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      舟山新木姜子幼苗對(duì)干旱脅迫的生理響應(yīng)

      2017-11-14 09:46:30王一航趙路遙王國(guó)明朱愛(ài)意
      關(guān)鍵詞:木姜子復(fù)水凈光合

      王一航,趙路遙,王國(guó)明,朱愛(ài)意*

      舟山新木姜子幼苗對(duì)干旱脅迫的生理響應(yīng)

      王一航1,趙路遙1,王國(guó)明2,朱愛(ài)意1*1

      (1.浙江海洋大學(xué)國(guó)家海洋設(shè)施養(yǎng)殖工程技術(shù)研究中心,浙江舟山316022;2.舟山市農(nóng)林科學(xué)研究院,浙江舟山316003)

      以海島樹(shù)種舟山新木姜子(Neolitsea sericea)的一年生幼苗為材料,采用盆栽控水模擬干旱脅迫處理,研究苗木葉片在輕度、中度和重度干旱脅迫以及復(fù)水(土壤含水量分別為田間持水量的55%~60%、40%~45%、30%~35%和75%~80%)后的光合特性、保護(hù)酶活性、滲透調(diào)節(jié)物質(zhì)含量等生理指標(biāo)隨時(shí)間的動(dòng)態(tài)變化。結(jié)果表明:在中度及重度干旱脅迫下葉片的總?cè)~綠素含量、凈光合速率、蒸騰速率及氣孔導(dǎo)度明顯下降,而在重度干旱脅迫下葉片的胞間CO2濃度呈現(xiàn)先降低后升高的趨勢(shì),說(shuō)明在重度干旱脅迫中期以及中度干旱脅迫期間,葉片凈光合速率的下降主要受到氣孔限制因素的影響,而在重度干旱脅迫后期則是受到非氣孔限制因素的影響。復(fù)水后蒸騰速率仍處于較低水平,葉片的氣孔調(diào)節(jié)功能有所喪失。干旱脅迫提高了葉片的水分利用效率,但在重度干旱脅迫下葉片的水分利用效率從脅迫中期開(kāi)始呈明顯的下降趨勢(shì)。在中度及重度干旱脅迫下舟山新木姜子葉片的丙二醛含量、超氧化物歧化酶及過(guò)氧化物酶活性均呈先升高后降低的趨勢(shì),說(shuō)明丙二醛的產(chǎn)生與清除達(dá)到了一個(gè)動(dòng)態(tài)平衡。干旱脅迫使葉片細(xì)胞膜透性顯著增加,葉片通過(guò)提高合成可溶性糖和脯氨酸緩解滲透壓,使葉片細(xì)胞膜透性在干旱脅迫中后期逐漸降低;但在重度干旱脅迫下葉片的細(xì)胞膜透性在復(fù)水后仍保持在較高水平,表明細(xì)胞膜遭受到了一定的損傷。綜上所述,在干旱脅迫下舟山新木姜子能快速調(diào)節(jié)葉片氣孔,清除活性氧,進(jìn)行滲透調(diào)節(jié),降低蒸騰速率、丙二醛含量,增加細(xì)胞膜透性,提高水分利用效率,從而減少干旱帶來(lái)的損傷,但是持久、嚴(yán)重的干旱使葉片的氣孔調(diào)節(jié)功能喪失,細(xì)胞膜受損。

      舟山新木姜子;干旱脅迫;光合特性;保護(hù)酶;滲透調(diào)節(jié)物質(zhì)

