白林利, 韓文嬌, 李昌曉

(西南大學生命科學學院,三峽庫區(qū)生態(tài)環(huán)境教育部重點實驗室,重慶400715)

模擬水淹對水杉苗木生長與生理生化特性的影響

白林利, 韓文嬌, 李昌曉*

(西南大學生命科學學院,三峽庫區(qū)生態(tài)環(huán)境教育部重點實驗室,重慶400715)

通過對在不同土壤水分處理下水杉(Metasequoiaglyptostroboides)保護酶系[超氧化物歧化酶(superoxide dismutase,SOD)、過氧化物酶(peroxidase,POD)、抗壞血酸過氧化物酶(ascorbate peroxidase,ASP)、過氧化氫酶(catalase,CAT)]活性及滲透調節(jié)物質(可溶性蛋白質、游離脯氨酸)和細胞膜脂過氧化產物[丙二醛(malondialdehyde,MDA)]含量以及光合特性、生物量的測定,探討水杉對三峽庫區(qū)水位變化的響應特性和耐水淹適應能力。模擬三峽庫區(qū)消落帶土壤水分變化格局,以二年生水杉苗木為試驗材料,設置對照組(control,CK)、半淹組(half-submersion,HS)和全淹組(full-submersion,FS)3個處理。結果表明:在水淹脅迫下,SOD、POD、ASP、CAT活性以及游離脯氨酸含量均升高。在水淹脅迫下,水杉葉片MDA含量與CK相比差異不顯著,無統(tǒng)計學意義。HS凈光合速率(net photosynthetic rate,Pn)顯著高于CK；FS的根冠比顯著高于CK,但與HS相比差異不顯著,無統(tǒng)計學意義。全淹植株呈葉芽形式,水淹植株存活率均達100%。在淹水期間,由于抗氧化酶、滲透調節(jié)物質、光系統(tǒng)Ⅱ的積極響應,水杉表現(xiàn)出極強的水分適應能力。因此,可以考慮將水杉列為三峽庫區(qū)消落帶植被構建的候選樹種之一。

水杉； 水分脅迫； 生長； 生理生化

三峽工程給長江流域的生態(tài)環(huán)境帶來了巨大影響[1],因三峽工程的興建,三峽庫區(qū)生態(tài)系統(tǒng)的水文循環(huán)、生物多樣性格局和庫區(qū)氣候等正在發(fā)生著一系列改變[2],在庫區(qū)消落帶內人工構建植被、減少污染物質進入水體、保持庫岸水土、維持和增強消落帶的生態(tài)功能尤為重要。現(xiàn)有消落帶與原有消落帶相比,水淹時間更長、水淹程度更深,并且是在冬季水淹,這將很可能打亂庫岸帶植物的生理節(jié)律,影響這些庫岸植物的光合作用與生長發(fā)育。重建和恢復消落帶植被面臨嚴峻的考驗,而其中的關鍵就是對耐水淹樹種的篩選[3]。因此,本文將耐水淹作為切入點,研究樹種耐水淹的生理生化機制,為三峽庫區(qū)消落帶植被構建提供參考。

水杉(Metasequoiaglyptostroboides)是三峽庫區(qū)庫岸帶典型的鄉(xiāng)土樹種,別稱水沙,屬杉科水杉屬；其根系發(fā)達,耐寒與耐受多種水分逆境的能力較強,是亞熱帶地區(qū)平原綠化的優(yōu)良樹種[4]。目前對水杉的研究多集中于基因結構[5-7]、膜結構[8]、化學成分[9-14]、生長特性[15-17]和光合作用[18-19]等方面。但關于水杉對水分脅迫的響應缺乏生長、生化、光合特性的系統(tǒng)性研究,尤其是在三峽庫區(qū)消落帶土壤水分變化條件下水杉苗木的生理生態(tài)學特性鮮有報道,特別是對全淹條件下的變化情況不得而知。

