水淹对水芹叶片结构和光系统II光抑制的影响

通过探讨在水淹条件下水芹(Oenanthe javanica)叶片结构的变化以及出水对其光系统II功能和光抑制的影响, 阐明水芹光合机构在水淹条件下及出水后死亡的可能原因。结果表明: 水淹条件下新生沉水功能叶光系统II(PSII)最大光化学效率(Fv/Fm) 、电子传递活性与对照叶片差异很小, 但水淹使气生功能叶的Fv/Fm显著降低; 植株总生物量呈负增长趋势; 活体弱光条件下, 沉水叶出水后2小时叶片相对含水量(RWC)和Fv/Fm无显著变化; 中等光强和强光条件下其RWC和Fv/Fm迅速降低; 离体条件下, 5小时的中等光强对沉水叶的Fv/Fm影响不显著, 在随后的弱光下能恢复到出水时的初始状态; 强光能使沉水叶的Fv/Fm大幅降低, 且弱光下不能恢复到出水时的初始水平; 在解剖结构上, 水芹沉水叶的叶片总厚度、上下表皮厚度和气孔大小都显著低于气生叶, 而且沉水叶没有明显的栅栏组织分化, 但是沉水叶上表皮的气孔密度显著高于气生叶。研究结果表明, 水淹使水芹原气生叶PSII功能迅速衰退, 但对新生沉水叶片影响很小。水芹植株出水后, 沉水叶片结构变化使其在光下保水能力下降, 而强光导致了光合机构的光抑制和反应中心失活。田间条件下两者共同作用则加剧了对叶片光合机构的破坏, 进而致使其死亡。     

水淹对水芹叶片结构和光系统Ⅱ光抑制的影响

通过探讨在水淹条件下水芹（Oenanthe javanica）叶片结构的变化以及出水对其光系统II功能和光抑制的影响,阐明水芹光合机构在水淹条件下及出水后死亡的可能原因。结果表明：水淹条件下新生沉水功能叶光系统Ⅱ（PSⅡ）最大光化学效率（Fv/Fm）、电子传递活性与对照叶片差异很小,但水淹使气生功能叶的Fv/Fm显著降低;植株总生物量呈负增长趋势;活体弱光条件下,沉水叶出水后2小时叶片相对含水量（RWC）和Fv/Fm无显著变化;中等光强和强光条件下其RWC和Fv/Fm迅速降低;离体条件下,5小时的中等光强对沉水叶的Fv/Fm影响不显著,在随后的弱光下能恢复到出水时的初始状态;强光能使沉水叶的Fv/Fm大幅降低,且弱光下不能恢复到出水时的初始水平;在解剖结构上,水芹沉水叶的叶片总厚度、上下表皮厚度和气孔大小都显著低于气生叶,而且沉水叶没有明显的栅栏组织分化,但是沉水叶上表皮的气孔密度显著高于气生叶。研究结果表明,水淹使水芹原气生叶PSⅡ功能迅速衰退,但对新生沉水叶片影响很小。水芹植株出水后,沉水叶片结构变化使其在光下保水能力下降,而强光导致了光合机构的光抑制和反应中心失活。田间条件下两者共同作用则加剧了对叶片光合机构的破坏,进而致使其死亡。     

不同叶龄杂交酸模叶片光合速率及PSⅡ光化学效率诱导对NaCl胁迫的响应

通过气体交换和叶绿素荧光分析方法研究了杂交酸模(Rumex K-1)幼叶、功能叶和衰老叶的光合速率及PSⅡ光化学效率诱导对NaCl胁迫的响应特征。结果表明,老叶的光合作用对盐胁迫最为敏感,幼叶次之,功能叶对盐胁迫的抗性最强。对照植株幼叶、功能叶和老叶的光合诱导速率相差不大,幼叶和功能叶光合诱导后期受气孔限制的影响。盐胁迫后幼叶和功能叶的光合诱导推迟,出现了一个新的光合适应阶段;老叶仍有部分电子传递功能,但已丧失碳同化能力。盐胁迫后气孔导度不再是叶片光合碳同化诱导过程的限制因素,不同叶龄叶片PSⅡ光化学效率启动所需时间远远小于光合速率启动所需时间,盐胁迫对叶片的PSⅡ光化学效率诱导过程几乎没有影响。     

