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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(More)
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(More)
High resolution digital imaging was used to identify sites of photo-oxidative stress responses in Arabidopsis leaves non-invasively, and to demonstrate the potential of using a suite of imaging techniques for the study of oxidative metabolism in planta. Tissue-specific photoinhibition of photosynthesis in individual chloroplasts in leaves was imaged by(More)
Analysis 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.(More)
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(More)
The light-dependent production of ATP and reductants by the photosynthetic apparatus in vivo involves a series of electron and proton transfers. Consideration is given as to how electron fluxes through photosystem I (PSI), using absorption spectroscopy, and through photosystem II (PSII), using chlorophyll fluorescence analyses, can be estimated in vivo.(More)
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 ␥-glutamylcysteine synthetase (␥-ECS), foliar levels of GSH were raised threefold.(More)
ASCORBATE PEROXIDASE 2 (APX2) encodes a key enzyme of the antioxidant network. In excess light-stressed Arabidopsis leaves, photosynthetic electron transport (PET), hydrogen peroxide (H(2)O(2)) and abscisic acid (ABA) regulate APX2 expression. Wounded leaves showed low induction of APX2 expression, and when exposed to excess light, APX2 expression was(More)
Epipelic diatoms are important components of microphytobenthic biofilms. Cultures of four diatom species (Amphora coffeaeformis, Cylindrotheca closterium, Navicula perminuta and Nitzschia epithemioides) and assemblages of mixed diatom species collected from an estuary were exposed to elevated levels of ultraviolet-B (UV-B) radiation. Short exposures to UV-B(More)
In Arabidopsis leaves, high light stress induces rapid expression of a gene encoding a cytosolic ascorbate peroxidase (APX2), whose expression is restricted to bundle sheath cells of the vascular tissue. Imaging of chlorophyll fluorescence and the production of reactive oxygen species (ROS) indicated that APX2 expression followed a localised increase in(More)