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1.
蒙古栎和紫椴幼苗对光环境转变的光合作用响应   总被引:2,自引:1,他引:1  
比较研究了从温室5%光强转到10%、30%和100%光强处理下,蒙古栎(Quercus mongolica)和紫椴(Tilia amurensis)幼苗的光合能力和叶绿素荧光的响应,揭示了两个树种对光环境变化的不同适应情况及其光保护机制。结果表明,光强转换后两种幼苗都发生了严重光抑制,蒙古栎幼苗的最大光化学效率(Fv/Fm)在光强转变后第3天降到最低(0.52),紫椴幼苗在光强转变后第1天就降到了最低(0.67),蒙古栎降低幅度明显高于紫椴。之后随着光适应时间的延长逐渐恢复到原有水平,说明短时期的光抑制没有对两种幼苗的光合机构造成光损伤;从不同光照条件来看,无论是最大净光合速率(Pmax),还是实际光化学效率(ФPSⅡ),2种幼苗均为30%光强下的值高于10%和100%光强,说明过低或过高的光强都不利于幼苗的生长发育,只有适当的中光才利于幼苗的生长发育;与30%光强相比,蒙古栎幼苗100%光强下PmaxFv/FmФPSⅡ、NPQ的变化幅度远大于紫椴幼苗,表明高光强对蒙古栎幼苗的影响要大于紫椴;100%光强下,2种幼苗均通过大量增加非光化学淬灭(NPQ)、类胡萝卜素和叶绿素之比(Car/Chl)耗散过剩光能,降低单位鲜重叶绿素含量(Chl)以减少光能吸收,避免了光合机构光破坏。  相似文献   

2.
甜瓜幼苗叶片光合变化特性   总被引:3,自引:1,他引:2  
为探讨甜瓜光响应变化特性与环境因子的关系,选择光响应曲线适宜测定的时段,以甜瓜幼苗为试材,将1 d分为3个时段:10:00-12:00、12:00-15:00和15:00-17:00,每个叶位叶片测定1 d,并采用直角双曲线修正模型拟合光响应曲线,研究不同时段下甜瓜叶片光响应曲线、光响应参数的变化趋势和不同叶位叶片光响应参数特性。结果表明:当环境中光合有效辐射增强,叶面温度(Tl)升高,空气相对湿度(RH)降低;当环境中光合有效辐射减弱,Tl降低,RH升高。10:00-12:00光响应曲线和12:00-15:00的第1-4叶光响应曲线呈双曲线,在强光下趋向饱和状况,12:00-15:00的第5叶光合速率和15:00-17:00光合速率在强光下出现明显的光抑制现象。1 d的不同时段均表现为10:00-12:00最大净光合速率(Pmax)和光饱和点(LSP)最高,12:00-17:00降低;12:00-15:00光补偿点(LCP)和暗呼吸速率(Rd)较高,其它两个时段较低,10:00-17:00光补偿点量子效率(φc)、气孔导度(Gs)和胞间CO2浓度(Ci)总体呈降低趋势,气孔限制值(Ls)升高。10:00-15:00相同时段测得的不同叶位叶片光响应参数,以第4-5叶光合性能较好,15:00-17:00以第3叶Pmax最高,第5叶次之;10:00-17:00 GsCi以第5叶较低,第1叶较高,Ls以第5叶较高,第1叶较低。RH为影响Pmax的主要决策因子,测定时段、叶面饱和蒸汽压亏缺(Vpdl)和Tl为主要限制因子。10:00-12:00适宜进行光响应曲线测定,气孔限制为不同时段光合作用不同的主要因素,非气孔限制为影响不同叶位叶片光合作用的主要因素。  相似文献   

