摘要:【目的】探明硅對(duì)堿性鹽脅迫下陽(yáng)光玫瑰葡萄葉片光系統(tǒng)Ⅱ(PSⅡ)的影響,進(jìn)一步解釋硅元素提高植物抗性的機(jī)制,為硅肥在葡萄生產(chǎn)中的應(yīng)用提供理論依據(jù)。【方法】以一年生陽(yáng)光玫瑰葡萄扦插苗為材料,對(duì)其分別施用硅酸鈉(Na2SiO3,2 mmol·L-1)、堿性鹽(NaHCO3,100 mmol·L-1)、兩者混合溶液(Na2SiO3+NaHCO3,2 mmol·L-1+100 mmol·L-1),以蒸餾水為對(duì)照,每7d對(duì)根系進(jìn)行澆灌1次,分4次進(jìn)行,總計(jì)1 L。處理后60d,測(cè)定其葉綠素?zé)晒鈪?shù)。【結(jié)果】與對(duì)照相比,單一Na2SiO3處理后陽(yáng)光玫瑰葉片PSⅡ最大光化學(xué)效率(Fv/Fm)和性能指數(shù)(PIabs)升高,NaHCO3處理則顯著降低,而Na2SiO3和NaHCO3復(fù)合處理后較NaHCO3處理顯著升高,緩解了堿性鹽對(duì)葉片PSⅡ活性的抑制;與對(duì)照相比,NaHCO3處理下OJIP曲線上L、K、J點(diǎn)的相對(duì)熒光強(qiáng)度和相對(duì)可變熒光值明顯升高,最大光化學(xué)效率(φPo)、電子傳遞的量子產(chǎn)額(φEo)、光合電子傳輸效率(ΨEo)值下降,而在Na2SiO3和NaHCO3復(fù)合處理后較NaHCO3處理趨勢(shì)則相反,且φPo、φEo、ΨEo值升高顯著;與對(duì)照相比,NaHCO3處理下單位葉面積吸收的光能(ABS/CSm)、單位葉面積捕獲的光能(TRo/CSm)、單位葉面積電子傳遞的能量(ETo/CSm)、單位面積的反應(yīng)中心數(shù)量(RC/CSm)和單位面積光合反應(yīng)中心用于電子傳遞的能量(ETo/RC)值最低,而Na2SiO3和NaHCO3復(fù)合處理后較NaHCO3處理顯著升高;DIo/CSm、ABS/RC值則表現(xiàn)出相反的趨勢(shì)?!窘Y(jié)論】NaHCO3對(duì)葡萄葉片造成的傷害主要表現(xiàn)在降低單位葉面積中光合反應(yīng)中心的數(shù)量,抑制單位反應(yīng)中心的電子傳遞能力,而Na2SiO3可通過(guò)增加反應(yīng)中心的數(shù)量,增強(qiáng)對(duì)光能的吸收與捕獲能力,緩解單位反應(yīng)中心的電子傳遞,提升光合效率,進(jìn)而緩解鹽脅迫對(duì)植物造成的傷害。
關(guān)鍵詞:陽(yáng)光玫瑰葡萄;PSⅡ;葉綠素?zé)晒猓还杷徕c;碳酸氫鈉
中圖分類(lèi)號(hào):S663.1文獻(xiàn)標(biāo)志碼:A文章編號(hào):1009-9980(2024)07-1359-09
Effect of Na2SiO3 on leaf photosystemⅡ(PSⅡ)under alkaline salt stress in Shine Muscat grape
LI Guanyu,MAChuang,TIAN Shufen*,WANG Chaoxia,WANG Rong
(College of Horticulture and Landscape Architecture,Tianjin Agricultural University,Tianjin 300392,China)
Abstract:【Objective】Soil salinization poses as a significant environmental factor that constrains grape productivity and quality.Silicon,recognized as a beneficial element,demonstrates a commend-able mitigating effect against a range of biotic and abiotic stresses.Its influence on photosynthetic rate plays a pivotal role in determining crop yield.Nevertheless,the underlying mechanism by which silicon alleviates the damage inflicted on photosystemⅡ(PSⅡ)by stress remains elusive.In this experiment,the chlorophyll fluorescence parameters were measured and the effect of silicon on the PSII of Shine Muscat grape leaves was explored under salt stress,so as to provide not only a theoretical support for the alleviation of fluorescence characteristics of grape leaves under salt stress by silicon salt,but also a technical guidance for grape cultivation in saline alkali soil.【Methods】Forty annual grapevine cuttings of Shine Muscat,exhibiting uniform and robust growth without any signs of pests or diseases,were se-lected as the experimental subjects.Four treatments were established:control(distilled water),sodium silicate(Na2SiO3,2 mmol·L-1),alkaline salt(NaHCO3,100 mmol·L-1),and a combined treatment with both Na2SiO3 and NaHCO3(2 mmol·L-1+100 mmol·L-1).Each treatment was replicated for ten times to ensure reproducibility and statistical reliability.The grape cuttings were irrigated with 1 L of the re-spective treatment solutions,administered in four equal installments of 0.25 L each,to gradually achieve the desired concentration gradient.All other management practices remained uniform across all treatments.Chlorophyll fluorescence parameters were measured using a Handy PEA rapid fluorescence analyzer(Hansatech,UK).The rapid chlorophyll fluorescence induction