompre with the CF tretment (P < 0.05; Figure 4). Thus, low P N in grmineous ropssuhsmize(ze mys L.) n rie (Oryz stiv L.) is pprently ssoite with lower levels of quntity of pigments [33, 34]. Nitrogen plys n importnt role uring photosynthesis, sinetheproteinsoftheclvinylenthylkoisrepresent themjorityoflefnitrogen.photosynthesisofrieleves signifintly inreses with inresing nitrogen ontent of leves [35, 36]. Me [36] showe tht the mximum rte of CO 2 ssimiltionperunitlefre(mesureunerlightsturte, mient ir onition) ws lmost proportionl to thenla.therefore,thephotosynthetipityoflevesis losely relte to the nitrogen ontent [37]. In our stuies, thetncnnlainthecftretmentweresignifintly higher thn tht in the nonflooe irrigtion tretments (P < 0.05; Tle 3). The results suggest tht the unerlying reson whih limite photosyntheti pity ws minly the lower nitrogen ontent in the nonflooe irrigtion tretments, ompre with tht in the CF tretment. Although the performneoftheroottivityouleoneoftheimportnt resons tht restrite the sorption of nitrogen [38], it is still very neessry to onut the future experiment to fin out the sientifi soun reson for the low nitrogen ontent in the nonflooe irrigtion. Jones [39] suggeste tht the vlues of C i n P N n e useful riterion to etermine whether photosynthesis is limite y stomtl losure or metoli impirment. Compre with norml (ontrol) tretment, erese in P N longsie erese in C i inites stomtl limittion of photosynthesis, wheres if the P N ereses while C i inreses, then nonstomtl limittion (metoli impirment) of photosynthesis is preominnt [40]. Uner the nonflooe irrigtion tretments, the C i ws lso higher thn in the CF tretment uring the t quisition perio (Figure 5()), ut their P N vlues were signifintly lower thn those in the CF tretment (P < 0.05; Figure 5()). In ition, the g s vlues rnge from 0.12 to 0.23 mol m 2 s 1 uner the nonflooe irrigtion tretments, whih ws signifintly lower thn in the CF tretment (P < 0.05; Figure 5()). The low g s woul proly erese the levels of riulouse isphosphte, impir ATP synthesis, n even inhiit Ruio tivity [40], whih together woul inhiit P N.

11 The Sientifi Worl Journl 11 Fv/Fm Fo Dys fter nthesis () Dys fter nthesis () 0.0 () () 3.5 Fv /Fm NPQ 0.0 Dys fter nthesis () Dys fter nthesis () 0.0 () () Φ PSII q p 0.0 Dys fter nthesis () Dys fter nthesis () 0.0 CF CF (e) (f) Figure 6: The F V /F m (), Fo (), F V /F m (), NPQ (), Φ PSII (e), n q p (f) of ultivr Ninggeng28 (Oryz stiv L.) uner ifferent tretments from the 16th y fter nthesis to the 19th y fter nthesis in Shihezi. The CF inites onventionl flooing, n the,, n re plsti film mulhing with rip irrigtion, plsti film mulhing with furrow irrigtion, n no mulhing with furrow irrigtion, respetively. Vertil rs represent SE of the men; the SE ws lulte ross five replites for eh yer n verge for the 2 yers. Vlues of eh mesurement te followe y the sme letter inite no signifint ifferenes (P < 0.05) oring to lest-signifint-ifferene test.

