胡文海 葉子飄 閆小紅 楊旭升

(1.井岡山大學(xué)生命科學(xué)學(xué)院，吉安 343009； 2.江西省生物多樣性與生態(tài)工程重點(diǎn)實(shí)驗(yàn)室，吉安 343009； 3.井岡山大學(xué)數(shù)理學(xué)院，吉安 343009)

越冬期廣玉蘭陽(yáng)生葉和陰生葉PSⅡ功能及捕光色素分子內(nèi)稟特性的比較研究

胡文海1,2葉子飄2,3閆小紅1,2楊旭升1

(1.井岡山大學(xué)生命科學(xué)學(xué)院，吉安 343009； 2.江西省生物多樣性與生態(tài)工程重點(diǎn)實(shí)驗(yàn)室，吉安 343009； 3.井岡山大學(xué)數(shù)理學(xué)院，吉安 343009)

捕光色素分子的內(nèi)稟特性不僅決定了光能的吸收與傳遞，也將影響到激發(fā)能向光化學(xué)反應(yīng)、熱耗散和葉綠素?zé)晒獾姆峙?。本文采用葉綠素?zé)晒饧夹g(shù)和光合電子流對(duì)光響應(yīng)機(jī)理模型，研究了越冬期廣玉蘭(Magnoliagrandiflora)陽(yáng)生葉和陰生葉兩種不同光環(huán)境下葉片PSⅡ功能及其捕光色素分子內(nèi)稟特性的差異，以探索廣玉蘭越冬的光保護(hù)策略。結(jié)果表明：越冬期低溫導(dǎo)致葉片輕微光抑制的發(fā)生，全光照加劇了陽(yáng)生葉光抑制程度，而弱光環(huán)境有利于陰生葉光抑制的恢復(fù)。陽(yáng)生葉可通過降低葉綠素含量和捕光色素分子數(shù)量以減少對(duì)光能的吸收，并且具有較強(qiáng)的光化學(xué)和熱耗散能力以保護(hù)光合機(jī)構(gòu)免受低溫強(qiáng)光傷害。而陰生葉雖然其光化學(xué)反應(yīng)能力相對(duì)較弱，但具有較強(qiáng)的熱耗散能力，可有效地保護(hù)其免受短時(shí)曝露在強(qiáng)光下的傷害。

廣玉蘭；越冬期；PSⅡ功能；捕光色素分子內(nèi)稟特性，光保護(hù)策略

植物光合作用包括光反應(yīng)和暗反應(yīng)兩個(gè)過程，葉綠素分子吸收光能后裂解水分子，同時(shí)形成質(zhì)子梯度和驅(qū)動(dòng)電子流形成ATP和NADPH并用于碳同化。當(dāng)葉片吸收光能超出了碳同化所需時(shí)，過剩的激發(fā)能可形成三線態(tài)的葉綠素分子用于產(chǎn)生活性氧，并對(duì)光合機(jī)構(gòu)造成傷害[1～2]。分布于亞熱帶及其以北地區(qū)的常綠植物在冬季常處于低溫強(qiáng)光的生長(zhǎng)環(huán)境[3]，低溫抑制了光合碳同化的進(jìn)行，但未影響葉片對(duì)光能的吸收與傳遞，光能吸收與利用的失衡增加了光抑制甚至光氧化傷害的潛在風(fēng)險(xiǎn)[4～7]。因此，常綠植物必然擁有一系列光保護(hù)策略以順利越冬[1]。一方面，常綠植物能夠通過葉片運(yùn)動(dòng)和卷曲[8～9]、葉綠素含量減少[10]等來(lái)減少對(duì)光能的吸收[11]；另一方面，常綠植物通過依賴于葉黃素循環(huán)的熱耗散[1,6,10]、PSⅡ反應(yīng)中心功能下調(diào)[12～13]、圍繞PSⅠ的環(huán)式電子傳遞[14]等能量耗散途徑以保護(hù)光合機(jī)構(gòu)。常綠植物能否免受光抑制順利越冬，既取決于植物本身的光系統(tǒng)功能和光保護(hù)途徑強(qiáng)弱，也受到環(huán)境因素的影響[15～16]。此外，植物葉片對(duì)光能的吸收、激發(fā)、傳遞和轉(zhuǎn)換等過程受捕光色素分子的空間結(jié)構(gòu)和電荷分布等內(nèi)稟特性所決定，不同的植物以及同種植物在不同環(huán)境下其內(nèi)稟特性也不相同，從而影響到其對(duì)光能的吸收與利用[17～20]。目前相關(guān)研究主要集中于常綠植物葉片對(duì)冬季低溫強(qiáng)光長(zhǎng)期適應(yīng)后的光保護(hù)策略，而對(duì)處于不同光環(huán)境下的陽(yáng)生葉和陰生葉PSⅡ功能以及捕光色素分子內(nèi)稟特性的差異，及其對(duì)光強(qiáng)變化的快速響應(yīng)過程研究相對(duì)較少。為此，我們選擇園林綠化中常見的常綠植物廣玉蘭(MagnoliaGrandifloraL.)為材料，利用葉綠素?zé)晒饧夹g(shù)對(duì)越冬期廣玉蘭陽(yáng)生葉和陰生葉的PSⅡ功能開展研究，以期從光合機(jī)構(gòu)的內(nèi)稟特性及其環(huán)境適應(yīng)性的角度來(lái)探索廣玉蘭的越冬光保護(hù)策略。

