武文明,王世濟(jì),陳洪儉,崔權(quán)仁,竟麗麗

(安徽省農(nóng)業(yè)科學(xué)院煙草研究所/玉米研究中心 合肥 230031)

氮肥后移促進(jìn)受漬夏玉米根系形態(tài)恢復(fù)和提高花后光合性能*

武文明,王世濟(jì)**,陳洪儉,崔權(quán)仁,竟麗麗

(安徽省農(nóng)業(yè)科學(xué)院煙草研究所/玉米研究中心 合肥 230031)

江淮地區(qū)受梅雨影響,玉米苗期易發(fā)生漬害,如何通過(guò)合理運(yùn)籌氮肥達(dá)到減災(zāi)效果值得研究。以夏玉米品種‘隆平206’為試驗(yàn)材料,研究不同氮肥運(yùn)籌方式[氮肥全部基施(N1)、基肥70%+拔節(jié)肥30%(N2)、基肥50%+拔節(jié)肥50%(N3)和基肥30%+拔節(jié)肥50%+大喇叭口肥20%(N4)]對(duì)苗期受漬夏玉米根系形態(tài)和花后光合性能恢復(fù)的影響,以期為苗期受漬夏玉米合理施肥提供理論依據(jù)。結(jié)果表明,苗期漬水7 d抑制根系生長(zhǎng),根重、根長(zhǎng)度、根表面積和根直徑均顯著降低,漬水對(duì)根系形態(tài)指標(biāo)抑制效應(yīng)表現(xiàn)為:根長(zhǎng)度>根表面積>根直徑。氮肥后移對(duì)漬水后根系生長(zhǎng)有顯著的補(bǔ)償效應(yīng),氮肥后移量增加,根重、根長(zhǎng)度和根表面積顯著增加。漬水脅迫解除后18 d,N1-N4處理根長(zhǎng)度較漬水前提高1.9～5.1倍,根表面積提高6.3～10.3倍,根直徑提高0.7～1.0倍,氮肥后移對(duì)根系形態(tài)指標(biāo)補(bǔ)償生長(zhǎng)效應(yīng)強(qiáng)弱表現(xiàn)為:根表面積>根長(zhǎng)度>根直徑。漬水使群體葉面積系數(shù)降低9.3%～22.5%,氮肥后移可提高群體葉面積系數(shù),較全部基施處理提高3.2%～20.7%。苗期漬水7 d顯著降低灌漿期間穗位葉片的光合能力,凈光合速率下降,灌漿中期和末期凈光合速率分別下降16.1%和28.9%,灌漿后期光合能力下降幅度高于對(duì)照,非氣孔限制是導(dǎo)致漬水脅迫下凈光合速率下降的主要原因。漬水脅迫下,氮肥后移處理改善了穗位葉光合性能,光合能力優(yōu)于氮肥前移處理。在苗期易導(dǎo)致漬害的地區(qū)適當(dāng)減少基肥比例,后移氮素至拔節(jié)期和大喇叭口期,能夠?qū)κ軡n夏玉米起到較好的補(bǔ)償生長(zhǎng)效應(yīng)。

夏玉米;漬水;氮肥后移;根系生長(zhǎng);光合特性

玉米(Zea mays)是安徽省江淮地區(qū)增產(chǎn)潛力大的糧食作物,由于苗期正值江淮地區(qū)的梅雨季節(jié),易發(fā)生苗期漬害。玉米苗期遇到連續(xù)降雨或洪澇災(zāi)害造成土壤漬水,影響植株的正常生長(zhǎng)發(fā)育[1-3],苗期漬害已成為制約玉米高產(chǎn)穩(wěn)產(chǎn)的一個(gè)重要的非生物脅迫因子[4-5]。玉米苗期漬水,根系長(zhǎng)期處于低氧狀態(tài),導(dǎo)致根系活力降低,礦質(zhì)元素吸收減少,干物質(zhì)積累大幅度下降[5-6]。研究表明土壤漬水,葉片氣孔關(guān)閉,蒸騰速率下降,光合速率降低,隨著漬水時(shí)間的延長(zhǎng),葉綠素含量和光合作用相關(guān)功能酶活性下降,PSⅡ光化學(xué)效率降低,葉片早衰[7-9]。