kinetic curves(OJIP)and asso-ciated parameters were recorded for grape leaves from each treatment.Ten leaves per treatment were as-sayed,with each measurement repeated for five times to ensure accuracy.Prior to measurement,the leaves were dark-adapted for 20 minutes using leaf clips,followed by a 1-second saturation pulse of 3000μmol·m-2·s-1 light to induce fluorescence.The OJIP fluorescence induction curves were subjected to JIP-test analysis to normalize the relative fluorescence values.The differences in fluorescence values between the treatments and the control(CK)were represented asΔVt.Additionally,JIP-test analysis was performed on the OJIP curves to extract additional fluorescence parameters.Based on these find-ings,the schematic diagrams were constructed to illustrate the structure and function of leaf and chloro-plast membranes,providing a visual representation of the physiological responses of grape leaves to the treatments.【Results】The results showed that,in comparison to the control(CK),the Fv/Fm and PIabs val-ues of Shine Muscat grape leaves exhibited an increase,following the treatment with Na2SiO3 alone.Conversely,the application of NaHCO3 led to a significant decrease in these parameters.The combined treatment with Na2SiO3 and NaHCO3 resulted in a significant enhancement compared to the NaHCO3 treatment alone,indicating that silicon effectively mitigated the inhibitory effect of the alkaline salt on leaf PSII activity.The analysis of the OJIP curve revealed that,compared to CK,the relative fluores-cence intensity and relative variable fluorescence values at points L,K,and J were significantly elevat-ed with NaHCO3 treatment,and meanwhileφPo,φEo,ΨEo and Sm decreased by 15.04%,38.17%,27.31%and 4.44%,respectively.However,after the combined treatment with Na2SiO3 and NaHCO3,the trend was opposite to that of NaHCO3 treatment,andφPo,φEo andΨEo values significantly increased by 15.52%,54.71%and 34.18%,respectively.Additionally,the photosynthetic performance indices,includ-ingABS/CSm,TRo/CSm,ETo/CSm,RC/CSm and ETo/RC,were found to be the lowest under NaHCO3 treat-ment condition,with decreases of 11.06%,24.42%,45.01%,31.12%and 20.27%,respectively,com-pared to CK.The combined application of Na2SiO3 and NaHCO3 significantly increased these values by 15.50%,33.37%,78.44%,28.58%and 39.37%,respectively,compared to the NaHCO3 treatment.The DIo/CSm and ABS/RC values showed opposite trends.Compared to CK,the difference was not signifi-cant after Na2SiO3 treatment,while it increased significantly under NaHCO3 treatment condition,in-creasing by 104.86%and 28.72%,respectively.Compared to NaHCO3 treatment,the combined treat-ment with Na2SiO3 and NaHCO3 significantly decreased by 10.93%and 64.09%.【Conclusion】In sum-mary,the detrimental effects of NaHCO3 on grape leaves were primarily evident in diminishing the den-sity of reaction centers per unit leaf area and suppressing the electron transfer capacity of individual re-action centers.Conversely,Na2SiO3 exhibited beneficial properties,augmenting the number of reaction centers,elevating the absorption and entrapment capabilities of light energy,and mitigating the electron transfer impediment in each reaction center.Consequently,it alleviated the adverse impact of salt stress on plants.
