Monitoring moderate Cu and Cd toxicity by chlorophyll fluorescence and P700 absorbance in pea leaves

We investigated the effect of moderate Cu²⁺ and Cd²⁺ stress by applying chlorophyll (Chl) fluorescence and P₇₀₀ absorbance measurements to monitor the photosynthetic electron transport activity of 3-week-old Pisum sativum L. cv. Petit Proven?al plants grown in a modified Hoagland solution containing 50 ??M CuSO₄ or 5 ??M CdCl₂. Both heavy metals caused a slight inhibition in PSII photochemistry as indicated by the decrease in the effective quantum efficiency of PSII (??_PSII), the maximum electron transport capacity (ETR_max), and the maximum quantum yield for electron transport (??). PSI photochemistry was also affected by these heavy metals. Cu²⁺ and Cd²⁺ decreased the quantum efficiency of PSI (??_PSI) as well as the number of electrons in the intersystem chain, and the Cu²⁺ treatment significantly reduced the number of electrons from stromal donors available for PSI. These results indicate that PSII and PSI photochemistry of pea plants are both sensitive to moderate Cu²⁺ and Cd²⁺ stress, which in turn is easily detected and monitored by Chl fluorescence and P₇₀₀ absorbance measurements. Therefore, monitoring the photochemistry of pea plants with these noninvasive, yet sensitive techniques offers a promising strategy to study heavy metal toxicity in the environment.     

Simultaneous estimation of chlorophyll a and lipid contents in microalgae by three-color analysis

A method of rapid determination of chlorophyll a and lipid contents of microalgae based on colorimetric analysis of the digital images of the microalgae is proposed. The color variation of microalgae during cultivation is evaluated by the brightness of the three primary colors (red, green, and blue). The brightness values of the three primary colors are modeled as two linear correlation functions (RGB model) for microalgal chlorophyll a and lipid contents, respectively. The chlorophyll a and lipid contents predicted by the proposed model are compared with that determined by the standard methods. The good agreement of the model predictions with experimental results is demonstrated with a squared correlation coefficient (R(2)) of 0.99 for chlorophyll a and lipid. The reliability of the RGB model was verified in real cultivations of the microalgae in a photobioreactor. Growth dynamics, contents of chlorophyll a and lipid corresponded very well with previously reported studies.     

典型城区与郊区环境大叶黄杨气体交换及叶绿素荧光特性比较

采用Li-6400便携式光合作用测定系统对夏秋季典型城区与郊区环境下大叶黄杨的气体交换和叶绿素荧光特性进行了现场实验比较研究.研究显示,叶片净光合速率的大小由总光合速率(光合能力)和呼吸速率共同决定,城区环境温度较高、相对湿度较低、大气CO2浓度较高, 不同月份城区和郊区样点大叶黄杨的净光合速率差异显著性存在不同.城区环境下大叶黄杨的胞间CO2浓度、叶面水气压亏缺、蒸腾速率高于郊区环境.城区环境中温度、大气CO2浓度等的变化会影响叶片呼吸作用,造成呼吸速率升高或是降低,城区环境中污染物浓度变化也会损伤叶片光合结构从而导致总光合能力降低,这两者都会引起净光合速率的变化.通过大叶黄杨叶片叶绿素荧光指标的进一步对比分析发现,城区大叶黄杨叶片叶绿素总量、叶绿素a/b、Fv/Fm、Fv/Fo、qP、ΦPSⅡ、ETR降低,但qN升高.表明叶片叶绿体PSⅡ的功能受到负面影响.城区大叶黄杨叶片荧光参数的变化,从微观机制上表明城区环境中污染物浓度的上升导致叶绿素及叶绿体光合结构受损的确是叶片光合能力下降的主要原因之一.     