      海島的地理隔離性質(zhì),以及外來(lái)物種的引進(jìn)和不適當(dāng)?shù)墓芾韺?dǎo)致海島生態(tài)系統(tǒng)比內(nèi)陸更加脆弱。在海島發(fā)展過(guò)程中,由于伐林造田、外來(lái)物種的引入以及現(xiàn)代化城市的發(fā)展,海島頂級(jí)植物群落面臨被清除的威脅,生態(tài)環(huán)境遭到嚴(yán)重破壞[1-4]。近年來(lái),植被恢復(fù)成為生態(tài)系統(tǒng)修復(fù)的主要工作[5-6]。海島造林在改善海島生態(tài)環(huán)境、促進(jìn)經(jīng)濟(jì)發(fā)展等方面有重要的意義[7]。然而與內(nèi)陸地區(qū)相比,海島造林立地條件較為惡劣,諸如土壤貧瘠、淡水資源貧乏、季節(jié)性干旱頻繁等,樹(shù)苗的存活率常常低于50%,在干旱年份甚至降為0[8]。舟山列島作為代表性的海島,小島眾多,淡水資源普遍比較貧乏,年平均降水量也較低,季節(jié)性缺水現(xiàn)象十分顯著,小島造林條件較為惡劣。水分虧缺會(huì)嚴(yán)重影響植物的生長(zhǎng)及代謝水平,但植物只有適應(yīng)這種環(huán)境才能生存。

      研究表明,一些樟科植物具有一定的抗旱能力。有學(xué)者在對(duì)水分脅迫下幼苗光合或生理特性的研究中發(fā)現(xiàn),黑殼楠表現(xiàn)出較強(qiáng)的耐澇性和耐旱性,且耐澇、耐旱的能力高于香樟[9-10];香樟在輕度干旱脅迫下能通過(guò)體內(nèi)抗氧化系統(tǒng)和滲透調(diào)節(jié)系統(tǒng)維持其正常生長(zhǎng)[11];浙江楠幼苗具有較強(qiáng)的水分調(diào)節(jié)能力,能適應(yīng)輕度干旱和水澇,抵抗重度干旱[12];楠木在生理層面對(duì)干旱和水澇都有一定的適應(yīng)機(jī)制[13];普陀樟和香楠的抗旱能力高于其他海島樹(shù)種[14]。

      舟山新木姜子(Neolitsea sericea)屬于樟科常綠喬木,生長(zhǎng)于海岸石縫,根系發(fā)達(dá),抗風(fēng)耐旱,耐鹽堿,生長(zhǎng)適應(yīng)性強(qiáng),引種范圍廣,是優(yōu)良的海島造林樹(shù)種,同時(shí)也是國(guó)家二級(jí)珍稀保護(hù)植物,1996年被評(píng)為舟山市市樹(shù),多用于行道與花園中[15]。舟山新木姜子作為舟山海島原著樟科植物能夠適應(yīng)干旱、貧瘠的土壤環(huán)境,說(shuō)明此物種進(jìn)化出了適應(yīng)水分虧缺的特殊機(jī)制。本研究以舟山新木姜子為材料,采用土培方式模擬干旱脅迫,通過(guò)定期觀察苗木在干旱脅迫下生理指標(biāo)的動(dòng)態(tài)變化,明確干旱強(qiáng)度與植物光合特性、抗氧化酶活性物質(zhì)、滲透調(diào)節(jié)物質(zhì)及細(xì)胞膜透性等的相互關(guān)系,以探討舟山新木姜子的抗旱機(jī)制,為海島地區(qū)綠化造林提供理論依據(jù)。

      1 材料與方法

      1.1 材料與處理

      試驗(yàn)苗種為一年生舟山新木姜子盆栽苗,2016年7月購(gòu)于舟山市農(nóng)林科學(xué)研究院苗木基地。試驗(yàn)用土為普通圃地土[10],基本理化性質(zhì)如下:持水量45.83%,體積質(zhì)量(容重)1.33 g/cm3,pH 5.51,有機(jī)質(zhì)14.32 g/kg,全氮0.76 g/kg。栽植用花盆的盆口直徑為20 cm,高18 cm,每盆裝入普通圃地土3 kg,每個(gè)花盆栽植苗木1株。

