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Photosynthesis Research

Arjina Shrestha, Xin Song, Margaret M Barbour
The temperature response of mesophyll conductance to CO2 diffusion (gm ) has been shown to vary considerably between species but remains poorly understood. Here, we tested the hypothesis that increases in chloroplast surface area with increasing temperature, due to the formation of chloroplast protrusions, caused observed positive responses of gm to temperature. We found no evidence of chloroplast protrusions. Using simultaneous measurements of carbon and oxygen isotope discrimination during photosynthesis to separate total gm (gm13 ) into cell wall and plasma membrane conductance (gm18 ) and chloroplast membrane conductance (gcm ) components, we explored the temperature response in genotypes of soybean and barley, and sunflower plants grown at differing CO2 concentrations...
February 15, 2019: Photosynthesis Research
Haoran Zhou, Erol Akçay, Brent R Helliker
Measurements of photosynthetic assimilation rate as a function of intercellular CO2 (A/Ci curves) are widely used to estimate photosynthetic parameters for C3 species, yet few parameters have been reported for C4 plants, because of a lack of estimation methods. Here, we extend the framework of widely used estimation methods for C3 plants to build estimation tools by exclusively fitting intensive A/Ci curves (6-8 more sampling points) for C4 using three versions of photosynthesis models with different assumptions about carbonic anhydrase processes and ATP distribution...
February 13, 2019: Photosynthesis Research
Liang Zheng, Johan Ceusters, Marie-Christine Van Labeke
Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway present in a variety of genera including many epiphytic orchids. CAM is under circadian control and can be subdivided into four discrete phases during a diel cycle. Inherent to this specific mode of metabolism, carbohydrate availability is a limiting factor for nocturnal CO2 uptake and biomass production. To evaluate the effects of light quality on the photosynthetic performance and diel changes in carbohydrates during the CAM cycle...
February 11, 2019: Photosynthesis Research
Greg Cook, Amber Teufel, Isha Kalra, Wei Li, Xin Wang, John Priscu, Rachael Morgan-Kiss
Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C...
February 7, 2019: Photosynthesis Research
Shuai Liu, Su Li, Xiao-Yang Fan, Guo-Di Yuan, Tao Hu, Xian-Meng Shi, Jun-Biao Huang, Xiao-Yan Pu, Chuan-Sheng Wu
Chlorophyll content in lichens is routinely used as an accurate indicator of lichen vigor, interspecific differences, and the effect of site-related environmental parameters. Traditional methods of chlorophyll extraction are destructive, time-consuming, expensive, and inoperable, especially when measuring large quantities of chlorophyll. However, non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens. Considering the characteristics of lichens such as rough blade surface and absence of chlorophyll b in cyanolichens, we compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content...
February 7, 2019: Photosynthesis Research
Daoyong Yu, Jinxiao Lan, Naseer Ullah Khan, Quan Li, Fengxi Xu, Guihong Huang, Hai Xu, Fang Huang
Photosystem I (PSI) generates the most negative redox potential found in nature, and the performance of solar energy conversion into alternative energy sources in artificial systems highly depends on the thermal stability of PSI. Thus, understanding thermal denaturation is an important prerequisite for the use of PSI at elevated temperatures. To assess the thermal stability of surfactant-solubilized PSI from cyanobacteria Arthrospira Platensis, the synergistic denaturation effect of heat and surfactant was studied...
February 6, 2019: Photosynthesis Research
Paul Mathis, Eliane Nabedryk, André Verméglio
Jacques Breton spent his 39 years of professional life at Saclay, a center of the French Atomic Energy Commission. He studied photosynthesis with various advanced biophysical tools, often developed by himself and his numerous coworkers, obtaining a large number of new information on the structure and the functioning of antenna and of reaction centers of plants and bacteria: excitation migration in the antenna, orientation of molecules, rate of primary reactions, binding of pigments and electron transfer cofactors...