氮素對(duì)玉米器官建成具有重要作用,施氮后增產(chǎn)效果明顯[10]。張起君[11]研究發(fā)現(xiàn),合理施肥在玉米增產(chǎn)諸因素中起28%～30%的作用。土壤中的氮素和施入農(nóng)田中的氮素必須經(jīng)根系吸收才能進(jìn)入作物體內(nèi),因此,根系生長(zhǎng)性狀與肥料吸收密切相關(guān)。Yu等[12]研究表明局部高濃度硝酸鹽處理能夠誘導(dǎo)根系側(cè)根長(zhǎng)度的增加,且能夠增加植株氮素吸收量。牛曉麗等[13]研究表明水氮雙重脅迫后局部恢復(fù)氮素供應(yīng),根系氮素吸收速率在時(shí)間和空間上均可得到恢復(fù);因此合理的氮素供應(yīng)使得根系較好生長(zhǎng)。根系的生長(zhǎng)代謝和活力變化可直接影響到地上部的生長(zhǎng)發(fā)育。漬害后植株光合性能下降[14],合理的氮肥運(yùn)籌能改善作物光合特性。較高的施氮水平能維持低氮敏感品種花后葉片光合速率和全氮含量[15]。氮肥供應(yīng)不足降低葉片葉綠素含量,加速葉片死亡[16];氮肥虧缺條件下增施氮肥可以改善葉片光合性能和氣孔限制等[17],提高PSⅡ系統(tǒng)實(shí)際光化學(xué)量子產(chǎn)量,減輕漬害導(dǎo)致的光抑制和光損傷[8],且氮肥后移能夠減輕苗期漬害對(duì)夏玉米產(chǎn)量的影響[5]。以往關(guān)于根系研究多集中于干旱脅迫情況下,關(guān)于苗期漬害逆境下夏玉米植株根系特征如何變化,氮肥后移對(duì)苗期受漬夏玉米根系和光合特性有何影響研究尚不深入。為此,本文通過(guò)開(kāi)展田間試驗(yàn),研究不同氮肥運(yùn)籌方式對(duì)苗期受漬夏玉米根系特征和光合生理特性的影響,以期明確氮肥對(duì)苗期受漬夏玉米根系和冠層生長(zhǎng)發(fā)育的調(diào)控效應(yīng)。

1 材料與方法

1.1 試驗(yàn)區(qū)基本情況

試驗(yàn)于2014—2015年在安徽省農(nóng)業(yè)科學(xué)院合肥崗集基地(31°57′27.7″N,117°11′51.81″E)進(jìn)行。供試土壤為黏盤黃褐土,0～20 cm土層含有機(jī)質(zhì)21.6 g·kg-1、水解氮118.4 mg·kg-1、速效鉀269.6 mg·kg-1和速效磷25.4 mg·kg-1。2014年6—9月平均氣溫23.5℃,降雨量734 mm;2015年6—9月平均氣溫25.7℃,降水量794 mm。

1.2 試驗(yàn)設(shè)計(jì)

供試玉米品種為‘隆平206’,密度為75 000株·hm-2。設(shè)置玉米苗期4～5葉期漬水7 d處理,其間保持田面1～2 cm的水層,漬水期間無(wú)降水;未漬水處理為對(duì)照。漬水處理和對(duì)照均設(shè)4個(gè)氮肥運(yùn)籌方式,分別為氮肥全部基施(N1)、基肥70%+拔節(jié)肥30%(N2)、基肥50%+拔節(jié)肥50%(N3)和基肥30%+拔節(jié)肥50%+大喇叭口肥20%(N4),漬水脅迫解除后2 d撒施拔節(jié)肥;大喇叭口期追施大喇叭口肥(開(kāi)溝撒施覆土)。全生育期純氮總施用量為240 kg·hm-2,氮肥種類為尿素。各小區(qū)于播種前施P2O5112.5 kg·hm-2、K2O 112.5 kg·hm-2,撒施于地表后耕翻入土。

