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Chlorophyll a fluorescence and ultrastructural changes in chloroplast of water hyacinth as indicators of environmental stress

LAGE-PINTO, Frederico; OLIVEIRA, Jurandi G.; CUNHA, Maura Da; SOUZA, Cristina M. M.; REZENDE, Carlos E.; AZEVEDO, Ricardo A.; VITORIA, Angela P.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
75.74%
Chlorophyll a fluorescence parameters and transmission electron microscopy (TEM) were used to assess the stress conditions in water hyacinth along the Paraiba do Sul River (PSR), an important River in southeastern Brazil. The data were obtained at the end of the dry season of 2005 and at the end of the wet season of 2006. Changes in F-o and F-m parameters were observed as differentiated responses, depending on the season. Non-photochemical dissipation (qN and NPQ) from plants was greater in the most industrialized region of the PSR in both seasons. However, F-v/F-m for all samples ranged between 0.77 and 0.81, showing that high maximum quantum yield was maintained. Although the F-v/F-m suggests that the plants were exhibiting normal photochemical activities, ultrastructural changes in chloroplasts showed thylakoids disorganization. Plants from the most industrialized region showed non-stacking grana thylakoids disposition. In spite of these alterations, the membrane integrity was maintained, suggesting an adaptation to adjustment to adverse environmental conditions. (C) 2008 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2004/15012-5]; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[471091/2004-9]; Universidade Estadual do Norte Fluminense

Alterations in chlorophyll a fluorescence, pigment concentrations and lipid peroxidation to chilling temperature in coffee seedlings

Oliveira, Jurandi Gonçalves de; Aguiar Alves, Pedro Luís da Costa; Vitória, Angela Pierre
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 71-76
ENG
Relevância na Pesquisa
95.97%
Coffea arabica L. is considered to be sensitive to low temperatures throughout its life cycle. In some Brazilian regions, seedling production occurs under shade conditions and during the winter, with average temperatures of around 10 °C. The formation and functioning of the photosynthetic apparatus are strongly controlled by temperature. This study aimed to assess the changes that occurred in pigment contents, lipid peroxidation and variables of chlorophyll a fluorescence during the greening process of coffee seedlings submitted to chilling. Results indicate that saturation of the photosynthetic activity of coffee seedlings occurred before saturation of the accumulation of chloroplastid pigments. Pigment accumulation during the greening process is far beyond the metabolic needs for the maintenance of photosynthetic activity, more specifically of photosystem II. Coffee seedlings attained a quantum yield equivalent to that of the control with approximately half the chlorophyll a and b contents and around 40% of the carotenoid. Low temperature decreases the metabolism of seedlings, consequently reducing free radical production and lipid peroxidation. The chilling temperature (10 °C) used inhibited the accumulation of chloroplast pigments...

Use of Physiological Parameters in Screening Drought Tolerance in Sugarcane Genotypes

de Almeida Silva, Marcelo; Jifon, John L.; Sharma, Vivek; da Silva, Jorge A.G.; Caputo, Marina M.; Damaj, Mona B.; Guimarães, Eduardo R.; Ferro, Maria I.T.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 191-197
ENG
Relevância na Pesquisa
75.8%
The physiological response of four commercial sugarcane genotypes to water stress was evaluated by measuring the photochemical efficiency of the photosystem II (chlorophyll a fluorescence ratio, F v/F m), estimated chlorophyll content (SPAD unit), leaf temperature (LT) and leaf relative water content (RWC). A field trial was established in the subtropical area with well-watered and water-stressed genotypes, in completely randomized blocks with four replicates in a 4 × 2 × 3 factorial design (genotype × irrigation × evaluation date). Physiological measurements were done during a 90 day-period of formative stage of plants. The analysis of variance showed that the interaction of genotype × irrigation × evaluation date had a significant effect for three physiological markers tested, F v/F m, SPAD unit and RWC. Under non-stressed conditions, all genotypes showed similar responses for the four markers. Under water deficiency stress, two drought-tolerant genotypes, HOCP01-523 and TCP89-3505 displayed higher values for F v/F m, SPAD unit and RWC, and lower values for LT, and could be classified as tolerant. It is therefore possible to use these physiological water stress associated traits as scorable marker traits for selecting drought-tolerant sugarcane genotypes in future breeding programs. © 2011 Society for Sugar Research & Promotion.