田间大豆叶片成长过程中的光合特性及光破坏防御机制

田间大豆叶片在成长进程中光饱和光合速率持续提高,但气孔导度的增加明显滞后.尽管叶片在成长初期就具有较高的最大光化学效率,但是仍略低于发育成熟的叶片.随着叶片的成长,光下叶片光系统Ⅱ实际效率增加;非光化学猝灭下降.幼叶叶黄素总量与叶绿素之比较高,随着叶面积的增加该比值下降,在光下,幼叶的脱环氧化程度较高.因此认为大豆叶片成长初期就能够有效地进行光化学调节;在叶片生长过程中依赖叶黄素循环的热耗散机制迅速建立起来有效抵御强光的破坏.     

越冬期广玉兰阳生叶和阴生叶PSⅡ功能及捕光色素分子内禀特性的比较研究

捕光色素分子的内禀特性不仅决定了光能的吸收与传递,也将影响到激发能向光化学反应、热耗散和叶绿素荧光的分配。本文采用叶绿素荧光技术和光合电子流对光响应机理模型,研究了越冬期广玉兰（Magnolia grandiflora）阳生叶和阴生叶两种不同光环境下叶片PSⅡ功能及其捕光色素分子内禀特性的差异,以探索广玉兰越冬的光保护策略。结果表明：越冬期低温导致叶片轻微光抑制的发生,全光照加剧了阳生叶光抑制程度,而弱光环境有利于阴生叶光抑制的恢复。阳生叶可通过降低叶绿素含量和捕光色素分子数量以减少对光能的吸收,并且具有较强的光化学和热耗散能力以保护光合机构免受低温强光伤害。而阴生叶虽然其光化学反应能力相对较弱,但具有较强的热耗散能力,可有效地保护其免受短时曝露在强光下的伤害。     

不同光强对入侵种三裂叶豚草表型可塑性的影响

通过人工遮光,研究了不同光照强度下入侵植物三裂叶豚草的形态、生物量分配以及光合特性的表型可塑性.结果表明:与对照相比,遮光条件下,三裂叶豚草的株高、冠宽、单株叶面积、比叶面积和叶生物量比重显著增加,总生物量、单位叶面积生物量和根冠比减小;在全光照条件下,其冠宽和单株叶面积较小,根冠比较大,有利于高温强光下减少水分散失,表现出对不同光强较强的形态和生物量可塑性.遮光使三裂叶豚草叶片的日均净光合速率、蒸腾速率和气孔导度下降,胞间CO2浓度上升.正午光照最强时,低遮光处理植株的净光合速率、蒸腾速率和气孔导度最大.中遮光和高遮光条件下,其叶绿素含量显著增加,叶绿素a/b显著减小,有利于提高三裂叶豚草的光能利用效率,以适应弱光环境.     

D,L-甘油醛处理引起的小麦叶片表观光合量子效率的降低（英文）

D,L-甘油醛(磷酸核酮糖激酶抑制剂,10mmol/L)处理小麦旗叶1 h可降低叶片净光合速率和表观量子效率.同时,光系统Ⅱ光化学效率(△F/Fm′)、电子传递速率(ETR)和单位叶面积ATP含量均降低,而胞间二氧化碳浓度(Ci)和叶绿素荧光非光化学猝灭(NPQ)增加.这些结果说明,D,L-甘油醛引起的小麦旗叶表观量子效率降低是由于光合碳同化受阻对光合电子传递的反馈抑制.     

