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Dive into the research topics where Neil R. Baker is active.

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Featured researches published by Neil R. Baker.


Biochimica et Biophysica Acta | 1989

The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence

Bernard Genty; Jean-Marie Briantais; Neil R. Baker

Measurements of the quantum yields of chlorophyll fluorescence and CO2 assimilation for a number of plant species exposed to changing light intensity and atmospheric CO2 concentrations and during induction of photosynthesis are used to examine the relationship between fluorescence quenching parameters and the quantum yield of non-cyclic electron transport. Over a wide range of physiological conditions the quantum yield of non-cyclic electron transport was found to be directly proportional to the product of the photochemical fluorescence quenching (qQ) and the efficiency of excitation capture by open Photosystem II (PS II) reaction centres (Fv/Fm). A simple fluorescence parameter, ΔφF/φFm, which is defined by the difference in fluorescence yield at maximal φFm, and steady-state φFs, divided by φFm, can be used routinely to estimate changes in the quantum yield of non-cyclic electron transport. It is demonstrated that both the concentration of open PS II reaction centres and the efficiency of excitation capture by these centres will determine the quantum yield of non-cyclic electron transport in vivo and that deactivation of excitation within PS II complexes by non-photochemical processes must influence the quantum yield of non-cyclic electron transport.


Annual Review of Plant Biology | 2008

Chlorophyll Fluorescence: A Probe of Photosynthesis In Vivo

Neil R. Baker

The use of chlorophyll fluorescence to monitor photosynthetic performance in algae and plants is now widespread. This review examines how fluorescence parameters can be used to evaluate changes in photosystem II (PSII) photochemistry, linear electron flux, and CO(2) assimilation in vivo, and outlines the theoretical bases for the use of specific fluorescence parameters. Although fluorescence parameters can be measured easily, many potential problems may arise when they are applied to predict changes in photosynthetic performance. In particular, consideration is given to problems associated with accurate estimation of the PSII operating efficiency measured by fluorescence and its relationship with the rates of linear electron flux and CO(2) assimilation. The roles of photochemical and nonphotochemical quenching in the determination of changes in PSII operating efficiency are examined. Finally, applications of fluorescence imaging to studies of photosynthetic heterogeneity and the rapid screening of large numbers of plants for perturbations in photosynthesis and associated metabolism are considered.


Archive | 2004

Photosynthesis and the environment

Neil R. Baker

Preface. 1. Processing of Excitation Energy by Antenna Pigments T.G. Owens. 2. Control and Measurement of Photosynthetic Electron Transport in Vivo D.M. Kramer, A.R. Crofts. 3. Regulation of Light Utilization for Photosynthetic Electron Transport B. Genty, J. Harbinson. 4. Mechanisms of Photo Damage and Protein Degradation During Photoinhibition of Photosystem II B. Andersson, J. Barber. 5. Radical Production and Scavenging in the Chloroplasts K. Asado. 6. Metabolic Regulation of Photosynthesis M. Stitt. 7. Carbon Metabolism and Photorespiration: Temperature Dependence in Relation to Other Environmental Factors R.C. Leegood, G.E. Edwards. 8. Gas Exchange: Models and Measurements J.M. Cheeseman, M. Lexa. 9. Stomata: Biophysical and Biochemical Aspects W.H. Outlaw, Jr., et al. 10. Source-Sink Relations: The Role of Sucrose C.J. Pollock, J.F. Farrar. 11. Developmental Constraints on Photosynthesis: Effects of Light and Nutrition J.R. Evans. 12. Molecular Biological Approaches to Environmental Effects on Photosynthesis C.A. Raines, J.C. Lloyd. 13. Photosynthesis in Fluctuating Light Environments R.W. Pearcy, et al. 14. Leaf Photosynthesis Under Drought Stress G. Cornic, A. Massacci. 15. Photosynthetic Adjustment to Temperature S. Falk, et al. 16. Photosynthetic Responses to Changing Atmospheric Carbon Dioxide Concentration G. Bowes. 17. The Modification of Photosynthetic Capacity Induced by Ozone Exposure R.L. Heath. 18. Ultraviolet-B Radiation and Photosynthesis A.H. Teramura, L.H. Ziska. 19. Evaluation and Integration of Environmental Stress Using Stable Isotopes H. Griffiths. 20. Environmental Constraints on Photosynthesis: An Overview of Some Future Prospects N.R. Baker. Index.


Functional Ecology | 1989

Chlorophyll Fluorescence as a Probe of the Photosynthetic Competence of Leaves in the Field: A Review of Current Instrumentation

H. R. Bolhár-Nordenkampf; Stephen P. Long; Neil R. Baker; G. Oquist; U. Schreiber; Elisabeth G. Lechner

Chlorophyll fluorescence has been widely used in laboratory studies in understanding both the mechanism of photosynthesis itself and the mechanisms by which a range of environmental factors alter photosynthetic capacity. The measurement of chlorophyll fluorescence is both non-destructive and non-invasive, and thus has considerable potential for use in the field situation. Applications range simply from a means of rapidly identifying injury to leaves in the absence of visible symptoms to a detailed analysis of causes of change in photosynthetic capacity. This paper introduces the topic of chlorophyll fluorescence, its interpretation and its application in field studies, giving particular attention to interpretation and measurement of fluorescence induction kinetics and to the application of recently developed modulated light fluorimeters. Three commercial fluorimeters designed for field applications were compared: (1) Plant Stress Meter, BioMonitor AB, Sweden; (2) MFMS, Hansatech Ltd, UK; (3) PAM 101, H. Walz, Federal Republic of Germany. The structure and potential of each are briefly reviewed. It was beyond the scope of this comparison to examine the full potential of each instrument but measurements of the widely used parameter Fv/Fmax were made with each on: (1) Triticum aestivum L. leaves treated with the herbicide Atrazine; and (2) Picea abies (L.) Karst. samples collected from sites which were known to receive different levels of ambient air pollution. In both experiments, the results obtained from the three fluorimeters showed good agreement. The relative merits of each instrument to field applications are discussed. Key-words: Chlorophyll fluorescence, stress detection, fluorimeters, Atrazine treatment, photosynthesis, air pollutants, photosystem II