Chlorophyll a spatial inference using artificial neural network from multispectral images and in situ measurements

Ferreira, Monique S.; Galo, Maria de Lourdes B.T.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 519-532
ENG
Relevância na Pesquisa
75.78%
Considering the importance of monitoring the water quality parameters, remote sensing is a practicable alternative to limnological variables detection, which interacts with electromagnetic radiation, called optically active components (OAC). Among these, the phytoplankton pigment chlorophyll a is the most representative pigment of photosynthetic activity in all classes of algae. In this sense, this work aims to develop a method of spatial inference of chlorophyll a concentration using Artificial Neural Networks (ANN). To achieve this purpose, a multispectral image and fluorometric measurements were used as input data. The multispectral image was processed and the net training and validation dataset were carefully chosen. From this, the neural net architecture and its parameters were defined to model the variable of interest. In the end of training phase, the trained network was applied to the image and a qualitative analysis was done. Thus, it was noticed that the integration of fluorometric and multispectral data provided good results in the chlorophyll a inference, when combined in a structure of artificial neural networks.

Chlorophyll a fluorescence in rice plants exposed of herbicides of group imidazolinone

Sousa,C.P.; Pinto,J.J.O.; Martinazzo,E.G.; Perboni,A.T.; Farias,M.E.; Bacarin,M.A.
Fonte: Sociedade Brasileira da Ciência das Plantas Daninhas Publicador: Sociedade Brasileira da Ciência das Plantas Daninhas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
75.85%
The objective of this work was to investigate the injuries caused to the photosynthetic apparatus of three types of rice exposed to application of imidazolinone group herbicides. Two experiments were conducted using herbicides Imazethapyr+imazapic and Imazapyr+imazapic, in a split-plot experimental design, and a 3 x 3 factorial, with six replications. The first factor (A) consisted of the herbicide rates 0, 100 e 200 g ha-1 of Imazethapyr+imazapic and 0, 140 e 280 g ha-1 of Imazapyr+imazapic; factor B consisted of type of rice (cv. Puitá Inta CL, sensitive red rice ecotype and red rice ecotype with suspected herbicide tolerance to Imidazolinone). Chlorophyll a fluorescence parameters were evaluated in plants at 30 days after herbicide application, using a portable fluorometer (HandyPEA, Hanstech). The photosynthetic metabolism of cv. Puitá Inta CL was found to tolerate commercial dosages of both herbicides. High sensitivity to the herbicides was observed for the sensitive red rice ecotype, while the photosynthetic apparatus of red rice ecotype with suspected herbicide tolerance showed high tolerance to both herbicides applied at rates higher than the commercial rate. The application of chemical herbicides of the imidazolinone group on rice plants causes changes in the photosynthetic metabolism of plants...

Leaf water potential, gas exchange and chlorophyll a fluorescence in acariquara seedlings (Minquartia guianensis Aubl.) under water stress and recovery

Liberato,Maria Astrid Rocha; Gonçalves,José Francisco de Carvalho; Chevreuil,Larissa Ramos; Nina Junior,Adamir da Rocha; Fernandes,Andreia Varmes; Santos Junior,Ulysses Moreira dos
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
Relevância na Pesquisa
95.85%
The physiological performance of acariquara (Minquartia guianensis) seedlings submitted to water deficit and the recovery of physiological parameters during rehydration were investigated in a greenhouse experiment. The analyzed parameters were: leaf water potential, gas exchange and chlorophyll a fluorescence. After thirty-five days, non-irrigated plants exhibited a leaf water potential 70 % lower compared to control plants (irrigated daily) and the stomatal conductance reached values close to zero, inducing a severe decrease in gas exchange (photosynthesis and transpiration). Six days after the beginning of the rehydration of drought-stressed plants, the results demonstrated that water stress did not irreversibly affect gas exchange and quantum efficiency of photosystem II (PSII) in M. guianensis seedlings, since four to six days after rehydration the plants exhibited total recovery of the photosynthetic apparatus. We conclude that M. guianensis presented good tolerance to water stress and good capacity to recover the physiological performance related to leaf water status, photosynthesis and photochemical efficiency of PS II under hydric stress, suggesting substantial physiological plasticity during the juvenile phase for this tree species.

