鹽旱復合脅迫對小麥幼苗生長和水分吸收的影響

翁亞偉, 張 磊, 張 姍, 田中偉, 靳雪瑩, 李夢雅, 余鐘毓, 姜 東, 戴廷波

南京農業大學農學院/農業部作物生理生態與生產管理重點實驗室,江蘇省現代作物生產協同創新中心, 南京 210095

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鹽旱復合脅迫對小麥幼苗生長和水分吸收的影響

翁亞偉, 張 磊, 張 姍, 田中偉, 靳雪瑩, 李夢雅, 余鐘毓, 姜 東, 戴廷波*

南京農業大學農學院/農業部作物生理生態與生產管理重點實驗室,江蘇省現代作物生產協同創新中心, 南京 210095

為明確鹽害、干旱及鹽旱復合脅迫對小麥幼苗生長和水分吸收的影響,從而為鹽害和干旱脅迫下栽培調控提供理論依據。以2個抗旱性不同的小麥品種(揚麥16和耐旱型洛旱7號)為材料,采用水培試驗,以NaCl和PEG模擬鹽旱復合脅迫,研究了鹽旱復合脅迫下小麥幼苗生長、根系形態、光合特性及水分吸收特性的變化。結果表明,鹽、旱及復合脅迫下小麥幼苗的生物量、葉面積、總根長與根系表面積、葉綠素熒光和凈光合速率均顯著下降,但是復合脅迫處理的降幅卻顯著低于單一脅迫。鹽旱復合脅迫下根系水導速率和根系傷流液強度顯著大于單一脅迫,從而提高了小麥幼苗葉片水勢和相對含水量。鹽脅迫下小麥幼苗Na+/K+顯著大于復合脅迫,但復合脅迫下ABA含量卻顯著小于單一的鹽害和干旱脅迫。因此,鹽旱復合脅迫可以通過增強根系水分吸收及降低根葉中ABA含量以維持較高光合能力,這是鹽旱復合脅迫提高小麥適應性的重要原因。洛旱7號和揚麥16對鹽及鹽旱復合脅迫的響應基本一致,但在干旱脅迫下洛旱7號表現出明顯的耐性。

小麥；鹽旱復合脅迫；光合作用；根系水導速率；水分吸收

鹽害與干旱一直是制約農業生產的嚴重自然災害。近些年,鹽害和干旱發生頻率和強度愈來愈高,尤其是重大鹽害和干旱直接威脅到國家的長期糧食安全和社會穩定[1- 4]。有研究指出干旱時,土壤水分蒸發增強導致地表鹽分不斷積累,同時由于植物根系吸水使得地表土壤的水分減少、鹽分濃度增加[5-6],因此會形成鹽害與干旱的復合脅迫。小麥是我國重要糧食作物,小麥幼苗生長發育的好壞會直接影響產量和品質,并且小麥苗期處于干旱少雨的秋季與土壤返鹽的春季[7],因此明確鹽旱復合脅迫對小麥幼苗生長的影響及生理機制具有一定實際意義。鹽害與干旱都會造成滲透脅迫,增加植物根系吸水阻力,降低植物光合速率,限制植物生長；但目前對鹽旱復合脅迫研究,主要集中在探討滲透調節物質與抗逆境酶在復合脅迫中的作用,而對復合脅迫下植物對水分吸收和運輸以及光合能力的研究較少[7- 10]。由于作物種類和處理方式的不同,因此得出的一些不同的結論[8- 12]。 有研究指出：鹽與旱復合脅迫會加重對植物損傷[8,10]；但也有研究指出：植物面臨鹽與旱雙重脅迫時卻可以表現出一定的適應性[6- 7,11-13]。而且目前對其表現出適應性的原因解釋較少。因此本文在前人研究基礎上,采用水培試驗,以NaCl和PEG模擬鹽旱復合脅迫,選用2個抗旱性不同的小麥品種(揚麥16和耐旱型洛旱7號)為材料,分析復合脅迫下小麥幼苗根系吸水能力、葉片光合作用以及小麥幼苗生長的關系,明確小麥幼苗表現出適應性的原因,以期為揭示小麥幼苗對鹽旱復合脅迫的適應機制提供科學依據。