本文擬對不同水淹深度下水杉的生長與生理生化特性進行研究,探索水杉在不同水淹條件下的生理生化響應機制,為其在三峽庫區(qū)消落帶高海拔地段栽植提供理論依據。

1 材料與方法

1.1 試驗材料與處理方法

考慮到庫岸防護林體系建設多采用二年生苗木,本試驗以二年生的水杉苗木(取自四川省鄰水縣苗圃)為試驗材料。2012年11月20日帶土盆栽樹苗(土壤類型為紫色土,其性質見表1),每盆1株(盆中央內徑20 cm,盆高17 cm),共36株。置于西南大學三峽庫區(qū)生態(tài)環(huán)境教育部重點實驗室實驗基地大棚(海拔249 m,透明頂棚,四周開敞)進行培養(yǎng),于2013年1月18日進行試驗處理[苗高(97.05±1.53) cm]。結合三峽庫區(qū)消落帶水位變化情況,設置對照組(control,CK)、半淹組(half-submersion,HS)和全淹組(full-submersion,FS)3個處理,每組12株。其中,CK為常規(guī)供水組,保持土壤含水量為田間持水量的75%～80%[2]；HS苗盆放入水池中,池水保持淹沒至植物中段；FS苗盆也放入水池中,但池水保持沒過植物頂端20 cm。于2013年4月3日結束試驗進行各項指標的測定。

表1 供試土壤營養(yǎng)元素含量初始值

1.2 分析方法

2013年4月3日開始對不同處理組進行測定,每個處理組6株水杉苗木用于生長測定,6株用于生理生化測定。

1.2.2 生長與生物量測定 采用卷尺測量苗高、冠幅,用游標卡尺測量地徑,每個處理6株,測定時間2013年4月3日。隨后將試驗盆缽中的苗木小心挖出,用自來水沖凈根系,用根系分析儀(WinRHIZO,LC4800-Ⅱ LA2400)分析根系的總根長、總表面積和總體積。然后將根(收集斷根,并用吸水紙吸干根表面水分)、莖、葉分別放置在80 ℃烘箱中烘干至恒重,用分析天平稱量,計算根冠比。

1.2.3 生理生化指標的測定 2013年4月3日,將每個處理的6株水杉苗木葉片分別全部取完,保存于-80 ℃冰箱中,用于生理生化指標測定。超氧化物歧化酶(superoxide dismutase,SOD)活性測定采用氮藍四唑(nitro-blue tetrazolium,NBT)法[24]。過氧化物酶(peroxidase,POD)活性測定采用愈創(chuàng)木酚法[24]?？箟难徇^氧化物酶(ascorbate peroxidase,ASP)的測定采用文獻[25]的方法。過氧化氫酶(catalase,CAT)活性測定采用過氧化氫氧化法,以每分鐘內吸光值減少0.1為1個酶活力單位[24]。超氧根離子(O2-)測定采用高俊鳳[26]的方法,以μg/g表示O2-的含量。丙二醛(malondialdehyde,MDA)含量的測定采用硫代巴比妥酸(thiobarbituric acid,TBA)氧化法,可溶性蛋白質含量測定采用考馬斯亮藍顯色法,游離脯氨酸含量測定采用磺基水楊酸法,用茚三酮比色法測定其含量[24]。吸光值測定均采用紫外分光光度計。

1.2.4 數據處理 根據測定的各項指標,采用單因素方差分析(One-way ANOVA)揭示水分處理對水杉生長與光合生理的影響(GLM程序,SPSS 16.0),并用Tukey檢驗法進行多重比較,檢驗每個指標在處理間(α=0.05)的差異顯著性，結果用平均值±標準誤表示。

2 結果與分析

2.1 光合色素含量變化

不同處理對水杉苗木光合色素含量的影響顯著(圖1)。與CK相比,HS的葉綠素b(chlorophyll b,Chl b)、光合色素(photosynthetic pigments，Pp)均顯著降低,分別降低35.06%和21.21%；葉綠素a(chlorophyll a,Chl a)、類胡蘿卜素(carotene,Car)、葉綠素/類胡蘿卜素(chlorophyll/yellow carotene,Chl/Car)亦降低,相比差異不顯著,無統(tǒng)計學意義；而葉綠素a/b升高了22.89%,FS中的Chl a、Chl b、Car、Pp和Chl/Car卻均顯著低于CK與HS。與之相反,FS中的Chl a/b顯著高于CK與HS。