Use of physiological parameters as fast tools to screen for drought tolerance in sugarcane

Silva,Marcelo de A.; Jifon,John L.; Silva,Jorge A.G. da; Sharma,Vivek
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2007 EN
Relevância na Pesquisa
75.81%
Drought is one of the major limitations to plant productivity worldwide. Identifying suitable screening tools and quantifiable traits would facilitate the crop improvement process for drought tolerance. In the present study, we evaluated the ability of four relatively physiological parameters (variable-to-maximum chlorophyll a fluorescence ratio, F v/F m; estimated leaf chlorophyll content via SPAD index; leaf temperature, LT; and, leaf relative water content, RWC) to distinguish between drought tolerant and susceptible sugarcane genotypes subjected to a 90-d drought cycle. Eight field-grown genotypes were studied. By 45 d after the onset of treatments, the F v/F m, SPAD index and RWC of drought-stressed plants had declined significantly in all genotypes compared to values at the onset of well-watered treatments. However, the reductions were more severe in leaves of susceptible genotypes. Under drought stress, the tolerant genotypes as a group, maintained higher F v/F m (8%), SPAD index (15%), and RWC (16%) than susceptible genotypes. In general, LT of drought-stressed plants was higher (~4ºC) than that of well-watered plants but the relative increase was greater among drought susceptible genotypes. Under drought stress, LT of tolerant genotypes was on average 2.2ºC lower than that of susceptible genotypes. The results are consistent with the tolerant-susceptible classification of these genotypes and indicate that these tools can be reliable in screening for drought tolerance...

Assessment of in vivo fluorescence method for chlorophyll-a estimation in optically complex waters (Curuai floodplain, Pará - Brazil)

Ferreira,Rafael Damiati; Barbosa,Cláudio Clemente Faria; Novo,Evlyn Márcia Leão de Moraes
Fonte: Associação Brasileira de Limnologia Publicador: Associação Brasileira de Limnologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
66%
AIM: This paper describes an experiment carried out to evaluate in vivo fluorescence (IVF) as an alternative method for chlorophyll-a estimation in optically complex aquatic environment (Amazon floodplain lakes) METHODS: The experiment consisted of collecting in situ measurements at 26 sampling stations distributed throughout Curuai floodplain lakes. For each sampling station the following parameters were measured: temperature, turbidity, depth, Secchi depth, chlorophyll-a (Chl-a) concentration, total suspended solids (TSS) and dissolved organic carbon (DOC), concurrently with several transects of IVF. Two methods were tested for quantifying the fluorescence measurement to be used as input for the chlorophyll-a estimates: instantaneous IFV and average IVF. Global and regional models were tested and assessed by analyzing optically active components (Chl-a, DOC and TSS) of the water. RESULTS: Regardless of fluorescence estimating method, the results indicate that it was not possible to fit a global model for estimating Chl-a from IVF for all the lakes in the Curuai floodplain. Regional models provided contrasting results according to the concentration of optically active components. The best results were observed for aquatic systems with a single dominant component homogenously distributed throughout the lake. The results highlight the influence of the ratios Chl-a/TSS...

Xanthophyll cycle-dependent quenching of photosystem II chlorophyll a fluorescence: formation of a quenching complex with a short fluorescence lifetime.

