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C Yiotis, C Evans-Fitz Gerald, J C McElwain
Background and Aims: Fluctuations in [CO 2 ] have been widely studied as a potential driver of plant evolution; however, the role of a fluctuating [O 2 ]:[CO 2 ] ratio is often overlooked. The present study aimed to investigate the inherent physiological plasticity of early diverging, extant species following acclimation to an atmosphere similar to that across the Triassic-Jurassic mass extinction interval (TJB, approx. 200 Mya), a time of major ecological change. Methods: Mature plants from two angiosperm ( Drimys winteri and Chloranthus oldhamii ), two monilophyte ( Osmunda claytoniana and Cyathea australis ) and one gymnosperm ( Ginkgo biloba ) species were grown for 2 months in replicated walk-in Conviron BDW40 chambers running at TJB treatment conditions of 16 % [O 2 ]-1900 ppm [CO 2 ] and ambient conditions of 21 % [O 2 ]-400 ppm [CO 2 ], and their physiological plasticity was assessed using gas exchange and chlorophyll fluorescence methods...
March 11, 2017: Annals of Botany
Runa Antony, Amanda S Willoughby, Amanda M Grannas, Victoria Catanzano, Rachel L Sleighter, Meloth Thamban, Patrick G Hatcher, Shanta Nair
Snow overlays the majority of Antarctica and is an important repository of dissolved organic matter (DOM). DOM transformations by supraglacial microbes are not well understood. We use ultrahigh resolution mass spectrometry to elucidate molecular changes in snowpack DOM by in situ microbial processes (up to 55 days) in a coastal Antarctic site. Both autochthonous and allochthonous DOM is highly bio-available and is transformed by resident microbial communities through parallel processes of degradation and synthesis...
March 22, 2017: Environmental Science & Technology
Longteng Tang, Yanli Wang, Weimin Liu, Yongxin Zhao, Robert E Campbell, Chong Fang
Fluorescent protein (FP) based biosensors have become an important and promising tool to track metal ion movement inside living systems. Their working principles after light irradiation, however, remain elusive. To facilitate the rational design of biosensors, we dissect the fluorescence modulation mechanism of a newly developed excitation ratiometric green FP-based Ca(2+) biosensor, GEX-GECO1, using femtosecond stimulated Raman spectroscopy (FSRS) in the electronic excited state. Upon 400 nm photoexcitation, characteristic vibrational marker bands at ~1180 and 1300 cm(-1) show concomitant decay and rise dynamics, probing the progression of an ultrafast excited state proton transfer (ESPT) reaction...
March 22, 2017: Journal of Physical Chemistry. B
Chiara Gandini, Sidsel Birkelund Schmidt, Søren Husted, Anja Schneider, Dario Leister
Manganese (Mn) is an essential constituent of photosystem II (PSII) and therefore indispensable for oxygenic photosynthesis. Very little is known about how Mn is transported, delivered and retained in photosynthetic cells. Recently, the thylakoid-localized transporter PAM71 has been linked to chloroplast Mn homeostasis in Arabidopsis thaliana. Here, we characterize the function of its homolog in Synechocystis (SynPAM71). We used a loss-of-function line (ΔSynPAM71), wild-type (WT) cells exposed to Mn stress and strains expressing a tagged variant of SynPAM71 to characterize the role of SynPAM71 in cyanobacterial Mn homeostasis...
March 20, 2017: New Phytologist
Marten H Vos, Brandon J Reeder, Fevzi Daldal, Ursula Liebl
Correction for 'Ultrafast photochemistry of the bc1 complex' by Marten H. Vos et al., Phys. Chem. Chem. Phys., 2017, 19, 6807-6813.
March 17, 2017: Physical Chemistry Chemical Physics: PCCP
Phillip Christopher, Martin Moskovits
Surface plasmons have recently been harnessed to carry out processes such as photovoltaic current generation, redox photochemistry, photocatalysis, and photodetection, all of which are enabled by separating energetic (hot) electrons and holes-processes that, previously, were the domain of semiconductor junctions. Currently, the power conversion efficiencies of systems using plasmon excitation are low. However, the very large electron/hole per photon quantum efficiencies observed for plasmonic devices fan the hope of future improvements through a deeper understanding of the processes involved and through better device engineering, especially of critical interfaces such as those between metallic and semiconducting nanophases (or adsorbed molecules)...
