Comprison of the effets of symmetri n symmetri temperture elevtion n CO 2 enrihment on yiel n evpotrnspirtion of winter whet (Tritium estivum L.) Yunzhou Qio 1, Huiling Liu 2, Seppo Kellom ki 3, Heli Peltol 3, Yueyn Liu 1, Boi Dong 1, Chnghi Shi 1, Huizhen Zhng 4, Cho Zhng 3,5, Jinnn Gong 3, Fuyn Si 1, Dongxio Li 1, Xin Zheng 1 & Mengyu Liu 1 1 Key Lortory of Agriulturl Wter Resoures & Heei Key Lortory of Agriulturl Wter-Sving, Center for Agriulturl Resoures Reserh, Institute of Genetis n Developmentl Biology, Chinese Aemy of Sienes, 286 Huizhong Ro, Shijizhung 521, Chin 2 Shijizhung Center for Agriulturl Prout Qulity inspetion, Shijizhung 521, Chin 3 University of Estern Finln, Shool of forest Sienes, Joensuu, Yliopistoktu 7, Borelis Builing, Box 111, Fin- 811 Joensuu, Finln 4 Lirry of Shijizhung University, Shijizhung 535, Chin 5 Key Lortory of Geogrphi Informtion Siene, Ministry of Eution, Est Chin Norml University, Shnghi 2241, Chin Keywors Aovegroun iomss, grin yiel, root iomss, soil wter epletion, yiel omponents. Corresponene Mengyu Liu, Center for Agriulturl Resoures Reserh, Institute of Genetis n Developmentl Biology, Chinese Aemy of Sienes, 286 Huizhong Ro, Shijizhung 521, Chin. Tel: +86 311 85871562; Fx: +86 311 8581593; E-mil: mengyuliu@sjzim..n Funing Informtion The stuy ws jointly supporte y the key projet of Ntionl Siene & Tehnology Pillr Progrm of Chin (212BAD8B2, 213BAD5B2), the Ntionl Nturl Siene Fountion of Chin (3117415; 311191; 387411) n Heei Provine (C211533; C212533), the Knowlege Innovtion Progrm of the Chinese Aemy of Sienes (KSCX2-EW-Q- 25). The support of the Shool of Forest Sienes, University of Estern Finln, Finln, n the support of Lunheng Agro- Eo Experimentl Sttion of the Chinese Aemy of Sienes for this stuy re knowlege. Astrt Uner the hnging limte, symmetri wrming pttern woul e more likely uring y n night time, inste of symmetri one. Conurrently, the growth responses n wter use of plnts my e ifferent ompre with those estimte se on symmetri wrming. In this work, it ws ompre with the effets of symmetri (ETs) n symmetri (ET) elevtion of temperture lone, n in intertion with elevte ron ioxie onentrtion (), on the grin yiel (GY) n evpotrnspirtion in winter whet (Tritium estivum L.) se on pot experiment in the North Chin Plin (NCP). The experiment ws rrie out in six enlose-top hmers with following limte tretments: (1) mient temperture n mient CO 2 (CON), (2) mient temperture n elevte CO 2 (), (3) elevte temperture n mient CO 2 (ETs; ET), n (4) elevte temperture n elevte CO 2 (ETs, ET). In symmetri wrming, temperture ws inrese y 3 C n in symmetri one y 3.5 C uring night n 2.5 C uring ytime, respetively. As result, GY ws in ET n ETs 15.6 (P <.5) n 1.3% (P <.5) lower thn tht in CON. In ETs n ET tretments, GY ws 14.9 (P <.5) n 9.1% (P <.5) higher thn tht in CON. Opposite to GY, evpotrnspirtion ws 7.8 (P <.5) n 17.9% (P <.5) higher in ET n ETs tretments n 7.2 (P <.5) n 2.1% (P >.5) lower in ETs n ET tretments ompre with CON. Thus, GY of whet oul e expete to inrese uner the hnging limte with onurrent elevtion of CO 2 n temperture s result of inrese WUE uner the elevte CO 2. However, the gin woul e lower uner ET thn tht estimte se on ETs ue to higher evpotrnspirtion. Reeive: 27 Otoer 213; Revise: 1 Mrh 214; Aepte: 3 Mrh 214 Eology n Evolution 214; 4(1): 1994 23 oi: 1.12/ee3.181 1994 ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt. This is n open ess rtile uner the terms of the Cretive Commons Attriution Liense, whih permits use, istriution n reproution in ny meium, provie the originl work is properly ite.