2.2 光合指標

水淹結束時,與CK相比,HS中的Pn、CUE顯著增加,而Sc、Ci/Ca則顯著降低。HS中的Fv/Fm、PhiPS2有所增加,但與CK相比差異不顯著,無統(tǒng)計學意義(表2)。因FS中的葉芽呈未展開形式,無法測定其光合參數.此外,各處理組水杉苗木存活率都達100%,即水淹未影響水杉樹苗存活率。

2.3 滲透調節(jié)物質含量變化

在淹水脅迫下,水杉苗木體內脯氨酸含量不斷積累,且隨著脅迫程度的加劇積累越多。與CK相比,

CK:對照組;HS:半淹組;FS:全淹組.柱狀圖上的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。 CK: Control; HS: Half-submersion; FS: Full-submersion. Different lowercase letters above the histogram indicate significant difference at the 0.05 probability level．圖1 不同處理組光合色素的比較Fig.1 Comparison of photosynthetic pigments among treatment groups

表2 不同處理組光合參數的變化

Table 2 Changes of photosynthetic parameters among treatment groups

變量Variable對照組CK半淹組HSPn/[μmolCO2/(m2·s)]11.39±0.34b13.86±0.84aSc/[molH2O/(m2·s)]0.11±0.00a0.08±0.00bCi/Ca/(μmolCO2/mol)0.58±0.01a0.27±0.02bCUE=Pn/Ci0.05±0.00b0.16±0.02aFv/Fm0.77±0.00a0.78±0.00aPhiPS2=(F'm-Fs)/F'm0.08±0.00a0.09±0.00aETR39.98±1.10b46.70±1.17a

Pn：凈光合速率；Sc：氣孔導度；Ci：胞間CO2濃度；Ca：大氣CO2濃度；CUE：羧化效率；Fv/Fm：光系統(tǒng)Ⅱ的最大量子產量；PhiPS2：光系統(tǒng)Ⅱ的實際量子產量；ETR：電子傳遞速率。同行數據后不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。

Pn: Net photosynthetic rate; Sc: Stomatal conductance; Ci: Intercellular CO2concentration; Ca: Atmospheric CO2concentration; CUE: Carboxylation efficiency;Fv/Fm: The maximum quantum yield of PSⅡ; PhiPS2: The actual quantum yield of PSⅡ; ETR: Electron transfer rate. Values within a row followed by different lowercase letters show significantly different at the 0.05 probability level.

HS和FS的游離脯氨酸含量均顯著升高了34.46%和57.29%,而HS與FS相比差異不顯著,無統(tǒng)計學意義;與CK相比,在水淹結束時,HS可溶性蛋白質升高,但未達顯著水平,而FS則顯著降低(圖2).

2.4 葉片MDA與超氧根離子含量變化

在水淹結束時,HS、FS水杉苗木的MDA含量有所升高,但均與CK相比差異不顯著,無統(tǒng)計學意義；與CK相比,HS、FS水杉苗木的超氧根離子均有所降低,但均未達顯著水平(圖3)。

2.5 葉片保護酶系活性變化

在水淹脅迫下,SOD表現(xiàn)為上升的趨勢,HS顯著高于CK,而FS與CK相比差異不顯著,無統(tǒng)計學意義;與CK相比,HS、FS中的CAT活性均升高,但未達顯著水平;不同水分處理對水杉苗木POD活性的影響顯著,FS水杉苗木的POD活性顯著高于CK,HS顯著高于FS;與CK相比,HS、FS中CAT活性均升高,HS顯著高于CK與FS(圖3)。

CK:對照組;HS:半淹組;FS:全淹組.柱狀圖上的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。 CK: Control; HS: Half-submersion; FS: Full-submersion. Different lowercase letters above the histogram indicate significant difference at the 0.05 probability level．圖2 不同處理組脯氨酸、可溶性蛋白質含量的比較Fig.2 Comparison of free proline and soluble protein content among treatment groups

