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Photosynthesis

About: Photosynthesis is a research topic. Over the lifetime, 19789 publications have been published within this topic receiving 895197 citations.


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TL;DR: RNAi technology was applied to down-regulate the entire LHC gene family simultaneously to reduce energy losses by fluorescence and heat and increase photosynthetic efficiencies under high-light conditions, resulting in an increased efficiency of cell cultivation under elevated light conditions.
Abstract: The main function of the photosynthetic process is to capture solar energy and to store it in the form of chemical 'fuels'. Increasingly, the photosynthetic machinery is being used for the production of biofuels such as bio-ethanol, biodiesel and bio-H-2. Fuel production efficiency is directly dependent on the solar photon capture and conversion efficiency of the system. Green algae (e.g. Chlamydomonas reinhardtii) have evolved genetic strategies to assemble large light-harvesting antenna complexes (LHC) to maximize light capture under low-light conditions, with the downside that under high solar irradiance, most of the absorbed photons are wasted as fluorescence and heat to protect against photodamage. This limits the production process efficiency of mass culture. We applied RNAi technology to down-regulate the entire LHC gene family simultaneously to reduce energy losses by fluorescence and heat. The mutant Stm3LR3 had significantly reduced levels of LHCI and LHCII mRNAs and proteins while chlorophyll and pigment synthesis was functional. The grana were markedly less tightly stacked, consistent with the role of LHCII. Stm3LR3 also exhibited reduced levels of fluorescence, a higher photosynthetic quantum yield and a reduced sensitivity to photoinhibition, resulting in an increased efficiency of cell cultivation under elevated light conditions. Collectively, these properties offer three advantages in terms of algal bioreactor efficiency under natural high-light levels: (i) reduced fluorescence and LHC-dependent heat losses and thus increased photosynthetic efficiencies under high-light conditions; (ii) improved light penetration properties; and (iii) potentially reduced risk of oxidative photodamage of PSII.

331 citations

Journal ArticleDOI
TL;DR: It is predicted that increasing UV-B due to future stratospheric ozone depletion is unlikely to have any significant impact on the photosynthetic productivity of olive, lavender and rosemary in the field.
Abstract: The effects of drought on the photosynthetic characteristics of three Mediterranean plants (olive, Olea europea L.; rosemary, Rosmarinus officinalis L.; lavender, Lavandula stoechas L.) exposed to elevated UV-B irradiation in a glasshouse were investigated over a period of weeks. Drought conditions were imposed on 2-year-old plants by withholding water. During the onset of water stress, analyses of the response of net carbon assimilation of leaves to their intercellular CO2 concentration were used to examine the potential limitations imposed by stomata, carboxylation velocity and capacity for regeneration of ribulose 1,5-bisphosphate on photosynthesis. Measurements of chlorophyll fluorescence were used to determine changes in the efficiency of light utilization for electron transport, the occurrence of photoinhibition of photosystem II photochemistry and the possibility of stomatal patchiness across leaves. The first stages of water stress produced decreases in the light-saturated rate of CO2 assimilation which were accompanied by decreases in the maximum carboxylation velocity and the capacity for regeneration of ribulose 1,5-bisphosphate in the absence of any significant photodamage to photosystem II. Leaves of rosemary and lavender were more sensitive than those of olive during the first stages of the drought treatment and also exhibited increases in stomatal limitation. With increasing water stress, significant decreases in the maximum quantum efficiency of photosystem II photochemistry occurred in lavender and rosemary, and stomatal limitation was increased in olive. No indication of any heterogeneity of photosynthesis was found in any leaves. Drought treatment significantly decreased leaf area in all species, an important factor in drought-induced decreases in photosynthetic productivity. Exposure of plants to elevated UV-B radiation (0.47 W m(-2)) prior to and during the drought treatment had no significant effects on the growth or photosynthetic activities of the plants. Consequently, it is predicted that increasing UV-B due to future stratospheric ozone depletion is unlikely to have any significant impact on the photosynthetic productivity of olive, lavender and rosemary in the field.

