BACKGROUND & AIMS: -2

背景与目标： -2

BACKGROUND & AIMS: :Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning tunneling microscope manipulation and spectroscopy on a gold substrate at 4.6 K. Chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by the support of four CH(3) groups. By injecting tunneling electrons from the scanning tunneling microscope tip, we are able to bend the phytyl-chain, which enables the switching of four molecular conformations in a controlled manner. Statistical analyses and structural calculations reveal that all reversible switching mechanisms are initiated by a single tunneling-electron energy-transfer process, which induces bond rotation within the phytyl-chain.

背景与目标： : 通过在4.6 K的金基板上使用扫描隧道显微镜操纵和光谱学研究了单个叶绿素-a分子，这是维持地球生命的重要资源。叶绿素a通过其卟啉单元在Au(111) 上结合，而植物链通过四个CH(3) 基团的支持从表面升高。通过从扫描隧道显微镜尖端注入隧道电子，我们能够弯曲phytyl链，从而能够以受控方式切换四个分子构象。统计分析和结构计算表明，所有可逆的切换机制都是由单个隧穿电子能量转移过程启动的，该过程会引起植物链内的键旋转。

BACKGROUND & AIMS: :This study deals with effects of membrane excitation on photosynthesis and cell protection against excessive light, manifested in non-photochemical quenching (NPQ). In Chara corallina cells, NPQ and pericellular pH displayed coordinated spatial patterns along the length of the cell. The NPQ values were lower in H(+)-extruding cell regions (external pH approximately 6.5) than in high pH regions (pH approximately 9.5). Generation of an action potential by applying a pulse of electric current caused NPQ to increase within 30-60 s. This effect, manifested as a long-lived drop of maximum chlorophyll fluorescence (F(m)'), occurred at lower photosynthetic flux densities (PFD) in the alkaline as compared to acidic cell regions. The light response curve of NPQ shifted, after generation of an action potential, towards lower PFD. The release of NPQ by nigericin and the rapid reversal of action potential-triggered NPQ in darkness indicate its relation to thylakoid DeltapH. Generation of an action potential shortly after darkening converted the chloroplasts into a latent state with the F(m) identical to that of unexcited cells. This state transformed to the quenched state after turning on weak light that was insufficient for NPQ prior to membrane excitation of the cells. The ionophore, A23187, shifted NPQ plots similarly to the action potential effect, consistent with a likely role of a rise in the cytosolic Ca(2+) level in the action potential-induced quenching. The results suggest that a rapid electric signal, across the plasma membrane, might exert long-lived effects on photosynthesis and chlorophyll fluorescence through ion flux-mediated pathways.

背景与目标： : 本研究涉及膜激发对光合作用和细胞对过度光的保护的影响，表现为非光化学猝灭 (NPQ)。在Chara corallina细胞中，NPQ和细胞周pH沿细胞长度显示出协调的空间模式。在H(+) 挤出细胞区域 (外部pH约6.5) 中的NPQ值低于在高pH区域 (pH约9.5) 中的NPQ值。通过施加电流脉冲产生动作电位，导致NPQ在30-60 s内增加。与酸性细胞区域相比，这种效应表现为最大叶绿素荧光 (F(m)') 的长寿命下降，发生在碱性较低的光合通量密度 (PFD) 下。产生动作电位后，NPQ的光响应曲线向较低的PFD移动。nigericin释放NPQ以及在黑暗中动作电位触发的NPQ的快速逆转表明其与类囊体DeltapH的关系。变暗后不久产生动作电位将叶绿体转化为潜伏状态，其F(m) 与未激发的细胞相同。在打开弱光后，该状态转变为淬灭状态，在细胞膜激发之前，该弱光不足以用于NPQ。离子载体A23187与动作电位效应类似地移动了NPQ图，这与在动作电位诱导的猝灭中胞质Ca(2) 水平升高的可能作用一致。结果表明，跨质膜的快速电信号可能会通过离子通量介导的途径对光合作用和叶绿素荧光产生长期影响。