1 材料與方法

1.1 實驗材料與處理

于2014—2015年在南京農業大學牌樓試驗基地遮雨棚中進行水培試驗。供試材料為抗旱性不同的小麥品種洛旱7號(耐旱型品種)和揚麥16。選取飽滿且大小一致的種子,用15%過氧化氫浸種消毒10min后沖洗3—4次,移至鋪有兩層滅菌濾紙的周轉箱中,于20℃光照培養箱中黑暗條件下催芽,待種子露白后移至石英砂中培養。當小麥出現第二片真葉時,選擇健壯且長勢一致的幼苗,定植于裝1/2 Hoagland營養液的培養箱(38cm×32cm×27cm) 中,每箱30株,待4葉1心時進行脅迫處理。設干旱(D,12.7%PEG營養液,-0.25MPa)、鹽(S,50mmol/L NaCl營養液,-0.25MPa)和鹽旱復合脅迫(SD,含12.7% PEG+50mmol/LNaCl營養液,-0.45MPa)3個處理,以完全營養液為對照(CK),每處理重復3次,每重復5箱。溶液水勢采用WP4露點水勢儀測定,營養液pH5.5—6.0,用氣泵維持營養液溶氧濃度6—8mg/L,生長期平均溫度20℃/8℃(晝/夜)、光強300μmol m-2s-1,光照周期15h/9h(晝/夜)。

1.2 測定項目與方法

處理后7d,測定頂展葉片的水分狀況、相對電導率和光合參數,測定根系面積,并取樣品鮮樣于液氮中速凍保存,用于各生理指標進行測定。

1.2.1 植株干重和根冠比

取樣后110℃殺青10min,75℃烘干至恒重稱重。根冠比=根系干重/地上部。

1.2.2 葉片水勢和葉片相對含水量

采用WP4露點水勢儀測定頂展葉片的水勢。采用烘干法,測定葉片相對含水量,葉片相對含水量=(鮮生物量-干生物量)/(飽和鮮生物量-干生物量)×100%。

1.2.3 金屬離子

Na+、K+含量的測定,參照王寶山等的方法[14]。

1.2.4 根系形態

總根長、根系表面積和根系體積采用WinRHIZO全自動根系掃描分析儀測定。

1.2.5 激素(ABA)

激素測定按照酶聯免疫吸附測定法(ELISA)測定,參照中國農業大學提供的試劑盒。

1.2.6 光合生理參數和葉綠素熒光參數

光合生理參數的測定,采用 Li- 6400便攜式光合作用測定儀(美國)測定凈光合速率(Pn),氣孔導度(Gs),胞間CO2濃度(Ci)和蒸騰速率(Tr)。儀器采用開放式氣路,CO2濃度為385μmolL-1,選擇紅藍光源葉室,光合有效輻射為1000μmol m-2s-1。每處理取五片生長狀態一致的頂展葉測定。

葉綠素熒光參數采用PAM- 2000便攜式調制熒光儀(德國)測定。將葉片暗適應15 min,測PSⅡ最大光化學效率(Fv/Fm)。在3000μmol m-2s-1強閃光下,測PSⅡ實際光化學效率(Fv′/Fm′)。

1.2.7 葉綠素含量

稱0.1g頂展葉,剪碎放入50 mL提取液(V乙醇∶V丙酮=1∶1),在25℃黑暗條件下提取24 h,分光光度計測定吸光值,并計算葉綠素和類胡蘿卜素含量[15]。

1.2.8 根系導水速率和木質部傷流液

根系導水速率采用壓力室(3005型,美國SEC公司)測定。取小麥幼苗,剪除地上部并留茬1cm,清除切口液體 (以防污染),將根系放入壓力室中的蒸餾水中,施壓(每次增加0.2 MPa,增至1.0MPa),每個壓強下出流穩定后用脫脂棉吸取汁液,時間1min,萬分之一天平上稱量吸水前后脫脂棉的質量,其質量差為1min內通過測試根系的水流通量m(mg/min)。最后將測量過的根系稱重M(g),最后計算根系水導速率Lpr(mg g-1min-1MPa-1)。 然后向壓力室中的蒸餾水中添加HgCl2(50μmol/L),再次測量根系水導速率[16]。

