硒對(duì)不同水稻幼苗鎘脅迫的緩解作用及其對(duì)礦質(zhì)營養(yǎng)的影響

代鄒,王春雨,李娜,蔣明金,嚴(yán)奉君,徐徽,孫永健,馬均

(四川農(nóng)業(yè)大學(xué)水稻研究所/農(nóng)業(yè)部西南作物生理生態(tài)與耕作重點(diǎn)實(shí)驗(yàn)室,成都611130)

硒對(duì)不同水稻幼苗鎘脅迫的緩解作用及其對(duì)礦質(zhì)營養(yǎng)的影響

代鄒,王春雨,李娜,蔣明金,嚴(yán)奉君,徐徽,孫永健,馬均*

(四川農(nóng)業(yè)大學(xué)水稻研究所/農(nóng)業(yè)部西南作物生理生態(tài)與耕作重點(diǎn)實(shí)驗(yàn)室,成都611130)

摘要采用水培試驗(yàn),研究3μmol/L Se(亞硒酸鈉)對(duì)雜交秈稻品種宜香2115(籽粒低Cd積累)和川谷優(yōu)2348 (籽粒高Cd積累)幼苗在不同濃度(0、0.1和1 mmol/L)Cd脅迫下的緩解作用.結(jié)果表明:加Se顯著增加了不同濃度Cd脅迫下2個(gè)水稻品種幼苗的生物量、葉綠素a含量,但川谷優(yōu)2348葉綠素b含量下降;加Se可增加2個(gè)水稻品種體內(nèi)抗氧化物質(zhì)(抗壞血酸和谷胱甘肽)含量,且川谷優(yōu)2348的2種抗氧化物質(zhì)含量均高于宜香2115,表現(xiàn)出品種間差異;在1 mmol/L Cd脅迫下,Se主要通過促進(jìn)川谷優(yōu)2348合成更多的抗壞血酸和谷胱甘肽來提高對(duì)Cd的耐受性,而宜香2115主要通過Se促進(jìn)植物螯合肽的合成來降低Cd的毒害;加Se能使幼苗維持較高的根部活力,從而降低遭受Cd脅迫傷害的程度;隨著Cd脅迫程度增加,2個(gè)水稻品種幼苗地上部Cd含量顯著上升,加Se可直接抑制2個(gè)水稻品種對(duì)Cd的吸收;在Cd脅迫下,Se能降低2個(gè)水稻品種地上部Ca、Zn含量,但對(duì)Cu、Mn含量變化的影響存在品種間差異,而Se對(duì)2個(gè)水稻品種根部礦質(zhì)元素含量影響表現(xiàn)一致,即在Cd脅迫下根部Ca、Cu含量增加,Mn、Zn含量減少.

關(guān)鍵詞水稻;苗期;鎘脅迫;硒;緩解

隨著我國工農(nóng)業(yè)現(xiàn)代化進(jìn)程的加快,每年都有大量的重金屬通過礦山開采、工業(yè)排放、污水灌溉以及不合理的化肥施用等途徑進(jìn)入到土壤環(huán)境中,重金屬污染問題日益突出[1].鎘(Cd)作為土壤主要無機(jī)污染物之一,對(duì)植物和人體都有潛在威脅.植物體內(nèi)過量積累Cd,會(huì)導(dǎo)致植物葉片卷曲、生長停滯,嚴(yán)重的甚至造成根部壞死,最終使植株死亡[2].Cd通過食物鏈在人體內(nèi)富集則會(huì)對(duì)人體骨骼、腎臟等部位造成損傷.20世紀(jì)60年代發(fā)生在日本的“痛痛病”就是當(dāng)?shù)鼐用耖L期食用Cd超標(biāo)大米所致[3].聯(lián)合國環(huán)境規(guī)劃署在1984年將Cd列入全球12種危害物的首位.水稻是我國的主要糧食作物,全國有60%以上人口以大米為主食,水稻穩(wěn)產(chǎn)和稻米品質(zhì)安全關(guān)系到我國社會(huì)經(jīng)濟(jì)穩(wěn)定運(yùn)行的大局.Cd在土壤-水稻系統(tǒng)內(nèi)的高遷移性使其能大量積累在水稻體內(nèi),并最終轉(zhuǎn)運(yùn)到籽粒中.近年來,我國湖南、廣州等地曝光的“毒大米”就是因?yàn)樵贑d污染稻田進(jìn)行水稻生產(chǎn)而造成的,最終導(dǎo)致農(nóng)民嚴(yán)重的經(jīng)濟(jì)損失.

硒(Se)作為動(dòng)物體內(nèi)的必需微量元素,在動(dòng)物生長發(fā)育過程中起著重要的作用,其功能主要是參與動(dòng)物體內(nèi)谷胱甘肽過氧化物酶的合成[4].人體缺Se會(huì)導(dǎo)致人體功能的損傷和病變,心臟病、克山病及大骨節(jié)病等的發(fā)生都與Se攝入不足有重要聯(lián)系[5].近年來,關(guān)于Se是否為植物的必需元素還有爭論,但相關(guān)研究均表明Se對(duì)高等植物的生長發(fā)育有著重要作用[6-7].施Se可以抑制植物對(duì)砷(As)、汞(Hg)、鉛(Pb)和鎘(Cd)等重金屬的吸收或轉(zhuǎn)運(yùn)[8-9].因此,基于Se元素在植物中的積極作用,本文研究了施Se對(duì)籽粒Cd積累能力不同的水稻品種緩解Cd脅迫的作用機(jī)制,旨在為Cd污染土壤上生產(chǎn)低Cd稻米提供理論和實(shí)踐依據(jù).