基于叶绿素荧光成像及荧光参数分布特征的叶片光合异质性定量分析

植物叶片光合作用具有高度的空间异质性,叶绿素荧光成像技术为叶片光合异质性的研究提供了便利,但叶片光合异质性的定量分析并没有得到广泛应用。本文利用ImagingPAM叶绿素荧光成像系统,获得 中亚热带地区越冬期小叶榕（Ficus microcarpa）阳生叶和阴生叶的叶绿素荧光参数图像,并利用仪器的分析软件对其进行分析,定量比较了阳生叶和阴生叶的光合异质性特征。研究发现：越冬期小叶榕阳生叶的光合异质性和光抑制程度明显高于阴生叶,变异系数可作为光合异质性的定量指标。低温强光导致阳生叶坏死率（P_LN）达4.30%,并有53.30%的区域处于严重光抑制（0<F_v/F_m<0.627）,但仍有42.27%的区域仅为轻度光抑制（0.627≤ F_v/F_m<0.800）。而低温弱光并未造成阴生叶坏死和严重光抑制。通过对光系统Ⅱ（PSⅡ）的实际光合效率 （Y（Ⅱ））、调节性能量耗散的量子产额（Y（NPQ））和非调节性能量耗散的量子产额（Y（NO））荧光参数异质性的定量分析表明,阳生叶具有相对较高的光化学能力,阴生叶则具有相对较高的热耗散能力;冬季强光虽然会导致小叶榕阳生叶PSⅡ严重激发压积累,存在严重光抑制的潜在风险,但其致死面积并不大,叶片中仍存在一定面积低激发压的低风险区,而低温弱光下的阴生叶则主要以低风险区域为主。     

光波动频率影响黄瓜幼苗光合作用的机制

自然条件下环境光强往往是波动的,但波动光变化频率影响植物光合作用的机制尚不清楚.为了探讨植物光合作用对波动光频率的响应及机制,本文以黄瓜为材料,对植物生长、叶绿素含量、气体交换、叶绿素荧光以及抗氧化酶进行了研究.结果显示,相对于弱光(T4),强光下(T1, T2和T3)黄瓜株高、生物量、叶面积和比叶重均明显较高,但波动频率增加(T2, T3)能够导致这些参数值降低.强光与弱光处理相比其叶绿素总量较低,且随着波动光频率的提高叶绿素含量轻微下降.强光下的光合速率和气孔导度均高于弱光,不过随着强光波动频率增加,两者呈下降趋势.荧光诱导动力学的结果显示,尽管各处理间光系统Ⅱ(PSⅡ)最大光化学效率没有明显差异,但波动频率较大时黄瓜的PSⅡ的电子传递活性略有降低;而且增加强光波动频率还导致光系统Ⅱ天线转化效率(Fv′/Fm′)明显降低和非光化学猝灭(NPQ)大幅增加.此外,强光下黄瓜的酶促抗氧化系统的主要酶活性高于弱光,但波动光频率提高能够降低其活性.因此,提高波动光的频率不仅导致黄瓜光合能力下降,还导致其主要抗氧化酶的活性降低,所以增强的热耗散可能是其应对波动光下过剩激发能的重要机制.此外,本文还对黄瓜适应波动强光和稳态强光的差异进行了讨论.     

叶角、光呼吸和热耗散协同作用减轻大豆幼叶光抑制

研究了大豆叶片逐步展开过程中的色素组成、气体交换、荧光动力学以及叶片角度等特性。随着叶片展开程度的增加 ,叶绿素含量和叶绿素 a/ b比值增加 ;光合速率 (Pn)也增加 ,揭示叶片展开过程中光合机构是逐步完善的。自然状态下 ,不同展开程度的叶片均未发生明显的光抑制 ;但将叶片平展并暴露在 12 0 0μmol/ (m2 · s)光下时幼叶发生严重的光抑制 ,伴随叶面积的增加光抑制程度减轻。强光下 ,尽管幼叶光呼吸 (Pr)的测定值较低 ,但幼叶光呼吸与总光合之比 (Pr/ Pm)较高。将叶片平展置于强光下时 ,幼叶的实际光化学效率 (ΦPSII)明显下调 ,非光化学猝灭 (NPQ)大幅增加 ;幼叶叶黄素库较大 ,光下积累较多的脱环氧化组分 ,揭示幼叶依赖叶黄素循环的热耗散增强。自然条件下测量叶片角度 ,观察到在叶片展开过程中叶柄夹角逐渐增加 ;日动态过程中幼叶的悬挂角随光强增加而明显减小 ,完全展开叶的悬挂角变化幅度很小。叶片角度的变化使实际照射到幼叶叶表的光强减少。推测较强的光呼吸、依赖叶黄素循环的热耗散以及较大的叶角变化可能是自然状态下幼叶未发生严重光抑制的原因     

Induction characteristics and response of photosynthetic quantum conversion to changes in irradiance in mulberry plants