March 16, 2017: Annual Review of Physical Chemistry
D G Stavenga, M F Wehling, G Belušič
Several fly species have distinctly red-coloured eyes, meaning that the screening pigments that provide a restricted angular sensitivity of the photoreceptors may perform poorly in the longer wavelength range. The functional reasons for the red transparency and possible negative visual effects of the spectral properties of the eye-colouring screening pigments are discussed within the context of the photochemistry, arrestin binding, and turnover of the visual pigments located in the various photoreceptor types...
March 10, 2017: Journal of Physiology
Si Wu, James Blinco, Christopher Barner-Kowollik
The majority of photoreactions reported in the literature rely on wavelength within the UV and - to a lesser extent - visible regime for activation, either by directly triggering the reaction or by photocatalysis. However, photoreactions induced by near-infrared (NIR) light are highly attractive for biomedical applications as NIR light can penetrate deeper into tissue and causes less damage to photosensitive biological systems. Recently, upconverting nanoparticles (UCNPs) have been employed by us and others to assist NIR photo-induced reactions...
March 15, 2017: Chemistry: a European Journal
Yuying Gao, Jian Zhu, Hongyu An, Pengli Yan, Baokun Huang, Ruotian Chen, Fengtao Fan, Can Li
Phase junction is often recognized as an effective strategy to achieve efficient charge separation in photocatalysis and photochemistry. As a crucial factor to determine the photogenerated charges dynamics, there is an increasingly hot debate about the energy band alignment across the interface of phase junction. Herein, we reported the direct measurement of the surface potential profile over the interface of TiO2 phase junction. A built-in electric field up to 1 kV/cm from rutile to anatase nanoparticle was detected by Kelvin Probe Force Microscopy (KPFM)...
March 14, 2017: Journal of Physical Chemistry Letters
Luca Carena, Davide Vione
The APEX (Aqueous Photochemistry of Environmentally-occurring Xenobiotics) software previously developed by one of us was used to model the photochemistry of As(III) in paddy-field water, allowing a comparison with biotic processes. The model included key paddy-water variables, such as the shielding effect of the rice canopy on incident sunlight and its monthly variations, water pH, and the photochemical parameters of the chromophoric dissolved organic matter (CDOM) occurring in paddy fields. The half-life times (t1/2) of As(III) photooxidation to As(V) would be ~20-30 days in May...
March 11, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Y J Leong, N P Sanchez, H W Wallace, B Karakurt Cevik, C S Hernandez, Y Han, J H Flynn, P Massoli, C Floerchinger, E C Fortner, S Herndon, J K Bean, L Hildebrandt Ruiz, W Jeon, Y Choi, B Lefer, R J Griffin
The sources of submicron particulate matter (PM1) remain poorly characterized in the industrialized city of Houston. A mobile sampling approach was used to characterize PM1 composition and concentration across Houston based on high time resolution measurements of non-refractory PM1 and trace gases during the DISCOVER-AQ Texas 2013 campaign. Two pollution zones with marked differences in PM1 levels, character, and dynamics were established based on cluster analysis of organic aerosol mass loadings sampled at sixteen sites...
February 28, 2017: Journal of the Air & Waste Management Association
David E Couch, Henry C Kapteyn, Margaret M Murnane, William K Peters
Understanding the ultrafast dynamics of highly excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape...
March 17, 2017: Journal of Physical Chemistry. A
Marcelo P Gomes, Sarah G Le Manac'h, Louise Hénault-Ethier, Michel Labrecque, Marc Lucotte, Philippe Juneau
We studied the physiological mechanisms involved in the deleterious effects of a glyphosate-based herbicide (Factor(®) 540) on photosynthesis and related physiological processes of willow (Salix miyabeana cultivar SX64) plants. Sixty-day-old plants grown under greenhouse conditions were sprayed with different rates (0, 1.4, 2.1, and 2.8 kg a.e ha(-1)) of the commercial glyphosate formulated salt Factor(®) 540. Evaluations were performed at 0, 6, 24, 48, and 72 h after herbicide exposure. We established that the herbicide decreases chlorophyll, carotenoid and plastoquinone contents, and promotes changes in the photosynthetic apparatus leading to decreased photochemistry which results in hydrogen peroxide (H2O2) accumulation...