      試驗(yàn)于2016年7月在浙江海洋大學(xué)浙江省近海海洋工程技術(shù)重點(diǎn)實(shí)驗(yàn)室內(nèi)進(jìn)行。苗木栽植后經(jīng)過(guò)30 d的緩苗期,選取無(wú)病蟲(chóng)害、生長(zhǎng)基本一致的健壯幼苗120株,于8月21日開(kāi)始進(jìn)行干旱脅迫處理,10月5日開(kāi)始復(fù)水,10月15日結(jié)束試驗(yàn)。結(jié)合舟山往年夏秋氣候數(shù)據(jù),采用中央空調(diào)、日光燈和加濕器等對(duì)培養(yǎng)環(huán)境進(jìn)行人為控制,培養(yǎng)室環(huán)境設(shè)置為:白天光照13 h(7:00—20:00),光照強(qiáng)度5 000 lx,溫度27 ℃;夜晚時(shí)長(zhǎng)11 h(20:00—7:00),溫度22℃;濕度60%~70%。按土壤水分含量共設(shè)4個(gè)處理,分別為對(duì)照(CK)、輕度干旱脅迫(T1)、中度干旱脅迫(T2)和重度干旱脅迫(T3),其土壤含水量分別為土壤持水量的75%~80%、55%~60%、40%~45%和30%~35%。每個(gè)處理10株幼苗,3次重復(fù),分別在處理0、15、30、45 d以及復(fù)水至適宜水分10 d后進(jìn)行各項(xiàng)生理指標(biāo)測(cè)定。

      干旱脅迫處理開(kāi)始前將各盆苗木澆透,當(dāng)各處理組土壤水分含量分別自然降至處理范圍內(nèi)后開(kāi)始試驗(yàn)。試驗(yàn)期間密封花盆底部以防止水分流失,并利用稱量法控制各處理的土壤含水量,每隔1 d監(jiān)測(cè)1次水分含量,低于水分含量下限的通過(guò)插孔注射補(bǔ)水至上限。定期觀察和記錄苗木的形態(tài)變化,并調(diào)查存活率。

      1.2 測(cè)量指標(biāo)與方法

      每株選擇3片中上部葉片,標(biāo)記為測(cè)定葉片,在10:00—12:30測(cè)定其光合作用參數(shù)。用Li-6400便攜式光合作用測(cè)定儀(Li-COR公司,美國(guó))測(cè)定凈光合速率(net photosynthetic rate,Pn)、氣孔導(dǎo)度(stomatalconductance,Gs)、胞 間 CO2濃 度(intercellular CO2concentration,Ci)、蒸 騰 速 率(transpiration rate,Tr)等光合作用參數(shù)。根據(jù)測(cè)定的光合速率和蒸騰速率的比值(Pn/Tr),計(jì)算出水分利用效率(water use efficiency,WUE)。然后摘取葉片進(jìn)行以下指標(biāo)測(cè)定。

      單位葉面積總?cè)~綠素(total chlorophyll,Chl)含量測(cè)定采用丙酮-乙醇浸提法[11];超氧化物歧化酶(superoxide dismutase,SOD)活性測(cè)定采用氮藍(lán)四唑(NBT)法[16];過(guò)氧化物酶(peroxidase,POD)活性測(cè)定采用愈創(chuàng)木酚法[17];丙二醛(malondialdehyde,MDA)及可溶性糖含量測(cè)定采用硫代巴比妥酸法[18];游離脯氨酸含量測(cè)定采用酸性茚三酮比色法[19];葉片細(xì)胞膜透性測(cè)定采用相對(duì)電導(dǎo)率(Rc)法[20]。

      1.3 數(shù)據(jù)處理

      試驗(yàn)結(jié)果采用SPSS 19.0進(jìn)行多變量分析,用單因素分差分析進(jìn)行鄧肯多重檢驗(yàn)(p<0.05),利用Excel 2013進(jìn)行數(shù)據(jù)整理與繪圖。