Gilmore, A M; Hazlett, T L; Govindjee
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 14/03/1995 EN
Relevância na Pesquisa
75.96%
Excess light triggers protective nonradiative dissipation of excitation energy in photosystem II through the formation of a trans-thylakoid pH gradient that in turn stimulates formation of zeaxanthin and antheraxanthin. These xanthophylls when combined with protonation of antenna pigment-protein complexes may increase nonradiative dissipation and, thus, quench chlorophyll a fluorescence. Here we measured, in parallel, the chlorophyll a fluorescence lifetime and intensity to understand the mechanism of this process. Increasing the xanthophyll concentration in the presence of a pH gradient (quenched conditions) decreases the fractional intensity of a fluorescence lifetime component centered at approximately 2 ns and increases a component at approximately 0.4 ns. Uncoupling the pH gradient (unquenched conditions) eliminates the 0.4-ns component. Changes in the xanthophyll concentration do not significantly affect the fluorescence lifetimes in either the quenched or unquenched sample conditions. However, there are differences in fluorescence lifetimes between the quenched and unquenched states that are due to pH-related, but nonxanthophyll-related, processes. Quenching of the maximal fluorescence intensity correlates with both the xanthophyll concentration and the fractional intensity of the 0.4-ns component. The unchanged fluorescence lifetimes and the proportional quenching of the maximal and dark-level fluorescence intensities indicate that the xanthophylls act on antenna...

Quenching of Chlorophyll a Fluorescence in Response to Na+-Dependent HCO3- Transport-Mediated Accumulation of Inorganic Carbon in the Cyanobacterium Synechococcus UTEX 625.

Crotty, C. M.; Tyrrell, P. N.; Espie, G. S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1994 EN
Relevância na Pesquisa
65.95%
In the cyanobacterium Synechococcus UTEX 625, the yield of chlorophyll a fluorescence decreased in response to the transport-mediated accumulation of intracellular inorganic carbon (CO2 + HCO3- + CO32- = dissolved inorganic carbon [DIC]) and subsequently increased to a near-maximum level following photosynthetic depletion of the DIC pool. When DIC accumulation was mediated by the active Na+-dependent HCO3- transport system, the initial rate of fluorescence quenching was found to be highly correlated with the initial rate of H14CO3- transport (r = 0.96), and the extent of fluorescence quenching was correlated with the size of the internal DIC pool (r = 0.99). Na+-dependent HCO3- transport-mediated accumulation of DIC caused fluorescence quenching in either the presence or absence of the CO2 fixation inhibitor glycolaldehyde, indicating that quenching was not due simply to NADP+ reduction. The concentration of Na+ required to attain one-half the maximum rate of H14CO3- transport, at 20 [mu]M external HCO3-, declined from 9 to 1 mM as the external pH increased from 8 to 9.6. A similar pH dependency was observed when fluorescence quenching was used to determine the kinetic constants for HCO3- transport. In cells capable of Na+-dependent HCO3- transport...

Chlorophyll a Fluorescence Yield as a Monitor of Both Active CO2 and HCO3− Transport by the Cyanobacterium Synechococcus UTEX 625 1

Miller, Anthony G.; Espie, George S.; Canvin, David T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1988 EN
Relevância na Pesquisa
65.92%
Simultaneous measurements have been made of inorganic carbon accumulation (by mass spectrometry) and chlorophyll a fluorescence yield of the cyanobacterium Synechococcus UTEX 625. The accumulation of inorganic carbon by the cells was accompanied by a substantial quenching of chlorophyll a fluorescence. The quenching occurred even when CO2 fixation was inhibited by iodoacetamide and whether the accumulation of inorganic carbon resulted from either active CO2 or HCO3− transport. Measurement of chlorophyll a fluorescence yield of cyanobacteria may prove to be a rapid and convenient means of screening for mutants of inorganic carbon accumulation.