Keywords:Shine Muscat grape;PSⅡ;Chlorophyll fluorescence;Na2SiO3;NaHCO3
硅是地殼中的第二大元素,已被國(guó)際植物營(yíng)養(yǎng)研究所(IPIN)歸類(lèi)為有益元素[1]。大量研究表明,硅可以提高蘋(píng)果、葡萄、甜瓜等作物在鹽堿、高溫等非生物脅迫下的抗性[2-4]。然而,有關(guān)硅提高植物抗性的機(jī)制較復(fù)雜。Zhang等[5]研究發(fā)現(xiàn),硅提高植物的耐鹽性是通過(guò)沉積在細(xì)胞壁周?chē)鷱亩种颇は到y(tǒng)的退化,維持柵欄組織中葉綠體的形態(tài),進(jìn)而抵消鹽脅迫對(duì)葉片解剖結(jié)構(gòu)和超微結(jié)構(gòu)的不利影響。Dhi-man等[6]認(rèn)為硅可以增加植物葉片的葉綠體大小和葉綠素含量,從而提高鹽脅迫下植物的光合效率。Verma等[7]認(rèn)為硅在應(yīng)對(duì)脅迫時(shí),可以通過(guò)提高葉片氣孔導(dǎo)度和蒸騰速率來(lái)增強(qiáng)植株光合作用。Zhang等[8]發(fā)現(xiàn),在水分脅迫下,硅能夠提高番茄PetE、PetF、PsbP、PsbQ、PsbW和Psb28等相關(guān)光合基因的轉(zhuǎn)錄水平,調(diào)節(jié)光化學(xué)過(guò)程。這些研究說(shuō)明硅可有效調(diào)節(jié)光合作用的器官,提高光合效率,然而有關(guān)其在光能分配中的作用尚不清楚,特別是硅對(duì)葉綠體PSⅡ的結(jié)構(gòu)和功能影響還有待研究[9-10]。在光合系統(tǒng)中,PSⅡ負(fù)責(zé)將光能轉(zhuǎn)化為電能,當(dāng)逆境發(fā)生時(shí)PSⅡ也是光損傷的主要部位[11]。因此,筆者在本研究中通過(guò)研究光合系統(tǒng)中PSⅡ?qū)璧捻憫?yīng),探討硅對(duì)植物的光保護(hù)機(jī)制,為硅在植物生產(chǎn)中的應(yīng)用提供一定的理論基礎(chǔ)。
陽(yáng)光玫瑰葡萄(Shine Muscat)為日本培育的中晚熟歐美雜交品種,具有高糖、皮薄、粒大、香味濃郁的特點(diǎn),且抗病性強(qiáng),不易裂果,耐貯藏[12]。但中國(guó)葡萄栽培區(qū)大多為鹽堿土,影響著葡萄的生長(zhǎng)發(fā)育,制約著葡萄產(chǎn)業(yè)的發(fā)展[13]。目前有關(guān)葡萄耐鹽的研究主要集中在生長(zhǎng)調(diào)節(jié)劑的使用、抗鹽砧木的篩選、園區(qū)土壤的改良等方面,而有關(guān)硅對(duì)鹽脅迫下葡萄光合特性影響的研究較少[14-15]。因此,筆者在本研究中以陽(yáng)光玫瑰葡萄扦插苗為材料,通過(guò)研究其在堿性鹽脅迫下添加硅酸鈉對(duì)葉片葉綠素?zé)晒庀嚓P(guān)參數(shù)的影響,建立能量響應(yīng)模型,繪制葉綠體膜模式圖,探究硅對(duì)葡萄葉片PSⅡ的影響。
1材料和方法
1.1試驗(yàn)材料
試驗(yàn)在天津市北辰區(qū)天津農(nóng)學(xué)院葡萄研究中心進(jìn)行。試驗(yàn)于2022年12月上旬在葡萄園內(nèi)采集生長(zhǎng)勢(shì)相對(duì)一致且長(zhǎng)勢(shì)健壯、無(wú)病蟲(chóng)害的陽(yáng)光玫瑰葡萄枝條,進(jìn)行沙藏越冬處理。2023年3月下旬取出沙藏枝條,于日光溫室內(nèi)生根催芽,5月下旬扦插至在含有蛭石基質(zhì)的塑料花盆中,花盆高16.5 cm,外口徑25 cm。后進(jìn)行不同外源物質(zhì)的處理試驗(yàn),處理60 d后采集葉片。試驗(yàn)在日光溫室中進(jìn)行,環(huán)境因素一致,采樣數(shù)據(jù)具有一定代表性。