The chlorophyll fluorescence quenching and changes of absorbance in pea chloroplasts

Chlorophyll (Chl) fluorescence quenching parameters were measured in dark-adapted pea leaves and chloroplasts with the purpose to find the conditions of high and low non-photochemical quenching, that would be stable during a prolonged irradiation. A PAM fluorometer was used for measuring induction curves in the range of actinic radiation of 3-35 W m-2, with an ordinary value of about 15 W m-2. The effects of various mediators, i.e., ascorbate, methyl viologen (MV), dithiothreitol (DTT) and nigericin, on the quenching process were tested. Simultaneously, the absorbance was measured during a 15-20 min period of irradiation and after the actinic radiation was turned off, i.e., in the recovery period. The pH values of chloroplast suspensions were 5.5, 6.5 and 8.0, the largest non-photochemical quenching was observed at pH of 6.5. The irradiation of chloroplasts led to an absorption decrease within the entire photosynthetically active range, attaining saturation when the fluorescence reached Fs level, and to an absorption increase during the recovery period. Absorbance changes at the maximum of red band were 10-20 %. A decrease in Chl concentration (10 %) after irradiation was found only at pH of 5.5, when the recovery time was the longest, i.e., about 60 min. This revised version was published online in June 2006 with corrections to the Cover Date.     

渗透胁迫对绿豆叶圆片叶绿素荧光的影响

绿豆叶圆片用0、-0．3、-0．6、-1．2、-1．8、-2．4MPa等6个渗透梯度处理24h后,其叶绿素荧光的反应表明：光系统Ⅱ的潜在量子产量(FD／Fm)和电子传递受体(QA)的库容(pool size)均随胁迫强度的增大而减小,但QA库容的下降明显比Fg／Fm的下降缓和。结合原初荧光Fo和最大荧光Fm的变化,分析认为本实验中渗透胁迫并未导致明显的光系统Ⅱ反应中心的失活或破坏。造成光系统Ⅱ潜在量子效率降低的原因主要是通过光系统Ⅱ反应中心到Ⅱ的电子传递受到阻抑。     

Benthic microalgae: comparisons of chlorophyll a in mesocosms and field sites

A mesocosm facility is being developed by the CSIRO Division of Fisheries to study the movement, fate and impact of pollutants in coastal marine environments. Initially, we are studying coastal habitats in S.W Australia that are subject to wave action. A 12 week experiment assessed changes in biotic and abiotic components of sediment brought from the field into mesocosms. In these sediments, benthic microalgae are the major primary producers. Microalgal standing stocks were measured as the concentration of chlorophyll a and phaeopigments in the top 2 cm of sediment, and these measures were compared among mesocosms and field sites. Significant increases in chlorophyll a and phaeopigments, increased numbers of species and a shift from episammic to periphytic diatoms were observed, possibly caused by decreased water motion in mesocosms or other containment effects. Results from statistical power analyses suggested that our sampling was sufficiently well replicated and successfully incorporated variation at small spatial and temporal scales. Sampling effort used in this experiment should form the basis for future work with benthic microalgae.     

The influence of chlorophyll fluorescence on the light gradients and the phytochrome state in a green model leaf under natural conditions

Abstract. The effect of chlorophyll fluoresence on the spectral light gradients within a model green leaf was examined under different light qualities (day-light, sunset, canopy) and different quantum efficiencies. Light fluxes within the leaf tissue are nearly doubled in the emission domain of fluorescence but the effect on the phytochrome photoequilibrium is very small.     

微藻胞间植物激素甄别方法与研究进展

植物激素是一类微量的内源化合物,可能是微藻生命活动过程中的通用"语言".植物激素甄别是认知微藻群体感应和胞间通讯机制的关键.然而,由于植物激素具有超微量、性质复杂和干扰物质共存的特点,选择适宜的提取浓缩方法、提高检测灵敏度、减小基质效应和区分同分异构体仍是甄别植物激素的难点问题.本文综述了植物激素提取与检测的研究现状,...     