BACKGROUND & AIMS: :To assist with efforts to engineer a C4 photosynthetic pathway into rice, forward-genetic approaches are being used to identify the genes modulating key C4 traits. Currently, a major challenge is how to screen for a variety of different traits in a high-throughput manner. Here we describe a method for identifying C4 mutant plants with increased CO2 compensation points. This is used as a signature for decreased photosynthetic efficiency associated with a loss of C4 function. By exposing plants to a CO2 concentration close to the CO2 compensation point of a wild-type plant, individuals can be identified from measurements of chlorophyll a fluorescence. We use this method to screen a mutant population of the C4 monocot Setaria viridis (L.)P.Beauv. generated using N-nitroso-N-methylurea (NMU). Mutants were identified at a frequency of 1 per 157 lines screened. Forty-six candidate lines were identified and one line with a heritable homozygous phenotype selected for further characterisation. The CO2 compensation point of this mutant was increased to a value similar to that of C3 rice. Photosynthesis and growth was significantly reduced under ambient conditions. These data indicate that the screen was capable of identifying mutants with decreased photosynthetic efficiency. Characterisation and next-generation sequencing of all the mutants identified in this screen may lead to the discovery of novel genes underpinning C4 photosynthesis. These can be used to engineer a C4 photosynthetic pathway into rice.

背景与目标： : 为了协助将C4光合作用途径设计成水稻，正使用正向遗传方法来识别调节C4关键性状的基因。当前，一个主要挑战是如何以高通量的方式筛选各种不同的特征。在这里，我们描述了一种识别具有增加的CO2补偿点的C4突变植物的方法。这被用作与C4功能丧失相关的光合作用效率降低的标志。通过将植物暴露于接近野生型植物的CO2补偿点的CO2浓度，可以从叶绿素a荧光的测量中识别出个体。我们使用此方法筛选了使用N-亚硝基-N-甲基脲 (NMU) 产生的C4单子叶狗血虫 (L.)P.Beauv。的突变群体。以每157筛选的品系1的频率鉴定突变体。鉴定了46个候选品系，并选择了1个具有可遗传纯合表型的品系以进行进一步表征。该突变体的CO2补偿点增加到与C3水稻相似的值。在环境条件下，光合作用和生长显着降低。这些数据表明，该筛选能够鉴定光合效率降低的突变体。在此筛选中鉴定的所有突变体的表征和下一代测序可能会导致发现支撑C4光合作用的新基因。这些可用于将C4光合作用途径改造到水稻中。

BACKGROUND & AIMS: :The chlorophyll and carotenoid content, and the spectra of low-temperature fluorescence of the leaves, chloroplasts and isolated pigment-protein complexes in the perennial herbaceous wintergreen plant Ajuga reptans L. (bugle) in different seasons of the year were studied. During winter, these plants downregulate photosynthesis and the PSA is reorganised, including the loss of chlorophyll, possible reductions in the number of functional reaction centres of PSII, and changes in aggregation of the thylakoid protein complexes. We also observed a restructuring of the PSI-PSII megacomplex and the PSII-light-harvesting complex II supercomplex in leaves covered by snow. After snowmelt, the monomeric form of the chl a/b pigment-protein complex associated with PSII (LHCII) and the free pigments were also detected. We expect that snow cover provides favourable conditions for keeping photosynthetic machinery ready for photosynthesis in spring just after snowmelt. During winter, the role of the zeaxanthin-dependent protective mechanism, which is responsible for the dissipation of excess absorbed light energy, is likely to increase.

背景与目标： : 多年生草本冬绿植物Ajuga reptans L中的叶绿素和类胡萝卜素含量，以及叶片，叶绿体和分离的色素-蛋白质复合物的低温荧光光谱。(军号) 在一年中的不同季节进行了研究。在冬季，这些植物下调了光合作用，PSA被重组，包括叶绿素的损失，PSII功能反应中心数量的可能减少以及类囊体蛋白复合物聚集的变化。我们还观察到被雪覆盖的叶子中PSI-PSII巨复合体和PSII-采光复合体II超复合体的重组。融雪后，还检测到与PSII (LHCII) 相关的chl a/b色素-蛋白复合物的单体形式和游离色素。我们希望积雪为在融雪后的春季保持光合作用机械的准备提供有利条件。在冬季，玉米黄质依赖的保护机制的作用可能会增加，该机制负责消耗过多的吸收光能。