采用裂區(qū)設(shè)計(jì),漬水處理為主區(qū),氮肥處理為副區(qū),重復(fù)4次,小區(qū)面積3.6 m×6.0 m,各小區(qū)間隔50 cm。漬水處理時(shí),深挖50 cm埋不透水塑料布阻止各小區(qū)水分的流動(dòng)。其余栽培管理同高產(chǎn)大田。

1.3 測(cè)定項(xiàng)目與方法

1.3.1 根系形態(tài)特征測(cè)定

于漬水處理前1 d、漬水處理3 d、漬水處理7 d和漬水脅迫解除7 d、18 d取根系,取根時(shí)以植株為中心,距離植株40 cm處深挖40 cm,每小區(qū)4株,4次重復(fù)。根系取出后,用細(xì)水流沖洗干凈,剔除死根和雜物后,用蒸餾水漂洗干凈,105℃殺青30 min,80℃烘干至恒重。使用臺(tái)式掃描儀和WinRHIZO根系分析系統(tǒng)測(cè)定單位體積的根長(zhǎng)度(cm)、根表面積(cm2)和根直徑(mm)。

1.3.2 葉面積系數(shù)測(cè)定

于吐絲期測(cè)定群體葉面積系數(shù),每小區(qū)隨機(jī)取樣1株,4次重復(fù),采用直尺測(cè)定葉片長(zhǎng)度和最大寬度,葉面積=葉片最大長(zhǎng)度×最大寬度×0.75。

1.3.3 葉片光合速率測(cè)定

利用Li-6400便攜式光合作用測(cè)定系統(tǒng),設(shè)定人工光源光強(qiáng)1 500 μmol·m-2·s-1,于灌漿中期和灌漿末期晴天9:00—11:30,選取生長(zhǎng)進(jìn)程和生長(zhǎng)方向一致的植株,測(cè)定穗位葉凈光合速率[Pn,μmol(CO2)·m–2·s–1]、氣孔導(dǎo)度(Gs,mmol·m–2·s–1)、胞間CO2濃度(Ci,μmol·mol–1)、蒸騰速率[Tr,mmol(H2O)·m–2·s–1],每小區(qū)2株,4次重復(fù)。

1.4 數(shù)據(jù)處理及統(tǒng)計(jì)分析

采用Microsoft Excel 2003計(jì)算數(shù)據(jù);采用SPSS 13.0對(duì)漬水和氮肥運(yùn)籌方式進(jìn)行單因素方差分析。

2 結(jié)果與分析

2.1 氮肥運(yùn)籌方式對(duì)苗期受漬夏玉米根系形態(tài)特征的影響

2.1.1 根重

苗期漬水,玉米根系生長(zhǎng)受到明顯抑制,漬水處理根重顯著低于對(duì)照。漬水期間,N1-N4處理根重?zé)o顯著差異;漬水脅迫解除后追施拔節(jié)肥,N2-N4處理顯著高于N1。漬水脅迫解除7 d,N1-N4根重較對(duì)照分別下降68.6%、41.1%、39.1%和44.9%(圖1)。