331 citations

Journal ArticleDOI
TL;DR: The photosynthesis in silico: Understanding Complexity from Molecules to Ecosystems is a unique book that aims to show an integrated approach to the understanding of photosynthesis processes.
Abstract: Photosynthesis in silico: Understanding Complexity from Molecules to Ecosystems is a unique book that aims to show an integrated approach to the understanding of photosynthesis processes. In this volume using mathematical modeling processes are described from the biophysics of the interaction of light with pigment systems to the mutual interaction of individual plants and other organisms in canopies and large ecosystems, up to the global ecosystem issues. Chapters are written by 44 international authorities from 15 countries. Mathematics is a powerful tool for quantitative analysis. Properly programmed, contemporary computers are able to mimic complicated processes in living cells, leaves, canopies and ecosystems. These simulations mathematical models help us predict the photosynthetic responses of modeled systems under various combinations of environmental conditions, potentially occurring in nature, e.g., the responses of plant canopies to globally increasing temperature and atmospheric CO2 concentration. Tremendous analytical power is needed to understand nature's infinite complexity at every level. This book is not a list of equations and computer programs, but the emphasis is on analytical ideas facilitating the understanding of complex interactions governing the photosynthetic process on every level and between different levels of hierarchy. The book provides the necessary background on photosynthesis and demonstrates the benefits of the computer-aided quantitative analysis of its reactions; it is designed for graduate students and researchers in plant physiology, functional plant biology, plant biochemistry, systems biology, biophysics, bio-energy and bio-fuel. more on http://springer.com/978-1-4020-9236-7 2009. Approx. 520 p. ISBN: 978-1-4020-9236-7 ▶ 209,00 €; $279.00; SFr. 347.00; £188.00

329 citations

Journal ArticleDOI
18 May 2006-Nature
TL;DR: It is reported that the greater Cu requirement in an oceanic diatom, Thalassiosira oceanica, is entirely due to a single Cu-containing protein, plastocyanin, which was only known to exist in organisms with chlorophyll b and cyanobacteria.
Abstract: Diatoms are responsible for 40% of ocean production and are strongly limited by the lack of iron salts in the sea The shortage of this important nutrient may explain a surprising discovery: the oceanic diatom Thalassiosira oceanica uses a copper-containing plastocyanin for electron transport All other chlorophyll c-containing taxa, including coastal diatoms, use the iron-containing cytochrome c6 instead The use of these metalloproteins matches the availabilities of copper and iron in the ocean, and this new discovery suggests that copper is a potentially important nutrient in the open sea The supply of some essential metals to pelagic ecosystems is less than the demand, so many phytoplankton have slow rates of photosynthetic production and restricted growth1 The types and amounts of metals required by phytoplankton depends on their evolutionary history2 and on their adaptations to metal availability3,4, which varies widely among ocean habitats Diatoms, for example, need considerably less iron (Fe) to grow than chlorophyll-b-containing taxa2, and the oceanic species demand roughly one-tenth the amount of coastal strains5,6,7 Like Fe, copper (Cu) is scarce in the open sea, but notably higher concentrations of it are required for the growth of oceanic than of coastal isolates8 Here we report that the greater Cu requirement in an oceanic diatom, Thalassiosira oceanica, is entirely due to a single Cu-containing protein, plastocyanin, which—until now—was only known to exist in organisms with chlorophyll b and cyanobacteria Algae containing chlorophyll c, including the closely related coastal species T weissflogii, are thought to lack plastocyanin and contain a functionally equivalent Fe-containing homologue, cytochrome c6 (ref 9) Copper deficiency in T oceanica inhibits electron transport regardless of Fe status, implying a constitutive role for plastocyanin in the light reactions of photosynthesis in this species The results suggest that selection pressure imposed by Fe limitation has resulted in the use of a Cu protein for photosynthesis in an oceanic diatom This biochemical switch reduces the need for Fe and increases the requirement for Cu, which is relatively more abundant in the open sea