      2 結(jié)果與分析

      2.1 干旱脅迫對(duì)舟山新木姜子幼苗形態(tài)特征的影響

      如表1所示,在脅迫及復(fù)水期間,苗木在T1條件下表現(xiàn)正常。脅迫第15天時(shí),3株苗木在T3條件下出現(xiàn)葉片輕微下垂和卷曲;脅迫第30天時(shí),3株苗木在T2條件下出現(xiàn)葉片輕微下垂和卷曲,在T3條件下全株葉片輕微下垂,6株葉片卷曲明顯,并有6株生長(zhǎng)明顯比CK矮小;脅迫第45天時(shí),5株苗木在T2條件下出現(xiàn)葉片輕微下垂,3株出現(xiàn)葉片輕微卷曲,1株生長(zhǎng)矮小并且葉片明顯卷曲,在T3條件下全株葉片輕微下垂,并且卷曲嚴(yán)重,新老葉片都較短小,植株也較矮??;在復(fù)水后10 d,T1處理的苗木全部恢復(fù),T2處理的苗木基本恢復(fù)但仍有1株生長(zhǎng)矮小、葉片輕微卷曲,而T3處理的苗木依舊全株矮小、葉片短小,大部分葉片仍呈現(xiàn)出葉片輕微下垂和明顯卷曲。各處理的苗木均未出現(xiàn)失綠、枯落或死亡現(xiàn)象。

      表1 持續(xù)干旱脅迫對(duì)舟山新木姜子幼苗形態(tài)特征的影響Table 1 Effect of continuous drought stress on morphological characteristics of Neolitsea sericea

      2.2 干旱脅迫下舟山新木姜子幼苗葉片的光合響應(yīng)

      由圖1A可以看出,舟山新木姜子幼苗葉片單位面積的總?cè)~綠素(Chl)含量隨干旱脅迫時(shí)間的延長(zhǎng)而逐漸降低。其中T2與T3處理組在脅迫末期(45 d)的Chl含量顯著低于CK(p<0.05),分別為CK的66.4%與65.8%,而T1組在脅迫期間(0~45 d)與CK的差異無(wú)統(tǒng)計(jì)學(xué)意義。各處理組在復(fù)水后10 d的Chl含量均有回升的趨勢(shì),其中T2處理組在復(fù)水后顯著升高(p<0.05)。

      不同強(qiáng)度的干旱脅迫處理對(duì)幼苗葉片凈光合速率(Pn)的影響存在明顯差異(圖1B)。T1處理的葉片Pn隨脅迫時(shí)間的延長(zhǎng)呈現(xiàn)先升高后降低的趨勢(shì),在脅迫第30天時(shí)達(dá)到最大值,且顯著高于CK(p<0.05)。各處理組均在脅迫第45天時(shí)降至最低值,其中T3處理與CK相比差異有統(tǒng)計(jì)學(xué)意義(p<0.05)。T2及T3處理的Pn在復(fù)水后顯著升高(p<0.05),其中T2組比第45天時(shí)高出29.4%。

      由圖1C可以看出,各處理葉片的蒸騰速率(Tr)均隨脅迫時(shí)間的延長(zhǎng)逐漸降低,且在干旱脅迫第45天時(shí)均顯著低于CK(p<0.05)。復(fù)水后各處理無(wú)顯著變化,但T3組仍顯著低于CK(p<0.05)。

      圖1D為根據(jù)Pn/Tr計(jì)算得出的水分利用效率(WUE)的動(dòng)態(tài)變化。從中可以看出,各處理隨脅迫時(shí)間的延長(zhǎng)均呈先升高后降低的趨勢(shì),其中:T1組在第30天時(shí)升至最高值且顯著高于CK(p<0.05);T2、T3組在第15天時(shí)升至最高值,且T2組顯著高于CK(p<0.05);各處理組的WUE均在第45天時(shí)降到最低值,但與復(fù)水后10 d相比無(wú)顯著性差異,其中T2組在復(fù)水后10 d時(shí)仍保持較高的WUE,且顯著高于CK(p<0.05)。