1 材料與方法

1.1 試驗(yàn)材料

試驗(yàn)于2015年1月在井岡山大學(xué)校園內(nèi)進(jìn)行，供試廣玉蘭(MagnoliagrandifloraL.)植株高約4 m，一面向陽(yáng)，一面背陰靠近山坡。于晴天6:00和9:00選擇陽(yáng)生葉和陰生葉各5片，帶枝剪下插入水中帶回實(shí)驗(yàn)室進(jìn)行葉綠素?zé)晒獾臏y(cè)定。其中陽(yáng)生葉自7:00～16:30有太陽(yáng)光直射到葉片，12:00時(shí)葉表光照強(qiáng)度約為1 470 μmol·m-2·s-1；陰生葉全天無(wú)直射陽(yáng)光，12:00葉表面光照強(qiáng)度約為40 μmol·m-2·s-1。試驗(yàn)期間為連續(xù)晴天，氣溫為4～14℃。

1.2 測(cè)定項(xiàng)目和方法

1.2.1 葉綠素含量的測(cè)定

將進(jìn)行了葉綠素?zé)晒鉁y(cè)定的葉片打孔取樣，按Arnon的方法[21]，采用丙酮法進(jìn)行葉綠素含量的測(cè)定。

1.2.2 葉綠素?zé)晒鈪?shù)的測(cè)定

采用Dual-PAM-100/F(Heinz Walz GmbH,Effeltrich,Germany)進(jìn)行葉綠素?zé)晒獾臏y(cè)定。暗適應(yīng)葉綠素?zé)晒鈪?shù)的測(cè)定分別在6:00和9:00采集的葉片上進(jìn)行，首先將葉片暗適應(yīng)30 min后，分別測(cè)定其最小熒光(Fo)和最大熒光(Fm)，并計(jì)算PSⅡ最大光化學(xué)效率:

Fv/Fm=(Fm-Fo)/Fm

(1)

葉綠素?zé)晒饪焖俟馇€(Rapid light curves,RLCs)的測(cè)定依據(jù)Dual-PAM-100使用說(shuō)明，在9:00采集的葉片上進(jìn)行。在試驗(yàn)中我們分別采用光化光誘導(dǎo)10s(AL10s)和誘導(dǎo)120s(AL120s)兩種測(cè)量條件下進(jìn)行了RLCs的測(cè)定。首先進(jìn)行AL120s測(cè)量條件下的測(cè)定，將葉片暗適應(yīng)30 min后測(cè)定Fo和Fm，再依次開啟7～918 μmol·m-2·s-1的光化光，每個(gè)梯度的光化光照射葉片120 s，并由儀器直接記錄該測(cè)量條件下熒光快速光曲線。然后再進(jìn)行AL10s測(cè)量條件下的測(cè)定，將葉片再次進(jìn)行暗適應(yīng)30 min，測(cè)定Fo和Fm后再依次開啟7～918 μmol·m-2·s-1的光化光，此次每個(gè)梯度的光化光照射葉片10s，并記錄該測(cè)量條件下熒光快速光曲線。光化光由儀器內(nèi)置的LED光源提供635 nm波長(zhǎng)光，由儀器測(cè)定軟件直接給出光化學(xué)猝滅系數(shù)(qP)、非光化學(xué)猝滅系數(shù)(NPQ)和PSⅡ光合電子流(J)等葉綠素?zé)晒鈪?shù)。

1.2.3 光合生理參數(shù)的計(jì)算

1.2.4 數(shù)據(jù)統(tǒng)計(jì)