Y. Qio et l. Whet uner Elevte CO 2 & Asymmetri Wrming Introution Atmospheri CO 2 onentrtion hs inrese from 28 lmolmol 1 prior to the inustril revolution to 379 lmolmol 1 until 25 n my reh 7 lmolmol 1 y the en of the 21st entury (IPCC 27). Suh n inrese in CO 2 onentrtion might trigger rise in glol temperture y 1.4 5.8 C (IPCC 21). As result, growth of ifferent plnts will inevitly e ffete euse previling temperture n tmospheri CO 2 onentrtion together with wter vilility ffet the physiologil proesses of plnts (i.e., photosynthesis, respirtion, n trnspirtion, Aou-Hussein 212). Any negtive impts of foreseen limti hnge might ffet lso the vilility n qulity of foo rops suh s winter whet (Tritium estivum L.), whih is one of the most importnt foo rops not only in the North Chin Plin (NCP) ut lso elsewhere roun the worl. Bse on previous stuies, the elevtion of CO 2 lone hs een expete to inrese signifintly the grin yiel n the wter use effiieny in whet (Kimll n Iso 1983; Morison 1985; Drke et l. 1997; Amthor 21; Polley 22; Guo et l. 21; Qio et l. 21). This ws relte to the inrese in photosynthesis n erese in trnspirtion ue to reue stomtl perture (Kimll n Iso 1983). The onurrent elevtion of CO 2 hs lso een suggeste to t lest prtly ompenste the negtive effets of elevte temperture (Lwlor n Keys 1993; Ll et l. 1998, 1999; Chllinor n Wheeler 28). However, the most previous stuies in winter whet hve ssume equl elevtion of temperture uring ytime n nighttime (Peng et l. 24; Loell 27; Fng et l. 212). This ws espite the meteorologil oservtions n moel-se preitions sine 199s whih suggeste symmetri temperture inrese (ET), tht is, the inrese will e higher in nighttime thn in ytime (Krl et l. 1993; IPCC 21, 27). For exmple, in Chin, the men ily minimum temperture (night time) hs inrese 2 3 times more thn the mximum temperture (y time) uring the pst five ees (Ren et l. 25; Tn et l. 29). Growth responses to the symmetri inrese in minimum n mximum iurnl temperture hve een so fr stuie minly y using rop moeling, n prtiulrly in foo rops suh s rie (Oryz stiv L., Peng et l. 24; Loell 27; Mohmme n Trpley 29; Dong et l. 211; Zhng et l. 213), mize (Ze mys L., Dhkhw n Cmpell 1998), n soyen (Glyine mx (L.) Merr., Dhkhw n Cmpell 1998). To te, only few stuies hve resse the response of whet to higher night wrming without ytime wrming (Rosenzweig n Tuiello 1996; Dhkhw n Cmpell 1998; Loell 27; Loell n Ortiz-Monsterio 27; Prs et l. 28; Fng et l. 212). In generl, the physiologil n eologil tivities of prime importne for yiel n wter use of rops (i.e., photosynthesis, respirtion, n trnspirtion) ourre minly uring ytime exluing respirtion in night (Xi et l. 29). Higher elevtion of temperture uring nighttime might inrese respirtion losses of photossimiltes (Aou-Hussein 212) n erese rop yiel ompre with symmetri wrming in ytime n nighttime (Loell et l. 211). However, it ws still unler how symmetri n symmetri wrming in omintion with elevte CO 2 might ffet the yiel n wter use of winter whet. In the ove ontext, the im of this work ws to ompre the effets of symmetri n symmetri elevtion of temperture lone n in intertion with elevte CO 2 onentrtion, on the grin yiel n evpotrnspirtion in winter whet (Tritium estivum L.) in the North Chin Plin (NCP). It ws hypothesize tht the grin yiel of winter whet oul inrese less in the future uner the onurrent elevtion of CO 2 n symmetri elevtion of temperture thn tht with symmetri wrming. Mterils n Methos Climte tretments n plnt mteril Climte tretments The stuy ws onute t the Lunheng Agro-Eo Experimentl Sttion, Chinese Aemy of Sienes (37.53 N, 114.41 E; ltitue 5.1 m.s.l), in the North Chin Plin (NCP). The long-term mens of nnul temperture n preipittion uring the pst 3 yers were 12.2 C n 53 mm, respetively. To stuy the effets of symmetri (ETs) n symmetri (ET) elevtion of temperture lone n in intertion with elevte CO 2 onentrtion, on the grin yiel n evpotrnspirtion in winter whet, Six enlose-top hmers were rnomly ssigne to mient (AC: 396.1 29.2 lmolmol 1 ) or elevte (: 76.1 36.1 lmolmol 1 )CO 2 onentrtion in omintion with three temperture regimes (Amient temperture; ETs - symmetri elevtion of 3 C; ET - symmetri elevtion of 3 C, i.e. +3.5 C uring night, +2.5 C uring ytime). As result, we h following limte tretments: mient onitions (CON), symmetrilly elevte temperture (ETs), symmetrilly elevte temperture (ET), elevte CO 2 (), elevte CO 2 n symmetrilly elevte temperture (ETs), elevte CO 2, n symmetrilly elevte temperture (ET). For this work, winter whet (T. estivum L. v. Jimi22) ws sown t the experimentl sttion roun the ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt. 1995
Whet uner Elevte CO 2 & Asymmetri Wrming Y. Qio et l. hmers on 1 Otoer 21. Eighteen plnts of uniform size n with three tillers were selete n trnsplnte on 2 Mrh 211 to 6 stinless steel pots (imeter = 28 m, epth = 3 m), fter their roots were prune to similr size (plnts hs rehe the turning green stge). The 6 pots were rnomly ssigne to the six hmers (n = 1 pots per hmer). Six pots in eh hmer were smple regulrly every 5 y, n the remining four pots were left for finl hrvest n etermintion of wter use. Eh pot ws fille with 2 kg fom soil from the experimentl sttion n sturte with wter fter trnsplnting. The soil ws sieve (four mesh) n mixe homogeneously with N fertilizers (1.5 g ure). The totl N n ville N, P, n K ontents were 93 mgg 1, 77.49 mgkg 1, 47.6 mgkg 1, n 35.8 mgkg 1, respetively. Eh pot ws top-resse with 1.5 g ure t the jointing stge. All pots were weighe n irrigte every 3 y to mintin soil wter ontent etween 6% n 7% of fiel wter pity. Chmer esign n performne Chmer esign The hmer systems onsiste of two prts, frme n ontrolling system, ontining CO 2 n temperture ontrols system (Fig. 1). The frme ws me of luminum lloy with 3-mm-thik glss wlls. The groun re ws 9 m 2 (3 m 9 3 m) n the height ws 2.5 m, resulting in interior hmer volume of 22.5 m 3. A tringulr prism top (3 m 9 3m9.5 m) me of 3-mm-thik glss ws ple ove the hmer frme. One eletroni fn (E-fn I in Fig. 1) ws tthe to eh en (est en n west sies) of the prism (fing the insie to ring ooler ir into the hmer from outsie). An itionl fn (E-fn II in Fig. 1) ws tthe to the top of eh hmer fing the groun surfe (rops) to mix ir within the hmer. A CO 2 trnsmitter (BS3II; Hnwei Corportion, Zhengzhou, Chin), temperture trnsmitter (WB21; Qinming Corportion, Boji, Chin), n light n humiity sensor (Hoo U122; Onset Corportion, Cpe Ko, MA) were fixe oth t the enter of eh hmer