1　材料與方法

1.1試驗(yàn)材料與設(shè)計(jì)

選用前期篩選出的籽粒低Cd積累雜交稻品種宜香2115(籽粒含Cd量0.96 mg/kg)和籽粒高Cd積累雜交稻品種川谷優(yōu)2348(籽粒含Cd量2.41 mg/kg).2015年3月14日將消毒并經(jīng)催芽的水稻種子播于成都市溫江區(qū)惠和村2組的試驗(yàn)田里(在土壤中未檢測(cè)出Cd).在4月10日,秧苗達(dá)到4葉1心時(shí),選擇長勢(shì)一致的水稻幼苗,將根部用蒸餾水洗凈后,移栽到含1/2全營養(yǎng)液的塑料盆中進(jìn)行培養(yǎng);待水稻幼苗返青后改用全營養(yǎng)液培養(yǎng)(在四川農(nóng)業(yè)大學(xué)成都校區(qū)水稻研究所鋼架大棚內(nèi)進(jìn)行).營養(yǎng)液配方按國際水稻研究所常規(guī)配方配制.營養(yǎng)液每3 d更換一次,每天早晚各調(diào)節(jié)一次營養(yǎng)液p H至5.5± 0.05.試驗(yàn)采用裂區(qū)試驗(yàn)設(shè)計(jì),設(shè)品種為主區(qū)(P):宜香2115(P1),川谷優(yōu)2348(P2);硒為副區(qū)(S):不施Se(S0),施Se 3μmol/L(S1);3個(gè)Cd濃度為副副區(qū)(C):不加Cd(C0),0.1 mmol/L Cd(C1),1 mmol/L Cd(C2).共12個(gè)處理,每個(gè)處理2盆,共24盆.塑料盆內(nèi)徑52.5 cm,高21.6 cm.每盆用鉆孔塑料定植模板均勻布孔,孔距7.0 cm,每盆共21孔,每孔定植2苗.當(dāng)培養(yǎng)至5葉1心時(shí),分別用含有0和3μmol/L亞硒酸鈉外加不同濃度Cd的全營養(yǎng)液進(jìn)行處理,12 d后在每個(gè)處理的2盆中隨機(jī)取樣,用于相關(guān)指標(biāo)分析.

1.2測(cè)定項(xiàng)目與方法

生物量測(cè)定:每個(gè)處理從2盆中隨機(jī)取6穴水稻幼苗,先用0.1 mmol/L CaCl2溶液浸泡15 min以去掉附著在幼苗表面的Cd2+,然后用去離子水反復(fù)沖洗植株,再用吸水紙將植株表面多余的水分吸干,按地上部和根部將幼苗分成2部分,于烘箱中105℃殺青30 min,然后調(diào)節(jié)溫度至75℃烘至恒量并稱量.

采集幼苗倒數(shù)第2片完全展開葉用于葉綠素含量測(cè)定,葉綠體色素用95%乙醇浸提,分光光度法測(cè)定[10];根部活力用2,3,5-氯化三苯基四氮唑法測(cè)定[11];非蛋白巰基參考王芳等[12]的方法測(cè)定;抗氧化物質(zhì)(抗壞血酸和谷胱甘肽)按陳京都[13]的方法測(cè)定.非蛋白巰基和抗氧化物質(zhì)含量分別按地上部和根部進(jìn)行測(cè)定.

水稻體內(nèi)Cd及礦質(zhì)元素含量測(cè)定:分別稱取0.500 0 g已烘至恒量的地上部和根部植株樣品置于聚四氟乙烯燒杯中,加入20 m L體積比為3∶1的HNO3-HClO4混合酸,在電熱板上進(jìn)行濕法消解,消煮至無色透明時(shí),將溶液用去離子水轉(zhuǎn)移并定容至50 m L容量瓶中,然后用定量濾紙將定容的溶液過濾至100 m L干凈的聚乙烯塑料瓶中,使用電感耦合等離子發(fā)射光譜儀(IRIS IntrepidⅡ,美國Thermo公司)測(cè)定樣品中的Cd及礦質(zhì)元素含量.

1.3數(shù)據(jù)處理及分析

采用Excel 2013和Origin Pro 8.0進(jìn)行數(shù)據(jù)處理及作圖,采用DPS 7.05進(jìn)行方差分析.

2　結(jié)果與分析

2.1Se對(duì)Cd脅迫下水稻生物量的影響

由表1可以看出:宜香2115干物質(zhì)量及根冠比都顯著高于川谷優(yōu)2348;隨著Cd脅迫程度加重,水稻地上部和根部的干物質(zhì)量都急劇降低,宜香2115的根部降幅為32.1%～40.0%,地上部降幅為30.2%～47.5%,川谷優(yōu)2348相應(yīng)的降幅為31.8%～52.6%和27.5%～33.6%;在營養(yǎng)液中添加3μmol/L Se能增加水稻幼苗地上部和根部的干物質(zhì)量,且在Cd脅迫下,2個(gè)水稻品種加Se處理較相對(duì)應(yīng)的不加Se處理顯著增加了干物質(zhì)量;宜香2115的根冠比在1 mmol/L Cd或3μmol/L Se單獨(dú)處理下顯著高于其余處理,而川谷優(yōu)2348的根冠比卻在1 mmol/L Cd單獨(dú)處理下最低.這可能與2個(gè)品種的基因型差異有關(guān).