February 2, 2019: Photosynthesis Research
Vasily Kurashov, Ming-Yang Ho, Gaozhong Shen, Karla Piedl, Tatiana N Laremore, Donald A Bryant, John H Golbeck
Certain cyanobacteria can thrive in environments enriched in far-red light (700-800 nm) due to an acclimation process known as far-red light photoacclimation (FaRLiP). During FaRLiP, about 8% of the Chl a molecules in the photosystems are replaced by Chl f and a very small amount of Chl d. We investigated the spectroscopic properties of Photosystem I (PSI) complexes isolated from wild-type (WT) Synechococcus sp. PCC 7335 and a chlF mutant strain (lacking Chl f synthase) grown in white and far-red light (WL-PSI and FRL-PSI, respectively)...
February 1, 2019: Photosynthesis Research
Dariusz M Niedzwiedzki, Benjamin M Wolf, Robert E Blankenship
This work highlights spectroscopic investigations on a new representative of photosynthetic antenna complexes in the LHC family, a putative violaxanthin/vaucheriaxanthin chlorophyll a (VCP) antenna complex from a freshwater Eustigmatophyte alga FP5. A representative VCP-like complex, named as VCP-B3 was studied with both static and time-resolved spectroscopies with the aim of obtaining a deeper understanding of excitation energy migration within the pigment array of the complex. Compared to other VCP representatives, the absorption spectrum of the VCP-B3 is strongly altered in the range of the chlorophyll a Qy band, and is substantially red-shifted with the longest wavelength absorption band at 707 nm at 77 K...
January 30, 2019: Photosynthesis Research
D V Yanykin, M Malferrari, S Rapino, G Venturoli, A Yu Semenov, M D Mamedov
In the present study, we have investigated the effect of hydroxyectoine (Ect-OH), a heterocyclic amino acid, on oxygen evolution in photosystem II (PS II) membrane fragments and on photoinhibition of Mn-depleted PS II (apo-WOC-PS II) preparations. The degree of photoinhibition of apo-WOC-PS II preparations was estimated by the loss of the capability of exogenous electron donor (sodium ascorbate) to restore the amplitude of light-induced changes of chlorophyll fluorescence yield (∆F). It was found that Ect-OH (i) stimulates the oxygen-evolving activity of PS II, (ii) accelerates the electron transfer from exogenous electron donors (K4 [Fe(CN)6 ], DPC, TMPD, Fe2+ , and Mn2+ ) to the reaction center of apo-WOC-PS II, (iii) enhances the protective effect of exogenous electron donors against donor-side photoinhibition of apo-WOC-PS II preparations...
January 30, 2019: Photosynthesis Research
Yusuke Tsukatani, Yuu Hirose, Jiro Harada, Chinatsu Yonekawa, Hitoshi Tamiaki
Halorhodospira halochloris is an anaerobic, halophilic, purple photosynthetic bacterium belonging to γ-Proteobacteria. H. halochloris is also characteristic as a thermophilic phototrophic isolate producing bacteriochlorophyll (BChl) b. Here, we report the complete genome sequence of H. halochloris DSM 1059. The genetic arrangement for this bacterium's photosynthetic apparatus is of particular interest; its genome contains two sets of puf operons encoding the reaction center and core light-harvesting 1 (LH1) complexes having almost identical nucleotide sequences (e...
January 30, 2019: Photosynthesis Research
V T C B Alencar, A K M Lobo, F E L Carvalho, J A G Silveira
Mechanisms involving ammonium toxicity, excess light, and photosynthesis are scarcely known in plants. We tested the hypothesis that high NH4 + supply in presence of high light decreases photosynthetic efficiency of rice plants, an allegedly tolerant species. Mature rice plants were previously supplied with 10 mM NH4 + or 10 mM NO3 - and subsequently exposed to 400 µmol m-2  s-1 (moderate light-ML) or 2000 µmol m-2  s-1 (high light-HL) for 8 h. HL greatly stimulated NH4 + accumulation in roots and in a minor extent in leaves...
January 29, 2019: Photosynthesis Research
Matthew Brown, William Bryce Penta, Bethan Jones, Mike Behrenfeld
Marine phytoplankton experience a wide range of nutrient and light conditions in nature and respond to these conditions through changes in growth rate, chlorophyll concentration, and other physiological properties. Chlorophyll fluorescence is a non-invasive and efficient tool for characterizing changes in these physiological properties. In particular, the introduction of fast repetition rate fluorometry (FRRf) into studies of phytoplankton physiology has enabled detailed studies of photosynthetic components and kinetics...