n outsie the hmer. The height of the sensors n trnsmitters were move s the rops grew to oserve n ontrol the orresponing environmentl prmeters t the nopy. The CO 2 onentrtion insie the CO 2 -enrihe hmer ws ontinuously monitore n ontrolle y CO 2 ontrol system, whih onsiste of CO 2 gs ontiners, eletromgneti vlves, ir-mixing oxes, n CO 2 trnsmitters (Fig. 1). The CO 2 onentrtion insie the hmer ws sense, n the informtion trnsferre to PLC moule (XHS CS1; Chin), where it ws ompre with the trget CO 2 onentrtion (78 2 lmolmol 1 ). When the onentrtion ws lower thn 77 lmolmol 1, the mgneti vlve woul turn on n pure CO 2 gs woul e injete into 1-m 3 wooen ox. After eing mixe with ir, the CO 2 gs ws ilute to pproximtely 3 lmolmol 1 n then injete into the CO 2 - enrihe hmers y n ir lower through n ir intke pipe. The ir intke pipe ws fixe long the four sies of the glss wll 1.5 m ove the groun surfe n ws perforte with 4-mm-imeter holes every 2 m. With the CO 2 onentrtion pprohe 79 lmolmol 1, the ir lower slowe n the mgneti vlve ws shut off y the PLC moule. The CO 2 onentrtion in hmers expose to mient CO 2 (AC) ws not ontrolle..5 m E-fn I Glss.5 m Glss E-fn E-fnIIII Air intke pipe CO2 trnsmittesmitter Tem trn- PPFD RH Proe Proe Air mixing Air ox Blower Mgneti vlve CO2 gs 1.5 m Heter & ooler Temperture, CO2, RH, PPFD.5 m Door Glss Automti winow Glss PLC Moule 1 m 1 m 1 m Figure 1. Sie view n min omponents of the enlose-top hmer pplie in the present stuy. E-fn I re two eletroni fns tht re fixe on the est n west top wlls to ring the out ooler ir in when the temperture in hmers is out of ontrolling pity of freezers. The utomti winow will e opene n lose together with E-fn I eing turne on or off for the sme purpose. E-fn II is the eletroni fn tht is fixe on the top fing groun to mix ir in the hmers. The ir intke pipe, extening long the four wlls (totlly 12 m), is 2 m ove the groun n otte with holes every 2 m. 1996 ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt.
Y. Qio et l. Whet uner Elevte CO 2 & Asymmetri Wrming The temperture ontrol system (Fig. 1) onsiste of heter, ompressor (freezer), temperture trnsmitter, n uxiliry justing equipment (utomti winow n fixe fns). When the temperture trnsmitter sense hmer temperture tht ws higher or lower thn the preset trget temperture, the PLC moule woul signl to trigger the ompressor or eletroni heter to ool or wrm the ir in the hmers. The ooling n wrming ir entere the hmer through the sme pipe s the CO 2 gs (Fig. 1). We progrmme the PLC moule to open the utomti winow (to let in ool ir) n turn on the eletroni fn (to let out wrm ir) when the hmer temperture ws 1 C higher thn the trget temperture. Chmer performne The trget CO 2 enrihment of 78 lmolmol 1 n temperture elevtion were simulte well y the hmer systems (Fig. 2A n B). The ily verge CO 2 onentrtion oserve ws 76.1 36.1 lmolmol 1 in CO 2 -enrihe hmers (Fig. 2A). The orresponing CO 2 onentrtion in AC hmers ws 396.1 29.2 lmolmol 1 (Fig. 2A). The verge temperture of CON, ETs, n ET were 25.5 6.4 C, 28.5 6.4 C, n 28.5 6. C on 1 My 211, respetively (Fig. 2B). The verge temperture in ETs n ET hmer were 2.93.14 C n 2.95.53 C higher thn CON. The temperture of ET is 3.45.13 C n 2.46.14 C higher thn tht of CON in