BACKGROUND & AIMS: :Near infrared spectroscopy (NIRS) and mid-infrared spectroscopy (MIRS) in combination with chemometric analysis were applied to discriminate the geographical origin of grapevine leaves belonging to the variety "Touriga Nacional" during different vegetative stages. Leaves were collected from plants of two different wine regions in Portugal (Dão and Douro) over the grapes maturation period. A sampling plan was designed in order to obtain the most variability within the vineyards taking into account variables such as: solar exposition, land inclination, altitude and soil properties, essentially. Principal component analysis (PCA) was used to extract relevant information from the spectral data and presented visible cluster trends. Results, both with NIRS and MIRS, demonstrate that it is possible to discriminate between the two geographical origins with an outstanding accuracy. Spectral patterns of grapevine leaves show significant differences during grape maturation period, with a special emphasis between the months of June and September. Additionally, the quantification of total chlorophyll and total polyphenol content from leaves spectra was attempted by both techniques. For this purpose, partial least squares (PLS) regression was employed. PLS models based on NIRS and MIRS, both demonstrate a statistically significant correlation for the total chlorophyll (R2P = 0.92 and R2P = 0.76, respectively). However, the PLS model for the total polyphenols, may only be considered as a screening method, because significant prediction errors, independently of resourcing on NIRS, MIRS or both techniques simultaneously, were obtained.

背景与目标： : 近红外光谱 (NIRS) 和中红外光谱 (MIRS) 与化学计量分析相结合，用于区分不同营养阶段属于 “Touriga Nacional” 品种的葡萄叶的地理来源。在葡萄成熟期，从葡萄牙两个不同葡萄酒产区 (d ã o和Douro) 的植物中收集叶子。设计了一个采样计划，以便在葡萄园内获得最大的可变性，并考虑了诸如以下变量: 太阳暴露，土地倾斜度，海拔和土壤特性。主成分分析 (PCA) 用于从光谱数据中提取相关信息，并呈现可见的聚类趋势。NIRS和MIRS的结果都表明，有可能以出色的准确性区分这两个地理起源。葡萄叶片的光谱模式在葡萄成熟期显示出显着差异，尤其是在6月月份和9月月份之间。此外，两种技术都尝试从叶片光谱中定量总叶绿素和总多酚含量。为此，采用偏最小二乘 (PLS) 回归。基于NIRS和MIRS的PLS模型均显示出总叶绿素的统计学显着相关性 (分别为R2P   =   0.92和R2P   =   0.76)。但是，总多酚的PLS模型只能被认为是一种筛选方法，因为获得了明显的预测误差，而与同时使用NIRS，MIRS或两种技术的资源无关。

BACKGROUND & AIMS: :Thermoluminescence of intact photosynthetic organisms, leaves or algal cells, raises specific problems. The constitutive S2/3Q B (-) B bands constitute major probes of the state of photosystem II in vivo. The presence of a dark-stable acidic lumen causes a temperature downshift of B bands, specially the S3 B band, providing a lumen pH indicator. This is accompanied by a broadening of the S3 B band that becomes an envelope of elementary B bands. The occasional AT, Q and C bands are briefly examined in an in vivo context. It is emphasized that freezing below the nucleation temperature is not necessary for physiological studies, but a source of artefacts, hence should be avoided. In intact photosynthetic structures, a dark-electron transfer from stroma reductants to the quinonic acceptors of photosystem II via the cyclic/chlororespiratory pathways, strongly stimulated by moderate warming, gives rise to the afterglow (AG) luminescence emission that reflects chloroplast energy status. The decomposition of complex TL signals into elementary bands is necessary to determine the maximum temperature T m and the area of each of them. A comparison of TL signals after 1 flash and 2 flashes prevents from confusing the three main bands observed in vivo, i.e. the S2 and S3 B bands and the AG band. Finally, the thermoluminescence bands arising sometimes above 50 °C are mentioned. The basic principles of (thermo)luminescence established on isolated thylakoids should not be applied directly without a careful examination of in vivo conditions.

背景与目标： : 完整的光合生物，叶子或藻类细胞的热发光引起了特定的问题。组成性S2/3Q B (-) B带构成体内光系统II状态的主要探针。暗稳定的酸性腔的存在会导致B带 (特别是S3 B带) 的温度下降，从而提供腔pH指示剂。这伴随着S3 B波段的加宽，成为基本B波段的包络。在体内环境中简要检查了偶尔出现的AT，Q和C带。需要强调的是，对于生理研究而言，冻结在成核温度以下不是必需的，而是伪影的来源，因此应避免。在完整的光合结构中，通过循环/氯呼吸途径从基质还原剂到光系统II的奎尼离子受体的暗电子转移，受到中等温度的强烈刺激，会产生反映叶绿体能量状态的余辉 (AG) 发光发射。必须将复杂的TL信号分解为基本频带，以确定最高温度T m和每个频带的面积。1次闪光和2次闪光后的TL信号的比较防止混淆体内观察到的三个主要带，即S2和S3 B带和AG带。最后，提到了有时在50 °C以上出现的热致发光带。在分离的类囊体上建立的 (热) 发光的基本原理不应在没有仔细检查体内条件的情况下直接应用。