3.
以2年生连香树实生苗为材料,在田间通过黑色遮阳网设置全光照(L0)及透光率55%(L1)、25%(L2)和10%(L3)4种光环境,研究遮光对连香树幼苗光合作用及叶片解剖结构的影响。结果表明:(1)连香树幼苗叶片Pn在全光和L1处理下呈非典型的“乁”形变化,未出现“午休”现象,中午14:00出现极值,而在L2和L3处理下变化相对缓和,极值出现在中午12:00;叶片Gs呈现与Pn类似的变化趋势,而Ci则呈基本一致的凹形变化。(2)各处理PnGsTr的日均值均表现为L0>L1>L2>L3,而Ci的日均值则呈相反的顺序;PnGsTr、气温和光合有效辐射均呈极显著正相关关系(P<0.01)。(3)全光照连香树幼苗的光补偿点(LCP)、光饱和点(LSP)、暗呼吸速率(Rd)均显著高于遮光处理,并维持较高的Pn而未出现明显的光抑制;遮光导致幼苗的LCP、LSP、Rd显著降低,有利于充分利用弱光,以满足低光环境下植株的正常生长。(4)与全光照相比,遮光下连香树叶片气孔密度显著变小,但气孔器长度、气孔器宽度、单个气孔器面积显著增加,气孔器面积百分比减少,影响幼苗细胞内外的水分和气体传递。(5)遮光条件下,连香树叶片明显变薄,表皮细胞厚度减小,栅栏组织(PT)厚度降低,排列变得疏松,海绵组织(ST)厚度增加,PT/ST相应减小。(6)与全光照相比,强度遮光下(L2和L3)连香树幼苗生长受阻,苗高(H)和基径(D)明显减小,生物量模型D2H下降;而轻度遮光(L1)下幼苗H和D、H/D和D2H均未出现显著变化。研究发现,连香树具有一定的光忍耐性和喜光性,对光照条件的生态幅较宽,轻度遮光影响较小,但强度遮光对连香树幼苗气体交换参数和光合响应特征产生了显著影响,同时影响了叶片的解剖结构和气孔分布特征,从而影响连香树幼苗的生长形态。在育苗生产中,适度遮光有利于降低气温、减小蒸腾,但遮光后田间有效辐射强度应保持在自然光强的55%以上。  相似文献   

4.
为探讨红树植物光适应的生理生态策略,对6种真红树植物[无瓣海桑(Sonneratia apetala)、秋茄(Kandelia candel)、木榄(Bruguiera gymnorrhiza)、桐花树(Aegiceras corniculatum)、老鼠簕(Acanthus ilicifolius)、卤蕨(Acrostichum aureum)]和2种半红树植物[银叶树(Heritiera littoralis)、黄槿(Hibiscus tiliaceus)]的1 a生幼苗在不同生长光强(自然光强的100%、45%、30%、10%)下的光合光响应特征进行了研究。结果表明,不同生长光强对红树植物光响应特征的影响因物种而异,遮荫显著提高了秋茄和木榄的最大净光合速率(Pmax),而对其他红树植物的Pmax没有显著影响;秋茄在45%光强下具有较高的Pmax,木榄的Pmax则在45%和30%光强下显著高于其他2个处理。随着生长光强的下降,秋茄幼苗叶片的光饱和点显著上升,木榄、老鼠簕和卤蕨的光补偿点呈下降趋势,木榄和卤蕨的表观量子效率升高的同时暗呼吸速率下降。木榄、老鼠簕和卤蕨具有较强的耐荫性,适宜种植在光强较弱的林下;无瓣海桑、秋茄、桐花树、银叶树和黄槿则适宜作为中上层树种或在郁闭度较低的林下种植。  相似文献   

5.
干旱胁迫对玉米苗期叶片光合作用和保护酶的影响   总被引:25,自引:0,他引:25  
以玉米品种郑单958(抗旱性强)和陕单902(抗旱性弱)为材料,采用盆栽控水试验,设置3个干旱处理(轻度干旱,中度干旱,重度干旱)和正常灌水,研究了干旱胁迫对玉米苗期叶片光合速率、叶绿素荧光以及相关生理指标的影响。结果表明:(1)干旱胁迫下2个品种叶片净光合速率(Pn)和气孔导度(Gs)显著下降,胞间CO2浓度(Ci)出现了先下降后上升,而气孔限制值(Ls)上升后下降,说明中度干旱胁迫下叶片Pn下降是气孔因素引起的,重度干旱胁迫下Pn降低主要由非气孔因素引起的。(2)随着干旱胁迫的加剧,2个品种叶片光系统Ⅱ(PSⅡ)的实际量子产量(φPSⅡ)、电子传递速率(ETR)和光化学猝灭(qP)一直下降,而非光化学猝灭(qN)上升后下降,说明中度干旱下热耗散仍是植株重要光保护机制,重度干旱时叶片光合电子传递受阻,PSⅡ受到损伤。(3)干旱胁迫下2个品种叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高,说明干旱胁迫初期对保护系统酶活性升高有诱导作用,重度胁迫下活性氧清除酶的活性下降,导致细胞膜伤害。这些结果暗示,轻度和中度干旱胁迫下2个玉米品种通过减少光捕获、热耗散和酶活性调节协同作用稳定了光合机构功能,是Pn下降的气孔限制因素;而重度干旱胁迫下光系统Ⅱ和抗氧化酶系统损伤,是Pn下降的非气孔限制因素;郑单958的各生理参数比陕单902受旱影响小,干旱胁迫下仍具有较高的光合效率和较强的保护酶活性是郑单958抗旱的主要生理原因。  相似文献   