2.2Se對(duì)Cd脅迫下水稻葉綠體色素含量的影響

由表2可以看出:2個(gè)水稻品種葉綠素a和葉綠素b含量在統(tǒng)計(jì)學(xué)上差異顯著,而類胡蘿卜素含量差異不顯著;隨著Cd濃度增加,水稻葉片中的葉綠體色素含量均有所降低,加Se能有效緩解其含量下降;在重度Cd脅迫下,宜香2115的葉綠素a含量較川谷優(yōu)2348降幅更大;S1(3μmol/L Se)處理使宜香2115在0.1和1 mmol/L Cd脅迫下的葉綠素b含量分別比不加Se處理增加了21.9%和18.3%;加Se使川谷優(yōu)2348葉綠素b含量在3種Cd濃度下分別比不加Se處理下降了13.6%、20.6%和12.1%,但加Se處理間的葉綠素b含量在統(tǒng)計(jì)學(xué)上差異不顯著;Cd脅迫顯著降低了宜香2115的類胡蘿卜素含量,Se對(duì)宜香2115類胡蘿卜素含量沒有影響;加Se能夠顯著提高川谷優(yōu)2348在重度Cd脅迫下葉片類胡蘿卜素含量,比不加Se處理高10.7%.

2.3Se對(duì)Cd脅迫下水稻根系活力的影響

由圖1可知:Cd脅迫顯著降低了水稻苗期的根系活力,Cd濃度越大,根系活力越低;在不加Cd處理下,Se對(duì)根系活力影響不顯著;但施Se能顯著提高2個(gè)品種在0.1和1 mmol/L Cd脅迫下的根系活力,其中,宜香2115的根系活力分別提高了51.6%和90.2%,川谷優(yōu)2348分別提高了40.0%和63.6%.可見,Se對(duì)宜香2115根系所受Cd脅迫的緩解作用更強(qiáng).

表1　Se對(duì)不同濃度Cd脅迫下水稻干物質(zhì)量和根冠比的影響Table 1 Effects of Se on the biomass and root/shoot ratio of rice seedlings under different Cd concentrations

表2　Se對(duì)不同濃度Cd脅迫下水稻幼苗葉綠體色素含量的影響Table 2 Effects of Se on chloroplast pigment contents in rice under different Cd concentrations mg/g

圖1　不同處理下水稻幼苗根部活力Fig.1 Root activity of rice seedlings under different treatments

2.4Se對(duì)Cd脅迫下水稻抗壞血酸、谷胱甘肽和非蛋白巰基含量的影響

2.4.1對(duì)抗壞血酸含量的影響

由表3可以看出:宜香2115地上部和根部的抗壞血酸(ascorbic acid,As A)含量都顯著低于川谷優(yōu)2348;2個(gè)品種在對(duì)照(S0C0)處理下,其地上部和根部As A含量都最低;在不加Se處理下,隨著Cd濃度增加,宜香2115和川谷優(yōu)2348地上部As A含量在0.1和1 mmol/L Cd處理下分別比無Cd處理高45.7%、19.9%和57.8%、28.4%,加Se可促進(jìn)Cd脅迫下宜香2115和川谷優(yōu)2348地上部As A含量的增加;除川谷優(yōu)2348根部As A含量在S1C2(3 μmol/L Se+1 mmol/L Cd)處理下顯著高于單獨(dú)的Se處理外,其余各處理根部均表現(xiàn)為在0.1 mmol/ L Cd處理下As A含量最高,不加Cd與1 mmol/L Cd處理間在統(tǒng)計(jì)學(xué)上無顯著差異.

表3　Se對(duì)不同濃度Cd脅迫下水稻幼苗AsA、GSH和NPT含量的影響_Table 3 Effects of Se on As A,GSH,NPT contents in rice seedlings under different Cd concentrationsμmol/g

2.4.2對(duì)谷胱甘肽含量的影響

宜香2115地上部谷胱甘肽(glutathione,GSH)含量與川谷優(yōu)2348在統(tǒng)計(jì)學(xué)上差異不顯著,但根部GSH含量顯著低于川谷優(yōu)2348;在3種Cd濃度下,宜香2115和川谷優(yōu)2348在0.1 mmol/L Cd處理下地上部GSH含量最大,加Se能促進(jìn)3種Cd處理下地上部GSH含量的增加;在3種Cd處理中,加Se處理僅顯著提高宜香2115在0.1 mmol/L Cd處理下地上部GSH含量(增幅達(dá)22.1%),而可以顯著提高川谷優(yōu)2348在0.1和1 mmol/L Cd處理下根部GSH含量(增幅分別為22.1%和26.0%);在0、0.1和1 mmol/L Cd處理下,宜香2115和川谷優(yōu)2348根部GSH含量在加Se處理下比不加Se處理分別高10.3%、22.8%、23.1%和15.7%、29.4%、16.9%,且在0.1 mmol/L Cd處理下根部GSH含量最高,而1 mmol/L Cd處理使根部GSH含量在加Se或不加Se的3種Cd濃度下含量最低(表3).

2.4.3對(duì)非蛋白巰基含量的影響

由表3還可以看出:宜香2115地上部非蛋白巰基(non-protein thiols,NPT)含量顯著低于川谷優(yōu)2348,根部NPT含量高于后者,但在統(tǒng)計(jì)學(xué)上差異不顯著;在3個(gè)Cd濃度處理下,除宜香2115在S0C2處理下與對(duì)照(S0C0)差異不顯著外,2個(gè)品種地上部NPT含量在0.1和1 mmol/L Cd處理下顯著高于不加Cd處理;加Se使宜香2115和川谷優(yōu)2348在0、0.1和1 mmol/L Cd處理下比不加Se處理地上部NPT含量增加12.5%、46.6%、44.0%和2.0%、18.1%、19.2%;在3個(gè)Cd濃度處理下,宜香2115根部NPT含量顯著升高,加Se比不加Se處理在0.1和1 mmol/L Cd濃度下NPT含量分別增加13.3%和25.5%,而單獨(dú)加Se處理(S1C0)比對(duì)照(S0C0) NPT含量下降8.6%,在統(tǒng)計(jì)學(xué)上差異顯著;川谷優(yōu)2348在0.1和1 mmol/L Cd處理下根部NPT含量也顯著高于不加Cd處理,但在1 mmol/L Cd處理下NPT含量顯著低于0.1 mmol/L Cd處理;加Se同樣使川谷優(yōu)2348根部NPT含量在0.1和1 mmol/L Cd脅迫下比不加Se處理增加(增幅分別為24.1%和17.2%),但降低不加Cd處理的根部NPT含量,兩者在統(tǒng)計(jì)學(xué)上差異不顯著.