根系傷流液收集,參照李合生的方法略加改進。稱取約0.5g脫脂棉,剪除小麥幼苗地上部并留茬1cm,清除切口液體 (以防污染),然后迅速用脫脂棉包裹住切面,并用保鮮膜包好脫脂棉,收集12 h (19:00—7:00) 后,稱量法測定傷流量[15]。

1.3 數據處理

采用Excel軟件進行數據分析,采用Duncan新復極差法進行差異顯著性檢驗(α=0.05),采用Sigmaplot 12.5作圖。

2 結果與分析

2.1 鹽旱復合脅迫對小麥幼苗生長的影響

表1表明,2個小麥品種在鹽、干旱和鹽旱復合脅迫下干物重均顯著降低,且鹽脅迫下降低幅度最大,而鹽旱復合脅迫下減少最小。鹽脅迫下根冠比顯著降低,但干旱和鹽旱復合脅迫下根冠比顯著增加且干旱對其影響大于鹽旱復合脅迫；葉片面積在3種脅迫下均顯著減小,但復合脅迫對其影響最小,表明復合脅迫下小麥幼苗可保持較強的葉片生長和物質積累。品種間比較,洛旱7號在干旱脅迫下表現出明顯的抗性,但在鹽脅迫及復合脅迫下與揚麥16無顯著差異。

不同小寫字母表示處理間差異顯著(P<0. 05)

2.2 鹽旱復合脅迫對小麥幼苗根系形態的影響

表2表明,2個小麥品種在鹽、干旱和鹽旱復合脅迫下總根長、表面積以及根系體積顯著下降,其中鹽害對小麥幼苗的總根長、表面積以及根系體積影響最大而復合脅迫對其影響最小.這與干物質重積累結果一致.對洛旱7號和揚麥16的次生根和初生根研究表明：在單一的鹽害和干旱脅迫下次生根變化大于初生根；而在復合脅迫下初生根變化大于初生根.

表2 鹽旱復合脅迫對小麥幼苗的根長、根系表面積和根系體積的影響

2.3 鹽旱復合脅迫對小麥幼苗葉片水勢和葉片含水量的影響

圖1指出,2個小麥品種在脅迫下葉片水勢和相對含水量均顯著降低.復合脅迫下揚麥16葉片相對含水量顯著高于干旱,但是顯著低于鹽害脅迫；而其葉片水勢在鹽害和干旱脅迫下無顯著差異且顯著低于復合脅迫.復合脅迫下其葉片水勢和相對含水量與單一脅迫相比卻均有顯著提高.在復合脅迫下洛旱7號葉片相對含水量顯著低于鹽害脅迫,但與干旱脅迫差異不顯著；而在鹽害下其葉片水勢顯著小于干旱脅迫且顯著小于復合脅迫.這是因為洛旱7號作為耐旱品種,所以其在干旱脅迫下有較高水勢和含水量.說明揚麥16和洛旱7號在復合脅迫下有著較高的保水能力,洛旱7號在干旱脅迫下表現出抗性.

圖1 鹽旱復合脅迫對小麥幼苗葉片水勢和葉片相對含水量的影響Fig.1 Effects of salt combined with drought stress on leaf water potential and relative water content of wheat seedlings

2.4 鹽旱復合脅迫對小麥幼苗葉綠素含量的影響

圖2指出,在逆境下2個品種的Chl(a+b)含量顯著下降,而Chla/Chlb和Caro含量顯著升高,鹽旱復合脅迫下Chl(a+b)含量、Chla/Chlb和Caro含量顯著大于單一脅迫.鹽害脅迫下Chl(a+b)和Caro含量顯大于干旱,而Chla/Chlb顯著小于干旱脅迫.洛旱7號在干旱脅迫下葉綠素含量顯著大于鹽害,而揚麥16在兩種脅迫下差異不顯著,說明洛旱7號在干旱脅迫下表現出明顯的耐性.