Comparison of chlorophyll fluorescence emission characteristics of wheat leaf tissue and isolated thylakoids as a function of excitation wavelength

Abstract. Chlorophyll fluorescence emission spectra and the kinetics of 685 mm fluorescence emission from wheat leaf tissue and thylakoids isolated from such tissue were examined as a function of excitation wavelength. A considerable enhancement of fluorescence emission above 700 nm relative to that at 685 nm was observed from leaf tissue when it was excited with 550 nm rather than 450 nm radiation. Such excitation wavelength dependent changes in the emission spectrum occurred over an excitation spectral range of 440–660 nm and appeared to be directly related to the total quantity of radiation absorbed at a given excitation wavelength. Experiments with isolated thylakoid preparations demonstrated that changes in the fluorescence emission spectrum of the leaf were attributable to the optical properties of the leaf and were not due to the intrinsic characteristies of the thylakoid photochemical apparatus. This was not the case for the observed excitation wavelength dependent changes in the 685 nm fluorescence induction curve obtained from leaf tissue infiltrated with DCMU. Excitation wavelength dependent changes in the ratio of the variable to maximal fluorescence emission and the shape of the variable fluorescence induction were observed for leaf tissue. Isolated thylakoid studies showed that such changes in the leaf fluorescence kinetics were representative of the way in which the photochemical apparatus in vivo was processing the absorbed radiation at the different excitation wavelengths. The results are considered in the context of the use of fluorescence emission characteristics of leaves as non-destructive probes of the photochemical apparatus in vivo.     

The effect of phenols on the parameters of chlorophyll fluorescence and reactions of P700 in green algae Scenedesmus quadricauda

The effect of phenolics, present in wastes of pulp and paper industry, on photosynthesis in microalgae Scenedesmus quadricauda has been studied, analyzing the induction curves of prompt and delayed chlorophyll fluorescence and light curves of nonphotochemical quenching of fluorescence. Energization of photosynthetic membranes was impaired at low concentrations (0.1 mM) of phenol and pyrocatechol. At higher concentrations, phenol and pyrocatechol inhibited electron transport in PS II and increased the share of Q_B-nonreducing centers. As a result, the rate of P₇₀₀ reduction declined. These results indicate that the parameters of fluorescence induction curves can be used for detecting phenol and pyrocatechol in the environment at early stages of toxic effects.     

Effect of silver nanoparticles on the parameters of chlorophyll fluorescence and P700 reaction in the green alga Chlamydomonas reinhardtii

Acute toxicity of silver nanoparticle (AgNP) for photosynthesis in Chlamydomonas reinhardtii was studied using an M-PEA2 fluorimeter. Analysis of the fluorescence induction curves in the presence of AgNP at low concentrations revealed inhibited electron transport on the PS2 photosystem and increased content of Q_B-nonreducing centers. No direct effect of AgNP on the reactions of P₇₀₀ oxidation in PS1 was found, while the energization of the photosynthetic membranes was affected. Investigation of the parameters of the prompt and delayed fluorescence is proposed as a method for early detection of AgNP in the environment.     

Age-dependent response of maize leaf segments to cadmium treatment: effect on chlorophyll fluorescence and phytochelatin accumulation

The relationship between the age of leaf tissue and response of the photosynthetic apparatus and phytochelatin accumulation to Cd treatment was studied. Studies were carried out with seedlings of Zea mays L. cv. Hidosil grown in the presence of 100-200 mumol/L Cd for 14 days under low light conditions. The third leaf was divided into 3 segments of equal length differing in the stage of tissue maturity and used for measurements of chlorophyll content, chlorophyll fluorescence, glutathione and phytochelatin content and Cd accumulation. A close relationship between the age of leaf tissue and response of the photosynthetic apparatus to Cd was shown. Cadmium (200 mumol/L) reduced photochemical processes more in older than younger leaf segments as seen in the Chl fluorescence parameters Fv/F0, and t1/2, while the chlorophyll fluorescence decrease ratio (Rfd) was inhibited more strongly in younger ones. Fv/Fm was slightly affected. Cd-induced enhancement of GSH content was correlated with higher phytochelatin accumulation to a greater extent in younger than in older leaf segments. Phytochelatin level corresponded to changes of photochemical processes in older leaves. The peptide thiol:Cd molar ratio for the phytochelatins varied depending on Cd concentration and age of leaf segments. The protective role of phytochelatins for the photosynthetic apparatus is discussed.     