nighttime n ytime, respetively (Fig. 2B). Atmospheri reltive humiity (RH) n light intensity (espeilly the photosyntheti tive rition, PAR) were lso followe, euse they were losely relte to lef trnspirtion n photosyntheti rte. The RH of AC n tretment were 79.3 15.8% n 77.4 15.3%, respetively (Fig. 2C). The RH of AT, ETs, n ET tretment were similr to eh other (Fig. 2D). On sunny ys, the totl PAR insie eh hmer ws out 15% less thn tht outsie the hmer. In ition, light vilility ws reue in hmers ompre with outsie onitions espeilly in erly morning, lte fternoon, n louy ys when light intensity ws rther low. Regring the temperture ontrol, the rop own of the insie temperture through exhnging with outsie ooler tmosphere helpe to mintin the temperture roun the trget temperture when the sun light is too strong in reltion to the ooling n the freezing pity (Fig. 1). The RH ws lso similr etween the hmers with ifferent CO 2 onentrtions n ifferent tempertures (Fig. 2C n D). As the vpor pressure woul inrese with temperture elevtion n the sturte wter vpor pressure will inrese more thn the virtul vpor pressure, the RH woul e erese n the vpor pressure efiit (VPD) etween lef n ir woul e higher thn tht in the hmers with mient temperture. The ventiltion system helpe to keep similr RH etween hmers with ifferent tempertures. Mesurements Grin yiel n iomss Four pots in eh hmer were hrveste mnully t mturity (9 June 212). All 18 plnts from eh pot were use to etermine the men numer of spike numer per CO 2 onentrtion (μmol mol 1 ) Reltive humiity (%) 1 8 6 4 2 95 8 AC 65 AC (C) 5 : 4: 8: 12: 16: 2: Time Temperture (ºC) Reltive humiity (%) 4 3 2 1 95 8 AT ETs-AT ET-AT 65 AT ETs ET (D) 5 : 4: 8: 12: 16: 2: Time 4 3.5 3 2.5 2 1.5 1.5 Temperture ifferene (ºC) Figure 2. The CO 2 onentrtion, temperture, n temperture ifferene n the reltive humiity etween CO 2 (C) n temperture (D) tretment in the enlose-top hmers. Dt shown re reore every 1 min on 1 My 211. ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt. 1997
Whet uner Elevte CO 2 & Asymmetri Wrming Y. Qio et l. unit re of groun, kernels per spike, kernel weight, n hrvest inex (HI). Spikes were ounte efore hrvesting. Eonomi yiels n totl ovegroun iomss were etermine fter ir-rying to onstnt weight. HI ws the rtio of GY to totl ovegroun iomss. Roots hrteristis All roots in eh pot were smple to etermine root iomss n length, root length ensity (RLD), n root/ shoot rtio (RSR). After removing soil n orgni eris, root length ws mesure oring to Tennnt (1975). Roots were then oven-rie t 6 C to etermine ry weight. RLD ws lulte s root length per liter of soil. The root/shoot rtio ws lulte s the rtio of root iomss to ovegroun iomss. Soil moisture monitoring Soil volumetri wter ontents of the pots for hrvesting (n = 4 per tretment) ws mesure hourly using n FDR proe ple t mi epth in enter of eh pot n reore y t logger (RHD-5; Ruihu Eletronis Corportion, Hnn, Chin) uring the growing seson. Dt nlyses Evpotrnspirtion of the entire growing seson ws lulte using the wter lne eqution revite from Allen et l. (1998): Evpotrnspirtion ¼ SWD þ P þ I D þ CR R (1) where SWD ws soil wter epletion (initil soil wter ontent minus finl soil wter ontent), P ws preipittion, I ws irrigtion, D ws ringe