1.2試驗(yàn)設(shè)計(jì)
分別選取長(zhǎng)勢(shì)一致、生長(zhǎng)健壯且無(wú)病蟲(chóng)害的40株葡萄作為試驗(yàn)植株。試驗(yàn)設(shè)4個(gè)處理,每組處理10株苗,采用蒸餾水作為空白對(duì)照,單一硅處理使用2 mmol·L-1 Na2SiO3溶液,堿性鹽處理采用100 mmol·L-1的NaHCO3溶液,硅和堿性鹽復(fù)合處理采用2 mmol·L-1 Na2SiO3和100 mmol·L-1 NaHCO3的混合液。每株葡萄分別澆灌相應(yīng)處理溶液1 L,每隔7 d處理1次,分4次達(dá)到預(yù)定梯度,單次施用量為0.25 L。每次將花盆底部托盤(pán)中滲出液均返還基質(zhì),以保證試驗(yàn)期內(nèi)元素含量穩(wěn)定。其余管理?xiàng)l件保持一致。
1.3葉綠素?zé)晒庹T導(dǎo)動(dòng)力學(xué)曲線(OJIP)及熒光參數(shù)的測(cè)定
8月下旬利用快速熒光測(cè)定儀Handy-PEA(Han-satech,英國(guó))分別測(cè)定各處理陽(yáng)光玫瑰葡萄葉片的快速葉綠素?zé)晒庹T導(dǎo)動(dòng)力學(xué)曲線(OJIP)及相關(guān)參數(shù)(表1),每個(gè)處理測(cè)定10枚葉片,5次重復(fù)。測(cè)定前用葉片夾進(jìn)行暗適應(yīng)20 min,熒光以3000μmol·m-2·s-1的飽和光誘導(dǎo),照射時(shí)間為1 s。對(duì)OJIP熒光誘導(dǎo)曲線進(jìn)行JIP-test分析[16],對(duì)相對(duì)熒光值進(jìn)行標(biāo)準(zhǔn)化分析,計(jì)算相對(duì)可變熒光Vt,Vt=(Ft-Fo)/(Fm-Fo),式中:Ft表示不同時(shí)間點(diǎn)的相對(duì)熒光強(qiáng)度,計(jì)算相對(duì)可變熒光的差值ΔVt,ΔVt=Vt(處理)-Vt(對(duì)照)。同時(shí)對(duì)曲線進(jìn)行OJIP曲線JIP-test分析得到其他熒光參數(shù)。
1.4數(shù)據(jù)處理
數(shù)據(jù)統(tǒng)計(jì)采用SPSS 22.0進(jìn)行數(shù)據(jù)顯著性分析,以0.05水平作為顯著性相關(guān)的閾值,用Origin 2021制作基本圖表。
2結(jié)果與分析
2.1硅酸鈉對(duì)堿性鹽脅迫下陽(yáng)光玫瑰PSⅡ光化學(xué)效率和性能的影響
由表2可知,與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片可變熒光(Fv)和最大熒光(Fm)值分別增加了8.21%和7.20%,而NaHCO3處理則降低了24.42%和11.06%,差異顯著。與NaHCO3處理相比,Na2SiO3和NaHCO3復(fù)合處理的陽(yáng)光玫瑰葉片F(xiàn)v和Fm值分別增加了33.37%和15.50%,差異顯著。說(shuō)明Na2SiO3可以有效緩解由堿性鹽脅迫而造成植物葉片F(xiàn)v和Fm值的降低,提高植株葉片PSⅡ的活性。