中国桑寄生科植物叶表皮微形态

通过扫描电镜对中国桑寄生科桑寄生亚科8属18种和槲寄生亚科1属2种植物成熟叶的上、下叶表皮内表面和下表皮外表面进行了研究。内面观发现桑寄生科植物叶上、下表皮形状为多边形,垂周壁式样平直或稍弓形,常具有角质增厚,平周壁常覆盖厚角质或颗粒状、丝状角质增厚;气孔存在于上下表皮,通常下表皮较多,气孔的形状,特别是保卫细胞的形态在亚科间、属间或种间都具有一定的差异,气孔器类型为平列型或单圈型。下表皮表面观察了的角质膜和蜡质纹饰、气孔的形状,外部气孔缘及外部气孔缘内缘的特征。这些特征在亚科或属级水平上较为稳定,有的也表现出种间差异,有一定的分类价值。从气孔形态和外部气孔周围角质膜来看,两亚科显示出明显的不同:桑寄生亚科上、下表皮均具有内部气孔缘,而槲寄生亚科没有此结构;桑寄生亚科外部气孔周围角质膜增厚成环状,其上具增厚的条纹,而槲寄生亚科外部气孔周围角质膜增厚成脊状,不具条纹。这些特征支持槲寄生亚科作为独立1个科来处理。     

MODIS植被指数与水稻叶面积指数及叶片叶绿素含量相关性研究

利用光谱分辨率为3nm的ASD FieldSpec UV／VNIR光谱仪获得了2002和2003年水稻整个生长期的高光谱数据,同时对水稻叶面积指数(LAI)和叶绿素含量(CHL．Ｃ)进行了测定,对中分辨率成像光谱仪(MODIS)的增强植被指数(EVI)、归一化植被指数(NＤVI)以及红边位置(REP)与LAI及CHL．C之间的关系进行了研究．结果表明。LAI与冠层光谱在可见光、近红外波段相关性较好,叶绿素含量与冠层光谱在红光波段相关性较好．EVI、REP和LAI之间的相关关系不受水稻覆盖率的影响;NDVI与LAI的相关关系在水稻低覆盖率情况下较好;在水稻高覆盖率情况下。EVI和REP比NDVI与LAI之间的相关关系要好．MODIS-NDVI、EVI及REP与叶片叶绿素含量相关性较好．由此可见,EVI和REP可以有效地监测水稻LAI和CHL．C．     

Association of specific leaf weight, an estimate of chlorophyll, and chlorophyll concentration with apparent photosynthesis in soybean

Increasing specific leaf weight (SLW) may improve leaf apparent photosynthesis (AP) in soybean [Glycine max (L.) Merr.] but screening for SLW and AP is laborious. The Objectives of this study were (i) to determine the time course of SLW and chlorophyll concentration in experimental lines selected for differences in SLW and (ii) to evaluate the potential use of the Minolta 502 SPAD meter as a rapid estimator of SLW, AP and chlorophyll concentration in leaves of soybean. In 1991 and 1992, sixteen experimental lines representing extremes in SLW were grown at Urbana, IL, and West Lafayette, IN, with three replications at each location. SPAD values, SLW and AP were measured at the R2 (full flower), R4 (full pod) and R5 (beginning seed) growth stages. In 1992 SLW, SPAD values and chlorophyll concentration were measured weekly. Seasonal patterns of SPAD values, SLW, and chlorophyll concentration were very similar through R5. After R5, SLW continued to increase but SPAD values and chlorophyll concentration declined. SPAD values and SLW were highly correlated at the R2, R4 and R5 stages at both locations and in both years. Environmental conditions during this research were not suitable for maximum AP expression, which is likely why AP and SPAD values were correlated only at the R4 growth stage at Urbana in 1992. SPAD measurements were consistent across diverse environments and effectively separated the high SLW lines from the low SLW lines. Measuring with the Minolta 502 SPAD meter is rapid, simple and non-destructive and could be an alternative method for direct selection for SLW.Abbreviations AP- leaf apparent photosynthesis - CV- coefficient of variation - Rug- leaf rugosity - SLW- specific leaf weight - SPAD-L- SPAD value of the most recently expanded terminal leaflet - SPAD-P- SPAD value of leaflet used to measure AP - SPAD-S- SPAD value of leaflets used to measure SLW - SPAD-U- SPAD value of the terminal leaflet one node above the most recently expanded terminal leaflet The US Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged     