from the root zone, CR ws pillry rise to the root zone, n R ws runoff. Eqution (1) ws simplifie to eqution (2) y zeroing P, D, CR, n R, euse this ws n enlose-top hmer experiment with pot ultivtion: Evpotrnspirtion ¼ SWD þ I (2) WUE ws then lulte from the formul: WUE ¼ GY=Evpotrnspirtion (3) The hourly SWD ws lulte s the hourly erese of soil moisture, tht is, soil moisture t t = n o lok minus soil moisture t t = n + 1 o lok. Two sttistil nlyzing methos were pplie. First, two-wy ANOVA (SPSS version 11.5, SPSS, In., Chigo, IL) ws pplie to test the lone n intertive effets of CO 2 onentrtion * ETs n CO 2 onentrtion * ET on grin yiel, ovegroun iomss, root hrteristis, evpotrnspirtion, n wter use effiieny. In this ontext, the effets of symmetri n symmetri temperture elevtion were onsiere seprtely. The t nlyses followe pseuo-replite esign (Ceulemns et l. 22), in whih eh pot ws onsiere s n iniviul replite (thus, four replites). Seonly, one-wy ANO- VA ws pplie to test the ifferene of ll the investigte trits etween CON,, ETs, ET, ETs, ET. Results Grin yiel n yiel omponents Both symmetri (ETs) n symmetri elevtion (ET) of temperture reue GY ompre with mient onitions (CON), s result of signifint erese in grin numer (P <.5, Fig. 3A n C). Asymmetri wrming reue the GY more thn the symmetri wrming i. Elevtion in CO 2 lone () inrese GY the most ompre with CON (Fig. 3A) followe y onurrent elevtion of CO 2 n symmetri wrming (ETs) n onurrent elevtion of symmetri wrming (ET). The grin numer ws more sensitive to the elevtion of temperture n/or CO 2 thn thousn grin weight (Fig. 3C n D). Spike numer ws not ffete y limte tretments (P >.5, Fig. 3B), euse the tiller numer ws lrey forme when hmer experiment strte. Aovegroun iomss n hrvest inex (HI) Totl ovegroun iomss ws lso remrkly erese uner ETs n Et ompre to CON, ut less thn tht of grin yiel (Fig. 4A). Asymmetri wrming erese ovegroun iomss more thn symmetri wrming i. Elevte CO 2 lone inrese ovegroun iomss the most ompre with CON, followe y ETs n ET. Hrvest inex ws not sttistilly ffete y ny of limte tretments (Fig. 4B). Root iomss, root length ensity (RLD), n root/shoot rtio (RSR) Both symmetri n symmetri wrming reue root iomss on verge y 15.6% (P <.5) n RLD y 22.3% (P <.5) ompre with CON (Fig. 5A n B). Elevtion of CO 2 lone inrese the root iomss more thn RLD. However, root iomss inrese lso in ET n ETs ompre with CON, opposite to RLD. Both symmetri n symmetri elevtion of temperture (lone) erese RSR ompre with CON, wheres elevtion of CO 2 (lone) inrese it (Fig. 5C) s i ETs n ET. 1998 ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt.
Y. Qio et l. Whet uner Elevte CO 2 & Asymmetri Wrming Grin yiel (g m 2 ) 4 3 2 1 e e 4 35 3 25 Spike numer Grin numer 25 2 15 1 5 (C) e (D) 2 45 35 25 Grin weight (g) CON ET ETs ET ETs Tretments 15 CON ET ETs ET ETs Tretments Figure 3. The grin yiel, spike numer, grin numer (C), n grin weight (D) s ffete y elevte CO 2 onentrtion (, 76 lmolmol 1 ) in omintion with symmetri (ETs: eqully +3 C in ytime n nighttime) n symmetri (ET: +3.5 C uring night n +2.5 C uring ytime) wrming. Different letters inite sttistil ifferene t P <.5. Aove groun iomss (g m 2 ) 7 6 5 4 3 CON ET ETs ET ETs Tretments.6.5.4.3.2 CON ET ETs ET ETs Tretments