采用SPSS11.5軟件進(jìn)行方差分析，獨(dú)立樣本組間比較采用Independent-Samples T Test，單一因素兩兩比較采用one-way ANVOA的最小顯著性差異(LSD)檢驗(yàn)，分別在P<0.05水平上進(jìn)行分析。數(shù)據(jù)為平均值±標(biāo)準(zhǔn)誤差，表中不同字母表示在5%水平上處理間具有顯著性差異。

2 實(shí)驗(yàn)與分析

2.1越冬期陽(yáng)生葉和陰生葉PSⅡ光化學(xué)效率和熱耗散的比較

越冬期，陽(yáng)生葉和陰生葉Fv/Fm在6:00測(cè)定值沒有顯著差異，經(jīng)過陽(yáng)光照射后陽(yáng)生葉的Fv/Fm稍有下降，陰生葉則略有增加(圖1)。陽(yáng)生葉的qP顯著高于陰生葉，光適應(yīng)時(shí)間的延長(zhǎng)可促進(jìn)這兩種葉片qP的上升，尤其是陽(yáng)生葉qP的增加更為明顯。NPQ則表現(xiàn)為AL10s測(cè)量條件下陽(yáng)生葉明顯高于陰生葉，而AL120s下當(dāng)光強(qiáng)低于600 μmol·m-2·s-1時(shí)陰生葉高于陽(yáng)生葉(圖2)。

圖1 越冬期廣玉蘭陽(yáng)生葉和陰生葉PSⅡ最大光化學(xué)效率(Fv/Fm)的比較Fig.1 The maximal quantum efficiency of PSⅡ(Fv/Fm) for sun- and shading-leaf of M.grandiflora during overwintering

圖2 越冬期廣玉蘭陽(yáng)生葉和陰生葉光化學(xué)猝滅(qP)和非光化學(xué)猝滅(NPQ)對(duì)光的響應(yīng)曲線Fig.2 Light-response curves of photochemical quenching(qP) and non-photochemical quenching(NPQ) for sun- and shading- leaf of M.grandiflora during overwintering

圖3 越冬期廣玉蘭陽(yáng)生葉和陰生葉的光合電子流光響應(yīng)(J-PAR)曲線Fig.3 Light-response curves of photosynthetic electron flow(J-PAR) for sun- and shading- leaf of M.grandiflora during overwintering

2.2 光合電子流光響應(yīng)的比較

越冬期，廣玉蘭陽(yáng)生葉J高于陰生葉，并且在AL120s下的差異較AL10s下更顯著(圖3)。通過對(duì)J-PAR曲線擬合得到α、Jmax和PARsat等光合參數(shù)。結(jié)果表明，陰生葉的α、Jmax和PARsat在AL120s和AL10s間無(wú)顯著差異；而陽(yáng)生葉的Jmax和PARsat在AL120s下明顯高于AL10s；但AL10s下陽(yáng)生葉的Jmax和PARsat與陰生葉間無(wú)顯著差異(表1)。

表1越冬期廣玉蘭陽(yáng)生葉和陰生葉的初始斜率(α)、最大光合電子傳遞速率(Jmax)和飽和光強(qiáng)(PARsat)

Table1Initialslope(α),maximumphotosyntheticelectronflow(Jmax)andmaximumirradiance(PARsat)forsun-andshading-leafofM.grandifloraduringoverwintering

參數(shù)Parameters陽(yáng)生葉Sun-leaf陰生葉Shading-leafAL120sAL10sAL120sAL10sα0.288±0.059ab0.230±0.026b0.319±0.014a0.311±0.021aJmax(μmolelectrons·m-2·s-1)40.3±3.1a15.2±3.0b16.9±1.8b12.1±1.9bPARsat(μmolphotons·m-2·s-1)576.4±30.4a423.1±28.5b418.7±31.6b348.5±41.5b

2.3 捕光色素分子內(nèi)稟特性的比較

由表2可知：越冬期，廣玉蘭陰生葉葉綠素含量為陽(yáng)生葉的1.74倍，其Chla/b比值則為陽(yáng)生葉的76.7%，N0也高出陽(yáng)生葉70.3%。陽(yáng)生葉的σik高于陰生葉，并且不受光適應(yīng)時(shí)間長(zhǎng)短的影響；τmin則表現(xiàn)為陽(yáng)生葉明顯低于陰生葉，且τmin值大小受到光適應(yīng)時(shí)間長(zhǎng)短的影響，無(wú)論是陰生葉還是陽(yáng)生葉在AL120s測(cè)量條件下的τmin均低于AL10s。