BACKGROUND & AIMS: KEY MESSAGE:RGA/GAI and NAP interacted with each other, and NAP was involved in GA signaling as a role of regulating age-dependent and dark-induced leaf senescence in Arabidopsis. Leaf senescence is a significant biological process which is beneficial for plant growth, development, and generation alternation in Arabidopsis. Recent researches have shown gibberellins (GAs) could accelerate leaf senescence. Nevertheless, the GA signaling involved in leaf senescence process remains elusive. Here, we reported a new potential regulation mechanism of GA-mediated chlorophyll degradation and leaf senescence. In this study, we confirmed that NAP positively regulated age-dependent and dark-induced leaf senescence and NAP knockout mutant nap was hyposensitive to GA3 (an active form of GA) treatment. DELLA family proteins with highly conserved structural domain function as master growth repressors that integrated GA signaling and leaf senescence. We validated RGA and GAI could interact with NAP in vitro and in vivo, and subsequently impaired the transcriptional activities of NAP to induce SAG113 and AAO3 expression in nap protoplasts. Taken together, we suggest that NAP is a novel component of the regulatory network that modulates the progress of leaf senescence in GA signaling.

背景与目标： 关键信息: RGA/GAI和NAP相互作用，NAP作为调节拟南芥年龄依赖性和黑暗诱导的叶片衰老的作用参与GA信号传导。叶片衰老是一个重要的生物学过程，有利于拟南芥植物的生长，发育和世代交替。最近的研究表明，赤霉素 (GAs) 可以加速叶片衰老。尽管如此，叶片衰老过程中涉及的GA信号仍然难以捉摸。在这里，我们报道了GA介导的叶绿素降解和叶片衰老的新的潜在调控机制。在这项研究中，我们证实了NAP正向调节年龄依赖性和黑暗诱导的叶片衰老，并且NAP敲除突变体nap对GA3 (GA的一种活性形式) 处理不敏感。具有高度保守的结构域功能的DELLA家族蛋白作为整合GA信号传导和叶片衰老的主要生长阻遏物。我们验证了RGA和GAI可以在体外和体内与NAP相互作用，随后损害了NAP的转录活性，从而诱导了nap原生质体中SAG113和AAO3的表达。总之，我们建议NAP是调节GA信号中叶片衰老进程的调节网络的新组成部分。

BACKGROUND & AIMS: :As an important agronomic trait, the chlorophyll (Chl) content is closely related to photosynthesis in plants. A rice mutant Gc (Oryza sativa indica) was characterized previously by its enhanced Chl content (Chl b and total Chl) and exaggerated photosynthetic rate. Here, we describe the enhanced Chl content was caused by a mutation in the rice homolog of the DE-ETIOLATED1 (DET1) known to be involved in light transduction and morphogenesis in Arabidopsis and tomato. Sequence analysis revealed that the Gc mutant carried two fragment-insertions and a fragment-deletion upstream of the start codon of OsDET1, which led to enhance mRNA levels of OsDET1. Besides, the Gc mutant harbored a single T-to-C base transversion in the seventh exon of OsDET1, which resulted in leucine(328) to serine(328) localized in the highly conserved region. Genetic complementation demonstrated that OsDET1 mutation conferred the enhanced Chl content in the Gc mutant leaf. OsDET1 was richly expressed in green tissues, and its expression seems to be under circadian control. OsDET1-GFP fusion protein in onion epidermal cells showed that OsDET1 localized to the nucleus. These results indicated that OsDET1 mutation in Gc mutant increases Chl content in rice, which might be fundamental for enhanced photoresponsiveness.