圖2 鹽旱復合脅迫對小麥幼苗葉綠素含量的影響Fig.2 Effects of salt combined with drought stress on chlorophyll and carotenoid content in leaves of wheat seedlings

2.5 鹽旱復合脅迫對小麥幼苗光合特性的影響

由圖3可知凈光合速率在脅迫下會顯著下降,且鹽害對其影響最大,復合脅迫對其影響最小,在干旱下洛旱7號光合速率顯著高于揚麥16。洛旱7號在鹽害復合脅迫下Gs和Tr顯著高于鹽害和干旱單一脅迫；因此復合脅迫小麥幼苗保持較高的Gs和Tr,以維持較高的蒸騰拉力。鹽害下小麥幼苗Gs大于干旱,而Ci低于干旱,說明鹽害主要是通過非氣孔因素造成光合速率下降。

圖4指出：2個品種幼苗的Fv/Fm表現趨勢一致,在逆境下其顯著下降,鹽害對其影響最大,而鹽旱復合脅迫對其影響最小。逆境下小麥幼苗的Fv′/Fm′會顯著下降,且其表現趨勢與Fv/Fm表現趨勢一致。兩個品種幼苗在干旱脅迫下其Fv/Fm和Fv′/Fm′都顯著高于鹽害脅迫而顯著低于鹽旱復合脅迫,說明鹽害會造成小麥幼苗光合機構損傷,從而使得其光合能力下降,這與光合參數得出：鹽害主要是通過非氣孔因素造成光合速率下降的結論相一致。復合脅迫下小麥幼苗的光合機構受到的損傷較小,因而其光合能力下降較小。

圖3 鹽旱復合脅迫對小麥幼苗葉片光合參數的影響Fig.3 Effects of salt combined with drought stress on photosynthetic parameters in leaves of wheat seedlings

圖4 鹽旱復合脅迫對小麥幼苗葉綠素熒光參數的影響Fig.4 Effects of salt combined with drought stress on chlorophyll fluorescence parameters in leaves of wheat seedlings

2.6 鹽旱復合脅迫對小麥幼苗根系水導速率和傷流強度的影響

圖5表示未添加HgCl2和添加HgCl2后小麥幼苗的根系水導速率。水通道蛋白通道處的氨基酸殘基會與Hg2+發生反應,造成物理性阻塞,因此HgCl2是水通道蛋白專一抑制劑[16- 17]。未添加HgCl2時復合脅迫下的小麥幼苗根系水導速率顯著大于單一脅迫,說明復合脅迫小麥幼苗水分運輸能力較強；添加HgCl2后復合脅迫下根系水導速率顯著小于單一脅迫,說明復合脅迫下小麥幼苗會表達更多水通道蛋白以抵御逆境。圖5指出在復合脅迫下,小麥幼苗的傷流強度顯著高于干旱,與鹽害差異不顯著。說明鹽害和復合脅迫下小麥根系可以保持較高水分吸收能力。

圖5 鹽旱復合脅迫對小麥幼苗根系水導速率和根系傷流液強度的影響Fig.5 Effects of salt combined with drought stress on root hydraulic conductance and root bleeding intensity of wheat seedlings

2.7 鹽旱復合脅迫對小麥幼苗ABA含量和Na+/K+的影響

圖6指出在復合脅迫下,兩個品種小麥幼苗根葉中ABA含量顯著低于單一脅迫。說明單一脅迫下根系會產生更多的ABA傳至地上部引起氣孔關閉。表明復合脅迫下,小麥幼苗可以通過相對的降低ABA含量以促進氣孔開放增加蒸騰拉力,同時促進根系和地上部生長發育,用于抵御逆境。圖6指出與鹽害相比復合脅迫下小麥幼苗Na+/K+和ABA含量顯著下降,說明,復合脅迫下小麥幼苗會通過降低Na+/K+緩解離子毒害。

圖6 鹽旱復合脅迫對小麥幼苗含量和Na+/K+的影響Fig.6 Effects of salt combined with drought stress on on ABA content and Na+/K+ in leaves and roots of wheat seedlings