A study was conducted, using rapid time course of chlorophyll (Chl) fluorescence parameters, and light-response curves of Chl fluorescence parameters, to determine the induction requirements and response of photosystem II (PSII) photochemistry and non-photochemical reactions after changes in irradiance in greenhouse mulberry plants. The induction of PSII photochemistry rapidly approached to steady state after leaves were treated from darkness to low irradiance (LI). When irradiance of leaves changed from darkness to high irradiance (HI), a biphasic induction was observed. A slight photoinhibition occurred in the leaves exposed to sunlight coming to the greenhouse, whereas a chronic photoinhibition occurred in the leaves fully exposed to sunlight outside the greenhouse. The chronic photoinhibition was demonstrated by sustained reduction of maximal quantum yield of PSII photochemistry (Fv/Fm). Moreover, the leaves of mulberry plants in greenhouse were sensitive to abrupt changes in irradiance and the sensitivity of leaves suffered in a short-term (1h) high light treatment was reduced, based on the changes in photosynthetic quantum conversion. These results demonstrated an inducible response of photosynthetic quantum conversion to changes in irradiance in mulberry.     

遮荫对连翘光合特性和叶绿素荧光参数的影响

本文系统研究了不同程度的遮荫(0%、43%、70%、97%)处理对连翘叶片光合特性和叶绿素a荧光参数的影响。结果表明：随着遮荫程度增加,最大净光合速率、光补偿点、光饱和点、暗呼吸速率降低;净光合速率日变化均呈单峰型,峰值和光能利用率增加;叶绿素a b、叶绿素a、叶绿素b含量增加,叶绿素a/b降低;叶绿素a荧光参数Fv/Fm和Fv/Fo日变化呈单谷曲线,值均高于全光照的,且随着遮荫程度的提高其值均依次增加。这说明,连翘是一种耐荫性很强的植物,遮荫可使其降低光补偿点、光饱和点、净光合速率、暗呼吸速率以及叶绿素a/b,增加总叶绿素、叶绿素a、叶绿素b含量、光能利用率以及PSⅡ原初光能转化效率和潜在活性,从而增强其在弱光条件下的生长发育能力。     

遮荫对异株荨麻光合特性和荧光参数的影响

系统研究了全光照和不同程度的遮荫(43%,58%,73%,87%,97%)对异株荨麻光合特性和荧光参数的影响。结果表明,异株荨麻的光补偿点和光饱和点均较低,且随着遮荫程度的提高,其值以及暗呼吸速率均依次降低。净光合速率日变化曲线呈单峰型,光合速率高峰值和日平均光合速率均随着遮荫程度的提高而明显下降。蒸腾速率和气孔导度的日变化与光合速率的日变化趋势一致,遮荫对蒸腾作用和气孔导度均有显著的影响,随着遮荫程度的提高,蒸腾速率和气孔导度均显著下降。在各光照条件下,蒸腾速率与气孔导度呈显著正相关。蒸腾速率和气孔导度与光合速率的相关性随遮荫条件的不同而异,全光照条件下蒸腾速率与光合速率呈显著正相关,而所有遮荫条件下相关性不显著。气孔导度与光合速率在所有光照下相关性均不显著。各遮荫条件下叶片总叶绿素、叶绿素a、叶绿素b含量均显著高于全光照的,且随遮荫程度的提高叶绿素含量呈上升趋势,而叶绿素a/b的值则随着遮荫程度的提高而下降。叶绿素荧光参数PSⅡ内禀光能转化效率(Fv/Fm)和潜在活性(Fv/Fo)日变化呈单谷曲线。各遮荫条件下Fv/Fm和Fv/Fo值均高于全光照的,且随着遮荫程度的提高其值均依次增加。这说明,异株荨麻是一种耐荫性很强的植物,遮荫可使其降低光补偿点、光饱和点、净光合速率、暗呼吸速率以及叶绿素a/b,但增加总叶绿素、叶绿素a、叶绿素b含量、光能利用率以及PSⅡ原初光能转化效率和潜在活性,以增强在弱光条件下的生长发育能力。     

Photosynthetic responses to light in seedlings of selected Amazonian and Australian rainforest tree species