Photoadaptation in Marine Phytoplankton 1: Changes in Spectral Absorption and Excitation of Chlorophyll a Fluorescence

Neori, Amir; Holm-Hansen, Osmund; Mitchell, B. Greg; Kiefer, Dale A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1984 EN
Relevância na Pesquisa
75.99%
The optical properties of marine phytoplankton were examined by measuring the absorption spectra and fluorescence excitation spectra of chlorophyll a for natural marine particles collected on glass fiber filters. Samples were collected at different depths from stations in temperate waters of the Southern California Bight and in polar waters of the Scotia and Ross Seas. At all stations, phytoplankton fluorescence excitation and absorption spectra changed systematically with depth and vertical stability of the water columns. In samples from deeper waters, both absorption and chlorophyll a fluorescence excitation spectra showed enhancement in the blue-to-green portion of the spectrum (470-560 nm) relative to that at 440 nm. Since similar changes in absorption and excitation were induced by incubating sea water samples at different light intensities, the changes in optical properties can be attributed to photoadaptation of the phytoplankton. The data indicate that in the natural populations studied, shade adaptation caused increases in the concentration of photosynthetic accessory pigments relative to chlorophyll a. These changes in cellular pigment composition were detectable within less than 1 day. Comparisons of absorption spectra with fluorescence excitation spectra indicate an apparent increase in the efficiency of sensitization of chlorophyll a fluorescence in the blue and green spectral regions for low light populations.

Simultaneous Measurement of Oscillations in Oxygen Evolution and Chlorophyll a Fluorescence in Leaf Pieces 1

Walker, David A.; Sivak, Mirta N.; Prinsley, Roslyn T.; Cheesbrough, John K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1983 EN
Relevância na Pesquisa
75.86%
In spinach (Spinacia oleracea) and barley (Hordeum vulgare) leaves, chlorophyll a fluorescence and O2 evolution have been measured simultaneously following re-illumination after a dark interval or when steady state photosynthesis has been perturbed by changes in the gas phase. In high CO2 concentrations, both O2 and fluorescence can display marked dampening oscillations that are antiparallel but slightly out of phase (a rise or fall in fluorescence anticipating a corresponding fall or rise in O2 by about 10 to 15 seconds). Infrared gas analysis measurements showed that CO2 uptake behaved like O2 evolution both in the period of oscillation (about 1 minute) and in its relation to fluorescence. In the steady state, oscillations were initiated by increases in CO2 or by increases or decreases in O2. Oscillations in O2 or CO2 did not occur without associated oscillations in fluorescence and the latter were a sensitive indicator of the former. The relationship between such oscillations in photosynthetic carbon assimilation and chlorophyl a fluorescence is discussed in the context of the effect of ATP or NADPH consumption on known quenching mechanisms.

Low Measuring Temperature Induced Artifactual Increase in Chlorophyll a Fluorescence 1

Huner, Norman P. A.; Öquist, Gunnar; Sundblad, Lars-Göran
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1992 EN
Relevância na Pesquisa
75.82%
Measurement of in vivo chlorophyll a fluorescence at temperatures lower than 20°C can cause an artifactual, nonphotochemically related overestimation of variable fluorescence leading to the calculation of negative values for the nonphotochemical quenching parameter and an underestimation of the photochemical quenching parameter. This artifact is observed only upon exposure of the leaf sample to actinic light. We suggest that a temperature differential between the fiber-optic probe and the leaf sample results in the deposition of water vapor on the probe that distorts the light path such that an increased modulated fluorescence signal is observed. This artifact is eradicated by ensuring that the end of the fiber-optic probe is kept free of condensation.

Global spectral-kinetic analysis of room temperature chlorophyll a fluorescence from light-harvesting antenna mutants of barley.