3 討論

研究指出,植物面臨鹽與旱雙重脅迫時表現出一定的適應性,鹽旱復合脅迫植物[10- 12]。鹽害和干旱植物的,光合能力因此本研究主要通過對鹽旱復合下小麥幼苗吸水能力、光合能力及其關系研究以闡述植物面臨鹽與旱雙重脅迫時表現出適應性的原因。

滲透脅迫會導致根系傷流強度下降,引起氣孔關閉并導致蒸騰拉力降低,使得植物體吸水困難[18-19]。本試驗中,與單一鹽、旱脅迫相比復合脅迫下小麥幼苗的根系傷流強度和根系水導速率的增加,使得小麥幼苗葉片水勢和相對含水量升高,保證了小麥幼苗相對高效光合作用。相對高效光合作用使得小麥幼苗的氣孔導度和蒸騰速率增加,提高了植株的蒸騰拉力,進一步增強小麥幼苗的吸水動力。

滲透脅迫會導致植物產生大量ABA使其生長發育受抑制生理活性降低,并引起光合速率下降[18-20]。鹽害下由于Na+的過多積累,在引起滲透脅迫同時亦會造成植物的Na+/K+失衡甚至是離子毒害[21],導致光合器官損傷,引起光合速率的下降[22-23]。本研究中：復合脅迫下小麥幼苗體內的Na+/K+顯著低于單一的鹽害脅迫,復合脅迫下小麥幼苗的體內的ABA含量顯著高于單一脅迫,而其葉面積,葉綠素含量,Fv/Fm和Fv′/Fm′顯著大于單一脅迫,因此復合脅迫下小麥幼苗可以保持較高光合能力。

本研究表明,與干旱相比小麥幼苗在復合脅迫下可以保持較高水分吸收能力以提高植株含水量,與鹽害相比在復合脅迫下小麥幼苗會通過降低Na+/K+緩解離子毒害,從而保證相對高效的光合速率,因此表現出一定的適應性,與前人研究結果相一致[6- 7,11]。

4 結論

與單一鹽、旱脅迫相比,鹽旱復合脅迫提高了小麥幼苗根系吸水能力和葉片含水量,降低了Na+/K+和ABA含量,從而緩解了對葉片光合能力的抑制,保證了小麥的生長,使之表現出一定的適應性。因此,維持較高的水分吸收和降低Na+/K+是小麥在鹽旱復合脅迫下表現出適應性重要原因。

[1] Yang S L, Chen K, Wang S S, Gong M. Osmoregulation as a key factor in drought hardening-induced drought tolerance inJatrophacurcas. Biologia Plantarum, 2015, 59(3): 529-536.

[2] Weng B S, Zhang P, Li S N. Drought risk assessment in China with different spatial scales. Arabian Journal of Geosciences, 2015, 8(12): 10193-10202.

[3] Narjesi V, Mardi M, Hervan E M, Azadi A, Naghavi M R, Ebrahimi M, Zali A A. Analysis of Quantitative Trait Loci (QTL) for grain yield and agronomic traits in wheat (TriticumaestivumL.) under normal and salt-stress conditions. Plant Molecular Biology Reporter, 2015, 33(6): 2030-2040.

[4] 王寧, 楊杰, 黃群, 蘇桂蘭, 周紅, 許慶華, 董合林, 嚴根土. 鹽脅迫下棉花K+和Na+離子轉運的耐鹽性生理機制. 棉花學報, 2015, 27(3): 208-215.

[5] 毛海濤，樊哲超，何華祥，邵東國，王曉菊. 干旱、半干旱區平原水庫對壩后鹽漬化的影響. 干旱區研究, 2016, 33(1): 74-79.

[6] 解衛海, 馬淑杰, 祁琳, 張振華, 柏新富. Na+吸收對干旱導致的棉花葉片光合系統損傷的緩解作用. 生態學報, 2015, 35(19): 6549-6556.

[7] 陳成升, 謝志霞, 劉小京. 旱鹽互作對冬小麥幼苗生長及其抗逆生理特性的影響. 應用生態學報, 2009, 20(4): 811-816.