背景与目标： 作为重要的农艺性状，叶绿素 (Chl) 含量与植物的光合作用密切相关。水稻突变体Gc (Oryza sativa indica) 以前的特征是其Chl含量 (Chl b和总Chl) 和光合速率过高。在这里，我们描述了Chl含量的增加是由已知与拟南芥和番茄的光转导和形态发生有关的DE-ETIOLATED1 (DET1) 的水稻同源物突变引起的。序列分析表明，Gc突变体在OsDET1的起始密码子上游携带两个片段插入和一个片段缺失，从而提高了OsDET1的mRNA水平。此外，Gc突变体在OsDET1的第七外显子中具有单个T-C碱基转位，这导致亮氨酸 (328) 到丝氨酸 (328) 位于高度保守的区域。遗传互补表明，OsDET1突变使Gc突变体叶片中的Chl含量增加。OsDET1在绿色组织中表达丰富，其表达似乎处于昼夜节律控制之下。洋葱表皮细胞中的OsDET1-GFP融合蛋白显示OsDET1定位于细胞核。这些结果表明，Gc突变体中的OsDET1突变会增加水稻中的Chl含量，这可能是增强光响应能力的基础。

BACKGROUND & AIMS: :Vegetative buds represent developmental stage of Norway spruce (Picea abies L. Karst.) needles where chloroplast biogenesis and photosynthetic activity begin. We used the analyses of polyphasic chlorophyll a fluorescence rise (OJIP) to compare photosystem II (PSII) functioning in vegetative buds and fully photosynthetically active mature current-year needles. Considerably decreased performance index (PIABS) in vegetative buds compared to needles pointed to their low photosynthetic efficiency. Maximum quantum yield of PSII (Fv/Fm) in buds was slightly decreased but above limited value for functionality indicating that primary photochemistry of PSII is not holdback of vegetative buds photosynthetic activity. The most significant difference observed between investigated developmental stages was accumulation of reduced primary quinine acceptor of PSII (QA-) in vegetative buds, as a result of its limited re-oxidation by passing electrons to secondary quinone acceptor, QB. We suggest that reduced electron transfer from QA- to QB could be the major limiting factor of photosynthesis in vegetative buds.

背景与目标： : 营养芽代表挪威云杉 (Picea abies L. Karst。) 针的发育阶段，叶绿体生物发生和光合活性开始。我们使用多相叶绿素a荧光上升 (OJIP) 的分析来比较光系统II (PSII) 在营养芽和完全光合作用的成熟当年针中的功能。与针叶相比，营养芽的性能指数 (PIABS) 大大降低，这表明它们的光合作用效率低。芽中PSII的最大量子产量 (Fv/Fm) 略有降低，但高于功能的极限值，这表明PSII的主要光化学作用并不抑制营养芽的光合活性。在研究的发育阶段之间观察到的最显着差异是营养芽中PSII (QA-) 的初级奎宁受体的减少积累，这是由于其通过将电子传递给次级醌受体QB而受到限制的再氧化。我们建议减少从QA到QB的电子转移可能是营养芽光合作用的主要限制因素。

BACKGROUND & AIMS: :We report the first direct decomposition of the fluorescence lifetime heterogeneity during multiphasic fluorescence induction in dark-adapted leaves by multi-frequency phase and modulation fluorometry (PMF). A very fast component, assigned to photosystem I (PSI), was found to be constant in lifetime and yield, whereas the two slow components, which are strongly affected by the closure of the reaction centers by light, were assigned to PSII. Based on a modified "reversible radical pair" kinetic model with three compartments, we showed that a loosely connected pigment complex, which is assumed to be the CP47 complex, plays a specific role with respect to the structure and function of the PSII: (i) it explains the heterogeneity of PSII fluorescence lifetime as a compartmentation of excitation energy in the antenna, (ii) it is the site of a conformational change in the first second of illumination, and (iii) it is involved in the mechanisms of nonphotochemical quenching (NPQ). On the basis of the multi-frequency PMF analysis, we reconciled two apparently antagonistic aspects of chlorophyll a fluorescence in vivo: it is heterogeneous with respect to the kinetic structure (several lifetime components) and homogeneous with respect to average quantities (quasi-linear mean tau-Phi relationship).