2.1.2 根長(zhǎng)度

對(duì)照處理,生育前期N1和N2處理根長(zhǎng)度顯著高于N3和N4;追施拔節(jié)肥后16 d(漬水脅迫解除后18 d),N3和N4處理根長(zhǎng)度顯著高于N1。苗期漬害7 d抑制根系生長(zhǎng),隨漬水時(shí)間的延長(zhǎng),根長(zhǎng)度較漬水前下降幅度增大。漬水3 d,N1-N4處理根長(zhǎng)度較漬水前分別下降16.9%、13.2%、0.6%和1.1%;漬水7 d,N1-N4根長(zhǎng)度分別下降55.4%、55.4%、24.9%和34.6%。漬水脅迫解除后追施拔節(jié)肥,N3和N4處理根長(zhǎng)度恢復(fù)速度優(yōu)于N1和N2。脅迫解除7 d,N3和N4處理根長(zhǎng)度均高于漬水前;脅迫解除18 d,N1-N4處理均已恢復(fù)生長(zhǎng),較漬水前提高1.9倍、2.3倍、4.4倍和5.1倍(圖1)。表明漬水脅迫后追施拔節(jié)肥,有利于根長(zhǎng)度的快速恢復(fù)。

不同氮肥處理間,漬水前N1處理根長(zhǎng)度顯著高于N3和N4;漬水7 d,不同氮肥處理間根長(zhǎng)度無(wú)顯著差異。脅迫解除后7 d,N4處理根長(zhǎng)度較N1、N2和N3處理分別高13.4%、12.9%和5.4%。漬水脅迫解除18 d,N4處理根長(zhǎng)度較N1、N2和N3處理高15.6%、8.2%和18.0%。表明氮肥后移對(duì)漬水后根長(zhǎng)度起到恢復(fù)生長(zhǎng)的效應(yīng)。

2.1.3 根表面積

苗期漬害7 d降低根表面積,降低趨勢(shì)同根長(zhǎng)度下降趨勢(shì)相同,但下降幅度小于根長(zhǎng)度。隨漬水時(shí)間延長(zhǎng),降低幅度增大。漬水3 d,N1-N4處理較漬水前根表面積分別下降9.2%、10.0%、11.8%和10.7%;漬水7 d,分別下降35.6%、39.9%、12.8%和30.4%。漬水脅迫解除后追施拔節(jié)肥根表面積恢復(fù),恢復(fù)速度較根長(zhǎng)度快;漬水脅迫解除18 d,根表面積較漬水處理前分別增大6.3倍、7.1倍、10.6倍和10.6倍。表明漬水脅迫后追施拔節(jié)肥,根表面積對(duì)氮素后移的響應(yīng)速度較根長(zhǎng)度快。

不同氮素處理間,漬水前N1根表面積顯著高于N3和N4;隨漬水時(shí)間延長(zhǎng),N1-N4處理間根表面積無(wú)顯著差異。脅迫解除7 d,根表面積表現(xiàn)為N4>N2>N3>N1,N4高于N1-N3處理29.5%、20.7%和25.8%。脅迫解除18 d,N4高于N1-N3處理10.7%、4.4%和6.1%,表明脅迫解除后,N4處理根表面積恢復(fù)速度高于N1-N3處理。與對(duì)照相比,漬水7 d,漬水處理N1-N4根表面積較對(duì)照分別下降42.0%、13.7%、47.2%和67.9%。漬水脅迫解除后7 d,N1-N4較對(duì)照分別下降34.8%、27.8%、27.4%和10.2%;漬水脅迫解除18 d,分別下降3.8%、4.7%、5.6%和4.0%。表明隨著脅迫解除追施拔節(jié)肥,利于根表面積的恢復(fù),與對(duì)照處理差異縮小,但仍低于對(duì)照處理。

2.1.4 根直徑

對(duì)照處理,追施拔節(jié)肥前,N1處理根直徑顯著高于N2-N4(圖1);追施拔節(jié)肥后,N4和N3處理顯著高于N1。漬水處理7 d,根直徑與漬水前無(wú)顯著差異。漬水脅迫解除后18 d,不同氮肥處理間根直徑無(wú)顯著差異,但較漬水前分別提高0.7倍、0.8倍、0.7倍和1.0倍;且N4處理較N1-N3處理根直徑分別提高10.9%、4.4%和10.9%。表明漬水脅迫后根直徑恢復(fù)速度慢于根長(zhǎng)度和根表面積。