表2越冬期廣玉蘭兩種生態(tài)型葉片的葉綠素含量和捕光色素分子物理參數(shù)

Table2Chlorophyllcontentandphysicalparametersoflight-harvestingpigmentmoleculesfortwoeco-typesleavesofM.grandifloraduringoverwintering

參數(shù)Parameters陽(yáng)生葉Sun-leaf陰生葉Shading-leafAL120sAL10sAL120sAL10s葉綠素含量Chlorophyllcontent(mg·m-2)135.2±8.5b235.7±25.8aChla/b5.12±0.04a3.92±0.18bN0(×1015)4.61±0.25b7.85±0.78aσik(×10-21m2)8.67±0.70a8.64±1.34a5.73±0.41b5.53±0.25bτmin(ms)12.32±1.36d42.17±5.42c64.70±2.27b98.95±11.38a

注：N0.捕光色素分子總數(shù)；σik.本征光能吸收截面；τmin.處于激發(fā)態(tài)的捕光色素分子最小平均壽命

Note:N0.Numbers of light-harvesting pigment molecules;σik.Eigen-absorption cross-section;τmin.Minimum average lifetime in an excite state

圖4 越冬期廣玉蘭兩種生態(tài)型葉片的有效光能吸收截面和與本征光能吸收截面之比對(duì)光的響應(yīng)曲線Fig.4 Light-response curves of the effective light absorption cross-section() and the ratio of and eigen-absorption cross-section(/σik) for two eco-types leaves of M.grandiflora during overwintering

Nk和Nk/N0則隨著光強(qiáng)的增加而非線性增加。雖然陽(yáng)生葉的Nk明顯低于陰生葉，但其Nk/N0卻高于陰生葉；AL120s測(cè)量條件下陽(yáng)生葉的Nk和Nk/N0均低于AL10s；而陰生葉僅有Nk在AL120s下略低于AL10s，Nk/N0則沒有差異(圖5)。

圖5 越冬期廣玉蘭兩種生態(tài)型葉片處于最低激發(fā)態(tài)的捕光色素分子數(shù)(Nk)和Nk與總捕光色素分子的比值(Nk/N0)對(duì)光的響應(yīng)曲線Fig.5 Light-response curves of the photosynthetic pigment numbers in the lowest state(Nk) and the ratio of Nk and the photosynthetic pigment numbers in the ground state(Nk/N0) for two eco-types leaves of M.grandiflora during overwintering

3 討論

冬季低溫抑制了常綠植物葉片Calvin-Benson循環(huán)中光合酶活性，但并未對(duì)原初反應(yīng)光能吸收與傳遞產(chǎn)生影響[4,13]。因此，處于低溫強(qiáng)光環(huán)境下的陽(yáng)生葉遭受光抑制的風(fēng)險(xiǎn)遠(yuǎn)大于弱光環(huán)境下的陰生葉[22]。然而，冬季的低溫強(qiáng)光并不會(huì)造成在其適生地的常綠植物發(fā)生不可逆的光抑制傷害。我們的研究結(jié)果表明，越冬期陽(yáng)光照射導(dǎo)致了廣玉蘭陽(yáng)生葉輕微的可逆光抑制發(fā)生，經(jīng)過夜間黑暗后可得到一定程度的恢復(fù)；而處于弱光環(huán)境下的陰生葉夜間低溫會(huì)導(dǎo)致葉片可逆光抑制的發(fā)生，在白天溫度回升后其光抑制可得到完全恢復(fù)(圖1)。由此可見，越冬期低溫是導(dǎo)致廣玉蘭葉片發(fā)生光抑制的直接原因，太陽(yáng)光直接照射可加劇葉片光抑制程度，但是廣玉蘭陽(yáng)生葉和陰生葉光抑制均為可逆光抑制，說(shuō)明越冬期低溫和強(qiáng)光并未對(duì)廣玉蘭葉片光合機(jī)構(gòu)造成傷害[23]。

植物防御光抑制的策略可通過減少光能的吸收，和(或)增強(qiáng)光能耗散兩方面來(lái)實(shí)現(xiàn)。原初反應(yīng)的光能吸收、傳遞和退激發(fā)等過程受天線色素分子的內(nèi)稟特性所決定，是一個(gè)純粹的物理過程[24～25]。捕光色素分子吸收光能后由基態(tài)躍遷至激發(fā)態(tài)，激發(fā)能主要分配到相互競(jìng)爭(zhēng)的光化學(xué)反應(yīng)、熱耗散和葉綠素?zé)晒馊龡l途徑[26]，因此，捕光色素分子的內(nèi)稟特性不僅決定了光能的吸收與傳遞，也將影響到其后激發(fā)能的分配。