CK:對照組;HS:半淹組;FS:全淹組.柱狀圖上的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。 CK: Control; HS: Half-submersion; FS: Full-submersion. Different lowercase letters above the histogram indicate significant difference at the 0.05 probability level．圖3 不同處理組MDA、超氧根離子、SOD、POD、ASP、CAT的比較Fig.3 Comparison of MDA, O2-, SOD, POD, ASP, CAT among treatment groups

2.6 生長指標

2.6.1 苗高、地徑、冠幅 在水淹結束時,各處理組的苗高、地徑、冠幅都呈上升趨勢；與CK相比,HS、FS苗高的凈增長顯著降低,地徑的凈增長與CK相比差異不顯著,無統(tǒng)計學意義；HS水杉苗木冠幅的凈增長顯著高于FS,而與CK相比差異不顯著,無統(tǒng)計學意義(圖4)。

2.6.2 根長、根表面積、根體積 在水淹脅迫下,水杉苗木的根長,根表面積,根體積表現(xiàn)出一個共同的變化趨勢,即與CK相比,HS升高,FS降低；HS水杉苗木的根長、根表面積顯著高于FS,而與CK相比差異不顯著,無統(tǒng)計學意義(圖5)。

2.6.3 生物量分配 與CK相比,HS與FS的根所占比例顯著升高;HS葉所占比例與CK相比差異不顯著,FS莖所占比例與CK相比差異也不顯著,無統(tǒng)計學意義。同時,FS的根冠比顯著高于CK,但與HS相比差異不顯著,無統(tǒng)計學意義(表3)。

CK:對照組;HS:半淹組;FS:全淹組.柱狀圖上的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。 CK: Control; HS: Half-submersion; FS: Full-submersion. Different lowercase letters above the histogram indicate significant difference at the 0.05 probability level．圖4 不同處理組水杉的苗高、地徑、冠幅變化Fig.4 Changes of height, ground diameter, crown diameter of M. glyptostroboides among treatment groups

CK:對照組;HS:半淹組;FS:全淹組.柱狀圖上的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。 CK: Control; HS: Half-submersion; FS: Full-submersion. Different lowercase letters above the histogram indicate significant difference at the 0.05 probability level．圖5 不同處理組根長、根表面積、根體積的比較Fig.5 Comparison of root length, root surface area, root volume among treatment groups

表3 不同處理組水杉各器官在生物量中所占的比例

同行數據后的不同小寫字母表示在0.05水平差異有統(tǒng)計學意義。

CK： Control; HS: Half-submersion； FS： Full-submersion. Values within row followed by different lowercase letters show significantly differences at the 0.05 probability level.

3 討論

3.1 水淹對水杉苗木細胞膜的影響及其滲透調節(jié)物質的響應

滲透調節(jié)是植物適應逆境的一種重要的生理機制,植物通過代謝活動增加細胞內的溶質降低滲透勢,維持膨壓,從而使體內各種與膨壓有關的生理過程正常進行[27-28]。脯氨酸被認為是有效的滲透調節(jié)物質之一,有助于細胞或組織持水[29]。在水淹脅迫下,水杉苗木游離脯氨酸含量增加(圖2),超氧根離子含量與對照相比差異不顯著(圖3),表明水杉產生脯氨酸能適應水分脅迫,調節(jié)細胞的滲透勢和清除活性氧[30]。FS可溶性蛋白質含量顯著降低,HS有所增加,但未與CK產生顯著差異(圖2),說明全淹脅迫使水杉苗木的正常代謝過程受到干擾,抑制蛋白質的合成并誘導蛋白質的降解,從而使植株體內的蛋白質含量降低[31]；同時也表明水杉苗木對水淹逆境有一種內在的生理適應機制[32]。就本研究所測的滲透調節(jié)物質而言,從可溶性蛋白質含量相對較低,增幅平穩(wěn)并沒有對脅迫表現(xiàn)出明顯增幅加大來看,脯氨酸是水杉應對水分脅迫較為主導的滲透調節(jié)物質,它對活性氧有專一的消除作用,可保護細胞膜免受損害[33]。