圖1 氮肥運(yùn)籌模式對(duì)苗期受漬夏玉米根重和形態(tài)特征的影響(2015年)Fig.1 Effect of nitrogen fertilization mode on root dry weight and morphological characteristics of summer maize under waterlogging at seedling stage (2015)

2.2 氮肥運(yùn)籌方式對(duì)苗期受漬夏玉米群體葉面積系數(shù)的影響

苗期漬水抑制葉片的生長(zhǎng),漬水處理LAI顯著低于對(duì)照處理。2014年,吐絲期漬水處理N1–N4較對(duì)照分別下降15.3%、13.5%、13.3%和10.0%;2015年漬水處理N1–N4較對(duì)照分別下降22.5%、20.2%、17.0%和9.3%(圖2)。苗期漬水影響玉米植株葉片生長(zhǎng),降低群體綠葉面積,不利于玉米光合生產(chǎn)。

2014年,漬水條件下N4處理LAI顯著高于其他氮肥處理,氮肥后移提高吐絲期LAI。2014年,漬水處理N3和N4較N1提高3.2%和6.7%,對(duì)照N3和N4較N1提高0.8%和0.4%;2015年,漬水處理N3和N4較N1提高3.8%和20.7%,對(duì)照N4較N1提高3.1%。

圖2 2014年和2015年氮肥運(yùn)籌方式對(duì)苗期受漬夏玉米吐絲期LAI的影響Fig.2 Effect of nitrogen fertilization mode on leaf area index (LAI) at spinning stage of summer maize under waterlogging at seedling stage in 2014 and 2015

2.3 氮肥運(yùn)籌方式對(duì)苗期受漬夏玉米光合特性的影響

漬水處理顯著降低穗位層葉片的凈光合速率、氣孔導(dǎo)度和蒸騰速率。灌漿中期和灌漿末期凈光合速率、氣孔導(dǎo)度和蒸騰速率分別較對(duì)照下降16.1%和28.9%、25.0%和12.1%、5.1%和10.9%。胞間CO2濃度變化規(guī)律則相反,較對(duì)照分別上升19.3%和61.3%。灌漿中期和末期兩次光合參數(shù)分析表明,漬水處理灌漿末期凈光合速率、氣孔導(dǎo)度和蒸騰速率較灌漿中期分別下降38.9%、31.1%和21.8%;對(duì)照分別下降27.9%、41.2%和16.8%(表1),漬水處理凈光合速率和蒸騰速率下降幅度高于對(duì)照。

灌漿中期不同氮肥處理間穗位層葉片凈光合速率、氣孔導(dǎo)度和蒸騰速率無(wú)顯著差異。灌漿末期N4處理凈光合速率、氣孔導(dǎo)度和蒸騰速率顯著高于N1和N2。漬水處理,灌漿末期N4處理凈光合速率、氣孔導(dǎo)度和蒸騰速率較N1和N2處理分別提高63.3%和55.3%、43.2%和7.0%、34.5%和12.3%(表1),表明氮肥后移提高灌漿后期穗位層葉片的凈光合速率、氣孔導(dǎo)度和蒸騰速率。