Gilmor, A M; Itoh, S; Govindjee
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 29/10/2000 EN
Relevância na Pesquisa
75.93%
This study presents a novel measurement, and simulation, of the time-resolved room temperature chlorophyll a fluorescence emission spectra from leaves of the barley wild-type and chlorophyll-b-deficient chlorina (clo) f2 and f104 mutants. The primary data were collected with a streak-camera-based picosecond-pulsed fluorometer that simultaneously records the spectral distribution and time dependence of the fluorescence decay. A new global spectral-kinetic analysis programme method, termed the double convolution integral (DCI) method, was developed to convolve the exciting laser pulse shape with a multimodal-distributed decay profile function that is again convolved with the spectral emission band amplitude functions. We report several key results obtained by the simultaneous spectral-kinetic acquisition and DCI methods. First, under conditions of dark-level fluorescence, when photosystem II (PS II) photochemistry is at a maximum at room temperature, both the clo f2 and clo f104 mutants exhibit very similar PS II spectral-decay contours as the wild-type (wt), with the main band centred around 685 nm. Second, dark-level fluorescence is strongly influenced beyond 700 nm by broad emission bands from PS I, and its associated antennae proteins...

Emissão de fluorescência e produção de massa seca em feijão e soja em função da aplicação de nitrogênio em cobertura; Emission of the fluorescence and production dry matter in bean and soybean a function of application of nitrogen in covareage

MAFEI, Maloní Montanini
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Biologia; Ciências Biolóicas Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Biologia; Ciências Biolóicas
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
65.99%
Nitrogen is considered an essential element for plants, since it is involved in the composition of various biomolecules such as ATP, NADH, NADPH, proteins, enzymes and chlorophyll. The chlorophyll is a pigment from the leaves of plants, which is directly associated with the potential of photosynthetic activity, as well as the nutritional status of the plant. The use of the variable fluorescence of chlorophyll has been widespread, especially in the study of photosynthetic capacity of plants, as a nondestructive method that allows qualitative and quantitative analysis of the absorption and utilization of light energy by photosynthetic apparatus. The objective of this research was to quantify the emission of the chlorophyll a fluorescence (F0, initial fluorescence; Variable-Fv, Fm-Maximum, Terminal-Ft and Efficiency Fotoquímica- Fv/Fm) in photosystem II and the dry matter in bean (Phaseolus vulgaris L .) and soybean (Glycine max (L.) Merr.) submitted the application of nitrogen in the form of ammonium sulfate in coverage. The experimental design was completely randomized in factorial formed by two legumes, two readings and two levels of nitrogen N0 = 0.000 g.kg-1 (control) and N1 = 0,060 g.kg-1. Nitrogen fertilization with ammonium sulfate in coverage influenced the minimum fluorescence (F0) and not influenced by other variables of fluorescence in bean and soybean. Increased the dry mass of branches for the bean...

Atividade fotossint??tica em plantas do g??nero Prunus; Photosynthetic activity in plants of the genus Prunus

MARTINAZZO, Emanuela Garbin
Fonte: Universidade Federal de Pelotas; Biologia; Programa de P??s-Gradua????o em Fisiologia Vegetal; UFPel; BR Publicador: Universidade Federal de Pelotas; Biologia; Programa de P??s-Gradua????o em Fisiologia Vegetal; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
66%
The growth and development of plants of the rosaceae family present variations of physiological processes during the annual cycle. Plant species that occur over a heterogeneous environment are subject to conditions of multiple stresses due to the variety of weather conditions. In this context, water stress, flooding or deficit, has a profound impact on ecological and agricultural systems. The kinetics of chlorophyll a fluorescence is a quite sensitive to environmental stress, and small changes in structure and operation, can be easily detected by their analysis. This work was divided into three experiments, with the aim of evaluating the variation of the kinetics of chlorophyll fluorescence in the plants of the genus Prunus. The first was conducted in the field, the Centro Agropecu??rio da Palma, with six treatments (rootstocks) associated with Maciel. They were accompanied by a period of approximately 150 days the length of the leaf chlorophyll content and chlorophyll a fluorescence kinetics. The second and third experiments were conducted in a greenhouse to cultivate plum America (P. salicina) cultivar and hybrid-cup "GxN-9" (P.dulcis Mill. X P.persica L. Batsch) respectively. In both experiments, plants were kept for 11days under water restriction and 10 days of flooding...