329 citations

Journal ArticleDOI
TL;DR: In this article, a tree of life is constructed from the small subunit of the rRNA molecule and from these sequences a Tree of Life emerges providing a reconstruction of the evolutionary relationships among organisms.
Abstract: There are 2 principal avenues of inquiry relevant to reconstructing the history of the sulfur cycle. One avenue relies on the comparison of molecular sequences derived from biologically essential proteins and genetic material. Most sequence information is available from the small subunit of the rRNA molecule and from these sequences a Tree of Life emerges providing a reconstruction of the evolutionary relationships among organisms. Near the root of the tree are numerous bacteria1metabolizing sulfur species including organisms living from dissimilatory elemental sulfur reduction, dissimilatory sulfate reduction, and anoxygenic photosynthesis. These metabolisms are likely very ancient. Many of the deep-branching bacteria of the sulfur cycle are active at very high temperatures (hyperthermophiles) and are commonly found in modern sulfide-rich hydrothermal systems. One can imagine a primitive early Earth terrestrial ecosystem housed around active hydrothermal areas with anoxygenic photosynthesis producing organic matter and oxidized sulfur species. These oxidized sulfur species could have been used as electron acceptors in the mineralization of organic matter, completing the carbon cycle. The evolution of oxygenic photosynthesis provided for dramatically increased rates of carbon production, and a much wider range of ecosystems for both carbon production, and carbon oxidation. Either associated with, or following, the evolution of oxygenic photosynthesis is the emergence of lineages housing most of the bacteria of which we are familiar, including most of the bacteria of the sulfur cycle. The geologic record can provide direct evidence for the state of chemical oxidation of the Earth-surface, with possible indications of when specific bacterial metabolisms first occurred. We offer the following scenario for the evolution of the Earth-surface environment based on the available geological evidence. By 3.5 Ga anoxygenic photosynthesis was established and provided a weak source of sulfate to the global ocean with sulfate concentrations likely 91 mM. In some instances locally high concentrations of sulfate could accumulate and precipitated as evaporitic sulfate minerals. There is no compelling evidence for sulfate reduction at this time. The first evidence for sulfate reduction is found between 2.7 and 2.5 Ga, and the first evidence for oxygen production by oxygenic photosynthesis is found at around 2.8 Ga. Even so, levels of seawater sulfate remained low, below 1 mM, and did not increase to G1 mM until around 2.3 Ga. This increase in sulfate levels may have been promoted by a rise in atmospheric oxygen concentration at this time. Throughout the Archean and early Proterozoic the deep oceans contained appreciable concentrations of dissolved ferrous iron, and banded iron formations (BIFs) were a common form of chemical sediment. Sulfate levels increased slowly, and by 1.8 Ga sulfate concentrations were sufficient to increase rates of sulfate reduction to greater than the delivery flux of iron to the oceans. Sulfide accumulated and precipitated ferrous iron from solution. It is proposed that the oceans remained sulfide-rich until the Neoproterozoic, where renewed deposition of banded iron formations occurred at around 0.75 Ga. It is possible that during the Neoproterozoic, decreased carbon production resulted from an ice covered ‘‘Snowball Earth’’ reducing rates of sulfate reduction below rates of iron delivery to the oceans, promoting BIF formation. At around this time high carbon burial rates increased levels of atmospheric oxygen toG10 percent present-day levels, promoting the widespread oxidation of marine surface sediments and an evolutionary radiation of sulfide oxidizing bacteria. * Institute of Biology, Odense University, Campusvej 55, 5230 Odense M, Denmark. ** Department of Earth Sciences, Leeds University, Leeds LS2 9JT, United Kingdom. 1 Throughout this text the term bacteria refers to prokaryotic organisms from both of the Domains Bacteria and Archaea. When written as Bacteria, organisms of the Domain Bacteria are referred to. [AMERICAN JOURNAL OF SCIENCE, VOL. 299, SEPT./OCT./NOV., 1999, P. 697–723]

329 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20232,453
20225,090
2021738
2020732
2019616