背景与目标： : 我们报告了通过多频相位和调制荧光法 (PMF) 在暗适应叶片中多相荧光诱导过程中荧光寿命异质性的首次直接分解。发现分配给光系统I (PSI) 的非常快的组件在寿命和产量上是恒定的，而两个慢的组件则被分配给PSII，这两个慢的组件受到光关闭反应中心的强烈影响。基于具有三个区室的改进的 “可逆自由基对” 动力学模型，我们证明了松散连接的颜料复合物 (假定为CP47复合物) 在PSII的结构和功能方面起着特定的作用: (i) 它解释了PSII荧光寿命的异质性作为激发能量在天线中的分隔，(ii) 它是照明的第一秒中构象变化的部位，并且 (iii) 它参与了非光化学猝灭 (NPQ) 的机制。在多频PMF分析的基础上，我们调和了体内叶绿素a荧光的两个明显拮抗方面: 它在动力学结构 (几个寿命分量) 方面是异质的，而在平均量方面是均匀的 (准线性平均tau-Phi关系)。

BACKGROUND & AIMS: :Effects of artemisinin (derived from Artemisia annua) on the photosynthetic activity of Microcystis aeruginosa was investigated by using chlorophyll a (Chl a) fluorescence transient O-J-I-P and JIP-test after exposure to elevated artemisinin concentration. High artemisinin concentration resulted in a significant suppression in photosynthesis and respiration. Results showed that the OJIP curves flattened and the maximal fluorescence yield reached at the J step under artemisinin stress. The decreased values of the energy needed for the RCs' closure (Sm) and the number of oxidation and reduction (N) suggested that the reduction times of primary bound plastoquinone (Q(A)) was also decreased. The absorption flux (ABS/RC) per photosystem II (PSII) reaction center and the electron transport flux (ET(0)/RC) decreased with increasing artemisinin concentration. Excess artemisinin had little effect on the trapping flux (TR(0)/RC). The results showed that the decrease of photosynthesis in exposure to excess artemisinin may be a result of the inactivation of PSII reaction centers and the inhibition of electron transport in the acceptor side.

背景与目标： : 采用叶绿素a (Chl a) 荧光瞬变O-J-I-P和JIP-试验，研究了青蒿素 (黄花蒿) 对铜绿微囊藻光合活性的影响。青蒿素浓度高导致光合作用和呼吸作用的显着抑制。结果表明，在青蒿素胁迫下，OJIP曲线变平，在J步达到最大荧光产率。RCs' 闭合 (Sm) 所需的能量值以及氧化和还原次数 (N) 的降低表明，伯结合的质体醌 (Q(A)) 的还原时间也降低了。随着青蒿素浓度的增加，每个光系统II (PSII) 反应中心的吸收通量 (ABS/RC) 和电子传输通量 (ET(0)/RC) 降低。过量青蒿素对捕集通量 (TR(0)/RC) 影响不大。结果表明，暴露于过量青蒿素的光合作用降低可能是PSII反应中心失活和受体侧电子传输受到抑制的结果。

BACKGROUND & AIMS: :Salinity is one of the major stresses that limits crop production worldwide and affects most physiological activities in plants. In order to study the genetic control of salt stress in the model legume Medicago truncatula Gaertn., an experiment was undertaken to determine the genetic variability and to identify quantitative trait loci (QTLs) controlling several traits related to plant growth and physiology in a population of recombinant inbred lines. Shoot and root DW, relative water content, leaf area, chlorophyll content, chlorophyll fluorescence parameters, and Na+ and K+ in shoots and roots were measured. The experiment was carried out with three replications. ANOVA showed a large genetic variation and transgressive segregation for the traits studied, suggesting putative complex tolerance mechanisms. A total of 21 QTLs were detected under control conditions and 19 QTLs were identified under 100mm salt stress conditions, with three QTLs being common to both situations. The percentage of total phenotypic variance explained by the QTLs ranged from 4.6% to 23.01%. Overlapping QTLs for different traits were also observed, which enables us to discriminate independent traits from linked ones. The results should be helpful information for further functional analysis of salt tolerance in M. truncatula.