[8] Sun C X, Gao X X, Fu J Q, Zhou J H, Wu X F. Metabolic response of maize (ZeamaysL.) plants to combined drought and salt stress. Plant and Soil, 2015, 388(1-2): 99-117.

[9] Zhang X K, Lu G Y, Long W H, Zou X L, Li F, Nishio T. Recent progress in drought and salt tolerance studies inBrassicacrops. Breeding Science, 2014, 64(1): 60-73.

[10] Slama I, Ghnaya T, Messedi D, Hessini K, Labidi N, Savoure A, Abdelly C. Effect of sodium chloride on the response of the halophyte speciesSesuviumportulacastrumgrown in mannitol-induced water stress. Journal of Plant Research, 2007, 120(2): 291-299.

[11] 劉建新, 王金成, 王瑞娟, 賈海燕. 旱鹽交叉脅迫對燕麥幼苗葉片生理特性的影響. 干旱地區農業研究, 2014, 32(3): 24-28.

[12] Hussain M I, Lyra D A, Farooq M, Nikoloudakis N, Khalid N. Salt and drought stresses in safflower: a review. Agronomy for Sustainable Development, 2016, 36: 4.

[13] Meggio F, Prinsi B, Negri A S, Di Lorenzo G S, Lucchini G, Pitacco A, Failla O, Scienza A, Cocucci M, Espen L. Biochemical and physiological responses of two grapevine rootstock genotypes to drought and salt treatments. Australian Journal of Grape and Wine Research, 2014, 20(2): 310-323.

[14] 王寶山, 趙可夫. 小麥葉片中Na、K提取方法的比較. 植物生理學通訊, 1995, 31(1): 50-52.

[15] 李合生. 植物生理生化實驗原理和技術. 北京: 高等教育出版社, 2006.

[16] Adiredjo A L, Navaud O, Grieu P, Lamaze T. Hydraulic conductivity and contribution of aquaporins to water uptake in roots of four sunflower genotypes. Botanical Studies, 2014, 55: 75.

[17] Zarebanadkouki M, Ahmed M A, Carminati A. Hydraulic conductivity of the root-soil interface of lupin in sandy soil after drying and rewetting. Plant and Soil, 2015, 398(1-2): 267-280.

[18] Ma Y, Qin F. ABA Regulation of Plant Responses to Drought and Salt Stresses//Zhang D, ed: Abscisic Acid: Metabolism, Transport and Signaling. Netherlands: Springer, 2014: 315-336.

[19] 馬富舉, 李丹丹, 蔡劍, 姜東, 曹衛星, 戴廷波. 干旱脅迫對小麥幼苗根系生長和葉片光合作用的影響. 應用生態學報, 2012, 23(3): 724-730.

[20] Habibi G, Ajory N. The effect of drought on photosynthetic plasticity inMarrubiumvulgareplants growing at low and high altitudes. Journal of Plant Research, 2015, 128(6): 987-99.

[21] Wang H, Zhang M S, Guo R, Shi D C, Liu B, Lin X Y, Yang C W. Effects of salt stress on ion balance and nitrogen metabolism of old and young leaves in rice (OryzasativaL.). BMC Plant Biology, 2012, 12: 194.

[22] Valifard M, Mohsenzadeh S, Kholdebarin B. Sodium chloride induced changes in photosynthetic performance and biochemical components ofSalviamacrosiphon. Indian Journal of Plant Physiology, 2015, 20(1): 79-85.

[23] Medeiros C D, Neto J R C F, Oliveira M T, Rivas R, Pandolfi V, Kido é A, Baldani J I, Santos M G. Photosynthesis, antioxidant activities and transcriptional responses in two sugarcane (SaccharumofficinarumL.) cultivars under salt stress. Acta Physiologiae Plantarum, 2014, 36(2): 447-459.