2.5Se對(duì)水稻植株Cd含量的影響

由于在0 mmol/L Cd處理下均未在水稻植株中檢測(cè)到Cd,因此,圖2比較了不同施Cd處理間植株體內(nèi)Cd含量的變化.從中可以看出:水稻地上部Cd含量隨著Cd處理濃度的加大而極顯著提高,在不加Se處理下宜香2115和川谷優(yōu)2348在1 mmol/L Cd處理下的地上部Cd含量分別是各自0.1 mmol/L Cd處理下的26倍和22倍;加Se能夠降低植株地上部對(duì)Cd的吸收,且在高Cd濃度下作用更顯著;在1 mmol/L Cd處理下,加Se使宜香2115和川谷優(yōu)2348地上部Cd含量比不加Se處理分別下降了40.0%和17.3%.加Se處理的水稻根部Cd含量也低于不加Se處理,但降幅不同;宜香2115和川谷優(yōu)2348在0.1和1 mmol/L Cd脅迫下,加Se比不加Se處理的Cd含量分別低7.8%、41.7%和28.8%、25.3%(圖2).

圖2　不同處理下水稻地上部和根部Cd含量Fig.2 Cd contents in rice shoots and roots under different treatments

2.6Se對(duì)水稻植株礦質(zhì)元素含量的影響

從表4可以看出:宜香2115地上部礦質(zhì)元素只有Cu含量顯著高于川谷優(yōu)2348;隨著Cd處理濃度的增加,2個(gè)品種地上部Ca含量顯著增加,且都在1 mmol/L Cd處理下最高,加Se處理降低了宜香2115和川谷優(yōu)2348在0、0.1和1 mmol/L 3種Cd脅迫下地上部Ca含量,分別比不加Se處理低13.8%、7.0%、5.6%和11.0%、6.4%、10.0%;加Se在0.1 mmol/L Cd處理下能顯著增加宜香2115地上部Cu含量,卻導(dǎo)致川谷優(yōu)2348比不加Se處理降低46.7%;2個(gè)品種地上部Mn含量隨著Cd處理濃度升高而顯著下降,在0.1和1 mmol/L Cd處理下,宜香2115地上部Mn含量在加Se與未加Se處理間在統(tǒng)計(jì)學(xué)上差異不顯著,但加Se使未添加Cd處理的地上部Mn含量下降37.2%,而川谷優(yōu)2348在0、0.1和1 mmol/L Cd處理下,加Se處理比各自不加Se處理的Mn含量分別下降38.0%、21.0%和42.8%,在統(tǒng)計(jì)學(xué)上差異顯著;隨著Cd脅迫濃度增加,2個(gè)品種地上部Zn含量顯著升高,加Se與不加Se處理使宜香2115和川谷優(yōu)2348地上部Zn含量在0、0.1和1 mmol/L 3種Cd濃度脅迫下分別下降8.3%、15.5%、28.2%和22.9%、9.1%、14.5%.

表4　Se對(duì)不同濃度Cd脅迫下水稻幼苗地上部及根部Ca、Cu、Mn和Zn含量的影響Table 4 Effects of Se on Ca,Cu,Mn and Zn contents in rice shoot and root under different Cd concentrationsμg/g

從表4還可以看出:0.1 mmol/L Cd處理顯著提高了宜香2115根部Ca含量,而1 mmol/L Cd處理卻顯著降低了其根部Ca含量,加Se處理比不加Se處理顯著增加了3個(gè)Cd濃度脅迫下宜香2115根部Ca含量,增幅分別為7.2%、4.9%和6.3%,而加Se處理比不加Se處理僅顯著提高了川谷優(yōu)2348在0.1和1 mmol/L Cd脅迫下根部Ca含量,增幅分別為6.6%和29.1%,但顯著降低了不添加Cd處理的根部中的Ca含量;0.1 mmol/L Cd處理能顯著提高2個(gè)品種根部中的Cu含量,加Se處理較不加Se處理提高了2個(gè)品種根部Cu含量,在0、0.1和1 mmol/L Cd脅迫下,加Se使宜香2115根部Cu含量分別增加了5.6%、26.5%和40.7%,而川谷優(yōu)2348在不加Cd處理下,加Se未改變其根部Cu含量,而在其余2個(gè)Cd濃度處理下分別增加33.6%和19.5%;2個(gè)品種根部Mn含量都隨著Cd脅迫濃度的增加而顯著下降,在1 mmol/L Cd脅迫下Mn含量最低,加Se能進(jìn)一步減少2個(gè)品種根部中的Mn含量,其中,加Se使宜香2115在0、0.1和1 mmol/L Cd脅迫下較不加Se處理下降36.1%、40.9%和48.6%,川谷優(yōu)2348相應(yīng)的降幅分別為32.8%、9.4%和13.8%;在1 mmol/L Cd脅迫下,2個(gè)品種根部Zn含量最低,與不加Se處理相比,加Se處理顯著降低了宜香2115和川谷優(yōu)2348在不添加Cd處理下的根部Zn含量,降幅分別為17.6%和34.3%.