背景与目标： : 盐度是限制世界范围内作物产量并影响植物大部分生理活动的主要压力之一。为了研究豆科植物模型中盐胁迫的遗传控制，进行了一项实验，以确定遗传变异性并确定控制与植物生长和生理有关的几个性状的数量性状基因座 (qtl)。重组自交系。测量了芽和根的DW，相对含水量，叶面积，叶绿素含量，叶绿素荧光参数以及芽和根中的Na和K。实验进行了三次重复。方差分析显示所研究性状具有较大的遗传变异和海侵分离，表明假定的复杂耐受机制。在对照条件下共检测到21个qtl，在100毫米盐胁迫条件下鉴定出19个qtl，这两种情况共有三个qtl。由qtl解释的总表型方差的百分比范围为4.6% 至23.01%。还观察到不同性状的重叠qtl，这使我们能够将独立性状与相关性状区分开。该结果对于进一步分析M. truncatula的耐盐性应该是有用的信息。

BACKGROUND & AIMS: Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

背景与目标： 叶绿素荧光的测量已被证明是一种快速，无创且可靠的方法，可评估不断变化的环境中的光合作用。在这项研究中，在细胞暴露于过量Hg (最高20微米) 2小时后，通过叶绿素荧光分析研究了过量Hg对蓝藻S. platensis光合性能的急性毒性。从快速荧光动力学确定的结果表明，Hg诱导Q(B) 非还原性PSII反应中心的比例显着增加。在光合作用稳态下测得的荧光参数表明，Hg浓度的增加导致PSII光化学的最大效率，开放的PSII反应中心捕获激发能量的效率以及PSII电子传输的量子产率降低。汞还导致光化学和非光化学猝灭系数降低。汞可能通过敏感，快速地抑制光合作用的量子产量而对蓝细菌产生急性毒性。这种变化发生在可以通过其他常规测量评估的任何其他可见损伤之前。我们的结果还表明，叶绿素荧光分析可以用作评估藻类对重金属污染的光合性能变化的早期阶段的有用生理工具。

BACKGROUND & AIMS: :Chlorophyll is a deleterious molecule that generates reactive oxygen species and must be converted to nontoxic molecules during plant senescence. The degradation pathway of chlorophyll a has been determined; however, that of chlorophyll b is poorly understood, and multiple pathways of chlorophyll b degradation have been proposed. In this study, we found that chlorophyll b is degraded by a single pathway, and elucidated the importance of this pathway in avoiding cell death. In order to determine the chlorophyll degradation pathway, we first examined the substrate specificity of 7-hydroxymethyl chlorophyll a reductase. 7-hydroxymethyl chlorophyll a reductase reduces 7-hydroxymethyl chlorophyll a but not 7-hydroxymethyl pheophytin a or 7-hydroxymethyl pheophorbide a. These results indicate that the first step of chlorophyll b degradation is its conversion to 7-hydroxymethyl chlorophyll a by chlorophyll b reductase, although chlorophyll b reductase has broad substrate specificity. In vitro experiments showed that chlorophyll b reductase converted all of the chlorophyll b in the light-harvesting chlorophyll a/b protein complex to 7-hydroxymethyl chlorophyll a, but did not completely convert chlorophyll b in the core antenna complexes. When plants whose core antennae contained chlorophyll b were incubated in the dark, chlorophyll b was not properly degraded, and the accumulation of 7-hydroxymethyl pheophorbide a and pheophorbide b resulted in cell death. This result indicates that chlorophyll b is not properly degraded when it exists in core antenna complexes. Based on these results, we discuss the importance of the proper degradation of chlorophyll b.

背景与目标： : 叶绿素是一种有害分子，会产生活性氧，在植物衰老过程中必须转化为无毒分子。已经确定了叶绿素a的降解途径; 然而，对叶绿素b的了解甚少，并且已经提出了叶绿素b降解的多种途径。在这项研究中，我们发现叶绿素b被一条途径降解，并阐明了该途径在避免细胞死亡中的重要性。为了确定叶绿素降解途径，我们首先检查了7-羟甲基叶绿素a还原酶的底物特异性。7-羟甲基叶绿素a还原酶还原7-羟甲基叶绿素a，但不还原7-羟甲基phophytin a或7-羟甲基phophorebide a。这些结果表明，叶绿素b降解的第一步是通过叶绿素b还原酶将其转化为7-羟甲基叶绿素a，尽管叶绿素b还原酶具有广泛的底物特异性。体外实验表明，叶绿素b还原酶将采光叶绿素a/b蛋白复合物中的所有叶绿素b转化为7-羟甲基叶绿素a，但并未完全转化核心天线复合物中的叶绿素b。当将核心触角包含叶绿素b的植物在黑暗中孵育时，叶绿素b没有被适当降解，并且7-羟甲基phophorbide a和phophorbide b的积累导致细胞死亡。该结果表明，当叶绿素b存在于核心天线复合体中时，其降解不正确。基于这些结果，我们讨论了适当降解叶绿素b的重要性。