Summary Seedlings of the Caesalpinoids Hymenaea courbaril, H. parvifolia and Copaifera venezuelana, emergent trees of Amazonian rainforest canopies, and of the Araucarian conifers Agathis microstachya and A. robusta, important elements in tropical Australian rainforests, were grown at 6% (shade) and 100% full sunlight (sun) in glasshouses. All species produced more leaves in full sunlight than in shade and leaves of sun plants contained more nitrogen and less chlorophyll per unit leaf area, and had a higher specific leaf weight than leaves of shade plants. The photosynthetic response curves as a function of photon flux density for leaves of shade-grown seedlings showed lower compensation points, higher quantum yields and lower respiration rates per unit leaf area than those of sun-grown seedlings. However, except for A. robusta, photosynthetic acclimation between sun and shade was not observed; the light saturated rates of assimilation were not significantly different. Intercellular CO₂ partial pressure was similar in leaves of sun and shade-grown plants, and assimilation was limited more by intrinsic mesophyll factors than by stomata. Comparison of assimilation as a function of intercellular CO₂ partial pressure in sun- and shade-grown Agathis spp. showed a higher initial slope in leaves of sun plants, which was correlated with higher leaf nitrogen content. Assimilation was reduced at high transpiration rates and substantial photoinhibition was observed when seedlings were transferred from shade to sun. However, after transfer, newly formed leaves in A. robusta showed the same light responses as leaves of sun-grown seedlings. These observations on the limited potential for acclimation to high light in leaves of seedlings of rainforest trees are discussed in relation to regeneration following formation of gaps in the canopy.     

Interactive effects of nitrogen and irradiance on sustained xanthophyll cycle engagement in Eucalyptus nitens leaves during winter

Eucalyptus nitens is a species that is adapted to low temperature. This study examines xanthophyll-cycle engagement in E. nitens seedlings exposed to cold-induced photoinhibitory conditions under different levels of irradiance and nutrient status. Xanthophyll-cycle pool size indicated an increased requirement for light energy dissipation under high irradiance and low nutrient status. Greater sensitivity to photoinhibition of non-shaded seedlings indicated that sustained xanthophyll-cycle engagement may occur in response to damaged chlorophyll. Within irradiance treatments, fertilised seedlings had higher photochemical efficiency and faster recovery from photoinhibition than unfertilised seedlings. These results demonstrate that fertilised compared to unfertilised seedlings can utilise a greater proportion of incident light under cold temperature conditions     

喜光榕树和耐荫榕树光适应机制的差异

100%和36%光强下生长的喜光的斜叶榕的光合能力高于耐荫的假斜叶榕,而热耗散能力与之相似,说明强光下斜叶榕主要通过光合作用利用光能和热耗散、假斜叶榕主要通过热耗散防御光破坏.100%光强下生长的两种榕树的日间光抑制程度相似,但叶表光强相同情况下各光强下生长的假斜叶榕的光抑制均比斜叶榕严重.100%光强下假斜叶榕叶片悬挂角大于斜叶榕,导致日间叶表光强低于斜叶榕,这可能是两种榕树日间光抑制程度相似的原因,表明叶片悬挂角的适应变化对假斜叶榕有重要的意义.     

Rapid and Specific Modulation of Stomatal Conductance by Blue Light in Ivy (Hedera helix) : An Approach to Assess the Stomatal Limitation of Carbon Assimilation

Low intensity (0.015 millimole per square meter per second) blue light applied to leaves of Hedera helix under a high intensity red light background (0.50 millimole per square meter per second red light) induced a specific stomatal opening response, with rapid kinetics comparable to those previously reported for stomata with `grass type' morphology. The response of stomatal conductance to blue light showed a transient `overshoot' behavior at high vapor pressure difference (2.25 ± 0.15 kiloPascals), but not at low vapor pressure difference (VPD) (0.90 ± 0.10 kilo-Pascal). The blue light-induced conductance increase was accompanied by an increase in net photosynthetic carbon assimilation, mediated by an increase in the intercellular concentration of carbon dioxide. Values of assimilation once the blue light-stimulated conductance increase reached steady state were less than those at the peak of the overshoot, but the ratios of assimilation to transpiration (A/E) and blue light-stimulated ΔA/ΔE were greater during the steady-state response than during the overshoot. These results indicate that significant stomatal limitation of assimilation can occur, but that this limitation may improve water use efficiency under high VPD conditions. Under high intensity red light, the decline in A/E associated with an increase in VPD was minimized when conductance was stimulated by additional low intensity blue light. This effect indicates that the blue light response of stomata may be important in H. helix for the optimization of water use efficiency under natural conditions of high irradiance and VPD.