在水分脅迫下,植物體內丙二醛(MDA)和活性氧的產生及積累是植物的主要生理響應特征之一[34]。MDA是膜脂過氧化產物之一,其對細胞具有很強的毒性,并且參與破壞生物膜的結構和功能,通常利用其表示細胞膜脂過氧化程度及植物對逆境條件反應的強弱[35-36]。超氧根離子傷害植物的機制之一在于參與啟動膜脂過氧化或脂膜脫酯作用[37],從而破壞膜結構。HS、FS水杉葉片MDA含量與CK相比差異不顯著,說明水淹脅迫未對水杉苗木造成膜脂損害,顯示出水杉具有良好的耐水淹特性。本研究同時發(fā)現(xiàn),在淹水結束時,淹水處理組水杉苗木的O2-含量與CK相比差異不顯著，SOD、POD、ASP和CAT均比CK高(圖3),說明水杉苗木為了抵御水分脅迫的毒害作用,形成了復雜的抗氧化防御系統(tǒng)[38]。水杉苗木保護酶系統(tǒng)在短期內能維持活性氧的動態(tài)平衡,通過提高保護酶活性以加強清除活性氧、減少其對細胞膜傷害[36],這應是水杉苗木適應水淹環(huán)境的重要機制之一[39]。

3.2 水杉對水分脅迫的保護酶系統(tǒng)響應

SOD、POD、ASP和CAT是植物體內參與活性氧代謝的主要酶,SOD催化分解O2-,使之轉化為過氧化氫(H2O2)；POD、ASP和CAT則被認為是植物清除H2O2的酶[40],它們的活性變化在一定程度上反映了植物體內活性氧的代謝情況[41]。在本研究中,HS水杉苗木的SOD、POD顯著高于CK；而O2-含量、ASP和CAT均與CK相比差異不顯著,表明在半淹脅迫下,水杉苗木啟動SOD表達,產生大量的SOD清除O2-；在清除H2O2的過程中,POD起到了最主要的作用,這與Takemura等[42]對木欖(Bruguieragymnorrhiza)的研究結果相似,這些酶的表達是水杉苗木對水淹脅迫的適應性響應[43]。FS水杉苗木的SOD、O2-含量和CAT與CK相比差異均不顯著,而POD、ASP顯著高于CK,但POD顯著低于HS。說明與半淹脅迫相比,在全淹脅迫下,水杉苗木主要通過升高ASP活性來清除H2O2,這應和其清除活性氧從而誘導提高保護酶活性與保護細胞膜有關,同時也是對水淹脅迫適應的結果[44]。

3.3 水杉對水分脅迫的光合與生長響應

水淹會使植株葉片的葉綠素降解,含量下降[45]。本研究發(fā)現(xiàn),水淹使水杉苗木Chl、Car、Chl/Car下降,表明光合色素的降解是水杉苗木應對水淹脅迫的方式之一[46-47]。與CK相比,盡管水淹組水杉苗木Chl/Car下降,但其比值仍大于3(植物葉片內的葉綠素與類胡蘿卜素含量之比通常約為3∶1[48]),提高了葉綠素在光合色素中的相對含量,確保有足夠的反應中心色素,進而提高光合能力。而與CK相比,水淹組水杉苗木Chl a/b卻顯著上升(圖1),表明水淹后水杉苗木的捕光色素降解得快,而光系統(tǒng)反應中心色素降解得慢[49],通過調節(jié)葉片Chl a與Chl b的比值來維持其較高的光合能力[50]。有研究表明,在水淹脅迫下,Chl a/b的比值上升[51],但也有研究認為下降[52]。本研究發(fā)現(xiàn),淹水處理組的Chl a/b顯著高于CK(圖1),支持了Smethurst等[51]的研究結果。這極有可能是樹種的不同所引起,不同的樹種可能具有不同的耐水淹能力和響應特性,產生這種差異的原因還有待進一步研究。