Hrvest inex Figure 4. The totl ovegroun iomss n hrvest inex s ffete y elevte CO 2 onentrtion (, 76 lmolmol 1 ) in omintion with symmetri (ETs: eqully +3 C in ytime n nighttime) n symmetri (ET: +3.5 C uring night n +2.5 C uring ytime) wrming. Different letters inite sttistil ifferene t P <.5. Evpotrnspirtion n WUE Both symmetri n symmetri wrming inrese evpotrnspirtion (Fig. 6A). Wter uptke ws higher uner ETs thn uner ET. Elevtion of CO 2 (lone) erese wter onsumption remrkly. Uner onurrent elevtion of CO 2 n symmetri wrming, evpotrnspirtion erese signifintly ompre with CON (P <.5), Unlike in ETs (P >.5). The hourly soil wter epletion (SWD, Fig. 7A n B) rte egn to inrese t 9 AM, h the mxim t 1 PM n egn to erese until 8 PM. Therefter, the SWD rte onve negtive, implying tht soil wter ws eing rehrge through pillry from eeper soils. erese evpotrnspirtion primrily uring the ytime, from 1 AM to 5 PM (Fig. 7A). Soil wter in tretments ws replenishe overnight (from 9 PM to 8 AM) through pillrity, t lower rte thn in mient CO 2 tretments. ETs n ET oth use higher SWD uring the ytime, ut ifferenes still existe etween them (Fig. 7B). Both ETs n ET minly inrese SWD from 12 AM to 6 PM, while ETs lso resulte in higher SWD thn ET from 1 PM to 4 PM. The ifferene in soil wter loss n lso e expline y pillry rehrge (Fig. 7B). ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt. 1999
Whet uner Elevte CO 2 & Asymmetri Wrming Y. Qio et l. 12 9 6 3 Root iomss (g m 2 ) CON ET ETs ET ETs Tretments 4 32 24 16 8 Root length ensity (m l 1 ) CON ET ETs ET ETs Tretments (C).2.15.1.5. Root/shoot rtio CON ET ETs ET ETs Tretments Figure 5. The root iomss, root length ensity, n root/shoot rtio (C) s ffete y elevte CO 2 onentrtion (, 76 lmolmol 1 ) in omintion with symmetri (ETs: eqully +3 C in ytime n nighttime) n symmetri (ET: +3.5 C uring night n +2.5 C uring ytime) wrming. Different letters inite sttistil ifferene t P <.5. Evpotrnspirtion (kg m 2 ) 26 22 18 14 1 e. CON ET ETs ET ETs CON ET ETs ET ETs Tretments Tretments 2.5 2. 1.5 1..5 Wter use effiieny (g kg m 2 ) Figure 6. The evpotrnspirtion n wter use effiieny s ffete y elevte CO 2 onentrtion (, 76 lmolmol 1 ) in omintion with symmetri (ETs: eqully +3 C in ytime n nighttime) n symmetri (ET: +3.5 C uring night n +2.5 C uring ytime) wrming. Different letters inite sttistil ifferene t P <.5. SWD (v% h 1 ) 1.2.8.4.4 AC ETs ET AT 1.2.8.4.4 SWD (v% h 1 ).8.8 9: 11: 13: 15: 17: 19: 21: 23: 1: 3: 5: 7: 9: 11: 13: 15: 17: 19: 21: 23: 1: 3: 5: 7: 212-5-17 212-5-18 212-5-17 212-5-18 Dte n time Dte n time Figure 7. The hourly soil wter epletion s ffete y elevte CO 2 onentrtion (, 76 lmolmol 1 ) n symmetri (ETs: eqully +3 C in ytime n nighttime) versus symmetri (ET: +3.5 C uring night n +2.5 C uring ytime) wrming. AC - mient CO 2, AT, mient temperture. WUE ws reue y ETs n ET ompre with CON, opposite not only to elevtion of CO 2 lone ut lso to onurrent elevtion of CO 2 n symmetri or symmetri elevtion of temperture (Fig. 6B). The two wrming ptterns h similr effet on WUE ut ue to ifferent response egree of GY n evpotrnspirtion. On verge, 21.8% (P <.5) erese oserve in WUE y ET ompre to CON ws ue to 15.6% (P <.5) 2 ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt.