      由圖1E可知,脅迫期間各處理葉片的氣孔導(dǎo)度(Gs)隨脅迫時(shí)間的變化趨勢(shì)與Pn相似,均在第45天時(shí)降至最低值。復(fù)水后各處理的Gs顯著回升(p<0.05),其中T1組顯著高于CK與脅迫第45天時(shí)T1的Gs值(p<0.05)。

      由圖1F可以看出:T1與T2處理的胞間CO2濃度(Ci)在脅迫期間呈先升高后降低的趨勢(shì),但變化并不明顯,復(fù)水后也無(wú)明顯變化;而T3處理的Ci呈現(xiàn)出相反的趨勢(shì),在第30天時(shí)顯著降低至CK的74%左右(p<0.05),在第45天時(shí)又升高至與CK無(wú)顯著性差異,復(fù)水后繼續(xù)升高并顯著高于脅迫第45天時(shí)的Ci值(p<0.05)。

      2.3 干旱脅迫對(duì)舟山新木姜子幼苗葉片抗氧化酶活性的影響

      圖1 在干旱脅迫下舟山新木姜子葉片光合指標(biāo)的動(dòng)態(tài)變化Fig.1 Dynamic changes of photosynthetic indexes in the leaves of Neolitsea sericea under drought stress

      由圖2可以看出:T1處理的SOD與POD活性在處理15~55 d時(shí)分別維持在(264.9±4.9)U/g和(917.8±143.9)U/(g·min)的穩(wěn)定水平,但T1處理的POD活性均顯著高于CK(p<0.05);T2與T3處理的SOD活性在第15天時(shí)升至最高值并顯著高于CK(p<0.05),分別是CK的2.653倍和2.996倍,而POD活性在第30天時(shí)升至最高值并顯著高于CK(p<0.05),分別是CK的3.775倍與4.891倍,隨后至45 d時(shí),T2、T3處理的SOD與POD活性逐漸降低,但POD活性仍顯著高于CK(p<0.05);復(fù)水后各處理的POD活性均顯著降低,但T3處理組仍顯著高于CK(p<0.05)。

      圖2 在干旱脅迫下舟山新木姜子幼苗葉片的超氧化物歧化酶(SOD)及過(guò)氧化物酶(POD)活性的動(dòng)態(tài)變化Fig.2 Dynamic changes of the superoxide dismutase(SOD)and peroxidase(POD)activities in the leaves of Neolitsea sericea under drought stress

      2.4 干旱脅迫對(duì)舟山新木姜子幼苗葉片滲透調(diào)節(jié)物質(zhì)的影響

      各處理組葉片的脯氨酸含量均隨脅迫時(shí)間的延長(zhǎng)而呈升高的趨勢(shì)(圖3A)。T1處理組在第30及45天時(shí)與CK存在統(tǒng)計(jì)學(xué)上的顯著差異(p<0.05);T2、T3處理組均在第15天時(shí)顯著高于CK(p<0.05),并在第45天時(shí)升至最高值,分別是CK的9.219倍與10.952倍。復(fù)水后各處理葉片的脯氨酸含量均顯著降低,但T2與T3組仍顯著高于CK(p<0.05)。

      由圖3B可以看出,各處理組葉片的可溶性糖含量在干旱處理15~45 d期間均顯著高于CK(p<0.05),其中T3處理組在第45天時(shí)升至最高,且顯著高于其他處理組(p<0.05)。各處理在復(fù)水后10 d時(shí)的可溶性糖含量均顯著低于45 d,但T2處理組仍顯著高于CK(p<0.05)。

      圖3 在干旱脅迫下舟山新木姜子幼苗葉片脯氨酸及可溶性糖含量的動(dòng)態(tài)變化Fig.3 Dynamic changes of the proline and soluble sugar contents in the leaves of Neolitsea sericea under drought stress