6.
以‘绿博6号’黄瓜幼苗为试材,采用营养液培法研究不同浓度外源硅(0、0.5、1.0、1.5和2.0 mmol/L)对肉桂酸(cinnamic acid,CA)模拟自毒胁迫(3.0 mmol/L CA)下黄瓜幼苗生长、光合参数和叶绿素荧光参数的影响。结果表明:(1)自毒胁迫显著抑制了黄瓜幼苗的生长、根系形态建成和生物量的积累,显著降低了净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和叶绿素(Chl a、Chl b和Chl t)含量,并显著降低了叶片中PSⅡ的电子传递速率(ETR)、PSⅡ实际光化学效率[Y(Ⅱ)]和光化学淬灭系数(qP)。(2)添加适宜浓度外源硅可有效缓解自毒胁迫对黄瓜幼苗生长的影响,并提高其PnGsTr和叶绿素含量,在一定程度上维持叶片光合系统的稳定。(3)添加适宜浓度外源硅能使自毒胁迫下黄瓜叶片的Fv/Fm、ETR、Y(Ⅱ)qP显著升高,而非光化学淬灭系数(NPQ)则显著下降。研究发现,添加适宜浓度外源硅能提高自毒胁迫下黄瓜幼苗的叶绿素含量、Fv/Fm、ETR、Y(Ⅱ)qP,使光合机构趋于稳定,抑制Pn的下降,缓解自毒胁迫对光合系统的损伤,从而增强黄瓜幼苗对自毒胁迫的抗性,并以1.0 mmol/L外源硅处理的效果最佳。  相似文献   

7.
孙悦燕  郭跃东 《西北植物学报》2022,42(10):1739-1748
选取大田环境下3年生黄檗幼苗,采用人工控制双因素随机区组试验,在不同光照[全光照(S0)、轻度遮光21.4%(S1)和重度遮光8.7%(S2)]和不同氮添加[无添加对照(F0)、轻度添加(F1)和重度添加(F2)]条件下,测定黄檗幼苗叶片的相对叶绿素含量(SPAD值)、气体交换参数及碳氮化学计量特征,探讨黄檗幼苗对遮阴和施氮的响应机制。结果表明:(1)随着遮光程度增强,黄檗幼苗叶片的SPAD值、蒸腾速率(Tr)、气孔导度(Gs)、碳氮比(C∶N)和瞬时光合氮利用率(PNUE)均呈现先增后降的趋势,两种遮光条件下SPAD均显著高于全光照环境;黄檗幼苗叶片的净光合速率(Pn)、水分利用率(WUE)和气孔限制值(Ls)逐渐降低;而叶片氮(N)和碳(C)含量均呈先降后升的趋势。(2)随氮添加量增加,黄檗幼苗叶片的PnWUELs、N和C含量均呈先增后降趋势,TrGs和PNUE则逐渐下降,而C∶N逐渐增加。(3)黄檗幼苗叶片的Pn在各光氮组合处理间均无显著差异;SPAD含量以S1F0、S2F0和S1F2处理组合显著较高,而以全光照(S0)处理组合显著最低;TrGs以轻度遮光(S1)处理组合明显较高,而以S2F1、S0F2、S2F2明显较低;WUELs均以S0F2显著最高,S2F2处理组合显著最低。黄檗幼苗叶片N和C含量在重度遮光/轻度氮添加(S2F1)时具有较大值,而其C∶N和PNUE在轻度遮光/无氮添加(S1F0)时具有较大值。(4)隶属函数综合评价认为,黄檗幼苗对光氮复合作用总体属中等耐受型,轻度遮光时不添加氮肥(S1F0)和轻度氮添加(S1F1)及全光照时轻度氮添加(S0F1)为适于幼苗生长的光氮组合。研究发现,光环境是影响黄檗幼苗光合作用和更新的主导因子,但黄檗苗期能耐受一定的遮阴胁迫;光照不受限制时,适当增加氮肥有利于黄檗幼苗生长;光照受限(重度遮光)时,施氮则抑制叶片叶绿素合成,降低了幼苗光能利用率,不利于其生长。  相似文献   