January 11, 2019: Photosynthesis Research
Gaozhong Shen, Daniel P Canniffe, Ming-Yang Ho, Vasily Kurashov, Art van der Est, John H Golbeck, Donald A Bryant
In diverse terrestrial cyanobacteria, Far-Red Light Photoacclimation (FaRLiP) promotes extensive remodeling of the photosynthetic apparatus, including photosystems (PS)I and PSII and the cores of phycobilisomes, and is accompanied by the concomitant biosynthesis of chlorophyll (Chl) d and Chl f. Chl f synthase, encoded by chlF, is a highly divergent paralog of psbA; heterologous expression of chlF from Chlorogloeopsis fritscii PCC 9212 led to the light-dependent production of Chl f in Synechococcus sp. PCC 7002 (Ho et al...
January 3, 2019: Photosynthesis Research
Artur Sawicki, Robert D Willows, Min Chen
Chlorophylls (Chls) are pigments involved in light capture and light reactions in photosynthesis. Chl a, Chl b, Chl d, and Chl f are characterized by unique absorbance maxima in the blue (Soret) and red (Qy ) regions with Chl b, Chl d, and Chl f each possessing a single formyl group at a unique position. Relative to Chl a the Qy absorbance maximum of Chl b is blue-shifted while Chl d and Chl f are red-shifted with the shifts attributable to the relative positions of the formyl substitutions. Reduction of a formyl group of Chl b to form 7-hydroxymethyl Chl a, or oxidation of the vinyl group of Chl a into a formyl group to form Chl d was achieved using sodium borohydride (NaBH4 ) or β-mercaptoethanol (BME/O2 ), respectively...
January 2, 2019: Photosynthesis Research
Volha U Chukhutsina, Alfred R Holzwarth, Roberta Croce
Photosynthesis starts when a pigment in the photosynthetic antennae absorbs a photon. The electronic excitation energy is then transferred through the network of light-harvesting pigments to special chlorophyll (Chl) molecules in the reaction centres, where electron transfer is initiated. Energy transfer and primary electron transfer processes take place on timescales ranging from femtoseconds to nanoseconds, and can be monitored in real time via time-resolved fluorescence spectroscopy. This method is widely used for measurements on unicellular photosynthetic organisms, isolated photosynthetic membranes, and individual complexes...
November 26, 2018: Photosynthesis Research
Brendon Conlan, Govindjee, Johannes Messinger
With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on 'soft money' in several laboratories around the world for many years, as well as his research achievements...
November 26, 2018: Photosynthesis Research
Yanyan Su
The influence of six different light regimes throughout the photosynthetically active radiation range (from 400 to 700 nm, including blue, green, yellow, red-orange, red, and white) at two intensities (100 and 300 µmol photons m-2  s-1 ) on pigmentation was assessed for the centric marine diatom Coscinodiscus granii for the first time. Chlorophyll (Chl) a and fucoxanthin were the dominating pigments in all treatments. The cellular concentrations of light harvesting pigment (Chl a, Chl c1 + c2, and fucoxanthin) were higher at 100 than at 300 µmol photons m-2  s-1 at all wavelengths, with the largest increases at red and blue light...
November 26, 2018: Photosynthesis Research
Steven M Theg
No abstract text is available yet for this article.
December 2018: Photosynthesis Research
Philip M Day, Steven M Theg
Chloroplasts are descendants of an ancient endosymbiotic cyanobacterium that lived inside a eukaryotic cell. They inherited the prokaryotic double membrane envelope from cyanobacteria. This envelope contains prokaryotic protein sorting machineries including a Sec translocase and relatives of the central component of the bacterial outer membrane β-barrel assembly module. As the endosymbiont was integrated with the rest of the cell, the synthesis of most of its proteins shifted from the stroma to the host cytosol...
December 2018: Photosynthesis Research
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