3　討論

3.1Se對(duì)Cd脅迫下水稻幼苗生物量的影響作用

Cd是植物非必需元素,過量的Cd添加會(huì)導(dǎo)致植株生物量下降[14-15].Se是否為植物的必需元素還存在爭論,但Se對(duì)植物抵抗Cd脅迫的有益作用已有相關(guān)證據(jù)[4,1617].本研究在相同Cd脅迫條件下,籽粒高Cd積累品種川谷優(yōu)2348生物量小于籽粒低Cd積累品種宜香2115,這可能與2個(gè)水稻品種對(duì)Cd的敏感性和耐受性差異有關(guān)[13,18].Se的加入能夠有效緩解Cd脅迫造成的生物量下降,可能是因?yàn)镾e提高了水稻體內(nèi)抗氧化系統(tǒng)活性,減少了Cd脅迫誘導(dǎo)產(chǎn)生的過量活性氧對(duì)水稻幼苗的傷害,維持了水稻正常的光合生產(chǎn)[19].在本試驗(yàn)中,加Se使2個(gè)水稻品種幼苗抗氧化物質(zhì)As A和GSH含量升高,使水稻體內(nèi)活性氧能迅速清除,從而使葉綠素、細(xì)胞質(zhì)膜等物質(zhì)降解減慢,維持了水稻光合生產(chǎn)的正常進(jìn)行.此外,在未加Cd處理下,川谷優(yōu)2348根干物質(zhì)量在加Se處理下顯著低于未加Se處理.這與FENG等[20]的研究結(jié)果一致,即高濃度Se會(huì)抑制水稻根部的生長.

3.2Se緩解水稻幼苗Cd脅迫的機(jī)制

在本研究中,加Se可以促進(jìn)3種Cd脅迫下2個(gè)水稻品種葉綠素a的合成.這與前人的研究結(jié)果一致[6,21].吳之琳等[22]指出,Se能通過重建葉綠體并增加葉綠素含量以緩解重金屬脅迫.本研究結(jié)果表明,加Se處理能顯著降低川谷優(yōu)2348葉綠素b含量.這與前人的研究結(jié)果[6]相反,可能與Se的使用濃度有關(guān).根部作為水稻首先遭受Cd脅迫的部位,其活力大小能夠在一定程度上反映植物對(duì)Cd脅迫的耐受能力.張娜等[23]研究表明,低濃度Se可促進(jìn)紫云英的生長,但高濃度Se對(duì)紫云英生長有抑制作用.本研究結(jié)果表明,加Se對(duì)水稻幼苗根部活力在Cd脅迫下有顯著的促進(jìn)作用.這可能是因?yàn)镾e可以恢復(fù)Cd脅迫下根部生長,維持根部構(gòu)型,保持細(xì)胞器功能的完整性[24].

As A和GSH是植物體內(nèi)重要的抗氧化物質(zhì),對(duì)Cd脅迫下產(chǎn)生的活性氧的清除具有重要作用[25].本研究結(jié)果表明,加Se能促進(jìn)2個(gè)品種地上部和根部As A及GSH含量的增加,在S1C2(3μmol/L Na2SeO3+1 mmol/L Cd)處理下,川谷優(yōu)2348地上部As A和GSH含量以及根部中的As A含量都顯著高于Se單獨(dú)處理(S1C0),而宜香2115在S1C2處理下沒有這種變化:表明在高Cd脅迫下,川谷優(yōu)2348比宜香2115能更高效地合成As A和GSH,以減少其受到的氧化脅迫.何俊瑜[26]指出,在Cd脅迫下植物體內(nèi)的NPT含量主要代表植物螯合肽(phytochelatins,PCs)和GSH之和.本研究結(jié)果表明,施Se處理使2個(gè)水稻品種在Cd脅迫下NPT含量增加,但宜香2115根部NPT含量在S1C2處理下最大,而川谷優(yōu)2348在S1C2處理下卻比S1C1(3μmol/L Na2SeO3+0.1 mmol/L Cd)處理下其含量顯著下降:表明Se可以促進(jìn)宜香2115根部合成更多的PCs,以緩解Cd的毒害.

本研究結(jié)果表明,施Se能夠直接抑制水稻對(duì)Cd的吸收.其原因是Se和Cd互相競爭根部中的相關(guān)蛋白質(zhì)結(jié)合位點(diǎn),導(dǎo)致Cd與根部中的蛋白質(zhì)結(jié)合概率下降所致[27].在1 mmol/L Cd脅迫下,施Se使宜香2115地上部和根部Cd含量較川谷優(yōu)2348相應(yīng)部位Cd含量大幅降低:表明宜香2115能更高效利用Se來拮抗Cd的吸收.這些結(jié)果說明,Se對(duì)不同籽粒Cd積累能力的水稻幼苗吸收Cd的抑制作用與品種及Cd的處理濃度密切相關(guān).