Effects of salt with drought stress on growth and water uptake of wheat seedlings

WENG Yawei, ZHANG Lei, ZHANG Shan, TIAN Zhongwei, JIN Xueying, LI Mengya,YU Zhongyu, JIANG Dong, DAI Tingbo*

AgronomyCollegeofNanjingAgriculturalUniversity/KeyLaboratoryofCropPhysiologyEcologyandProductionManagementofMinistryofAgriculture/JiangsuCollaborativeInnovationCenterforModernCropProduction,Nanjing210095,China

Salt and drought stress are two major limiting factors to wheat (TriticumaestivumL.) productivity. In north or northwest China, salt and drought stress often occur simultaneously owing to less rainfall and higher evaporation in winter and spring, which results in higher wheat yield loss. Recently, several studies have indicated that certain crop species exhibit lower growth inhabitation under the combined stress of salt and drought compared with salt and drought stress separately, but less information about adaptation mechanisms of these plants is available. Drought-tolerant and susceptible cultivars may possess variable morphological and metabolic adaptation processes in response to salt and drought stress that may contribute differently to their adaptation capability towards stress conditions. This study aims to investigate the combined effects of salt with drought stress(SD) on wheat seedling growth and water absorption characteristics, therefore providing a theoretical basis for wheat cultivation and management under salt and drought stress conditions. For this purpose two wheat cultivars, Yangmai16 (drought-susceptible) and Luohan7 (drought-tolerant), were used in a hydroponic experiment to investigate the effects of SD on root morphology, photosynthesis, and water absorption characteristics at the seedling stage of wheat. Sodium chloride(NaCl) and polyethylene glycol 6000(PEG) were applied to solution to simulate salt and drought stress, respectively. Leaf gas exchange, chlorophyll fluorescence parameters, leaf water potential and root hydraulic conductivity was determined, and hormone concentrations were estimated according to the enzyme-linked immunosorbentassaymethod. The results showed that both salt and drought stress significantly affected the plant growth and physiological activities for both wheat cultivars. However, the combined effects of SD on plant growth and dry matter production reduction were lower than their sole effects. The root length, root surface area and root volume in SD-treated plants were higher than those in single stress treated plants although these were significantly lower when compared with the control. This indicates that SD has less negative effects on root growth than the single stress does. Similarly, chlorophyll content, chlorophyll fluorescence parameters (Fv/FmorFv′/Fm′), net photosynthetic rate, and stomatal conductance under SD treatment were all significantly higher than the single salt or drought stress, showing that SD caused less damage to the photosynthetic apparatus than their single application. Root hydraulic conductivity and xylem sap intensity under SD were observed to be significantly higher than those for the single stress, which resulted in higher leaf water potential and relative water content under SD than under single stress. The Na+/K+ratio in leaves and roots under SD treatment were significantly lower than that for the single salt stress, and the abscisic acid (ABA) content in SD-treated plants was lower than that in single stress-treated plants, although those were significantly higher than those for the control, indicating that SD could reduce root ABA formation as compared to single stress. Compared with single salt and drought stress, SD not only improved the root water uptake capacity and leaf water status, but also decreased the Na+/K+and ABA content, hence alleviating inhibition of leaf photosynthetic capacity. Overall, maintaining a higher water absorption capacity and photosynthesis were the major contributors for wheat seedlings to adapt SD. Luohan7 and Yangmai16 responded similarly to salt and SD, whereas Luohan7 showed more obvious tolerance to drought stress than Yangmai16.

wheat; salt combined with drought; photosynthesis; root hydraulic conductivity; water uptake

10.5846/stxb201601040020

國家自然科學基金資助項目(31471443,31501262); 江蘇省自然科學基金資助項目(BK20140705)

2016- 01- 04; 網絡出版日期:2016- 08- 30

翁亞偉, 張磊, 張姍, 田中偉, 靳雪瑩, 李夢雅, 余鐘毓, 姜東, 戴廷波.鹽旱復合脅迫對小麥幼苗生長和水分吸收的影響.生態學報,2017,37(7):2244- 2252.

Weng Y W, Zhang L, Zhang S, Tian Z W, Jin X Y, Li M Y,Yu Z Y, Jiang D, Dai T B.Effects of salt with drought stress on growth and water uptake of wheat seedlings.Acta Ecologica Sinica,2017,37(7):2244- 2252.

*通訊作者Corresponding author.E-mail: tingbod@njau.edu.cn