Photosynthesis Research | 1997

Resolving chlorophyll a fluorescence images of photosynthetic efficiency into photochemical and non-photochemical components – calculation of qP and Fv-/Fm-; without measuring Fo-;

Kevin Oxborough; Neil R. Baker

Imaging of chlorophyll a fluorescence from leaves has enabled the spatial resolution of the fluorescence parameter, ΔF/Fm-;. Although this parameter provides a reliable estimate of photosynthetic efficiency under most conditions, the extent to which this efficiency is defined by (i) competition with other energy-dissipating processes operating at photosystem II and (ii) by processes on the reducing side of photosystem II, such as carbon assimilation, requires the use of additional parameters. Of particular value are qP, which quantifies the photochemical capacity of photosystem II, and Fv-;/Fm-;, which quantifies the extent to which photochemistry at photosystem II is limited by competition with thermal decay processes. Imaging of both qP and Fv-;/Fm-; requires measurement of Fo-; (the minimum fluorescence yield in the light-adapted state), which cannot be imaged with existing systems. In this paper, a method is described which estimates Fo-; through a simple equation involving the minimum fluorescence yield in the dark-adapted state (Fo), the maximum fluorescence yield in the dark-adapted state (Fm), and the maximum fluorescence yield in the light-adapted state (Fm-;). This method is tested here, through comparison of measured and calculated values of Fo-;. An example of the application of this method to analysis of photosynthetic performance in leaves, from images of chlorophyll a fluorescence, is also presented.


Current Opinion in Plant Biology | 2002

A photoprotective role for O2 as an alternative electron sink in photosynthesis

Donald R. Ort; Neil R. Baker

Photoprotection of the photosynthetic apparatus has two essential elements: first, the thermal dissipation of excess excitation energy in the photosystem II antennae (i.e. non-photochemical quenching), and second, the ability of photosystem II to transfer electrons to acceptors within the chloroplast (i.e. photochemical quenching). Recent studies indicate that the proportion of absorbed photons that are thermally dissipated through the non-photochemical pathway often reaches a maximum well before saturating irradiances are reached. Hence, photochemical quenching is crucial for photoprotection at saturating light intensities. When plants are exposed to environmental stresses and the availability of CO(2) within the leaf is restricted, the reduction of oxygen by both the photorespiratory and the Mehler ascorbate peroxidase pathways appears to play a critical photoprotective role, substituting for CO(2) in sustaining electron flow. Induction of high activity of the Mehler ascorbate peroxidase pathway may be associated with acclimation to environmental stress.


The Plant Cell | 1999

Elevated Glutathione Biosynthetic Capacity in the Chloroplasts of Transgenic Tobacco Plants Paradoxically Causes Increased Oxidative Stress

Gary Creissen; John L. Firmin; Michael J. Fryer; Baldeep Kular; Nicola Leyland; Helen Reynolds; Gabriela M. Pastori; Florence A. M. Wellburn; Neil R. Baker; A. R. Wellburn; Philip M. Mullineaux

Glutathione (GSH), a major antioxidant in most aerobic organisms, is perceived to be particularly important in plant chloroplasts because it helps to protect the photosynthetic apparatus from oxidative damage. In transgenic tobacco plants overexpressing a chloroplast-targeted γ-glutamylcysteine synthetase (γ-ECS), foliar levels of GSH were raised threefold. Paradoxically, increased GSH biosynthetic capacity in the chloroplast resulted in greatly enhanced oxidative stress, which was manifested as light intensity–dependent chlorosis or necrosis. This phenotype was associated with foliar pools of both GSH and γ-glutamylcysteine (the immediate precursor to GSH) being in a more oxidized state. Further manipulations of both the content and redox state of the foliar thiol pools were achieved using hybrid transgenic plants with enhanced glutathione synthetase or glutathione reductase activity in addition to elevated levels of γ-ECS. Given the results of these experiments, we suggest that γ-ECS–transformed plants suffered continuous oxidative damage caused by a failure of the redox-sensing process in the chloroplast.


Photosynthesis Research | 1993

Can CO2 assimilation in maize leaves be predicted accurately from chlorophyll fluorescence analysis

Gerald E. Edwards; Neil R. Baker

AbstractAnalysis is made of the energetics of CO2 fixation, the photochemical quantum requirement per CO2 fixed, and sinks for utilising reductive power in the C4 plant maize. CO2 assimilation is the primary sink for energy derived from photochemistry, whereas photorespiration and nitrogen assimilation are relatively small sinks, particularly in developed leaves. Measurement of O2 exchange by mass spectrometry and CO2 exchange by infrared gas analysis under varying levels of CO2 indicate that there is a very close relationship between the true rate of O2 evolution from PS II and the net rate of CO2 fixation. Consideration is given to measurements of the quantum yields of PS II (φPS II) from fluorescence analysis and of CO2 assimilation (


Philosophical Transactions of the Royal Society B | 2008

Improving water use in crop production.

James Morison; Neil R. Baker; Philip M. Mullineaux; William J. Davies


Biochimica et Biophysica Acta | 1981

Analysis of the slow phases of the in vivo chlorophyll fluorescence induction curve. Changes in the redox state of Photosystem II electron acceptors and fluorescence emission from Photosystems I and II

Michael Bradbury; Neil R. Baker

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Andrew N. Webber

University of Nebraska–Lincoln

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