      2.5 干旱脅迫對(duì)舟山新木姜子幼苗葉片丙二醛含量及細(xì)胞膜透性的影響

      各處理組葉片的丙二醛(MDA)含量均在干旱脅迫第15天時(shí)顯著升高(p<0.05)(圖4A)。T1、T3處理組在第15天時(shí)升至最高值,分別是CK的4倍及13.526倍,但隨著脅迫時(shí)間的延長(zhǎng),MDA含量逐漸降低;T2處理組的MDA含量在第30天時(shí)升至最高值,是CK的8倍,隨后在第45天時(shí)呈降低的趨勢(shì);復(fù)水后各處理的MDA含量均有所下降,其中T2、T3組下降顯著,但仍顯著高于CK(p<0.05)。

      相對(duì)導(dǎo)電率(Rc)隨脅迫時(shí)間的變化趨勢(shì)與MDA的變化趨勢(shì)類似(圖4B)。各處理組Rc均在第15天時(shí)顯著升高(p<0.05),并在第30天時(shí)達(dá)到最大值,分別比CK高出了185.7%、499.2%及822.6%。復(fù)水后各處理組的Rc均顯著下降,但T2與T3組仍顯著高于CK(p<0.05)。

      圖4 在干旱脅迫下舟山新木姜子幼苗葉片的丙二醛含量及相對(duì)電導(dǎo)率的動(dòng)態(tài)變化Fig.4 Dynamic changes of the malondialdehyde(MDA)content and relative conductivity(Rc)in the leaves of Neolitsea sericea under drought stress

      3 討論與結(jié)論

      干旱脅迫會(huì)導(dǎo)致植物體內(nèi)活性氧自由基增多,而過(guò)剩的自由基會(huì)引發(fā)膜脂過(guò)氧化,導(dǎo)致膜脂過(guò)氧化產(chǎn)物如丙二醛的積累,造成膜系統(tǒng)的損傷,嚴(yán)重時(shí)會(huì)導(dǎo)致植物細(xì)胞的死亡[21]。植物在逆境條件下會(huì)維持較高的抗氧化酶活性,這有利于清除活性氧,減輕對(duì)膜系統(tǒng)的損傷[22-23]。在本研究中,脅迫初期舟山新木姜子葉片的過(guò)氧化物酶、超氧化物歧化酶活性隨丙二醛含量及相對(duì)電導(dǎo)率的增加而顯著升高。隨著過(guò)氧化物酶活性持續(xù)增加,丙二醛的清除速度已超過(guò)了積累速度,相對(duì)電導(dǎo)率逐漸下降,超氧化物歧化酶活性也同步回落,這時(shí)植物體已對(duì)干旱環(huán)境有了初步適應(yīng)。同時(shí),也可以推斷超氧化物歧化酶在舟山新木姜子受到干旱脅迫時(shí)最先響應(yīng),而過(guò)氧化物酶對(duì)干旱脅迫的反應(yīng)相對(duì)遲緩但作用時(shí)間較長(zhǎng)。這與抗旱樹(shù)種紅花玉蘭[24]、普陀樟[25]、杠柳[26]的研究結(jié)果一致。

      在干旱脅迫下,植物能夠產(chǎn)生或吸收更多的滲透調(diào)節(jié)物質(zhì)如脯氨酸及可溶性糖等以調(diào)節(jié)體內(nèi)滲透壓,維持細(xì)胞膜的完整性并穩(wěn)定蛋白質(zhì)結(jié)構(gòu),從而保持生命活動(dòng)的正常進(jìn)行[27-29]。在干旱脅迫初期,舟山新木姜子葉片中可溶性糖和脯氨酸含量迅速大幅度提高,且隨著干旱脅迫的持續(xù)和強(qiáng)度的增加而升高,有效緩解了干旱脅迫的壓力,這與普陀樟[25]及杠柳[26]的研究結(jié)果一致。

