Operation and regulation of the lutein epoxide cycle in seedlings of Ocotea foetens

2010 ◽  
Vol 37 (9) ◽  
pp. 859 ◽  
Author(s):  
Raquel Esteban ◽  
Shizue Matsubara ◽  
María Soledad Jiménez ◽  
Domingo Morales ◽  
Patricia Brito ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Higher Plants ◽  
Daily Basis ◽  
Field Conditions ◽  
Photochemical Quenching ◽  
Complete Restoration ◽  
Non Photochemical Quenching ◽  
First Time

Two xanthophyll cycles are present in higher plants: the ubiquitous violaxanthin (V) cycle and the taxonomically restricted lutein epoxide (Lx) cycle. Conversions of V to zeaxanthin (Z) in the first and Lx to lutein (L) in the second happen in parallel under illumination. Unlike the V cycle, in which full epoxidation is completed overnight, in the Lx cycle, this reaction has been described as irreversible on a daily basis in most species (the ‘truncated’ Lx cycle). However, there are some species that display complete restoration of Lx overnight (‘true’ Lx cycle). So far, little is known about the physiological meaning of these two versions of the Lx cycle. Therefore, in the present work, the ‘true’ Lx cycle operation was studied in seedlings of Ocotea foetens (Aiton) Benth. under controlled and field conditions. Complete overnight recovery of the Lx pool in the presence of norfluorazon suggested that the inter-conversions between Lx and L represent a true cycle in this species. Furthermore, Lx responded dynamically to environmental conditions during long-term acclimation. Our data demonstrate the operation of a ‘true’ Lx cycle and, for the first time, its potential involvement in the regulation of non-photochemical quenching in situ. We propose dual regulation of Lx cycle in O. foetens, in which the extent of Lx restoration depends on the intensity and duration of illumination.

Natural ultraviolet radiation exposure alters photosynthetic biology and improves recovery from desiccation in a desert moss

2021 ◽  
Author(s):  
Jenna T B Ekwealor ◽  
Theresa A Clark ◽  
Oliver Dautermann ◽  
Alexander Russell ◽  
Sotodeh Ebrahimi ◽  
...  
Keyword(s):  
Ultraviolet Radiation ◽  
Thermal Quenching ◽  
Photochemical Quenching ◽  
Seasonal Fluctuations ◽  
Syntrichia Caninervis ◽  
Ultraviolet Radiation Exposure ◽  
Dryland Ecosystems ◽  
Solar Uv ◽  
Non Photochemical Quenching

Abstract Plants in dryland ecosystems experience extreme daily and seasonal fluctuations in light, temperature, and water availability. We used an in situ field experiment to uncover the effects of natural and reduced levels of ultraviolet radiation (UV) on maximum PSII quantum efficiency (Fv/Fm), relative abundance of photosynthetic pigments and antioxidants, and the transcriptome in the desiccation-tolerant desert moss Syntrichia caninervis. We tested the hypotheses that: (i) S. caninervis plants undergo sustained thermal quenching of light [non-photochemical quenching (NPQ)] while desiccated and after rehydration; (ii) a reduction of UV will result in improved recovery of Fv/Fm; but (iii) 1 year of UV removal will de-harden plants and increase vulnerability to UV damage, indicated by a reduction in Fv/Fm. All field-collected plants had extremely low Fv/Fm after initial rehydration but recovered over 8 d in lab-simulated winter conditions. UV-filtered plants had lower Fv/Fm during recovery, higher concentrations of photoprotective pigments and antioxidants such as zeaxanthin and tocopherols, and lower concentrations of neoxanthin and Chl b than plants exposed to near natural UV levels. Field-grown S. caninervis underwent sustained NPQ that took days to relax and for efficient photosynthesis to resume. Reduction of solar UV radiation adversely affected recovery of Fv/Fm following rehydration.

Measuring Radon and Thoron Levels in Sri Lanka

2013 ◽  
Vol 718-720 ◽  
pp. 721-724
Author(s):  
Deepal Subasinghe Nalaka ◽  
Mahakumara Prasad ◽  
Thusitha B. Nimalsiri ◽  
Nuwan B. Suriyaarchchi ◽  
Takeshi Iimoto ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Environmental Conditions ◽  
In Situ Measurements ◽  
Physical Factors ◽  
Preliminary Results ◽  
Radon Measurements ◽  
First Time