3 討論

根系是植物吸收水分和養(yǎng)分的主要器官,根系形態(tài)和空間分布影響?zhàn)B分吸收。合理施肥可營(yíng)造良好的根際土壤環(huán)境,保證玉米根際養(yǎng)分的有效供應(yīng)[18]。氮肥促進(jìn)根系生長(zhǎng),增加根毛密度,增強(qiáng)根系生理功能[19]。10葉展追氮提高0～20 cm土層中根重和根表面積分布;吐絲期追氮可提高根系在20～40 cm土層中分布和根系活力[20]。本研究結(jié)果表明,正常供水條件下,隨著基肥施氮的減少,苗期根重、根長(zhǎng)度、根表面積無(wú)明顯變化,但追施拔節(jié)肥后,根系形態(tài)指標(biāo)均快速提升。氮肥后移至大喇叭口期和吐絲期可使耕層無(wú)機(jī)氮供應(yīng)較好地與作物吸收同步[21]。適宜的施氮量與追肥時(shí)期的耦合效應(yīng)可實(shí)現(xiàn)夏玉米產(chǎn)量和品質(zhì)的同步提升,且大幅度降低土壤硝態(tài)氮淋溶[22]。苗期漬害逆境下玉米根系生長(zhǎng)不同于正常供水處理,苗期漬害抑制了玉米根系的生長(zhǎng),根系干物質(zhì)積累大幅度下降;根長(zhǎng)度、根表面積、根直徑均顯著降低,這可能是由于漬水后玉米主胚根和次生根生長(zhǎng)均受到抑制,根系變粗變短,分叉減少,幾乎沒(méi)有根毛,且一部分根系窒息死亡[6],從而導(dǎo)致根長(zhǎng)度和根表面積降低,其中根長(zhǎng)度較漬水前下降24.9%～55.4%,根表面積下降12.8%～39.9%,根直徑下降2.7%～5.3%,3個(gè)形態(tài)指標(biāo)受漬水抑制程度大小為:根長(zhǎng)度>根表面積>根直徑,這與梁哲軍等[6]研究結(jié)果一致。漬水脅迫解除后追施氮肥,改善土壤肥力,促進(jìn)根系生長(zhǎng),根系恢復(fù)生長(zhǎng)能力較全部基施處理強(qiáng),氮素后移對(duì)漬水后根系形態(tài)指標(biāo)恢復(fù)生長(zhǎng)的補(bǔ)償效應(yīng)強(qiáng)弱表現(xiàn)為:根表面積>根長(zhǎng)度>根直徑。氮素供應(yīng)對(duì)玉米根系的生長(zhǎng)和形態(tài)、分布、生理及分泌等有明顯影響[23]。施氮主要通過(guò)提高表土層根系鮮重、根系總鮮重與總干重及中下層根系含氮量實(shí)現(xiàn)夏玉米增產(chǎn)[24]。生育前期少量供氮對(duì)根系生長(zhǎng)無(wú)抑制作用,而供氮水平進(jìn)一步提高,則對(duì)根系生長(zhǎng)有抑制作用[23,25]。因此,基施氮肥比例相對(duì)降低,對(duì)植株的生長(zhǎng)并沒(méi)有抑制作用,氮素施用量相對(duì)后移至拔節(jié)期和大喇叭口期能夠保證后期充足的氮素供應(yīng),且對(duì)漬害后根系恢復(fù)生長(zhǎng)起到很好的補(bǔ)償效應(yīng)。因此,在玉米苗期降水過(guò)多地區(qū),降水造成大量氮素以形式淋溶到土壤深處,且夏玉米前期生長(zhǎng)較慢,若生育前期投入過(guò)多氮肥,易導(dǎo)致嚴(yán)重的氮素淋洗,造成玉米生育后期氮素供應(yīng)不足現(xiàn)象[5],因此該地區(qū)應(yīng)采取氮素后移的運(yùn)籌方式,保證氮素供應(yīng)與作物吸收同步。

表1 不同氮肥運(yùn)籌方式對(duì)苗期受漬灌漿中后期玉米光合特性的影響(2015年)Table 1 Effect of nitrogen fertilization mode on photosynthetic characteristics at mid and late grain-filling stages of summer maize under waterlogging at seedling stage (2015)