8.
以2年生闽楠幼苗为材料,探讨不同遮荫处理[0(CK,全光照) 和30%、50%、70%遮荫]对闽楠[Phoebe bournei (Hemsl.) Yang]幼苗光合作用及其叶片解剖结构的影响,为闽楠的合理栽培及人工林混交树种的配置提供理论依据。结果表明:(1)与全光照处理(CK)相比,闽楠幼苗叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、最大净光合速率(Pnmax) 、光饱和点(LSP)、光补偿点(LCP)及暗呼吸速率(Rd)均随遮荫强度的增加而显著下降;在30%和50%遮荫下,幼苗能通过提高水分利用效率(WUE)和表观量子效率(AQY),增加叶绿素含量来充分利用弱光环境;70%遮荫处理则影响闽楠幼苗的正常生长。(2)遮荫降低了闽楠幼苗叶片的气孔密度,但单个气孔器的面积显著增加;遮荫处理下,闽楠叶片和主脉明显变薄;栅栏组织和海绵组织厚度降低,排列稀疏,栅海比减小,有利于提高对光能的利用效率。(3)闽楠幼苗根、茎、叶及总生物量均在全光照下最大,遮荫抑制了植株生物量的积累。研究发现,闽楠幼苗在遮荫处理下生物量积累和光合效率降低,但同时在叶片解剖结构和功能上表现出对遮荫的适应性,从而表现出一定的耐荫性。  相似文献   

9.
以2年生苹果矮化砧木M9 T337为试材,采用盆栽试验法,设置浇灌清水(CK)和盐碱胁迫(0.1 mol/L NaCl+NaHCO3溶液)+ 喷施5种浓度的H2O2 [0(T1)、0.2 mmol/L(T2)、0.4 mmol/L(T3)、0.6 mmol/L(T4)、0.8 mmol/L(T5)] 处理,测定各处理叶片叶绿素含量、光合气体交换参数、渗透调节物质含量、抗氧化酶活性和细胞膜透性,并利用相关性与主成分分析进行综合评价,以探讨外源过氧化氢(H2O2)增强其盐碱耐性的生理机制。结果表明:(1)随着盐碱胁迫(T1)的时间延长,M9 T337幼苗叶片叶绿素a(Chl a)含量、叶绿素b (Chl b)含量、叶绿素总量(Chl t)、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、可溶性蛋白(SP)含量均呈逐渐下降趋势;胞间CO2浓度(Ci)、可溶性总糖(TSS)含量、脯氨酸(Pro)含量、过氧化氢酶(CAT)活性、抗坏血酸过氧化物酶(APX)活性、相对电导率(REC)、丙二醛(MDA)含量均呈上升趋势;超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性均呈先升后降趋势。(2)与CK相比,盐碱胁迫+外源H2O2(T2- T5)处理后M9 T337幼苗叶片各指标均呈现不同幅度变化,且存在明显浓度效应,并以T3(0.4 mmol/L H2O2)处理叶片的Chl a、Chl b、Chl t、SP和Gs降幅最小,Ci、REC、MDA升幅最小,TSS、Pro、APX升幅最大。(3)M9 T337幼苗叶片PnTrGs、Chl a、Chl b、Chl t、SP、SOD、POD呈显著正相关,与Ci、MDA、CAT、APX、REC呈显著负相关。(4)综合评价表明,各处理对M9 T337幼苗叶片生理特性的效应依次为:CK>T3>T4>T2>T5>T1。研究发现,叶面喷施适宜浓度H2O2可有效改善盐碱胁迫下M9 T337幼苗光合能力,显著提高抗氧化酶活性和渗透调节物质的含量,降低细胞膜透性,从而达到缓解盐碱胁迫的作用,并以0.4 mmol/L H2O2处理效果最佳。  相似文献   