3.3Se對(duì)Cd脅迫下水稻礦質(zhì)營養(yǎng)的影響作用

Cd脅迫除了因其造成植株活性氧傷害從而導(dǎo)致植物代謝紊亂外,Cd脅迫還導(dǎo)致了參與多種生理代謝過程的礦質(zhì)元素含量變化,從而使相關(guān)代謝過程受到影響[28-29].本研究結(jié)果表明,施Se降低了2個(gè)水稻品種地上部Ca、Zn含量,但宜香2115和川谷優(yōu)2348地上部Cu、Mn含量在Se、Cd處理下的變化趨勢(shì)卻存在差異;對(duì)根部而言,Se處理能增加2個(gè)品種在Cd脅迫下的Ca、Cu含量,降低2個(gè)品種在Cd脅迫下的Mn、Zn含量.URAGUCHI等[3]指出,水稻體內(nèi)負(fù)責(zé)Fe運(yùn)輸?shù)霓D(zhuǎn)運(yùn)蛋白OsIRT1、與Mn運(yùn)輸密切相關(guān)的轉(zhuǎn)運(yùn)蛋白OsNramp5等不僅可以轉(zhuǎn)運(yùn)Fe、Mn等金屬離子,對(duì)Cd的吸收也有作用.Se可能影響此類轉(zhuǎn)運(yùn)蛋白的表達(dá),造成水稻對(duì)礦質(zhì)元素吸收量的變化.

4　結(jié)論

0.1和1 mmol/L Cd脅迫均導(dǎo)致籽粒Cd積累能力不同的水稻品種幼苗生物量的下降,施Se可以降低Cd脅迫對(duì)幼苗生物量的影響,保持在Cd脅迫下根部活力處于較高水平,促進(jìn)Cd脅迫下2個(gè)水稻品種葉綠素a的合成,但施Se加速了川谷優(yōu)2348葉綠素b的降解.在1 mmol/L Cd脅迫下,Se能促進(jìn)川谷優(yōu)2348合成更多的As A和GSH以應(yīng)對(duì)Cd脅迫;宜香2115主要利用NPT中的PCs來降低Cd的傷害.Se能直接降低水稻對(duì)Cd的吸收,且Se主要對(duì)地上部Cu、Mn含量存在影響,并具有品種間差異.

參考文獻(xiàn)(References):

[1] 翁伯琦,劉朋虎,張偉利,等.農(nóng)田重金屬污染防控思路與技術(shù)對(duì)策研究.生態(tài)環(huán)境學(xué)報(bào),2015,24(7):1253-1258. WENG B Q,LIU P H,ZHANG W L,et al.Ideas and countermeasures research on heavy metal pollution prevention and control for farmland.Ecology and Environmental Sciences,2015,24(7):1253-1258.(in Chinese with English abstract)

[2] LICHTFOUSE E,WAHID A,ARSHAD M,et al. Cadmium phytotoxicity:Responses,mechanisms and mitigation strategies:A review//LICHTFOUSE E.Organic Farming,Pest Control and Remediation of Soil Pollutants. Netherlands:Springer,2009:371-403.

[3] URAGUCHI S,FUJIWARA T.Rice breaks ground for cadmium-free cereals.Current Opinion in Plant Biology, 2013,16(3):328-334.

[4] 李彥.硒對(duì)小白菜鹽脅迫的緩解效應(yīng)及其機(jī)理研究.山東,泰安:山東農(nóng)業(yè)大學(xué),2008:44-46. LI Y.Alleviate effect of selenium on pakchoi cabbage under salt stress and its mechanism.Tai'an,Shandong:Shandong Agricultural University,2008:44-46.(in Chinese with English abstract)

[5] 宋亞蕊.富硒茶油的品質(zhì)特性及抗氧化功能特性研究.長沙:中南林業(yè)科技大學(xué),2014:1-4. SONG Y R.Study on the quality characteristics and antioxidant functions of selenium-riched Camellia oleifera oil.Changsha:Central South University of Forestry and Technology,2014:1-4.(in Chinese with English abstract)

[6] MOZAFARIYAN M,SHEKARI L,HAWRYLAKNOWAK B,et al.Protective role of selenium on pepper exposed to cadmium stress during reproductive stage. Biological Trace Element Research,2014,160(1):97-107.

[7] GUERRERO B,LLUGANY M,PALACIOS O,et al.Dual effects of different selenium species on wheat.Plant Physiology and Biochemistry,2014,83:300-307.

[8] 譚周磁,陳嘉勤,薛海霞.硒(Se)對(duì)降低水稻重金屬Pb,Cd,Cr污染的研究.湖南師范大學(xué)自然科學(xué)學(xué)報(bào),2000,23(3): 80-83. TAN Z C,CHEN J Q,XUE H X.Studies on the pole of selenium(Se)in decreasing Pb,Cd,and Cr pollution to rice. Journal of Natural Science of Hunan Normal University, 2000,23(3):80-83.(in Chinese with English abstract)

[9] 劉華琳.玉米對(duì)砷污染的生理生態(tài)響應(yīng).山東,泰安:山東農(nóng)業(yè)大學(xué),2008:96. LIU H L.Physiological and ecological responses of maize to arsenic pollution.Tai'an,Shandong:Shandong Agricultural University,2008:96.(in Chinese with English abstract)

[10] 趙春江.數(shù)字農(nóng)業(yè)信息標(biāo)準(zhǔn)研究:作物卷.北京:中國農(nóng)業(yè)出版社,2004:410-411. ZHAO C J.Research on Information Standards for Digital Agriculture:Crops.Beijing:China Agriculture Press,2004: 410-411.(in Chinese)

[11] 熊慶娥.植物生理學(xué)實(shí)驗(yàn)教程.成都:四川科學(xué)技術(shù)出版社, 2003:30-31. XIONG Q E.Experimental Course of Plant Physiology. Chengdu:Sichuan Science and Technology Press,2003:30-31.(in Chinese)