PSⅡ最大光化學(xué)量子產(chǎn)量(Fv/Fm)是反映PSⅡ活性中心光能轉(zhuǎn)化效率的重要參數(shù)[17]。由表2可知,與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片F(xiàn)v/Fm值增加了1.03%;NaHCO3處理的葉片F(xiàn)v/Fm值顯著降低了15.06%。Na2SiO3和NaHCO3復(fù)合處理較NaHCO3處理的陽(yáng)光玫瑰葉片F(xiàn)v/Fm值顯著增加了15.49%。NaHCO3處理后葉片的Fv/Fm值有所上升,且Na2SiO3和NaHCO3復(fù)合處理后較NaHCO3處理上升顯著,PSⅡ活性中心光能轉(zhuǎn)化效率有所提高,可有效緩解堿性鹽脅迫。
如表2所示,性能指數(shù)(PIabs)在Na2SiO3處理時(shí)達(dá)到最大值。與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片PIabs值增加了24.93%;在NaHCO3處理后PIabs值顯著降低了76.66%。與NaHCO3處理相比,Na2SiO3和NaHCO3復(fù)合處理后PIabs值增加了217.60%,差異顯著。表明Na2SiO3的添加可增強(qiáng)以光能吸收為基礎(chǔ)的性能指數(shù),緩解NaHCO3對(duì)光系統(tǒng)的脅迫,提高光合系統(tǒng)自身的保護(hù)能力,從而提升光合效率。
2.2硅酸鈉對(duì)堿性鹽脅迫下陽(yáng)光玫瑰快速葉綠素?zé)晒庹T導(dǎo)動(dòng)力學(xué)曲線(OJIP)的影響
如圖1所示,硅酸鈉對(duì)堿性鹽脅迫下陽(yáng)光玫瑰葉綠素?zé)晒庹T導(dǎo)動(dòng)力學(xué)曲線產(chǎn)生了顯著的影響。由圖1-A可知,隨著時(shí)間的延長(zhǎng),NaHCO3處理后的OJIP曲線趨于平緩,對(duì)照、Na2SiO3和Na2SiO3+NaH-CO3處理組的熒光強(qiáng)度隨時(shí)間的延長(zhǎng)逐漸增加。因原始OJIP曲線變異性受外界影響較大,將其進(jìn)行標(biāo)準(zhǔn)化處理,隨后與Vt(對(duì)照)做差,得出圖1-B。由圖1-B可知,Na2SiO3處理后陽(yáng)光玫瑰葉片的相對(duì)熒光強(qiáng)度和相對(duì)可變熒光ΔVt在L點(diǎn)(0.15 ms)、K點(diǎn)(0.3 ms)、J點(diǎn)(2.0 ms)均低于對(duì)照,NaHCO3處理組則在L點(diǎn)(0.15 ms)、K點(diǎn)(0.3 ms)、J點(diǎn)(2.0 ms)顯著高于對(duì)照。與NaHCO3處理相比,Na2SiO3和NaHCO3復(fù)合處理在K點(diǎn)、J點(diǎn)的相對(duì)熒光強(qiáng)度(Vk和Vj)變化幅度較小。Vk和Vj的升高均表明NaHCO3處理后使葉片PSⅡ的電子供體側(cè)和受體側(cè)受到嚴(yán)重?fù)p害,而經(jīng)Na2SiO3和NaHCO3復(fù)合處理后Vk和Vj下降,損害程度降低,堿性鹽脅迫有所緩解。
2.3硅酸鈉對(duì)堿性鹽脅迫下陽(yáng)光玫瑰PSⅡ反應(yīng)中心量子產(chǎn)額和通量比的影響
如圖2可知,與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片的最大光化學(xué)效率(t=0時(shí),φPo)、電子傳遞的量子產(chǎn)額(t=0時(shí),φEo)、光合電子傳輸效率(t=0時(shí),ΨEo)和熒光曲線面積(Sm)值分別增加了1.05%、12.28%、11.31%和11.80%;NaHCO3處理后葉片的φPo、φEo、ΨEo、Sm值分別下降了15.04%、38.17%、27.31%和4.44%,且差異顯著。Na2SiO3和NaHCO3復(fù)合處理較NaHCO3處理的陽(yáng)光玫瑰葉片φPo、φEo、ΨEo值分別顯著增加了15.52%、54.71%、34.18%,Sm值則下降了1.61%,差異不顯著。表明Na2SiO3的加入顯著抑制了由NaHCO3引起的φEo、ΨEo值的降低。
