Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 7 )

2019 ( 89 )

2018 ( 437 )

2017 ( 462 )

Custom range...

Search Results: 1 - 10 of 53705 matches for " Chlorophyll a fluorescence "
All listed articles are free for downloading (OA Articles)
Page 1 /53705
Display every page Item
Gas Exchanges and Antioxidant Activity in Copaifera langsdorffii Desf. Seedlings after Flooding  [PDF]
Derek Brito Chaim Jardim Rosa, Silvana de Paula Quint?o Scalon, Thais Cremon, Daiane Mugnol Dresch
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.95075
Abstract: The Copaifera langsdorffii Desf. seedlings, popularly known as “copaiba” or diesel tree, present a natural occurrence in the riparian forests of the Brazilian Cerrado, however, not much is known about their capacity to recover from flooding, particularly when the focus is on their establishment and use in programs for the recovery of degraded areas near watercourses and subject to flooding. The objective of this study was to evaluate over time the recovery of the efficiency of the photosynthetic apparatus and the antioxidant activity of C. langsdorffii seedlings flooded during different periods. The pots with the seedlings were placed in a plastic tank and submerged with water, and were removed from the flood condition every 21 days (0, 21, 42, 63 and 84 days), and evaluated every 30 days (0, 30, 60, 90 and 120 days). The seedlings tolerated the flooding for up to 42 days, recovering after suspension of this condition. Seedlings flooded for 63 and 84 days showed lower recovery capacity after flooding, independently of the evaluation period. Under these conditions, lower efficiency of the photosynthetic apparatus, gas exchange, photo assimilate production and seedling quality were observed.
Biomass accumulation, photochemical efficiency of photosystem II, nutrient contents and nitrate reductase activity in young rosewood plants (Aniba rosaeodora Ducke) submitted to different NO3-:NH4+ ratios
Barreto, Denize Caranhas de Sousa;Gon?alves, José Francisco de Carvalho;Santos Júnior, Ulysses Moreira dos;Fernandes, Andreia Varmes;Bariani, Adriana;Sampaio, Paulo de Tarso Barbosa;
Acta Amazonica , 2007, DOI: 10.1590/S0044-59672007000400008
Abstract: the rosewood (aniba rosaeodora ducke) is a native tree species of amazon rainforest growing naturally in acidic forest soils with reduced redox potential. however, this species can also been found growing in forest gaps containing oxide soils. variations in the forms of mineral nitrogen (no3- or nh4+) may be predicted in these different edaphic conditions. considering that possibility, an experiment was carried out to analyze the effects of different no3-:nh4+ ratios on the growth performance, mineral composition, chloroplastid pigment contents, photochemical efficiency photosystem ii (psii), and nitrate redutase activity (rn, e.c. on a. rosaeodora seedlings. nine-month-old seedlings were grown in pots with a washed sand capacity of 7.5 kg and submitted to different no3-:nh4+ ratios (t1 = 0:100%, t2 = 25:75%, t3 = 50:50%, t4 = 75:25%, and t5 = 100:0%). the lowest relative growth rate was observed when the no3-:nh4+ ratio was equal to 0:100%. in general, high concentrations of no3- rather than nh4+ favored a greater nutrient accumulation in different parts of the plant. for the chloroplastid pigment, the highest chl a, chl b, chltot, chl a/b and chltot/cx+c contents were found in the treatment with 75:25% of no3-:nh4+, and for chl b and cx+c it was observed no difference. in addition, there was a higher photochemical efficiency of psii (fv/fm) when high no3- concentrations were used. a linear and positive response for the nitrate reductase activity was recorded when the nitrate content increased on the culture substrate. our results suggest that a. rosaeodora seedlings have a better growth performance when the no3- concentrations in the culture substrate were higher than the nh4+ concentrations.
Photochemical efficiency in bean plants (Phaseolus vulgaris L. and Vigna unguiculata L. Walp) during recovery from high temperature stress
Costa, Ernany Santos;Bressan-Smith, Ricardo;Oliveira, Jurandi Gon?alves de;Campostrini, Eliemar;Pimentel, Carlos;
Brazilian Journal of Plant Physiology , 2002, DOI: 10.1590/S1677-04202002000200004
Abstract: bean (phaseolus vulgaris l., cv. carioca and cv. negro huasteco) and cowpea plants (vigna unguiculata l. walp cv. epace 10) were grown in a growth chamber with ppf at leaf level of 200 mmol.m-2.s-1 and air temperature 25 + 1 oc. the first fully expanded pair of leaves of 12-day-old plants was submitted to high temperature stress (25, 30, 35, 40, 45 and 48 oc) for 1.5 h. the photochemical efficiency of psii during recovery was monitored by means of chlorophyll a fluorescence at six different times (0.5, 1, 2, 4, 24, and 48 h) after stress, at 25 oc, using a modulated fluorimeter. increasing temperature promoted an increase in ff at 45 oc, possibly associated with dissociation of the light harvesting complex from the reaction centre of psii, but a decrease was observed at 48 oc in all cultivars. fmax decreased at 48 oc in carioca and negro huasteco, but not in epace 10, showing a possible correlation between heat tolerance and fmax for this cultivar. the low values of fmax in carioca and negro huasteco indicated a loss of psii activity followed by death of these plants. fv/fmax did not vary in epace 10 but varied in carioca and negro huasteco with increasing temperatures.
Effect of Salinity Stress on Growth, Sugar Content, Pigments and Enzyme Activity of Rice
Mohammad Reza Amirjani
International Journal of Botany , 2011,
Abstract: V/FM), photon yield of PSII (φPSII), non-photochemical quenching (NPQ) and net photosynthetic rate (Pn) in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and φPSII, Pn as well as Pn and leaf area were found. Sugar content in shoots had a significant increase under salinity stress. The starch content of roots seedlings decreased NaCI stressed seedling. The contents of total, reducing and non reducing sugars increased in roots.