[12] 王芳,丁杉,張春華,等.不同鎘耐性水稻非蛋白巰基及鎘的亞細(xì)胞和分子分布.農(nóng)業(yè)環(huán)境科學(xué)學(xué)報(bào),2010,29(4):625-629. WANG F,DING S,ZHANG C H,et al.Non-protein thiols,subcellular and molecular distribution of cadmium in two rice cultivars with difference tolerance.Journal of Agro-Environment Science,2010,29(4):625-629.(in Chinese with English abstract)

[13] 陳京都.水稻鎘脅迫響應(yīng)差異機(jī)理和調(diào)控效應(yīng)的研究.江蘇,揚(yáng)州:揚(yáng)州大學(xué),2013:48-49. CHEN J D.Research on difference and mechanism of rice response under cadmium stress and regulation.Yangzhou, Jiangsu:Yangzhou University,2013:48-49.(in Chinese with English abstract)

[14] DAS P,SAMANTARAY S,ROUT G R.Studies on cadmium toxicity in plants:A review.Environmental Pollution,1997,98(1):29-36.

[15] JIANG X J,LUO Y M,LIU Q,et al.Effects of cadmium on nutrient uptake and translocation by Indian mustard. Environmental Geochemistry and Health,2004,26(2): 319-324.

[16] 袁思莉,余垚,萬亞男,等.硒緩解植物重金屬脅迫和累積的機(jī)制.農(nóng)業(yè)資源與環(huán)境學(xué)報(bào),2014,31(6):545-550. YUAN S L,YU Y,WAN Y N,et al.Mechanism of selenium mitigating stress and accumulation of heavy metals in plants.Journal of Agricultural Resources and Environment,2014,31(6):545-550.(in Chinese with English abstract)

[17] 劉春梅,羅盛國,王孟雪,等.硒對(duì)鎘脅迫下寒地水稻Cd、Zn、Fe、Cu、Mn含量的影響.水土保持學(xué)報(bào),2014,28(6):136-142. LIU C M,LUO SG,WANG M X,et al.Effects of selenium on cadmium,zinc,iron,copper,manganese content in rice under cadmium stress in cold climate.Journal of Soil and Water Conservation,2014,28(6):136-142.(in Chinese with English abstract)

[18] 曾翔.水稻鎘積累和耐性機(jī)理及其品種間差異研究.長沙:湖南農(nóng)業(yè)大學(xué),2006:67-80. ZENG X.Studies on physiological mechanism in cadmium accumulation and tolerance and its difference among genotypes of rice.Changsha:Hunan Agricultural University,2006:67-80. (in Chinese with English abstract)

[19] 郭鋒,樊文華,馮兩蕊,等.硒對(duì)鎘脅迫下菠菜生理特性、元素含量及鎘吸收轉(zhuǎn)運(yùn)的影響.環(huán)境科學(xué)學(xué)報(bào),2014,34(2): 524-531. GUO F,FAN W H,FENG L R,et al.Effects of selenium (Se)on the physiological characteristics,element contents, uptake and transportation of Cd in spinach under Cd stress. Acta Scientiae Circumstantiae,2014,34(2):524-531.(in Chinese with English abstract)

[20] FENG R W,LIAO G J,GUO J K,et al.Responses of root growth and antioxidative systems of paddy rice exposed to antimony and selenium.Environmental and Experimental Botany,2016,122:29-38.

[21] 周健.硫和硒對(duì)鎘脅迫下水稻幼苗生理生化特性及鎘的吸收分配影響研究.上海:華東理工大學(xué),2013:40-48. ZHOU J.Effects of sulfur and selenium on the physiological and biochemical characteristics and cadmium absorption and distribution in rice seedling under cadmium stress.Shanghai: East China University of Science and Technology,2013:40-48.(in Chinese with English abstract)

[22] 吳之琳,童心昭,尹雪斌,等.硒提高植物拮抗重金屬毒性的研究進(jìn)展.糧食科技與經(jīng)濟(jì),2014,39(2):22-27. WU Z L,TONG X Z,YIN X B,et al.Research progress of selenium in improving plant antagonistic metal toxicity. Grain Science and Technology and Economy,2014,39(2): 22-27.(in Chinese with English abstract)

[23] 張娜,袁菊紅,胡綿好.硒對(duì)紫云英的Hormesis效應(yīng)及其生理響應(yīng)研究.生物學(xué)雜志,2015,32(2):42-47. ZHANG N,YUAN J H,HU M H.Study of selenium on Hormesis effect and physiological response of Astragalus sinicus.Journal of Biology,2015,32(2):42-47.(in Chinese with English abstract)

[24] 彭玲,賈芬,田小平,等.硒對(duì)油菜根尖鎘脅迫的緩解作用.環(huán)境科學(xué)學(xué)報(bào),2015,35(8):2597-2604. PENG L,JIA F,TIAN X P,et al.Alleviation of cadmium stress on root tip of rape seedlings by selenium.Acta Scientiae Circumstantiae,2015,35(8):2597-2604.(in Chinese with English abstract)

[25] 孫惠莉,呂金印,賈少磊.硫?qū)︽k脅迫下小白菜葉片AsAGSH循環(huán)和植物絡(luò)合素含量的影響.農(nóng)業(yè)環(huán)境科學(xué)學(xué)報(bào), 2013,32(7):1294-1301. SUN H L,LüJ Y,JIA S L.Effects of sulfur on ascorbateglutathione cycle and the content of phytochelatins in the leaves of pakchoi(Brassica chinensis L.)under cadmium stress.Journal of Agro-Environment Science,2013,32(7): 1294-1301.(in Chinese with English abstract)

[26] 何俊瑜.水稻突變體對(duì)鎘敏感的生理生化及籽粒中鎘積累的基因型差異.杭州:浙江大學(xué),2006:87-88. HE J Y.The physiology and biochemistry of rice mutant to cadmium sensitivity and genotypic difference in cadmium accumulation in brown rice.Hangzhou:Zhejiang University, 2006:87-88.(in Chinese with English abstract)

[27] LIN L,ZHOU W H,DAI H X,et al.Selenium reduces cadmium uptake and mitigates cadmium toxicity in rice. Journal of Hazardous Materials,2012,235/236:343-351.