      干旱能使植物的光合作用受到抑制,通過(guò)氣孔限制和非氣孔限制來(lái)降低凈光合速率。當(dāng)凈光合速率和胞間CO2濃度同時(shí)減小時(shí),凈光合速率下降主要由氣孔導(dǎo)度引起,否則由非氣孔限制因素引起[30]。重度干旱脅迫處理的葉片總?cè)~綠素含量、凈光合速率、氣孔導(dǎo)度及胞間CO2濃度在脅迫試驗(yàn)中期均明顯下降,說(shuō)明此時(shí)葉片凈光合速率下降受到了氣孔限制因素的影響,而脅迫后期葉片總?cè)~綠素含量、凈光合速率、蒸騰速率及氣孔導(dǎo)度持續(xù)降至最低,胞間CO2濃度卻有所回升,說(shuō)明此時(shí)葉片中的葉綠體受損,氣孔調(diào)節(jié)功能有所喪失,凈光合速率的下降則主要受非氣孔限制因素的影響。對(duì)櫟屬植物的研究表明:一般輕度干旱脅迫不影響櫟屬植物幼苗的光合作用,甚至對(duì)光合作用有一定的促進(jìn)作用;但隨著干旱脅迫的加重,光合作用受到抑制,凈光合速率迅速下降[31]。在本研究中,舟山新木姜子幼苗的光合作用有著相似的表現(xiàn),即在輕度和中度干旱脅迫時(shí)能通過(guò)調(diào)節(jié)氣孔導(dǎo)度、蒸騰速率等維持較高的凈光合速率,使水分利用效率處于較高的水平,但在重度干旱脅迫下,凈光合速率則隨著干旱脅迫時(shí)間的延長(zhǎng)逐漸降低,水分利用效率也有所下降。

      復(fù)水10 d后,各處理組的超氧化物歧化酶活性、總?cè)~綠素含量、凈光合速率、氣孔導(dǎo)度及胞間CO2濃度均恢復(fù)至正常水平,而在中度或重度干旱脅迫下葉片的過(guò)氧化物酶活性、可溶性糖、脯氨酸、丙二醛含量及相對(duì)電導(dǎo)率均有大幅降低的趨勢(shì),說(shuō)明植物體尚需一定時(shí)間完全解除干旱響應(yīng);在重度干旱脅迫下的蒸騰速率仍處于較低水平,說(shuō)明葉片氣孔調(diào)節(jié)功能受到一定損傷。

      以上分析表明,雖然舟山新木姜子在長(zhǎng)期重度干旱脅迫下的生長(zhǎng)受到限制,葉片的氣孔調(diào)節(jié)功能喪失、細(xì)胞膜受損,導(dǎo)致葉片曲卷,但舟山新木姜子能通過(guò)積極調(diào)節(jié)自身抗氧化物質(zhì)、滲透調(diào)節(jié)物質(zhì)及提高水分利用效率等方式免受或緩解干旱帶來(lái)的傷害,迅速適應(yīng)輕度及中度干旱脅迫,在脅迫解除后能恢復(fù)正常生長(zhǎng),屬于較耐旱樹(shù)種,推測(cè)其可耐受的重度干旱脅迫時(shí)間為45 d。

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      Physiological responses in Neolitsea sericea seedlings to drought stress.Journal of Zhejiang University(Agric.&Life Sci.),2017,43(5):543-551

      WANG Yihang1,ZHAO Luyao1,WANG Guoming2,ZHU Aiyi1*
      (1.National Engineering Research Center of Marine Facilities Aquaculture,Zhejiang Ocean University,Zhoushan 316022,Zhejiang,China;2.Zhoushan Academy of Agriculture and Forestry Sciences,Zhoushan 316003,Zhejiang,China)