Photochemical efficiency in bean plants (Phaseolus vulgaris L. and Vigna unguiculata L. Walp) during recovery from high temperature stress
Costa Ernany Santos,Bressan-Smith Ricardo,Oliveira Jurandi Gon?alves de,Campostrini Eliemar
Brazilian Journal of Plant Physiology , 2002,
Abstract: Bean (Phaseolus vulgaris L., cv. Carioca and cv. Negro Huasteco) and cowpea plants (Vigna unguiculata L. Walp cv. Epace 10) were grown in a growth chamber with PPF at leaf level of 200 mumol.m-2.s-1 and air temperature 25 + 1 oC. The first fully expanded pair of leaves of 12-day-old plants was submitted to high temperature stress (25, 30, 35, 40, 45 and 48 oC) for 1.5 h. The photochemical efficiency of PSII during recovery was monitored by means of chlorophyll a fluorescence at six different times (0.5, 1, 2, 4, 24, and 48 h) after stress, at 25 oC, using a modulated fluorimeter. Increasing temperature promoted an increase in Fphi at 45 oC, possibly associated with dissociation of the light harvesting complex from the reaction centre of PSII, but a decrease was observed at 48 oC in all cultivars. Fmax decreased at 48 oC in Carioca and Negro Huasteco, but not in Epace 10, showing a possible correlation between heat tolerance and Fmax for this cultivar. The low values of Fmax in Carioca and Negro Huasteco indicated a loss of PSII activity followed by death of these plants. Fv/Fmax did not vary in Epace 10 but varied in Carioca and Negro Huasteco with increasing temperatures.
Differential responses of seven contrasting species to high light using pigment and chlorophyll a fluorescence
Mittal S.,N. Kumari,V. Sharma
Journal of Stress Physiology & Biochemistry , 2011,
Abstract: High light intensity may induce severe photodamage to chloroplast and consequently cause decreases in the yield capacity of plants and destruction of pigments, causing an overall yellowing of the foliage. Thus, study related to light adaptation becomes necessary to understand adaptation processes in higher plants on the basis of which they are characterized as full sunlight or shade plants. Chlorophyll can be regarded as an intrinsic fluorescent probe of the photosynthetic system. The ecophysiological parameter related to plant performance and fitness i.e. in-situ chlorophyll fluorescence measurements were determined for different plant species in the medicinal plant garden of Banasthali University, Rajasthan. Miniaturized Pulse Amplitude Modulated Photosynthetic Yield Analyzers are primarily designed for measuring effective quantum yield (ΔF/Fm’) of photosystem II under momentary ambient light in the field. Photosynthetic yield measurements and light-response curves suggested a gradation of sun-adapted to shade-adapted behaviour of these plants in following order Withania somnifera> Catharanthus roseus> Datura stamonium> Vasica minora> Vasica adulta> Rauwolfia serpentina. As indicated by light response curves and pigment analysis, Datura stramonium, Withania somnifera and Catharanthus roseus competed well photosynthetically and are favoured while Rauwolfia serpentina, Vasica minora, Vasica adulta and Plumbago zeylanica were observed to be less competent photosynthetically. These light response curves and resultant cardinal points study gave insight into the ecophysiological characterization of the photosynthetic capacity of the plant and provides highly interesting parameters like electron transport rate, photo-inhibition, photosynthetically active photon flux density and yield on the basis of which light adaptability was screened for seven medicinally important plants.
Model dependences of the deactivation of phytoplankton pigment excitation energy on environmental conditions in the sea
Miros?awa Ostrowska
Oceanologia , 2012,
Abstract: A semi-empirical, physical models have been derived of the quantum yield ofthe deactivation processes (fluorescence, photosynthesis and heat production)of excited states in phytoplankton pigment molecules. Besides some alreadyknown models (photosynthesis and fluorescence), this novel approachincorporates the dependence of the dissipation yield of the excitation energyin phytoplankton pigment molecules on heat. The quantitative dependences ofthe quantum yields of these three processes on three fundamental parameters ofthe marine environment are defined: the chlorophyll concentration in the surface water layer Ca(0) (the basin trophicity),the irradiance PAR(z) and the temperature temp(z) at the study site.The model is complemented with two other relevant models describing thequantum yield of photosynthesis and of natural Sun-Induced Chlorophyll a Fluorescence (SICF) in the sea, derived earlier by the author or with herparticipation on the basis of statistical analyses of a vast amount ofempirical material. The model described in the present paper enables theestimation of the quantum yields of phytoplankton pigment heat production forany region and season, in waters of any trophicity at different depths fromthe surface to depths of ca 60 m. The model can therefore be used to estimatethe yields of these deactivation processes in more than half the thickness ofthe euphotic zone in oligotrophic waters and in the whole thickness (anddeeper) of this zone in mesotrophic and eutrophic waters. In particular theserelationships may be useful for a component analysis of the budget of lightenergy absorbed by phytoplankton pigments, namely, its utilization influorescence, photochemical quenching and nonphotochemical radiationlessdissipation - i.e. direct heat production.
Green Fertilization Enhances the Photosynthetic Performance and the Growth of Leguminous Trees for Restoration Plantation in Central Amazon  [PDF]
Roberto Kirmayr Jaquetti, José Francisco de Carvalho Gon?alves, Jo?o Baptista Silva Ferraz, Marciel J. Ferreira, Ulysses Moreira dos Santos Junior, Claudivan Feitosa de Lacerda
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.516264