[28] 陳京都,何理,許軻,等.鎘脅迫對(duì)不同基因型水稻生長及礦質(zhì)營養(yǎng)元素吸收的影響.生態(tài)學(xué)雜志,2013,32(12): 3219-3225. CHEN J D,HE L,XU K,et al.Growth and nutritional element absorption of different rice genotypes under cadmium stress.Chinese Journal of Ecology,2013,32(12):3219-3225.(in Chinese with English abstract)

[29] SAFARZADEH S,RONAGHI A,KARIMIAN N.Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars.Archives of Agronomy and Soil Science,2013,59(2):231-245.

DAI Zou,WANG Chunyu,LI Na,JIANG Mingjin,YAN Fengjun,XU Hui,SUN Yongjian,MA Jun*
(Key Laboratory of Crop Physiology,Ecology,and Cultivation in Southwest China,Ministry of Agriculture/Rice Research Institute,Sichuan Agricultural University,Chengdu 611130,China)

Summary Substantial amounts of heavy metals including cadmium have been released to the environment by geological activities or by anthropogenic impacts and industrialization,such as mining,smelting activities,sewage sluge,and the unreasonable utility of fertilizers and pesticides.Cadmium(Cd)is a toxic heavy metal with high mobility and can be readily absorbed into rice plants and transported to human bodies through the food chain. Selenium(Se)is an essential element for animals and human beings,which usually acts as a co-factor in antioxidant enzymes in human bodies.Though Se is not considered as an essential element for plants,there are lots of evidence suggesting its beneficial effects for plant growth and resistance to heavy metal stress.However, little effort has been found about the comparative study of Se effects with respect to different grain Cd-accumulative rice seedlings.Therefore,the aim of the present study is to explore the mitigation mechanisms of Se to Cd stress in different rice cultivars.

In this research,a hydroponic experiment was conducted to study the alleviation role of Se in two hybrid rice variety(Yixiang 2115 with low grain Cd accumulation,Chuanguyou 2348 with high grain Cd accumulation) seedlings.Cd in the concentrations of 0,0.1,1 mmol/L with or without 3μmol/L Se(Na2SeO3)solutions were treated on the two rice seedlings.The root and shoot biomasses,chlorophyll contents,Cd concentration and contents of mineral nutrient elements were measured.

The results showed that,Se increased significantly the biomass and chlorophyll a content of the two rice seedlings under the Cd stress,but decreased the chlorophyll b content in Chuanguyou 2348,which had the high Cd content in grain.The contents of ascorbic acid and glutathione in the two rice seedlings also increased with the supplement of Se,but those were higher in Chuanguyou 2348 than in Yixiang 2115,showing the differences between the two varieties.Under the 1 mmol/L Cd stress,Se promoted the synthesis of ascorbic acid and reduced glutatione to alleviate Cd stress in Chuanguyou 2348,but accelerated the synthesis of phytochelatins in Yixiang 2115 to mitigate Cd stress.Se also mitigated the injuries of the Cd stress to roots,which kept root activity in higher level than those without Se supplementation.The Cd content in shoots of the two varieties increased sharply with the Cd concentration increasing in the nutrient solution.Se could inhibit the absorption of Cd in the two varieties directly.Se could decrease the contents of calcium(Ca)and zinc(Zn)in shoots of the two varieties under the Cd stresses,but induced different reactions on cuprum(Cu)and manganese(Mn)contents.To the roots,Se increased the Ca and Cu contents,but decreased the Zn and Mn contents in the two varieties under the Cd stress conditions.

It is concluded that,Se can mitigate inhibition of Cd stress to rice seedling growth by elevating seedling biomass,chlorophyll a content,changing the contents of ascorbic acid,glutathione and non-protein thiols, keeping higher root activity compared with only Cd treatment.Besides,Se can directly suppress Cd uptake in rice seedlings and mainly affects Cu and Mn concentrations in shoots between the two rice varieties.

Key wordsrice(Oryza sativa);seedling stage;cadmium stress;selenium;alleviation

Alleviation role and effects of selenium on mineral nutrients in rice(Oryza sativa)seedlings under cadmium stress.Journal of Zhejiang University(Agric.&Life Sci.),2016,42(6):720- 730

DOI:10.3785/j.issn.1008-9209.2016.01.141

中圖分類號(hào)S 511;S 143.7

文獻(xiàn)標(biāo)志碼A

基金項(xiàng)目:國家“十二五”科技支撐計(jì)劃(2011BAD16B05,2012BAD04B13,2013BAD07B13);四川省科技支撐計(jì)劃(2014NZ0040, 2014NZ0041,2014NZ0047);四川省育種攻關(guān)專項(xiàng)(2011NZ0098-15).

*通信作者(Corresponding author):馬均(http://orcid.org/0000-0001-6103-5635),E-mail:majunp2002@163.com

收稿日期(Received):2016 01 14;接受日期(Accepted):2016 04 19;網(wǎng)絡(luò)出版日期(Published online):2016 11 19

第一作者聯(lián)系方式:代鄒(http://orcid.org/0000-0003-2795-3058),E-mail:daizou1989@163.com

URL:http://www.zjujournals.com/agr/CN/article/download ArticleFile.do?attach Type=PDF&id=10433