Search results for "PHOTOS"
showing 10 items of 701 documents
Chlamydomonas reinhardtii in the landscape of pigments.
2004
▪ Abstract This review focuses on the biosynthesis of pigments in the unicellular alga Chlamydomonas reinhardtii and their physiological and regulatory functions in the context of information gathered from studies of other photosynthetic organisms. C. reinhardtii is serving as an important model organism for studies of photosynthesis and the pigments associated with the photosynthetic apparatus. Despite extensive information pertaining to the biosynthetic pathways critical for making chlorophylls and carotenoids, we are just beginning to understand the control of these pathways, the coordination between pigment and apoprotein synthesis, and the interactions between the activities of these…
Influence of Feeding and Oviposition by Phytophagous Pentatomids on Photosynthesis of Herbaceous Plants
2010
Abstract Feeding by herbivorous insects may change photosynthetic activity of host plants. We studied how feeding and oviposition by herbivorous stink bugs, Murgantia histrionica and Nezara viridula (Heteroptera: Pentatomidae), affect photosynthetic parameters of Brassica oleracea (savoy cabbage) and Phaseolus vulgaris (French bean). First, we measured photosynthetic gas exchange, chlorophyll fluorescence imaging, and emission of induced volatile organic compounds (VOC) immediately after feeding and during a post-feeding period. Photosynthesis decreased rapidly and substantially in B. oleracea and P. vulgaris infested by feeding bugs. Stomatal conductance did not decrease proportionally wit…
Lichen rehydration in heavy metal polluted environments: Pb modulates the oxidative response of both Ramalina farinacea thalli and its isolated micro…
2014
Lichens are adapted to desiccation/rehydration and accumulate heavy metals, which induce ROS especially from the photobiont photosynthetic pigments. Although their mechanisms of abiotic stress tolerance are still to be unravelled, they seem related to symbionts' reciprocal upregulation of antioxidant systems. With the aim to study the effect of Pb on oxidative status during rehydration, the kinetics of intracellular ROS, lipid peroxidation and chlorophyll autofluorescence of whole Ramalina farinacea thalli and its isolated microalgae (Trebouxia TR1 and T. TR9) was recorded. A genetic characterization of the microalgae present in the thalli used was also carried out in order to assess possib…
Sun-induced fluorescence - a new probe of photosynthesis: First maps from the imaging spectrometer HyPlant.
2015
Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first …
The molecular architecture of the thylakoid membrane from various classes of eukaryotic algae
1990
There is convincing consensus that the photosynthetic apparatus is of prokaryotic origin. The wide variety of algal plastids is mostly assumed to be the result of different endocytological events. Chloroplasts surrounded by two membranes as in rhodophytes and chlorophytes were considered as the association of a prokaryotic symbiont and a eukaryotic host, whereas algae having a chloroplast surrounded with more than two membranes can be delineated from an endocytological event of two eukaryotes (see S. Gibbs in this volume). Since chlorophyll b was neither combined with chlorophyll c nor with phycobiliproteins it was proposed that all present day chloroplasts can be integrated in three lines.…
Studies of Components of the Thylakoid Membrane of Undamaged and Damaged Spruce Trees at Different Mountain Sites
1993
During a five-year period, components of the thylakoid membrane in needles of the second generation of undamaged and damaged trees of Norway spruce were studied at three different mountain sites in West Germany. Visible signs of damage at these sites are a yellowing of the light-exposed sides of the needles as well as the loss of needles. The goal of this study was to determine damage-induced alterations in composition and physiological reactions of the thylakoid membranes in spruce needles. In order to meet this purpose, contents of chlorophyll a and b, electron transport rate of photosystem II, contents of the D 1 protein, cytochrome f, as well as P-700 were measured. The chlorophyll cont…
TIP family aquaporins play role in chloroplast osmoregulation and photosynthesis
2020
SUMMARYPhotosynthetic oxygen evolution by photosystem II requires water supply into the chloroplast to reach the thylakoid lumen. A rapid water flow is also required into the chloroplast for optimal oxygen evolution and to overcome osmotic stress. The mechanisms governing water transport in chloroplasts are largely unexplored. Previous proteomics indicated the presence of three aquaporins from the tonoplast intrinsic protein (TIP) family, TIP1;1, TIP1;2 and TIP2;1, in chloroplast membranes of Arabidopsis thaliana. Here we revisited their location and studied their role in chloroplasts. Localization experiments indicated that TIP2;1 resides in the thylakoid, whereas TIP1;2 is present in both…
Effect of Phosphinothricin (Glufosinate) on Photosynthesis and Photorespiration
1990
Phosphinothricin (PPT) causes a rapid inhibition of photosynthesis under atmospheric conditions (400 ppm CO2, 21% O2). However, under conditions (1000 ppm CO2, 2% O2) under which photorespiration cannot occur, there is no or only a very low rate of photosynthesis inhibition by phosphinothricin. Under both conditions, a strong NH4 +-accumulation is apparent caused through the inhibition of glutamine synthetase by phosphinothricin. This indicates, that NH4 +-accumulation cannot be the primary cause for photosynthesis inhibition by phosphinothricin, but a process in connexion with photorespiration plays a central role. Through the lack of amino donors, the transamination of glyoxylate to glyci…
Silica Entrapment for Significantly Stabilized, Energy-Conducting Light-Harvesting Complex (LHCII)
2014
The major light-harvesting chlorophyll a/b complex (LHCII) of the photosynthetic apparatus in green plants consists of a membrane protein and numerous noncovalently bound pigments that make up about one-third of the molecular mass of the pigment-protein complex. Due to this high pigment density, LHCII is potentially interesting as a light-harvesting component in synthetic constructs. However, for such applications its stability needs to be significantly improved. In this work, LHCII was dramatically stabilized by enclosing it within polymerizing colloidal silica. The entrapped LHCII stayed functional at 50 °C for up to 24 h instead of a few minutes in detergent solution and clearly showed e…
Biological Evaluation of the NIR-Emissive Ruby Analogue [Cr(ddpd) 2 ][BF 4 ] 3 as a Photodynamic Therapy Photosensitizer
2018
International audience; Photodynamic therapy relies on the bioavailability of photosensitizers with suitable photophysical, chemical and biochemical properties. Although the photophysical properties, stability and high water solubility of the chromium(III) complex [Cr(ddpd)2][BF4]3 (ddpd = N,N'-dimethyl-N,N'-dipyridin-2-ylpyridine-2,6-diamine) are very favorable, its photocytotoxicity against cancerous and non-cancerous cell lines has not yet been elucidated. We now report the cytotoxicity and photocytotoxicity of the complex [Cr(ddpd)2][BF4]3 against human cervical cancer cells, human primary glioblastoma cells, human glioblastoma astrocytoma cells and non-cancerous retinal pigment epithel…