The leguminous tree species Dipteryx odorata (Aubl.) Willd. and Inga edulis Mart. were grown in the field to reforest a degraded area. To investigate the photosynthetic responses and the initial growth of Amazonian forest species under fertilization, the study species were subjected to different treatments: T1 = unfertilized-control, T2 = chemical fertilization, T3 = green fertilization and T4 = green and chemical fertilization. D. odorata showed the highest absolute growth rates in height under treatments T4 (10.2 cm·month-1) and T2 (12.2 cm·month-1). I. edulis exhibited the best performance for this same parameter in T4 (23.0 cm·month-1). The highest photosynthesis values (Pn) for both D. odorata (13.1 μmol·m-2·s-1) and I. edulis (20.6 μ

A Possible Realization of Chlorophyll Lase  [PDF]
Mitali Konwar, G. D. Baruah
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.38060

The present work is concerned with a description of strong fluorescence from a sample of Alocasia culcullata schot (local name Kolia kasu) and possible realization of chlorophyll laser. The red florescence is most prominent when excited with broad band source like 30 mW green or blue solid state laser, but the acetone extract of plant leaves Allocasa cullcuta schot unusually exhibits the strong intensity in the red sector of the spectrum. A dark room can be easily illuminated with this red radiation. We have used this fact to explore a possible realization of chlorophyll laser which would be a natural environmental phenomenon.

The effect of chilling on the photosynthetic activity in coffee (Coffea arabica L.) seedlings: The protective action of chloroplastid pigments
Oliveira, Jurandi Gon?alves de;Alves, Pedro Luis C.A.;Magalh?es, Antonio Celso;
Brazilian Journal of Plant Physiology , 2002, DOI: 10.1590/S1677-04202002000200003
Abstract: coffea arabica is considered to be sensitive to low temperatures, being affected throughout its entire life cycle. injury caused by chilling (low temperatures above zero degree centigrade) is characterized primarily by inhibition of the photosynthetic process. the objective of this work was to evaluate the role of photosynthetic pigments in the tolerance of coffee (c. arabica l.) seedlings to chilling. the evaluation the photosynthetic activity was made by emission of chl a fluorescence at room temperature (25 oc) in vivo and in situ, using a portable fluorometer. the pigment content was obtained by extraction with 80 % acetone, while estimation of membrane lipid peroxidation was determined by measuring the mda content in leaf tissue extracts. the results indicated a generalized reduction in the quantum yield of psii when the seedlings were maintained in the dark. the reduction occurred in the seedlings submitted to chilling treatment as well as in the control ones. this demonstrates that not only chilling acts to cause an alteration in psii. it is possible that the tissue storage reserves had been totally exhausted, with the respiratory rate exceeding the photosynthetic rate; the later was nil, since the seedlings were kept in the dark. the efficiency in the capture, transfer and utilization of light energy in psii photochemical reactions requires a sequence of photochemical, biochemical and biophysical events which depend on the structural integrity of the photosynthetic apparatus. however, this efficiency was found to be related to the protective action of chloroplastid pigments, rather than to the concentration of these pigments.
Page 1 /53705
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.