12 12 The Sientifi Worl Journl Uner the nonflooe irrigtion tretments, oth P N n g s eline with soil wter potentil erese. The P N n g s lmost ompletely reovere fter supplementry irrigtion in the plsti mulhing tretments ( n tretments) ut not in the tretment (Figures 5() n 5()). This inite tht photoinhiition might not e permnent in the n tretments; tht is, it oul reover uring the grin-filling stge if the soil wter potentil remine etween 0 n 30 KP uring the entire growth perio. Moreover, the vlues of P N, g s,ne were higher uner the tretment thn uner the n tretments (Figures 5(), 5(), n 5()). The results show tht the tretment n signifintly improve rie photosyntheti performne uner nonflooe irrigtion. The use of hlorophyll fluoresene to monitor photosyntheti performne in plnts is now wiespre. Chl fluoresene is very sensitive tool to stuy the stressinue mge to photosystem 2 (PSII) [41]. The F V /F m vlueisfrequentlyusesninitorofstressesuseto PSII [18, 42]. Uner the nonflooe irrigtion tretments, the F V /F m vlues were signifintly lower thn tht in the CF tretment whih its vlue ws uring t quisition perio n fell shrply s the soil wter potentil reue from the 16th y fter nthesis to the 18th y fter nthesis (Figure6()). This result inite tht the rie rop oul e sujet to wter stress uring grinfilling stge. Also, inresing of F o vlue is usully onsiere s n importnt prmeter to estimte photoinhiition in mny plnts [19, 43]. Our results showe tht the F o shrply inrese when soil wter potentil roppe to 15 KP in the tretment, 20 KP in the tretment, n 36.50KPinthetretment,omprewiththtinthe CF tretment, n then reovere when soil wter potentil returne to 4.50 KP fter supplementry irrigtion for the n tretments (Figure 6()). These results imply tht nonflooe irrigtion ultivtion oul use rie to suffer from photoinhiition when the soil wter potentil rnges from 15 KP to KP. The plnts in the tretment were more tolernt to nonflooe irrigtion ultivtion prties n showe higher photosyntheti effiieny thn tht in n tretments. The Φ PSII reflets the effiieny of exittion energy pture y open retion enters of PSII. Two ftors ontriute to Φ PSII [27]: one eing the frtion of PSII enters in the open stte Q A (primry quinone eptor of PSII), for whih the quntittive vlue is equivlent to q p [18], n the other eing F V /F m [27]. Our stuies suggeste tht the ereses in Φ PSII uner nonflooe irrigtion were use y omintion of two proesses (Figures 6(), 6(e),n6(f)). Previous stuies inite tht erese in q p oul le to n inrese in the levels of toxi singlet oxygen form [44, 45]. Unfortuntely, we i not quntify retive oxygen speies (ROS) in the present stuy. Further reserh is require to etermine whether ROS re proue uner nonflooe onitions n to exmine their svenging mehnisms. In ition, the erese in F V /F m is onsiere to reflet protive n photoprotetive therml issiption proess in whih exess exittion energy is eplete efore it rehes the PSII enters [45]. Figure 6 shows tht the F V /F m vlues signifintly erese uner nonflooe irrigtion tretments n gretly erese s the soil wter potentil erese. These results inite tht therml issiption proesses were enhne efore exess energy rehe the PSII enters uner nonflooe irrigtion, espeilly when the soil wter potentilwslow,ninthetretment.inrief,uner nonflooe irrigtion tretments, totl therml issiption, inluing epletion of het y NPQ (Figure 6()) n y the proesses reflete y the F V /F m vlue (Figure 6()) pthwys, ws signifintly higher thn tht uner the CF tretment uring the whole oservtion perio. These pthwys oul e importnt photoprotetive mehnisms in rie plnts ultivte uner nonflooe irrigtion onitions. 5. Conlusions Uner nonflooe tretments, photosyntheti pity n grin-yielofrieplntsweresignifintlyereseompre with the CF tretment. Nonphotohemil quenhing (NPQ) plye n importnt role in proteting photosyntheti pprtus in flg lef of rie plnts ginst mge y nonflooe environments. To improve photosyntheti proutivity in nonflooe irrigtion, it oul e neessry to promote nitrogen ontent in flg lef. Also, the resons in regulting nitrogen metolism in flg lef re not ler in nonflooe irrigtion, n it nee to o follow-up stuies to fin out sientifi mehnisms. Arevitions llcf: Conventionl flooing Chl: Chlorophyll C i : InterellulrCO 2 onentrtion : Drip irrigtion with plsti mulhing DMPA: Dry mtter postnthesis DMPrA: Dry mtter prenthesis E: Trnspirtion rte : Furrow irrigtion with plsti mulhing : Furrow irrigtion with no mulhing F m : Mximl fluoresene yiel of rk-pte stte F m : Mximl fluoresene yiel of light-pte stte F o : Minimum fluoresene yiel of rk-pte stte F o : Miniml fluoresene yiel of light-pte stte F s : Stey-stte fluoresene yiel F V /F m : Mximl quntum yiel of PSII photohemistry F V /F m : PSII mximum effiieny FW: Fresh weight g s : Stomtlonutne LAI mx : Lef re inex t flowering stge NLA: Nitrogen ontent per lef re NPQ: Non-photohemil quenhing P N : Net photosyntheti rte

13 The Sientifi Worl Journl 13 q P : Photohemil quenhing oeffiient Φ PSII :EffetivequntumyielofPSII photohemistry SE: Stnr error TNC: Totl nitrogen ontent TTC: Triphenyltetrzolium hlorie. Conflit of Interests The uthors elre tht there is no onflit of interests regring the pulition of this pper. Aknowlegments The uthors thnk the Agriulturl Drought Reserh Institute of TinYe Group Compny for proviing the experimentl site. They re grteful for Grnts from The Ntionl High Tehnology Reserh n Development Progrm of Chin (2011AA100508). Referenes [1] G. S. 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