      Neolitseasericea;droughtstress;photosynthesischaracteristics;protectiveenzyme;osmoticadjustmentmaterial

      S 718.43;Q 945.78

      A

      10.3785/j.issn.1008-9209.2017.01.042

      Summary During development process of the Zhoushan archipelago,the original old-growth broadleaved forests on the islands have been severely destroyed due to intensive human activity.Neolitsea sericea(Lauraceae),distributed on a few islands of the Zhoushan archipelago,is facing the danger of extinction due to rapid degradation and destruction of original habitats.So far,plenty of studies on N.sericea have been focused on its population genetic diversity and genetic structure.Neolitsea sericea is well adaptable to the environment,thus can survive in the ravine on the islands.The strong tolerance of N.sericea to drought,wind,salt and barren soil also makes it optimal species for afforestation.However,few studies ondrought tolerance of N.sericea have been reported yet.

      國(guó)家海洋公益性行業(yè)科研專項(xiàng)(201305009-3)。

      朱愛(ài)意(http://orcid.org/0000-0002-7821-8558),E-mail:zay008@163.com

      (First author):王一航(http://orcid.org/0000-0001-9312-0527),E-mail:lapd-wyh@hotmail.com

      2017-01-04;接受日期(Accepted):2017-03-23

      Plant response to drought stress at a molecular level is a complex biological process,involving consideration of the stress effects and regulation events.Thus,it is of great importance to analyze the underlying mechanism systematically at the physiological level.

      In this study,one-year-old seedlings of N.sericea were selected as test materials.To obtain a more complete physiological mechanism in responses to drought stress,N.sericea was exposed under the conditions of four different relative water contents(normal water supply,light drought,moderate drought and severe drought)in soil for 45 days.The relative water content in soil of normal water supply,light drought,moderate drought,and severe drought was controlled in 75%-80%,55%-60%,40%-45%and 30%-35%of field capacity,respectively.All plants were rehydrated after drought treatments by normal water supply for 10 d.The relative water content in soil was controlled by pot-weighing method through the experiment.The dynamic changes of the physiological and photosynthetic traits in leaves were measured every 15 days of stress treatments and at the end of rehydration.The traits measured in this study include net photosynthetic rate(Pn),stomatal conductance(Gs),water use efficiency(WUE),intercellular CO2concentration(Ci),transpiration rate(Tr),total content of chlorophyll(Chl),superoxide dismutase(SOD)and peroxidase(POD)activities,proline content,malondialdehyde(MDA)content,soluble sugar content and relative conductivity(Rc).

      The results showed that the contents of Chl,Pn,Tr and Gs decreased constantly and significantly during severe drought,and the content of Ci decreased in 0-30 d but enhanced in 30-45 d during the severe drought,which indicated that the decrease of Pn was caused by stomatal limitation during the 0-30 d of severe drought,and by non-stomatal limitation during 30-45 d of severe drought.The continuous inhibition of Tr after rehydration from severe drought suggested the afunction of stomatal regulation.The drought stress increased the overall WUE of the leaves,although the WUE dropped significantly in 30-45 d of severe drought.The trend of MDA content,SOD and POD activities in N.sericea first increased and then decreased during the drought treatments,indicating the production and clearance of MDA had reached a dynamic balance.The significant increase of Rc indicated the elevation of cell membrane permeability.The overexpression of soluble sugar and proline in leaves during 30-45 d of drought treatment resulted in the reduction of Rc,which relieved the osmotic pressure in N.sericea.However,Rc staying at a high level after rehydration from severe drought indicated the damage of cell membrane.

      In conclusion,N.sericea can conduct the instant stomatal regulation,eliminate active oxygen and regulate the osmotic pressure effectively,decrease the Tr and MDA content,increase the cell membrane permeability and enhance the WUE of leaves,to reduce the damage under the drought stress.However,severe and persistent droughts lead to irreversible damage in leaves,such as the afunction of stomatal regulation and damage in cell membrane.

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