2017: Frontiers in Plant Science
Fei He, Min Sheng, Ming Tang
Arbuscular mycorrhizal (AM) fungi colonize roots improving plant water status and tolerance to drought. However, it is not clear whether the presence of AM would affect the photosynthesis and antioxidant gene-enzymes response, which help to alleviate drought stress of the host plant. Here, pot experiments were performed to investigate the effects of Rhizophagus irregularis, an AM fungus, on the tissue water content, photosynthesis, reactive oxygen species (ROS) production, antioxidant enzyme activity and gene expression in black locust (Robinia pseudoacacia L...
2017: Frontiers in Plant Science
Yonglan Tian, Petra Ungerer, Huayong Zhang, Alexander V Ruban
The impact of chronic photoinhibition of photosystem II (PSII) on the productivity of plants remains unknown. The present study investigated the influences of persistent decline in the PSII yield on morphology and productivity of Arabidopsis plants that were exposed to lincomycin at two different developmental stages (seedling and rosette stage). The results indicated that, although retarded, the lincomycin treated plants were able to accomplish the entire growth period with only 50% of the maximum quantum yield of primary photochemistry (Fv/Fm) of the control plants...
February 11, 2017: Journal of Plant Physiology
Zhi Li, Agustin E Pierri, Po-Ju Huang, Guang Wu, Alexei V Iretskii, Peter C Ford
We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium-manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal-metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re-Mn bonds to give mononuclear metal radicals...
March 5, 2017: Inorganic Chemistry
Ekaterina K Yotsova, Martin A Stefanov, Anelia G Dobrikova, Emilia L Apostolova
The effects of short-term treatment with phenylurea (DCMU, isoproturon) and phenol-type (ioxynil) herbicides on the green alga Chlorella kessleri and the cyanobacterium Synechocystis salina with different organizations of photosystem II (PSII) were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution measured by polarographic oxygen electrodes (Clark-type and Joliot-type). The photosynthetic oxygen evolution showed stronger inhibition than the PSII photochemistry...
March 4, 2017: Zeitschrift Für Naturforschung. C, A Journal of Biosciences
Alessio Valentini, Daniel Rivero, Felipe Zapata, Cristina García-Iriepa, Marco Marazzi, Raúl Palmeiro, Ignacio Fdez Galván, Diego Sampedro, Massimo Olivucci, Luis Manuel Frutos
The quantum yield of a photochemical reaction is one of the most fundamental quantities in photochemistry, as it measures the efficiency of the transduction of light energy into chemical energy. Nature has evolved photoreceptors in which the reactivity of a chromophore is enhanced by its molecular environment to achieve high quantum yields. The retinal chromophore sterically constrained inside rhodopsin proteins represents an outstanding example of such a control. In a more general framework, mechanical forces acting on a molecular system can strongly modify its reactivity...
March 2, 2017: Angewandte Chemie
Timothy A Doane
The participation of sunlight in the natural chemistry of the earth is presented as a unique field of study, from historical observations to prospects for future inquiry. A compilation of known reactions shows the extent of light-driven interactions between naturally occurring components of land, air, and water, and provides the backdrop for an outline of the mechanisms of these phenomena. Catalyzed reactions, uncatalyzed reactions, direct processes, and indirect processes all operate in natural photochemical transformations, many of which are analogous to well-known biological reactions...
2017: Geochemical Transactions
Anelia G Dobrikova, Ekaterina K Yotsova, Andreas Börner, Svetlana P Landjeva, Emilia L Apostolova
Тhe sensitivity to cadmium (Cd) stress of two near-isogenic wheat lines with differences at the Rht-B1 locus, Rht-B1a (tall wild type, encoding DELLA proteins) and Rht-B1c (dwarf mutant, encoding modified DELLA proteins), was investigated. The effects of 100 μM CdCl2 on plant growth, pigment content and functional activity of the photosynthetic apparatus of wheat seedlings grown on a nutrient solution were evaluated through a combination of PAM chlorophyll fluorescence, oxygen evolution, oxidation-reduction kinetics of P700 and 77 K fluorescence...
February 20, 2017: Plant Physiology and Biochemistry: PPB
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