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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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Journal ArticleDOI
25 May 2010-PLOS ONE
TL;DR: It is shown that diverse genera of cyanobacteria including biofilm-forming and pelagic strains have a conserved light-dependent electrogenic activity, i.e. the ability to transfer electrons to their surroundings in response to illumination, which illustrates that cyanobacterial electrogensic activity is an important microbiological conduit of solar energy into the biosphere.
Abstract: Background Cyanobacteria account for 20–30% of Earth's primary photosynthetic productivity and convert solar energy into biomass-stored chemical energy at the rate of ∼450 TW [1]. These single-cell microorganisms are resilient predecessors of all higher oxygenic phototrophs and can be found in self-sustaining, nitrogen-fixing communities the world over, from Antarctic glaciers to the Sahara desert [2]. Methodology/Principal Findings Here we show that diverse genera of cyanobacteria including biofilm-forming and pelagic strains have a conserved light-dependent electrogenic activity, i.e. the ability to transfer electrons to their surroundings in response to illumination. Naturally-growing biofilm-forming photosynthetic consortia also displayed light-dependent electrogenic activity, demonstrating that this phenomenon is not limited to individual cultures. Treatment with site-specific inhibitors revealed the electrons originate at the photosynthetic electron transfer chain (P-ETC). Moreover, electrogenic activity was observed upon illumination only with blue or red but not green light confirming that P-ETC is the source of electrons. The yield of electrons harvested by extracellular electron acceptor to photons available for photosynthesis ranged from 0.05% to 0.3%, although the efficiency of electron harvesting likely varies depending on terminal electron acceptor. Conclusions/Significance The current study illustrates that cyanobacterial electrogenic activity is an important microbiological conduit of solar energy into the biosphere. The mechanism responsible for electrogenic activity in cyanobacteria appears to be fundamentally different from the one exploited in previously discovered electrogenic bacteria, such as Geobacter, where electrons are derived from oxidation of organic compounds and transported via a respiratory electron transfer chain (R-ETC) [3], [4]. The electrogenic pathway of cyanobacteria might be exploited to develop light-sensitive devices or future technologies that convert solar energy into limited amounts of electricity in a self-sustainable, CO2-free manner.

224 citations

Journal ArticleDOI
TL;DR: The maintenance of PPDK and Rubisco large subunit amounts in M. × giganteus is consistent with the hypothesis that these proteins are critical to maintaining high rates of C4 photosynthesis at low temperature.
Abstract: Field-grown Miscanthus × giganteus maintains high photosynthetic quantum yields and biomass productivity in cool temperate climates. It is related to maize ( Zea mays ) and uses the same NADP-malic enzyme C 4 pathway. This study tests the hypothesis that M. × giganteus , in contrast to maize, forms photosynthetically competent leaves at low temperatures with altered amounts of pyruvate orthophosphate dikinase (PPDK) and Rubisco or altered properties of PPDK. Both species were grown at 25°C/20°C or 14°C/11°C (day/night), and leaf photosynthesis was measured from 5°C to 38°C. Protein and steady-state transcript levels for Rubisco, PPDK, and phospho enol pyruvate carboxylase were assessed and the sequence of C 4 -PPDK from M. × giganteus was compared with other C 4 species. Low temperature growth had no effect on photosynthesis in M. × giganteus , but decreased rates by 80% at all measurement temperatures in maize. Amounts and expression of phospho enol pyruvate carboxylase were affected little by growth temperature in either species. However, PPDK and Rubisco large subunit decreased >50% and >30%, respectively, in cold-grown maize, whereas these levels remained unaffected by temperature in M. × giganteus . Differences in protein content in maize were not explained by differences in steady-state transcript levels. Several different M. × giganteus C 4 -PPDK cDNA sequences were found, but putative translated protein sequences did not show conservation of amino acids contributing to cold stability in Flaveria brownii C 4 -PPDK. The maintenance of PPDK and Rubisco large subunit amounts in M. × giganteus is consistent with the hypothesis that these proteins are critical to maintaining high rates of C 4 photosynthesis at low temperature.

224 citations

Journal ArticleDOI
TL;DR: Despite the similar inhibitions of the CO2 assimilation rates, the wheat photochemistry showed much more sensitivity to Cd than to Zn exposure, which indicated that both metals disturbed photosynthetic electron transport processes which led to a 4- to 5-fold suppression of the efficiency of energy transformation in Photosystem II.
Abstract: A comparative study of the effects of exposure to high Cd2+ (50 µM) and excess Zn2+ (600 µM) on photosynthetic performance of hydroponically-grown durum wheat seedlings was performed. At day 8, Cd and Zn were added to the nutrient solution. After 7-days exposure, the chosen concentrations of both metals resulted in similar relative growth rate (RGR) inhibitions of about 50% and comparable retardations of the CO2 assimilation rates (about 30%) in the second developed leaf of wheat seedlings. Analysis of chlorophyll a fluorescence indicated that both metals disturbed photosynthetic electron transport processes which led to a 4- to 5-fold suppression of the efficiency of energy transformation in Photosystem II. Non-specific toxic effects of Cd and Zn, which prevailed, were an inactivation of part of Photosystem II reaction centres and their transformation into excitation quenching forms as well as disturbed electron transport in the oxygen-evolving complex. The specificity of the Cd and Zn modes of action was mainly expressed in the intensity of the toxicity effects: despite the similar inhibitions of the CO2 assimilation rates, the wheat photochemistry showed much more sensitivity to Cd than to Zn exposure.

224 citations

Journal ArticleDOI
TL;DR: The controlling factor in the inhibition of glycolysis and respiration by light is the increased ratio of ATP to ADP rather than a drop in the orthophosphate, which points to the existence of a photosynthetic reaction generating AMP.

224 citations

Journal ArticleDOI
TL;DR: In this paper, the Dillon-Rigler phosphorus loading model is extended to predict volumetric rates of photosynthesis (v and Āopt) in lakes where the N:P balance indicates control by phosphorus (N:P ⩾ 13).
Abstract: An analysis of growing season measurements of daily primary productivity, chlorophyll, water chemistry, and transparency from 58 north temperate lakes shows a strong correlation between volumetric rates of photosynthesis, chlorophyll, and nutrients. Mean daily rates of photosynthesis per unit volume euphotic zone, v, are correlated with mean chlorophyll concentration (r2 = 0.80). The mean daily rate of photosynthesis at optimal depth, Āopt, is highly correlated with mean total P(r2 = 0.95), and with mean total N(r2 = 0.91). In contrast, integral rates of photosynthesis are linked less tightly to nutrient concentration because of their simultaneous dependence on transparency. The Dillon-Rigler phosphorus loading model is extended to predict volumetric rates of photosynthesis (v and Āopt) in lakes where the N:P balance indicates control by phosphorus (N:P ⩾ 13).

224 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