10.
麻疯树幼苗对干旱胁迫的响应   总被引:18,自引:0,他引:18  
以不同浓度(5%~25%)的聚乙二醇(PEG-6000)模拟干旱胁迫处理麻疯树三叶期幼苗,研究了不同程度干旱胁迫下麻疯树叶片光合特性及其对干旱的耐受能力.结果表明:在较低浓度PEG(≤15%)处理下,随PEG浓度的增加,麻疯树叶片净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、PSⅡ实际光化学量子产量(ΦPSⅡ)、光化学猝灭(qP)和表观光合电子传递速率(ETR)下降,PSⅡ原初光能转化效率(Fv/Fm)轻微下降,水分利用效率(WUE)则逐渐升高,非光化学猝灭(NPQ)明显上升,初始荧光(Fo)无显著变化(P>0.05);在高浓度PEG(>15%)处理下,Ci随PEG浓度的增加而显著上升,Pn、Gs和WUE持续下降,Fv/Fm、ΦPSⅡ、qP和ETR下降幅度明显增大,Fo显著上升,而NPQ下降.低浓度PEG处理导致麻疯树叶片Pn下降主要是由气孔因素造成的;在高浓度PEG处理下,Pn的下降则是由非气孔和气孔因素的共同限制作用造成的.当PEG浓度<20%时,虽然出现Pn下降,但光合机构未受损伤.经15 d高浓度PEG处理的植株叶片,在胁迫解除后光合活性能够迅速恢复,且植株可以存活.说明麻疯树对干旱胁迫有较强的耐受能力.  相似文献   

11.
研究海岛棉(Gossypium barbadense)和陆地棉(G.hirsutum)两个棉花栽培种的光合作用特性,探讨两个栽培种光合机构的光抑制以及防御保护机制,以期为新疆棉花高光效品种选育和高产高效栽培实践提供理论基础。在新疆生态气候条件下,系统测定了海岛棉和陆地棉的叶片运动、叶片接受光量子通量密度(PFD)、叶片温度、叶绿素荧光参数、气体交换参数和光呼吸速率的日变化。研究结果表明:陆地棉叶片的"横向日性"较强而海岛棉较弱,导致海岛棉叶片接受PFD较低,但其叶片温度较高。海岛棉叶片的光合速率和气孔导度均显著低于陆地棉。在8:00-10:00(北京时间,下同)海岛棉叶片的光呼吸速率略低于陆地棉,其余时间段海岛棉和陆地棉叶片的光呼吸速率相似。不同栽培种间,叶片的最大光化学效率和实际光化学效率的日变化均无明显差异。除14:00-16:00以外,海岛棉叶片的表观电子传递速率和光化学猝灭系数均显著低于陆地棉。8:00以后,海岛棉叶片的非光化学猝灭显著高于陆地棉。因此,在新疆生态气候条件下,海岛棉和陆地棉叶片"横向日性"运动能力和气孔导度的差异导致叶片所处的光温环境不同,同时造成海岛棉叶片的碳同化能力较低。为阻止光合电子传递链的过度还原,减轻光合机构的光抑制,陆地棉叶片主要通过光合机构的电子流途径耗散激发能,而海岛棉叶片通过热耗散途径和相对较高的光呼吸能力来耗散激发能。  相似文献   

12.
要通过比较棉花(Gossypium hirsutum)幼叶和完全展开叶气体交换参数及叶绿素荧光特性的差异,探讨高光强下幼叶的光抑制程度及明确光保护机制间的协调机理.在田间自然条件下,以棉花刚展平的幼嫩叶片(幼叶)和面积已达到最大的完全展开叶片为研究对象,通过测定不同发育阶段叶片气体交换参数及叶绿素a荧光参数的变化,并运用Dual-PAM 100对不同发育阶段的叶片进行快速光响应曲线的拟合.结果表明:幼叶和完全展开叶片在光合、荧光特性方面表现出明显的差异.与完全展开叶相比,较低的叶绿素(Chl)含量和气孔导度(Gs)是幼叶较低净光合速率(Pn)的限制因素,从而直接导致其光系统Ⅱ(PSⅡ)实际光化学效率((φ)PSⅡ)和光化学猝灭系数(qP)的降低.在1 800 μmol·m-2·s-1光强以下,完全展开叶具有较强的围绕PSⅠ循环的电子流(CEF),有利于合成ATP,是其具有较高光合能力的原因之一.相同光强下,幼叶较低的光饱和点(LSP)更易受光抑制,但其PSⅡ原初光化学效率(Fv/Fm)的日变化幅度显著小于完全展开叶,说明强光下幼叶通过类胡萝卜素(Car)猝灭单线态氧、光呼吸(Pr)、热耗散(NPQ)以及PSⅠ-CEF等光保护机制能有效地耗散过剩的光能,从而避免其光合机构发生光抑制.  相似文献   