葉綠素?zé)晒饪焖俟馇€是近年發(fā)展出來(lái)的一種熒光光響應(yīng)測(cè)定方法。在試驗(yàn)中我們分別采用光化光誘導(dǎo)10 s(AL10s)和120 s(AL120s)兩種測(cè)量條件對(duì)RLCs進(jìn)行了測(cè)定。在AL10s測(cè)量條件下，由于每個(gè)梯度的光化光照射時(shí)間短至10 s，不足以啟動(dòng)該梯度光化光照射下碳同化的順利運(yùn)轉(zhuǎn)，因此所反映的葉綠素?zé)晒鈱?duì)光強(qiáng)變化的瞬間響應(yīng)受碳同化的影響較小，與光合機(jī)構(gòu)的內(nèi)在功能直接相關(guān)[29～30]。而在AL120s測(cè)量條件下，由于每一梯度光化光誘導(dǎo)時(shí)間延長(zhǎng)至120 s，已部分或穩(wěn)定啟動(dòng)了其后碳同化過程，因此反映了光反應(yīng)和暗反應(yīng)協(xié)同作用下光合機(jī)構(gòu)的功能。通過比較這兩種測(cè)量條件下的RLCs將有助于判斷越冬期常綠植物光保護(hù)的內(nèi)在特性及其對(duì)光強(qiáng)的響應(yīng)差異。

我們發(fā)現(xiàn)，在AL10s和AL120s的測(cè)量條件下，陽(yáng)生葉的qP和J均高于陰生葉，并且光誘導(dǎo)時(shí)間的延長(zhǎng)對(duì)陽(yáng)生葉qP和J的促進(jìn)作用也明顯高于陰生葉(圖2～3)，這表明陽(yáng)生葉具有比陰生葉更強(qiáng)的PSⅡ光化學(xué)能力，而且碳同化的啟動(dòng)有利于誘導(dǎo)其對(duì)光能的利用能力。相應(yīng)的，AL120s測(cè)量條件下陽(yáng)生葉的Jmax和PARsat均顯著高于陰生葉和AL10s下的陽(yáng)生葉(表1)，這也說(shuō)明了光照可有效誘導(dǎo)陽(yáng)生葉對(duì)強(qiáng)光的利用能力。

此外，兩種類型葉片均表現(xiàn)出NPQ隨著誘導(dǎo)光強(qiáng)的增加而迅速上升(圖2)，說(shuō)明廣玉蘭本身具有較強(qiáng)的熱耗散能力以防御強(qiáng)光傷害。同時(shí)，我們發(fā)現(xiàn)AL10s測(cè)量條件下陽(yáng)生葉NPQ對(duì)光強(qiáng)的響應(yīng)顯著高于陰生葉(圖2)，這表明陽(yáng)生葉具有很強(qiáng)的防御瞬間強(qiáng)光能力。然而，在AL120測(cè)量條件下陰生葉NPQ對(duì)光強(qiáng)的響應(yīng)顯著高于陽(yáng)生葉(圖2)，這表明較長(zhǎng)時(shí)間的光照可誘導(dǎo)陰生葉高熱耗散能力以減輕強(qiáng)光傷害。并且，陽(yáng)生葉的Chla/b比值是陰生葉的1.31倍(表2)，表明陽(yáng)生葉的光反應(yīng)中心(PSⅡ和PSⅠ)數(shù)量比陰生葉多，較長(zhǎng)時(shí)間的光誘導(dǎo)(AL120s)后碳同化的啟動(dòng)也有利于陽(yáng)生葉光化學(xué)反應(yīng)的進(jìn)行(圖2)，從而減少了吸收光能分配給熱耗散部分，這可能是AL120s測(cè)量條件下陽(yáng)生葉NPQ對(duì)光強(qiáng)的響應(yīng)低于陰生葉的原因所在。

