Ion homeostasis in the Chloroplast

peer reviewedThe chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis

Variability of sediment diatom assemblages of Lake Pont-de-Salars on the Viaur River (France)

Limnological surveys from the pelagic zone of Lake Pont-de-Salars were undertaken during the 1993-1996 period, which included the emptying of the whole-lake in summer 1995 and the first post year refilling. This reservoir was warm and monomictic and was determined to vary between oligo- and meso-eutrophic status from year to year. Three sediment cores were collected from the deepest zone and frozen in situ during the short drying period, just after the emptying and before the refilling of the reservoir. Analysis of the relative abundance and vertical distribution of diatom taxa was undertaken. The diatom vertical distribution, evident by visual biostratigraphy, is confirmed by the correspondence analysis (CA) despite of absence of sediment dating

Le développement des dinoflagellés toxiques benthiques du genre Ostreopsis en Méditerranée NO : présentation du projet MediOs 2.

National audienceLe développement des dinoflagellés toxiques benthiques du genre Ostreopsis en Méditerranée NO : présentation du projet MediOs 2

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in Monaco (NW Mediterranean sea).

Development of the benthic toxic dinoflagellate Ostreopsis cf. ovata in Monaco (NW Mediterranean sea)

Impacts des facteurs environnementaux sur le développement d'Ostreopsis cf. ovata durant les étés 2007 et 2008 à Monaco (Méditerranée Nord-Occidentale).

National audienceImpacts des facteurs environnementaux sur le développement d'Ostreopsis cf. ovata durant les étés 2007 et 2008 à Monaco (Méditerranée Nord-Occidentale)

Impact of environmental factors on Ostreopsis cf. ovata dynamic during the summers 2007 and 2008 in Monaco (NW Mediterranean Sea).

Impact of environmental factors on Ostreopsis cf. ovata dynamic during the summers 2007 and 2008 in Monaco (NW Mediterranean Sea)

Surveillance de la qualité des eaux de baignade : recherche et suivi du développement des dinoflagellés toxiques du genre Ostreopsis au niveau du littoral de Monaco

Rapport scientifiqueSurveillance de la qualité des eaux de baignade : recherche et suivi du développement des dinoflagellés toxiques du genre Ostreopsis au niveau du littoral de Monac

Quantification of Leaf Phloem Anatomical Features with Microscopy

Measurements of vein density and foliar minor vein phloem cell numbers, minor vein phloem cell sizes, and transfer cell wall ingrowths provide quantitative proxies for the leaf’s capacities to load and export photosynthates. While overall infrastructural capacity for sugar loading and sugar export correlated positively and closely with photosynthetic capacity, the specific targets of the adjustment of minor vein organization varied with phloem-loading mechanism, plant life-cycle characteristics, and environmental growth conditions. Among apoplastic loaders, for which sugar loading into the phloem depends on cell membrane-spanning transport proteins, variation in minor vein density, phloem cell number, and level of cell wall ingrowth (when present) were consistently associated with photosynthetic capacity. Among active symplastic loaders, for which sugar loading into the phloem depends on cytosolic enzymes, variation in vein density and phloem cell size were consistently associated with photosynthetic capacity. All of these anatomical features were also subject to acclimatory adjustment depending on species and environmental conditions, with increased levels of these features supporting higher rates of photosynthesis. We present a procedure for the preparation of leaf tissue for minor vein analysis, using both light and transmission electron microscopy, that facilitates quantification of not only phloem features but also xylem features that provide proxies for foliar water import capacity