Neil R. Baker

Bio: Neil R. Baker is an academic researcher from University of Essex. The author has contributed to research in topics: Chlorophyll fluorescence & Photosynthesis. The author has an hindex of 75, co-authored 200 publications receiving 29452 citations. Previous affiliations of Neil R. Baker include University of York & University of California, Los Angeles.

Chlorophyll fluorescence: a probe of photosynthesis in vivo

Abstract: 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.

Applications of chlorophyll fluorescence can improve crop production strategies: an examination of future possibilities

Abstract: Chlorophyll fluorescence has been routinely used for many years to monitor the photosynthetic performance of plants non-invasively. The relationships between chlorophyll fluorescence parameters and leaf photosynthetic performance are reviewed in the context of applications of fluorescence measurements to screening programmes which seek to identify improved plant performance. The potential role of chlorophyll fluorescence imaging in increasing both the sensitivity and throughput of plant screening programmes is examined. Finally, consideration is given to possible specific applications of chlorophyll fluorescence for screening of plants for tolerance to environmental stresses and for improvements in glasshouse production and post-harvest handling of crops.

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

Abstract: 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.

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

Abstract: 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

REACTIVE OXYGEN SPECIES: Metabolism, Oxidative Stress, and Signal Transduction

Abstract: Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.

Chlorophyll fluorescence—a practical guide

Abstract: typically written from a biophysicist’s or a molecular plant physiologist’s point of view (Horton and Bowyer, Chlorophyll fluorescence analysis has become one of 1990; Krause and Weis, 1991; Govindjee, 1995). The aim the most powerful and widely used techniques avail- of this review is to provide a simple, practical guide to able to plant physiologists and ecophysiologists. This chlorophyll fluorescence for those beginners who are review aims to provide an introduction for the novice interested in applying the technique in both field and into the methodology and applications of chlorophyll laboratory situations. Whilst the principles behind the fluorescence. After a brief introduction into the theor- measurements will be discussed briefly, the emphasis will etical background of the technique, the methodology be on the applications and limitations of this technique and some of the technical pitfalls that can be encoun- in plant ecophysiology. tered are explained. A selection of examples is then used to illustrate the types of information that fluorescence can provide. The basis of chlorophyll fluorescence measurements