13.
The olive tree (Olea europaea L.) is commonly grown in the Mediterranean area, where it is adapted to resist periods characterized by severe drought and high irradiance levels. Photosynthetic efficiency (in terms of Fv/Fm and ΦPSII), photochemical (qP) and nonphotochemical quenching (NPQ) were determined in two-year-old olive plants (cultivars Coratina and Biancolilla) grown under two different light levels (exposed plants, EP, and shaded plants, SP) during a 21-day controlled water deficit. After reaching the maximum level of drought stress, plants were rewatered for 23 days. During the experimental period, measurements of gas exchange and chlorophyll (Chl) fluorescence were carried out to study the photosynthetic performance of olive plants. The synergical effect of drought stress and high irradiance levels caused a reduction of gas exchange and photosynthetic efficiency and these decreases were more marked in EP. EP showed a higher degree of photoinhibition, a higher NPQ and a lower qP if compared to SP. Coratina was more sensitive to high light and drought stress but also showed a slower recovery during rewatering, whereas Biancolilla showed a less marked photosynthesis depression during drought and a considerable resilience during rewatering. The results confirm that photoinhibition due to high light intensity and water deficit can be an important factor that affects photosynthetic productivity in this species.  相似文献   

14.
Seasonal variability of maximum quantum yield of PSII photochemistry (Fv/Fm) was studied in needles of Taxus baccata seedlings acclimated to full light (HL, 100% solar irradiance), medium light (ML, 18% irradiance) or low light (LL, 5% irradiance). In HL plants, Fv/Fm was below 0.8 (i.e. state of photoinhibition) throughout the whole experimental period from November to May, with the greatest decline in January and February (when Fv/Fm value reached 0.37). In ML seedlings, significant declines of Fv/Fm occurred in January (with the lowest level at 0.666), whereas the decline in LL seedlings (down to 0.750) was not significant. Full recovery of Fv/Fm in HL seedlings was delayed until the end of May, in contrast to ML and LL seedlings. Fv/Fm was significantly correlated with daily mean (T mean), maximal (T max) and minimal (T min) temperature and T min was consistently the best predictor of Fv/Fm in HL and ML needles. Temperature averages obtained over 3 or 5 days prior to measurement were better predictors of Fv/Fm than 1- or 30-day averages. Thus our results indicate a strong light-dependent seasonal photoinhibition in needles of T. baccata as well as suggest a coupling of Fv/Fm to cumulative temperature from several preceding days. The dependence of sustained winter photoinhibition on light level to which the plants are acclimated was further demonstrated when plants from the three light environments were exposed to full daylight over single days in December, February and April and Fv/Fm was followed throughout the day to determine residual sensitivity of electron transport to ambient irradiance. In February, the treatment revealed a considerable midday increase in photoinhibition in ML plants, much less in HL (already downregulated) and none in LL plants. This suggested a greater capacity for photosynthetic utilization of electrons in LL plants and a readiness for rapid induction of photoinhibition in ML plants. Further differences between plants acclimated to contrasting light regimes were revealed during springtime de-acclimation, when short term regeneration dynamics of Fv/Fm and the relaxation of nonphotochemical quenching (NPQ) indicated a stronger persistent thermal mechanism for energy dissipation in HL plants. The ability of Taxus baccata to sustain winter photoinhibition from autumn until late spring can be beneficial for protection against an excessive light occurring together with frosts but may also restrict photosynthetic carbon gain by this shade-tolerant species when growing in well illuminated sites.  相似文献   