氮肥后移可明顯改善作物生長(zhǎng)中后期葉片光合性能。作為植物吸收水分和養(yǎng)分以及合成植物激素的器官,根系的生長(zhǎng)代謝和活力變化可直接影響到地上部的生長(zhǎng)發(fā)育,并影響地上部“光系統(tǒng)”的建成和產(chǎn)量形成[26-27]。漬水導(dǎo)致植株下部發(fā)黃葉片脫落,葉面積擴(kuò)張和新葉抽出均受抑制,葉型窄而薄[6]。漬水處理導(dǎo)致下部葉片的死亡,使得群體葉面積系數(shù)降低。氮肥后移通過(guò)提高作物生長(zhǎng)中后期土壤中礦質(zhì)態(tài)氮含量,增加根部的細(xì)胞分裂素合成和向葉的運(yùn)輸[28],增大穗位層和穗上層葉片的LAI來(lái)彌補(bǔ)穗下層LAI降低導(dǎo)致的群體LAI降低的趨勢(shì),且彌補(bǔ)的效應(yīng)大于漬害導(dǎo)致穗下層LAI降低的效應(yīng),進(jìn)而使得苗期漬害下氮肥后移的群體LAI較氮肥前移增大[5]。

光合作用是作物干物質(zhì)和產(chǎn)量形成的基礎(chǔ)[15]。有研究認(rèn)為氣孔限制是玉米淹水7 d植株光合速率下降的主要因素,而非氣孔限制則是淹水14 d植株光合速率下降的主要因素[6]。本研究結(jié)果表明,苗期漬水7 d,灌漿期間穗位葉片的凈光合速率下降,且生育后期下降幅度較快。與對(duì)照相比,漬水7 d灌漿期凈光合速率、氣孔導(dǎo)度降低,但胞間CO2濃度高于對(duì)照處理,表明苗期漬水后,灌漿期間穗位葉凈光合速率下降并不主要是由氣孔導(dǎo)度引起,可能是由葉肉細(xì)胞羧化能力降低的緣故[5,8]。漬水脅迫后植株生長(zhǎng)受到抑制,根系活力下降,葉片早衰,葉綠素含量降低和葉面積減小,光合作用受抑制進(jìn)而凈光合速率下降,最終可導(dǎo)致減產(chǎn)超20%[5-6,9,14]。氮素同樣影響植株光合效率,氮素供應(yīng)不足是影響作物產(chǎn)量的首要因素[17,29-30]。氮素供應(yīng)不足影響Rubisco和PEPC酶活性,酶活性降低導(dǎo)致灌漿后期凈光合速率下降。表明基施氮肥比例相對(duì)降低,氮素后移至拔節(jié)期和大喇叭口肥能夠通過(guò)增大穗位層和穗上層葉片的LAI來(lái)彌補(bǔ)穗下層LAI降低導(dǎo)致的群體LAI降低的趨勢(shì),延長(zhǎng)葉片光合功能期,提高光能截獲能力,改善灌漿期群體光合性能,進(jìn)而使得氮素后移處理植株光合能力較氮肥前移處理提高。

4 結(jié)論

苗期漬水抑制根系生長(zhǎng),脅迫解除后追施氮肥,對(duì)根系的生長(zhǎng)有明顯的補(bǔ)償效應(yīng)。苗期漬水顯著降低灌漿期間穗位葉片的光合能力,凈光合速率下降,且灌漿后期光合能力下降較對(duì)照處理快,非氣孔限制是導(dǎo)致漬水脅迫下凈光合速率下降的主要原因。在苗期易發(fā)生漬害的地區(qū),在施氮運(yùn)籌上采取基肥和后期追肥相結(jié)合及適當(dāng)增加后期施氮比例的適應(yīng)性的氮素管理策略,能夠?qū)κ軡n夏玉米起到較好的補(bǔ)償生長(zhǎng)效應(yīng)。

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Postponed nitrogen application enhances root morphology recovery and photosynthetic characteristics of summer maize waterlogging stressed at seedling stage*