2.4硅酸鈉對(duì)堿性鹽脅迫下陽(yáng)光玫瑰葉片光能吸收、捕獲和傳遞的影響
利用葉片模型將葉綠素?zé)晒鈪?shù)可視化。如圖3所示,與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片的ABS/CSm、TRo/CSm、ETo/CSm、REo/CSm和RC/CSm值分別增加了7.20%、8.21%、19.57%、21.10%和4.05%;NaHCO3處理的ABS/CSm、TRo/CSm、ETo/CSm、REo/CSm和RC/CSm值分別下降了11.06%、24.42%、45.01%、15.17%和31.12%,差異顯著。與NaHCO3處理相比,Na2SiO3和NaHCO3復(fù)合處理的陽(yáng)光玫瑰葉片ABS/CSm、TRo/CSm、ETo/CSm、REo/CSm和RC/CSm值分別顯著增加了15.50%、33.37%、78.44%、21.48%和28.58%。DIo/CSm值在NaHCO3處理后則顯著高于對(duì)照、Na2SiO3和Na2SiO3+NaHCO3,分別為42.02%、37.63%和28.69%,但對(duì)照、Na2SiO3以及Na2SiO3和NaHCO3復(fù)合處理間無(wú)差異。說(shuō)明Na2SiO3可增加單位葉面積中光合反應(yīng)中心數(shù)量,緩解由堿性鹽脅迫導(dǎo)致的光能利用率下降,抑制電子的大量積累,從而導(dǎo)致DIo/CSm的降低。
如圖4所示,與對(duì)照相比,Na2SiO3處理的陽(yáng)光玫瑰葉片的ETo/RC值增加了15.49%;NaHCO3處理的ETo/RC值顯著下降了20.27%。與NaHCO3處理相比,Na2SiO3和NaHCO3復(fù)合處理的陽(yáng)光玫瑰葉片ETo/RC值顯著增加了39.37%。陽(yáng)光玫瑰經(jīng)NaHCO3處理后,ABS/RC和DIo/RC值均顯著高于對(duì)照、Na2SiO3和Na2SiO3+NaHCO3處理組,ABS/RC分別高28.72%、25.20%、10.93%,DIo/RC分別高104.86%、108.28%、64.09%。這說(shuō)明堿性鹽脅迫使RC/CSm值降低后,Na2SiO3處理主要通過(guò)增加ETo/RC值,迫使剩余有活性的光合反應(yīng)中心的電子傳遞速率加快,同時(shí)降低熱耗散,以此提高光能利用率。
3討論
Fv/Fm和PIabs是研究葉片PSⅡ反應(yīng)中心光轉(zhuǎn)換效率和電子傳遞受抑制程度的重要指標(biāo)[18]。筆者在本研究中發(fā)現(xiàn),與對(duì)照相比,NaHCO3處理后陽(yáng)光玫瑰葉片的Fv、Fm、Fv/Fm和PIabs值顯著降低,但在Na2SiO3和NaHCO3復(fù)合處理后較NaHCO3處理顯著升高。說(shuō)明Na2SiO3可提高PSⅡ光化學(xué)效率,緩解堿性鹽脅迫對(duì)類(lèi)囊體造成的損傷。這與Kalaji等[19]的研究結(jié)果相似。說(shuō)明在堿性鹽脅迫下,光合機(jī)構(gòu)功能遭受破壞,Na2SiO3的添加可緩解堿性鹽脅迫對(duì)類(lèi)囊體造成的損傷,提高PSⅡ光化學(xué)效率。而添加Na2SiO3后光利用效率提高,可能與其對(duì)電子轉(zhuǎn)移鏈產(chǎn)生保護(hù)有關(guān)。Zhu等[20]的研究表明硅可增加PSⅡ反應(yīng)中心開(kāi)放的數(shù)量,更多地用于電子傳遞,電子傳遞速率提高。