植物葉片氣孔變小甚至關閉是植物對水淹逆境脅迫的通常響應方式之一[53]。本研究發(fā)現(xiàn),在水淹脅迫下,水杉苗木的Sc降低,與Mielke等[54]對美洲格尼帕樹(Genipaamericana)的研究結果相同。羅芳麗等[55]認為水淹導致植株部分葉組織無法進行光合作用而使植株的整體光合能力受到影響,植株未被水淹的葉組織光合能力可能會增強。淹水后HS水杉苗木Pn顯著高于CK(表2),其原因可能是植物的光合能力受光合產物需求的負反饋調節(jié)[56],這可能與水杉葉片在水淹期間具有較高羧化能力有關(表2),也是水杉苗木抗氧化酶、滲透調節(jié)物質與光合色素綜合作用的結果。本研究發(fā)現(xiàn),與CK相比,HS水杉苗木的Pn增加了33%,高于相同水淹深度處理后耐淹樹種水翁(Cleistocalyxoperculatus)[57]和落羽杉(Taxodiumdistichum)[58]。可見,在短暫的水淹時間(2013-01-18—2013-04-03)內,水杉苗木與一些耐淹樹種相比其光合能力受水淹影響較小。本研究還發(fā)現(xiàn),在半淹脅迫下,水杉苗木的Pn、Sc和Ci/Ca的變化(表2)表明,水杉苗木Pn升高的原因極有可能是在短期水淹脅迫下水杉苗木的光合酶活性和利用CO2的能力較強所致[59]。

葉綠素熒光檢測可以快速、靈敏地了解植物光合作用對外界環(huán)境因子的響應[60],植物葉片PSⅡ的最大光化學效率(Fv/Fm)可以作為PSⅡ潛在光化學活性的度量,在非脅迫條件下該參數變化極小,不受物種和生長條件的影響；在脅迫條件下該參數明顯下降,表明有功能的反應中心含量降低[55]。HS水杉葉片的Fv/Fm與CK相比差異不顯著,表明半淹脅迫對水杉有功能的PSⅡ反應中心影響較小,加之水杉苗木抗氧化系統(tǒng)與光合色素的積極響應,表明水杉確實有較強的水分適應能力[61]。與CK相比,HS水杉苗木有較高PhiPS2、電子傳遞速率(表2),表明水淹對水杉葉片光合器官及羧化酶的活性影響較小。

植物的生物量、苗高和地徑與其生長發(fā)育及營養(yǎng)物質的形成密切相關,對其所處的生長環(huán)境綜合表征作用明顯[62]。本研究發(fā)現(xiàn),不管是HS還是FS,水杉苗木苗高的凈增長都低于CK,淹水脅迫抑制了植物苗高的生長[63]。本研究還發(fā)現(xiàn),半淹脅迫對水杉的生長具有部分促進作用,與東北玉簪(Hostaclausa)[64]和烏桕(Sapiumsebiferum)[65]等表現(xiàn)相似。HS水杉根長、根表面積均比CK高,HS葉所占的比例,地徑、冠幅的凈增長與CK相比差異不顯著,這有可能與半淹脅迫下水杉苗木Pn顯著高于CK有關。而水淹組水杉苗木根所占比例,根冠比顯著高于CK(表3),說明二年生水杉苗木生物量較多分配在根部,加大根部化合物的貯存,以有效應對水淹脅迫下逆境條件[66-67]。

4 結論

本研究發(fā)現(xiàn),水杉苗木的生長和生理生化代謝受到水淹脅迫的影響,其水分適應性較強。在水淹脅迫下,水杉苗木引起膜脂過氧化以及光合色素含量降低,但由于體內滲透調節(jié)物質含量的增加和抗氧化防御系統(tǒng)的積極防御,可以緩解過多水分對水杉苗木造成的損害,從而沒有對Fv/Fm和Pn造成影響。在不同淹水條件下,水杉苗木存活率均達100%,表現(xiàn)出極強的適應水環(huán)境的能力。從本研究結果來看,水杉可以作為三峽庫區(qū)消落帶植被恢復的候選樹種之一。

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Effects of simulated waterlogging on growth, physiological and biochemical characteristics ofMetasequoiaglyptostroboidesseedlings.