WU Wenming,WANG Shiji**,CHEN Hongjian,CUI Quanren,JING Lili
(Tobacco Research Institute / Maize Research Center,Anhui Academy of Agricultural Sciences,Hefei 230031,China)

Maize is one of the main summer crops in Anhui Province.However,maize production in this region is often subjected to waterlogging stress at seedling stage.Nitrogen (N) is a key nutrient that influencing growth,yield and quality ofmaize,but what role it plays in relieving waterlogging stress on summer maize remains unclear.Thus field experiments were carried out to determine the effect of N application on the recovery of root morphology and photosynthetic characteristics of summer maize cultivar ‘Longping 206’ after waterlogging stress at seedling stage.Under both waterlogging and control (normal water) conditions,four treatments of different N application rates at land preparation,jointing stage,and big flare stage(N1:10∶0∶0;N2:7∶3∶0;N3:5∶5∶0 and N4:3∶5∶2) were set with a total N amount of 240 kg·hm–2.The results showed that waterlogging stress at seedling stage significantly inhibited maize root growth.Root weight,length,surface area and diameter significantly decreased compared with those of the control.The degree of inhibiting effect on root morphology was in the order of total root length >root surface area >root diameter.Delayed N application had a compensation effect on root growth after waterlogging.Eighteen days after waterlogging,total root length of N1 to N4 treatments increased by 1.9–5.1 folds that before waterlogging.Root surface area and diameter increased by 6.3–10.3 folds and 0.7–1.0 folds,respectively.The degree of compensation effect of delayed N application on root morphology was in the order of root surface area >total root length >root diameter.Waterlogging stress at seedling stage significantly decreased leaf area index (LAI) at spinning stage by a range of 9.3%–22.5%.Compared with N1 treatment,N2,N3 and N4 treatments increased LAI within 3.2%–20.7% under waterlogging treatment.Waterlogging induced a noticeable decline inPn,respectively by 16.1% and 28.9% compared with the control at mid grain-filling and late grain-filling stages.At late grain-filling stage,Pndecreased faster than that of control.Under waterlogging stress,non-stomatal restriction was the main factor driving the decline of photosynthetic capacity.Moreover,delayed N application improved photosynthetic capacity of ear leaf,which photosynthetic capacity was better than basal N application.In conclusion,the morphological characteristics of root and leaf along with the photosynthetic characteristics of maize under waterlogging responded positively to delayed N supplication.Therefore to improve the growth of maize in the study area (which could be affected by waterlogging at seedling stage),it was recommended to apply N at jointing and big-flare stages.

Summer maize;Waterlogging;Delayed nitrogen application;Root growth;Photosynthetic characteristics

Oct.26,2016;accepted Mar.3,2017

S513

:A

:1671-3990(2017)07-1008-08

10.13930/j.cnki.cjea.160951

武文明,王世濟(jì),陳洪儉,崔權(quán)仁,竟麗麗.氮肥后移促進(jìn)受漬夏玉米根系形態(tài)恢復(fù)和提高花后光合性能[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2017,25(7):1008-1015

Wu W M,Wang S J,Chen H J,Cui Q R,Jing L L.Postponed nitrogen application enhances root morphology recovery and photosynthetic characteristics of summer maize waterlogging stressed at seedling stage[J].Chinese Journal of Eco-Agriculture,2017,25(7):1008-1015

*安徽省農(nóng)業(yè)科學(xué)院學(xué)科建設(shè)基金項(xiàng)目(16A0927,15A0926)資助

** 通訊作者:王世濟(jì),主要研究方向?yàn)橛衩自耘嗌?。E-mail:wangymzx@163.com

武文明,主要研究方向?yàn)樽魑锷砩鷳B(tài)。E-mail:wuwm1126@163.com

2016-10-26 接受日期:2017-03-03

*This work was supported by the Discipline Construction Program of Anhui Academy of Agricultural Sciences (16A0927,15A0926).

** Corresponding author,E-mail:wangymzx@163.com