捕光色素分子吸收光能后從基態(tài)躍遷到激發(fā)態(tài)，如果過多的捕光色素分子處于激發(fā)態(tài)且不能及時(shí)通過光化學(xué)反應(yīng)、熱耗散和熒光退激發(fā)，將會(huì)對(duì)植物產(chǎn)生光抑制傷害[11,31]。高光強(qiáng)將導(dǎo)致捕光色素分子中處于激發(fā)態(tài)的數(shù)量增多，但光誘導(dǎo)時(shí)間的延長(zhǎng)顯著降低了陽(yáng)生葉的Nk、Nk/N0和τmin，但陰生葉下降不明顯(表2，圖5)。這意味著光誘導(dǎo)時(shí)間的延長(zhǎng)有效地啟動(dòng)了陽(yáng)生葉的光化學(xué)反應(yīng)(圖2)，使更多的激發(fā)能流向光系統(tǒng)，從而有利于減輕強(qiáng)光對(duì)植物葉片光抑制傷害的風(fēng)險(xiǎn)。對(duì)陰生葉而言，雖然光誘導(dǎo)時(shí)間的延長(zhǎng)可以誘發(fā)其熱耗散能力增強(qiáng)，但并未有效啟動(dòng)光化學(xué)反應(yīng)(圖2)，這可能是長(zhǎng)期處于弱光環(huán)境下導(dǎo)致陰生葉光合器官在形態(tài)結(jié)構(gòu)和生理功能上形成了對(duì)低光強(qiáng)環(huán)境的適應(yīng)性，短暫改變?nèi)肷涔鈴?qiáng)對(duì)其光能的吸收和利用進(jìn)程影響較小[32～33]。因此，如果將陰生葉轉(zhuǎn)移至強(qiáng)光下一段時(shí)間將會(huì)增加其發(fā)生光抑制的風(fēng)險(xiǎn)。

由此可見，越冬期的廣玉蘭陽(yáng)生葉具有較強(qiáng)的光化學(xué)和熱耗散能力，能快速地將處于激發(fā)態(tài)的捕光色素分子退激發(fā)以保護(hù)光合機(jī)構(gòu)免受低溫強(qiáng)光光抑制傷害；而陰生葉雖然其光化學(xué)能力相對(duì)較弱，但具有較強(qiáng)的熱耗散能力，可有效地保護(hù)其短時(shí)暴露在強(qiáng)光下時(shí)免受光抑制傷害。

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National Natural Science Foundation of China(31560069)；Project in the Educational Commission of Jiangxi Province(GJJ12724)

introduction：HU Wen-Hai(1973—),male,Professor,PhD,mainly engaged in research of physiological ecology of horticultural plants.

date:2016-10-26

PSⅡFunctionandIntrinsicCharacteristicsofLight-harvestingPigmentMoleculesforSun-andShading-leafinMagnoliagrandifloraDuringOverwintering

HU Wen-Hai1,2YE Zi-Piao2,3YAN Xiao-Hong1,2YANG Xu-Sheng1

(1.School of Life Sciences,Jingganshan University,Ji’an 343009；2.Key Laboratory for Biodiversity Science and Ecological Engineering,Jingganshan University,Ji’an 343009；3.Math and Physics College,Jingganshan University,Ji’an 343009)

Light absorption and energy transfer are determined by intrinsic characteristics of light-harvesting pigment molecules, which also have impacts on distribution of excited energy for photochemical reaction, heat dissipation and chlorophyll fluorescence. We compared the differences of the PSⅡ function and intrinsic characteristics of light-harvesting pigment molecules of sun- and shading-leaves to study the photoprotective strategies in overwinteringMagnoliagrandiflora. The slight photoinhibition was caused in leaves ofM.grandifloraby low temperature during overwintering. Natural sunlight enhanced photoinhibition in sunleaf, however, low light condition was propitious to the recovery of photoinhibition in shading-leaf. Sun-leaf had lower chlorophyll content and the numbers of light-harvesting pigment molecules(N0) to reduce light energy absorption. Sun-leaf also possessed higher photochemical function and thermal energy dissipation in PSⅡ, which would protect photosynthetic apparatus against damage by low temperature and high light. Shading-leaf exhibited lower capability of photochemical reaction, however, possessed greater thermal energy dissipation, which would alleviate photoinhibition of shadingleaf under temporal high light condition during overwintering.

MagnoliagrandifloraL.;overwintering;PSⅡ function;intrinsic characteristics of light-harvesting pigment molecules;photoprotective strategies

國(guó)家自然科學(xué)基金項(xiàng)目(31560069)；江西省教育廳科技計(jì)劃項(xiàng)目(GJJ12724)

胡文海(1973—)，男，教授，博士，主要從事園藝植物生理生態(tài)方面的研究。

2016-10-26

Q945.79

A

10.7525/j.issn.1673-5102.2017.02.017