Bai Linli, Han Wenjiao, Li Changxiao*

(KeyLaboratoryfortheEco-EnvironmentoftheThreeGorgesReservoirRegionoftheMinistryofEducation,CollegeofLifeSciences,SouthwestUniversity,Chongqing400715,China)

The disruption of natural flow regimes in river systems poses many challenges to riparian ecosystems and their native species. The construction of the Three Gorges Dam has altered the flow regimes of the upper Yangtze River and created a riparian zone with a vertical gap of 30 m. Because of the anti-seasonal change of the water level caused by annual water regulation, plants grown on the riparian zone of the Three Gorges Reservoir Area (TGRA) may suffer from submergence, and often display dynamic change characteristics. Such water level change is likely to disturb the normal ecophysiological rhythm of the native tree species of the riparian zone. These hydrological changes highlight the importance of screening suitable tree species for reforestation in the TGRA and similar environments. Thus, the native tree speciesMetasequoiaglyptostroboides, will most likely to experience continuous submergence or inundation. Current research onM.glyptostroboidesseedlings is more focused on genetic structure, membrane composition, chemical property, growth and photosynthesis, and the like. However, the eco-physiological implications of submersion onM.glyptostroboidesseedlings are not well known, especially under the condition of full-submersion.

The aim of this study was to investigate the responding characteristics of theM.glyptostroboidesseedlings to the water level change in the TGRA, and provide theoretical basis for species selection for revegetation in the riparian zone of the TGRA.

Measured indexes included protective enzymes such as superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (ASP) and catalase (CAT), osmotic adjustment substances such as soluble protein and free proline, and membrane lipid peroxidation such as malondialdehyde (MDA), as well as photosynthetic characteristics and biomass accumulation of the two-year oldM.glyptostroboidesseedlings to submergence, upon mimicking the water level change in the riparian zone of the TGRA. Based on soil moisture change pattern in the TGRA, water treatments including control (CK), half-submersion (HS), and full-submersion (FS) were applied.

The activities of SOD, POD, ASP, CAT and content of free proline ofM.glyptostroboidesseedlings in HS and FS group were higher than that in CK after submersion. Under submersion, MDA content in HS and FS group increased as compared with that in CK. The net photosynthetic rate ofM.glyptostroboidesseedlings in HS was significantly higher than that in CK. Root-shoot ratio in FS was significantly higher than that in CK, but no significant difference was detected between FS and HS. Leaves ofM.glyptostroboidesseedlings in FS were leaf bud, and survival rates were 100%.

The results indicated that antioxidant enzymes, osmotic adjustment substances and photosystem Ⅱ have a positive response during submersion,M.glyptostroboidesseedlings show strong adaptability to the submersion. Thus,M.glyptostroboidesshould be considered as one of the potential species for revegetation in the TGRA.

Metasequoiaglyptostroboides; water stress; growth; physiology and biochemistry

Journal of Zhejiang University (Agric. & Life Sci.), 2015,41(5):505-515

重慶市基礎與前沿研究計劃重點項目(CSTC2013JJB00004)；中央高校基本科研業(yè)務費專項資金(XDJK2013A011)；國家林業(yè)公益性行業(yè)科研專項(201004039)；留學回國人員科研啟動基金(教外司留[2010]1561號)。

聯(lián)系方式:白林利(http://orcid.org/0000-0002-0956-844X),E-mail:895845358@qq.com

2014-09-29;接受日期(Accepted):2015-01-21；網絡出版日期(Published online):2015-09-18

Q 945.78; S 718.43; S 791.35

A

*通信作者(Corresponding author):李昌曉(http://orcid.org/0000-0002-5090-6201),E-mail:lichangx@swu.edu.cn

URL:http://www.cnki.net/kcms/detail/33.1247.s.20150918.1743.004.html