15.
The effect of high irradiance (HI, photosynthetically active photon flux density of 1 300 μmol m−2 s−1) on net photosynthetic rate (P N), chlorophyll fluorescence parameters, and xanthophyll cycle components were studied in fruit tree bayberry leaves. HI induced the photoinhibition and inactivation of photosystem 2 (PS2) reaction centres (RCs), which was characterized by decreased P N, maximum yield of fluorescence after dark adaptation (Fm), photochemical efficiency of PS2 (Fv/Fm) and quantum yield of PS2 (ΦPS2), and increased reduction state of QA (1-qP) and non-photochemical quenching (NPQ). Initial fluorescence (F0) showed a decrease after the first 2 h, and subsequently increased from the third hour exposure to HI. Furthermore, a greater increase in the ratio (Fi-F0)/(Fp-F0) which is an expression of the proportion of the QB non-reducing PS2 centres, whereas a remarked decrease in the slope of Fi to Fp which represents the rate of QA reduction was observed in leaves after HI exposure. Additionally, HI caused an increase in the pool size of the xanthophyll cycle pigments and sustained elevated contents of zeaxanthin (Z), antheraxanthin (A), and de-epoxidation state (DES) at the end of the irradiation period. During HI, decreased Fm, Fv/Fm, ΦPS2, NPQ, slope of Fi to Fp, V+A+Z, and DES, and increased F0, 1-qP, ratio (Fi-F0)/(Fp-F0), and V were observed in dithiothreitol (DTT)-fed leaves compared to control ones under the same conditions. Hence photoinhibition caused by HI in bayberry was probably attributed to inactivation of PS2 RCs, and photoprotection from photodamage were mainly related to the xanthophyll cycle-dependent heat dissipation in excess photons.  相似文献   

16.
We investigated dependence of fluorescence parameters and phytoplankton biomass on the nitrogen source and irradiance in enriched flask studies with White Sea plankton from August-September 2007. Phytoplankton was exposed in situ for 18 d with addition of 180 μM/L of nitrogen in the forms of nitrate, urea, ammonia, and glycine under two levels of irradiance. Maximum quantum efficiency of PS2 (Fv/Fm) was determined in the samples adapted to darkness. Rapid light curves were obtained for each sample with the sequential increase of light intensity (8 levels). The maximal relative electron transport rate (rETRmax), the maximum light utilization coefficient (α), and the nonphotochemical quenching (NPQ) were calculated. The phytoplankton abundance increased on nitrogen addition, and the photosynthetic parameters changed. The values Fv/Fm reached 0.64–0.71, which indicated a good physiological state of algae and lack of nitrogen limitation. The dynamics of rETRmax and NPQ depended of the nitrogen source and irradiance, while α did not depend on nitrogen addition.  相似文献   

17.
We aimed to find out relations among nonphotochemical quenching (NPQ), gross photosynthetic rate (P G), and photoinhibition during photosynthetic light induction in three woody species (one pioneer tree and two understory shrubs) and four ferns adapted to different light regimes. Pot-grown plants received 100% and/or 10% sunlight according to their light-adaptation capabilities. After at least four months of light acclimation, CO2 exchange and chlorophyll fluorescence were measured simultaneously in the laboratory. We found that during light induction the formation and relaxation of the transient NPQ was closely related to light intensity, light-adaption capability of species, and P G. NPQ with all treatments increased rapidly within the first 1–2 min of the light induction. Thereafter, only species with high P G and electron transport rate (ETR), i.e., one pioneer tree and one mild shade-adapted fern, showed NPQ relaxing rapidly to a low steady-state level within 6–8 min under PPFD of 100 μmol(photon) m?2 s?1 and ambient CO2 concentration. Leaves with low P Gand ETR, regardless of species characteristics or inhibition by low CO2 concentration, showed slow or none NPQ relaxation up to 20 min after the start of low light induction. In contrast, NPQ increased slowly to a steady state (one pioneer tree) or it did not reach the steady state (the others) from 2 to 30 min under PPFD of 2,000 μmol m?2 s?1. Under high excess of light energy, species adapted to or plants acclimated to high light exhibited high NPQ at the initial 1 or 2 min, and showed low photoinhibition after 30 min of light induction. The value of fastest-developing NPQ can be quickly and easily obtained and might be useful for physiological studies.  相似文献   