在快速熒光動(dòng)力學(xué)曲線中,OJIP的瞬時(shí)值可反映葉片PSⅡ中電子傳遞的狀態(tài)[21]。筆者在本研究中發(fā)現(xiàn),NaHCO3處理下陽(yáng)光玫瑰的Vt和ΔVt在L、K、J點(diǎn)明顯升高,φEo、ΨEo值降低,而Na2SiO3和NaHCO3復(fù)合處理后表現(xiàn)出相反趨勢(shì)。該結(jié)果與Wang等[22]的研究結(jié)果相似。表明堿性鹽脅迫對(duì)放氧復(fù)合體造成損害,而J點(diǎn)的升高表明電子從P680至QA受到限制,添加Na2SiO3后,降低了鹽堿脅迫對(duì)放氧復(fù)合體的損害,促進(jìn)了光合水解,增加H+濃度,改善膜內(nèi)酸性環(huán)境,進(jìn)而增強(qiáng)ATPase活性,三羧酸循環(huán)(TCA)加快,從而促進(jìn)植物的生長(zhǎng)發(fā)育[23-24]。同時(shí),鹽堿脅迫后PSⅡ受體側(cè)的QA-大量積累,而Na2SiO3可以降低受體側(cè)QA的電子積累,增強(qiáng)受體側(cè)QA下游的電子的傳遞鏈將電子傳遞給QB電子的傳遞能力[21]。Na2SiO3緩解堿性鹽堿脅迫對(duì)光合系統(tǒng)的損傷也體現(xiàn)在增加PSⅡ反應(yīng)中心對(duì)光能的捕獲(φPo)和電子傳遞量子產(chǎn)額(ΨEo)、提高有活性的光合反應(yīng)中心的開(kāi)放程度和去鎂葉綠素(Pheo)到QA的電子傳遞能力、提高將電子通過(guò)QA傳遞到電子受體的比例(φEo)等方面,從而提高植物耐鹽性[22,25-26]。
逆境脅迫條件下,植物可調(diào)節(jié)能量的重新分配適應(yīng)外界環(huán)境,以達(dá)到自我保護(hù)的目的[27]。筆者在本研究中發(fā)現(xiàn),與對(duì)照相比,陽(yáng)光玫瑰經(jīng)NaHCO3處理后,ABS/CSm、TRo/CSm、ETo/CSm、RC/CSm和ETo/RC值最低,而Na2SiO3和NaHCO3復(fù)合處理較NaHCO3處理則顯著升高;DIo/CSm、ABS/RC值則表現(xiàn)出相反的趨勢(shì)。與魯倩君等[28]發(fā)現(xiàn)在NaCl和NaHCO3的復(fù)合脅迫下,不同品種葡萄的葉片ABS/CSm、TRo/CSm、ETo/CSm、RC/CSm值均呈下降趨勢(shì),DIo/CSm和ABS/RC值則升高的結(jié)果相似,說(shuō)明堿性鹽脅迫可造成單位面積內(nèi)部分反應(yīng)中心失活,葉片單位面積內(nèi)吸收光能、捕獲光能的能力低,電子傳遞能力下降,但為減少光系統(tǒng)的損傷,植物將吸收光能大部分以熱耗散的形式消耗。而Na2SiO3可以增加反應(yīng)中心數(shù)量,促進(jìn)了單位面積內(nèi)光能的吸收,增強(qiáng)天線色素對(duì)光能的捕獲能力,電子傳遞效率加快,同化能力升高,光合能力增強(qiáng)[22,26,29]。
4結(jié)論
硅顯著增加了在堿性鹽脅迫下陽(yáng)光玫瑰葉片的PIabs值、單位葉截面積中光合反應(yīng)中心的數(shù)量,以及對(duì)光能的吸收與捕獲,增強(qiáng)了電子傳遞能力,同時(shí)減少了植株的熱耗散,緩解了鹽脅迫造成的光系統(tǒng)的損傷,提高了光利用效率,提升了植物光合能力,從而增強(qiáng)了植物的耐鹽性。這為硅在葡萄栽培上的廣泛應(yīng)用提供了較好的理論基礎(chǔ)。
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