Y. Qio et l. Whet uner Elevte CO 2 & Asymmetri Wrming erese in GY n 7.8% (P <.5) inrese in evpotrnspirtion. The ounter prt for ETs oul e ttriute to the 1.3% (P <.5) erese in GY n 17.9% (P <.5) inrese in evpotrnspirtion. Disussion n Conlusions Our results inite tht symmetri wrming (lone) with slightly higher wrming in nighttime ompre with ytime erese GY n totl ovegroun iomss more thn the symmetri wrming i. This ws lso oserve y Loell et l. (211). This result might e expline y the inrese in respirtion loss of photossimiltes ue to higher night wrming (Aou-Hussein 212). On the ontrry to GY, in our work, evpotrnspirtion inrese uner elevte temperture. In generl, uner wrmer limte, lrger shre of wter from the preipittion n irrigtion woul e trnspire into vpor efore entering soil (Hou et l. 212). Furthermore, the trnspirtion woul inrese to ool leves (Aou-Hussein 212). In this work, evpotrnspirtion inrese more uner symmetri wrming onitions thn uner symmetri wrming, ompre with CON. In some previous stuies, no evportive loss hs een expete to our uring night (Peterson et l. 1995; Toiso n Vergni 28 Lovelli et l. 21). Thus, in priniple, higher inrese in ytime temperture oul e expete to inrese wter onsumption. In generl, smll inrese in temperture oul stimulte sustntilly rop yiel when the previling temperture is elow the optim for photosynthesis. The onverse is true when temperture ws ner or higher thn the optim (Bker n Allen 1993; Polley 22; Ortiz et l. 28; Aou-Hussein 212). The onurrent elevtion of CO 2 with symmetri or symmetri wrming n prtly ompenste the negtive effet of elevte temperture on rop yiel n wter use (Luwig n Asseng 26; Krishnn et l. 27). In this work, oth in ETs n in ET, yiel of whet inrese n wter onsumption (n evpotrnspirtion) erese, ompre with CON, or ETs n ET lone. The whet yiel is epenent on er numer (per unit groun re), grin numer per er, n iniviul grin mss (usully esrie y 1-grin weight). Aoring to Amthor (21), er numer is the yiel omponent whih ws onsistently promote y elevte CO 2. Our results of grin numer n thousn grin weight were well in line with finings reporte y Amthor (21). Er numer ws usully evelope efore wintering stge. When initite efore the jointing stge, CO 2 fumigtion hs shown ler effets on spike numer (see mny exmples in Amthor 21). In the present experiment, tiller numer ws not ffete y elevte CO 2 n wrming ptterns, whih might e ttriute to strting tretments fter the plnts turne green. The ontinuous hourly etetion n reoring of soil moisture provie n opportunity to exmine hourly wter use of whet rops, SWD n soil moisture ynmis. The elevte CO 2 reue SWD from 1 AM to 5 PM (Fig. 7A n B). In ft, most of the plnt physiologil tivities were ffete y CO 2 onentrtion only uring this time, euse light intensity is the riving energeti resoure for lef ron ssimiltion. Also Gri et l. (1998) reporte tht elevtion of CO 2 onentrtion to 55 lmolmol 1 resulte in 28% higher miy photosyntheti rte in spring-whet leves, with simultneous 36% reution in stomtl onutne. In our work, evportion n trnspirtion ourre lso uring the night, ut the mesure vlues were smll in reltion to inreses in soil moisture ue to pillrity. The negtive SWD t nighttime oul only e interprete s wter rehrge. Even so, the hourly SWD emonstrte erese in evpotrnspirtion ue to CO 2 elevtion. However, in the future, the estimtes of evpotrnspirtion shoul e more preise, through weighing pots hourly n the fresh weight of plnt mteril eing preisely sutrte from eh mesurement. To onlue, oth symmetri n symmetri wrming oul reue whet yiel n enhne evpotrnspirtion ompre with CON s ws emonstrte in our work. The symmetri wrming oul lso result in lrger reution in GY thn tht se on symmetri wrming. However, the rop yiel of whet oul e expete to inrese uner the hnging limte with onurrent elevtion of CO 2 n temperture s result of inrese WUE uner the elevte CO 2. But the expete inrese woul e surely lower uner ET thn tht estimte se on ETs ue to higher evpotrnspirtion. Aknowlegments The stuy ws jointly supporte y the key projet of Ntionl Siene & Tehnology Pillr Progrm of Chin (212BAD8B2, 213BAD5B2), the Ntionl Nturl Siene Fountion of Chin (3117415; 311191; 387411) n Heei Provine (C211533; C212533), the Knowlege Innovtion Progrm of the Chinese Aemy of Sienes (KSCX2-EW-Q-25). The support of the Shool of Forest Sienes, University of Estern Finln, Finln, n the support of Lunheng Agro-Eo Experimentl Sttion of the Chinese Aemy of Sienes for this stuy re knowlege. Conflit of Interest None elre. ª 214 The Authors. Eology n Evolution pulishe y John Wiley & Sons Lt. 21
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