Steady-state chlorophyll a fluorescence detection from canopy derivative reflectance and double-peak red-edge effects

Zarco-Tejada, Pablo J.; Pushnik, J. C.; Dobrowski, S. Z.; Ustin, S. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 972125 bytes; application/pdf
ENG
Relevância na Pesquisa
65.95%
A series of experiments carried out in a controlled environment facility to induce steady-state chlorophyll a fluorescence variation demonstrate that natural fluorescence emission is observable on the derivative reflectance spectra as a double-peak feature in the 690–710 nm spectral region. This work describes that the unexplained double-peak feature previously seen on canopy derivative reflectance is due entirely to chlorophyll fluorescence (CF) effects, demonstrating the importance of derivative methods for fluorescence detection in vegetation. Measurements were made in a controlled environmental chamber where temperature and humidity were varied through the time course of the experiments in both short- and long-term trials using Acer negundo ssp. californium canopies. Continuous canopy reflectance measurements were made with a spectrometer on healthy and stressed vegetation, along with leaf-level steady-state fluorescence measurements with the PAM-2000 Fluorometer during both temperature–stress induction and recovery stages. In 9-h trials, temperatures were ramped from 10 to 35 jC and relative humidity adjusted from 92% to 42% during stress induction, returning gradually to initial conditions during the recovery stage. Canopy reflectance difference calculations and derivative analysis of reflectance spectra demonstrate that a double-peak feature created between 688...

Global spectral-kinetic analysis of room-temperature chlorophyll-a fluorescence from light harvesting antenna mutants of barley.

Gilmore, Adam
Fonte: Royal Society of London Publicador: Royal Society of London
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
86.03%
This study presents a novel measurement, and simulation, of the time-resolved room temperature chlorophyll a fluorescence emission spectra from leaves of the barley wild-type and chlorophyll-b-deficient chlorina (clo) f2 and f104 mutants. The primary data were collected with a streak-camera-based picosecond-pulsed fluorometer that simultaneously records the spectral distribution and time dependence of the fluorescence decay. A new global spectral-kinetic analysis programme method, termed the double convolution integral (DCI) method, was developed to convolve the exciting laser pulse shape with a multimodal-distributed decay profile function that is again convolved with the spectral emission band amplitude functions. We report several key results obtained by the simultaneous spectral-kinetic acquisition and DCI methods. First, under conditions of dark-level fluorescence, when photosystem II (PS II) photochemistry is at a maximum at room temperature, both the clo f2 and clo f104 mutants exhibit very similar PS II spectral-decay contours as the wild-type (wt), with the main band centred around 685 nm. Second, dark-level fluorescence is strongly influenced beyond 700 nm by broad emission bands from PS I, and its associated antennae proteins...

Populations of photoinactivated photosystem II reaction centres characterised by chlorophyll a fluorescence lifetime in vivo

Matsubara, Shizue; Chow, Wah S (Fred)
Fonte: National Academy of Sciences (USA) Publicador: National Academy of Sciences (USA)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
75.88%
Photosystem (PS) II centers, which split water into oxygen, protons, and electrons during photosynthesis, require light but are paradoxically inactivated by it. Prolonged light exposure concomitantly decreased both the functional fraction of PSII reaction centers and the integral PSII chlorophyll (Chl) a fluorescence lifetime in leaf segments of Capsicum annuum L. Acceleration of photoinactivation of PSII by a pretreatment with the inhibitors/uncoupler lincomycin, DTT, or nigericin further reduced PSII Chl a fluorescence lifetimes. A global analysis of fluorescence lifetime distributions revealed the presence of at least two distinct populations of photoinactivated PSII centers, one at 1.25 ns, and the other at 0.58 ns. Light treatment first increased the 1.25-ns component, a weak quencher, at the expense of a component at 2.22 ns corresponding to functional PSII centers. The 0.58-ns component, a strong quencher, emerged later than the 1.25-ns component. The strongly quenching PSII reaction centers could serve to avoid further damage o themselves and protect their functional neighbors by acting as strong energy sinks.