18.
Kalanchoë daigremontiana, a CAM plant grown in a greenhouse, was subjected to severe water stress. The changes in photosystem II (PSII) photochemistry were investigated in water‐stressed leaves. To separate water stress effects from photoinhibition, water stress was imposed at low irradiance (daily peak PFD 150 μmol m?2 s?1). There were no significant changes in the maximal efficiency of PSII photochemistry (Fv/Fm), the traditional fluorescence induction kinetics (OIP) and the polyphasic fluorescence induction kinetics (OJIP), suggesting that water stress had no direct effects on the primary PSII photochemistry in dark‐adapted leaves. However, PSII photochemistry in light‐adapted leaves was modified in water‐stressed plants. This was shown by the decrease in the actual PSII efficiency (ΦPSII), the efficiency of excitation energy capture by open PSII centres (Fv′/Fm′), and photochemical quenching (qP), as well as a significant increase in non‐photochemical quenching (NPQ) in particular at high PFDs. In addition, photoinhibition and the xanthophyll cycle were investigated in water‐stressed leaves when exposed to 50% full sunlight and full sunlight. At midday, water stress induced a substantial decrease in Fv/Fm which was reversible. Such a decrease was greater at higher irradiance. Similar results were observed in ΦPSII, qP, and Fv′/Fm′. On the other hand, water stress induced a significant increase in NPQ and the level of zeaxanthin via the de‐epoxidation of violaxanthin and their increases were greater at higher irradiance. The results suggest that water stress led to increased susceptibility to photoinhibition which was attributed to a photoprotective process but not to a photodamage process. Such a photoprotection was associated with the enhanced formation of zeaxanthin via de‐epoxidation of violaxanthin. The results also suggest that thermal dissipation of excess energy associated with the xanthophyll cycle may be an important adaptive mechanism to help protect the photosynthetic apparatus from photoinhibitory damage for CAM plants normally growing in arid and semi‐arid areas where they are subjected to a combination of water stress and high light.  相似文献   

19.
To investigate the adaptive capacity to a strong light environment when planted on degraded land, we examined photosynthetic properties in relation to photoinhibition for the sun-leaves of six tropical fruit tree species native to Malaysia before and after transplanting. The six species were: Bouea macrophylla (Bm), Callerya atropurpurea (Ca), Canarium pilosum (Cp), Cynometra cauliflora (Cc), Morinda citrifolia (Mc) and Syzygium sp. (Ssp), which produce edible fruit for endemic animals and birds, and are candidates for corridor plantations. Based on the measurements performed before transplanting, the degree of chronic photoinhibition indicated by the decrease in pre-dawn F v/F m was well associated with an accumulation of excessive excitation energy in PSII indicated by a decrease in photochemical quenching (qP). Among the species, Ca and Mc showed lower degrees of photoinhibition with higher qP. Higher electron transport rates (ETR) were observed with higher qP whereas there was no significant relationship between regulatory thermal dissipation (indicated by ) and qP. Energy dissipation via electron transport was suggested to be important in keeping qP high and preventing photoinhibition when compared among species. Cc and Bm showed lower ETR and higher susceptibility to photoinhibition before and after transplanting. New Cp and Mc leaves developed after transplanting showed increased area-based leaf nitrogen content (N area) and stomatal conductance (gs) compared with those before transplanting resulting in higher light-saturated net photosynthetic rates (A max) and ETR, and contributing to mitigate photoinhibition. In contrast to these species, Ca achieved high A max with a water conservative manner (indicated by its relatively lower gs), where the higher carboxylation efficiency accompanied with the higher N area allowed them to maintain relatively high A max and ETR at lower intercellular CO2 concentration.  相似文献   

20.
X. Guan  S. Gu 《Photosynthetica》2009,47(3):437-444
In order to investigate the photoprotective function of photorespiration in grapevine under water stress, potted grapevines (Vitis vinifera L. cv. Cabernet Sauvignon) were randomly divided into three uniform groups for well-watered [watered every morning to keep the relative water content (RWC) of soil over 70 %], water-stress adapted (drought-adapted at 30 % relative soil water content for 30 days), and water stress without adaptation treatment (water-stressed to 30 % relative soil water content for 3 days). Net assimilation rate (A N), stomatal conductance (g s), substomatal CO2 concentration (C i), transpiration rate (E), actual photochemical efficiency of PSII (ΦPSII), and maximum photochemical efficiency of PSII (Fv/Fm) were recorded by combining measurements of gas exchange and chlorophyll fluorescence. Gross photorespiration (Pr), photosynthetic electron partitioning (JC/JT), photochemical quenching coefficient (qP), and non-photochemical quenching (NPQ) were also calculated. The ratio of net assimilation rate to transpiration rate (A N/E) was used as an indicator of water use efficiency (WUE). A N, apparent Pr, ΦPSII, Fv/Fm, qp, and g s decreased, NPQ increased, and gross Pr sustained at a high level under water stress. This suggests that both photorespiration and energy dissipation play important roles in protecting photosynthetic apparatus against photoinhibition. C i in water-stressed plants without adaptation treatment increased, which indicates the leaves suffered a non-stomatal limitation, while the water-stress adaped plants only suffered a stomatal limitation indicated by low C i.  相似文献   

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