Interactions and competition processes among tree species in young experimental mixed forests,assessed with chlorophyll fluorescence and leaf morphology

Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kaltenborn, Germany, and Satakunta, Finland) within a forest diversity experiment. Trees at Satakunta, planted in 1999, form a stratified canopy, while in Kaltenborn the trees are 7 years old, with no apparent canopy connection among broadleaf species. The following ChlF parameters from measured OJIP transient curves were examined: F_V/F_M (a proxy for maximum quantum yield); Ψ_Eo (a proxy for efficiency in transferring an electron from reduced QA to the electron transport chain); I‐P phase (a proxy for efficiency of reducing final acceptors beyond PSI); and PI_tot (total performance index for potential energy conservation from photons absorbed by PSII to reduction of PSI end acceptors). At Satakunta F_V/F_M and Ψ_Eo in Betula pendula were higher in monocultures and lower in mixed plots, perhaps due to increasing light availability in mixed plots, which can induce photoinhibition. The opposite trend was observed in Picea abies, which was shaded in mixed plots. At Kaltenborn F_V/F_M decreased in Fagus sylvatica and P. abies in mixed plots due to competition both above‐ and belowground. At Satakunta LMA increased in B. pendula leaves with increasing species richness. Leaf area of ten leaves was reduced in F. sylvatica in mixed plots at Kaltenborn. By up‐scaling the overall fluorescence response to plot level (PI_{tot_plot}), a significant positive correlation with tree diversity was found at Kaltenborn, but not at Satakunta. This could suggest that competition/facilitation processes in mixed stands play a significant role in the early stages of forest establishment, but then tend to be compensated in more mature stands.     

三种相思人工林和木荷林凋落叶分解的动态分析

对3种相思（Acacia Mill．）人工林和木荷（Schima superba Gardn．et．Champ．）林凋落叶的分解速率及磷和钾的动态变化进行了研究。结果表明,在分解过程中,卷荚相思（A．cincinnata F．Muell．）林、黑木相思（A．melanoxylon R．Br．）林、马占相思（A．magium Willd．）林和木荷林凋落叶干质量残留率分别为24．37％、13．51％、12．49％和41．86％,其中马占相思林的年分解系数最大,木荷林最小。凋落叶的磷含量大多呈上升趋势,其中黑木相思林和马占相思林表现为磷的净释放;卷荚相思林则在分解过程的前180d内表现为净固持,180d后表现为净释放;木荷林基本表现为磷的净固持。凋落叶的钾含量均为单调下降,且各林分均呈现出钾的净释放,分解末期各林分的钾释放率达90．14％～98．72％。与木荷林相比,3种相思人工林对土壤养分含量,特别是磷含量的维持非常有益。     

Clonal analysis of the development of the barley (Hordeum vulgare L.) leaf using periclinal chlorophyll chimeras

Barley seedlings that show mosaic expression of chlorophyll were selected from the progenies of mutagenized seeds. The sectored plants were grown under conditions that lead to the formation of lateral tillers, and a fraction of these had different kinds of leaf variegation. These sectorially and periclinally chimeric shoots were used to analyze the cellular organization of the barley shoot apex and the clonal development of the leaf. The shoot apex is organized in two cell lineages, L1 and L2. As well as giving rise to the epidermis, the L1 layer contributes to leaf mesophyll, particularly at the margins, but, on the adaxial side of leaf laminae, also in more central positions. The L1 layer alone is responsible for the formation of the hood, a flower homologue structure present in strains homozygoous for the dominant allele at the K (hooded ) locus. The relative contribution of L2 to leaf formation decreases in younger tillers and during tiller development from the basal to the flag leaf. Chimerism of the plants was generated by non-transmissible somatic events or by nuclear mutations. Received: 28 May 1998 / Accepted: 20 July 1998