For the first time in Sri Lanka, an attempt was made to measure the outdoor radon levels using CR 39 type passive radon detectors. Preliminary results indicate that in Sri Lanka, 220Rn isotope is more abundance than 222Rn isotope. These results were also confirmed by in-situ measurements. Sri Lanka has one of the highest 220Rn values in the region. It was also noted that environmental conditions and other physical factors have a significant effect on the outdoor radon measurements using passive discriminative detectors.

scholarly journals An optimised method for correcting quenched fluorescence yield

2014 ◽  
Vol 11 (3) ◽  
pp. 1243-1264 ◽  
Author(s):  
L. Biermann ◽  
C. Guinet ◽  
M. Bester ◽  
A. Brierley ◽  
L. Boehme
Keyword(s):  
Light Intensity ◽  
Southern Ocean ◽  
Fluorescence Emission ◽  
Euphotic Zone ◽  
Fluorescence Yield ◽  
High Light Intensity ◽  
High Light ◽  
Photochemical Quenching ◽  
Non Photochemical Quenching

Abstract. Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. Previously, this has been done using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, the assumption of homogeneity is not robust in oceanic regimes that support deep chlorophyll maxima. To account for these features, we correct from the limit of the euphotic zone, defined as the depth at which light is at ~1% of the surface value. This method was applied to fluorescence data collected by eleven animal-borne fluorometers deployed in the Southern Ocean over four austral summers. Six tags returned data showing evidence of deep chlorophyll features. Using the depth of the euphotic layer, quenching was corrected without masking subsurface fluorescence signals.

MORPHODYNAMICS OF THE SHORES OF THE VISTULA SPIT (THE BALTIC SEA) IN A PERIOD OF 2002-2015 BY RESULTS OF IN-SITU MEASUREMENTS

2017 ◽  
Author(s):  
Valentina Bobykina ◽  
Valentina Bobykina ◽  
Boris Chubarenko ◽  
Boris Chubarenko ◽  
Konstantin Karmanov ◽  
...  
Keyword(s):  
Erosion Rate ◽  
The South ◽  
The Baltic Sea ◽  
The North ◽  
Quantitative Characteristics ◽  
The Subject ◽  
The Baltic ◽  
First Time

For the first time, the quantitative characteristics of the Vistula Spit shore dynamics based on the ground-based monitoring data for 2002-2015 were presented. On the sea shore, 3 sections can be distinguished by the direction of coastal processes, i.e. the stable section to the north of the Strait of Baltiysk, the eroded 4-km section to the south of the Strait of Baltiysk, with maximum erosion rate up to 2 m/year; in the remaining area of the Spit (21 km) to the Polish border there is an alternation of stable, eroded and accumulative areas. Since 2011, a steady erosion (in the stable segments of the third section) and general weakening of the erosion rate (in the second section) have been recorded. 50% of the length of the lagoon shore was the subject to annual active erosion (0.2 - 1.4 m/year). The beaches of the sea and lagoon shores of the Vistula Spit were mainly composed of medium sands. The alongshore variability in particle size distribution on the sea and lagoon shores (according to the 2015 survey data) actually fail to correlate with long-term dynamic processes, with the exception of the steadily eroded 4-kilometer area on the sea coast to the south of the Strait of Baltiysk. Variations in the composition of sediment along the shore on the shoreline are most likely associated with the results of the latest wave processing (or storm processing and eolian transport in the case of an average beach sample).

Abandonment Solution for Wells With Gauge Cables: An Engineered Self-Sealing Cement System

2021 ◽  
Author(s):  
Anton Rublevskyi ◽  
Carl Johnson ◽  
Chuang Hwee Tay ◽  
Darren Main ◽  
Axle Herrera
Keyword(s):  
Simulation Software ◽  
Fluid Simulation ◽  
Cost Cutting ◽  
Ability To Regenerate ◽  
Well Abandonment ◽  
First Time ◽  
Safety And Environment ◽  
Production Tubing

Abstract With an increasing number of wells transitioning to their abandonment stages, associated operational efficiency and cost cutting have become a major focus in the industry. An operator had an objective to permanently abandon an offshore well that was suspended in 2016. The key challenge was to develop a long-term well abandonment solution leaving the completion tubing and gauge cables in the well. All the associated operations had to be completed utilizing a lightweight well intervention vessel. Traditionally, retrieving the entire 5 ½-in. production tubing during plug and abandonment operations has added operational complexity and costs, which increases the risk of exposure to health, safety, and environment (HSE) hazards. Alternatively, a sealant technique placing cement through and around the completion tubing with gauge cables in situ exists. However, this technique is associated with a heightened risk of leak path development over time. Ongoing experimental work suggested that enhancements to the conventional cement sealant systems are beneficial to improve long-term sealing; thus, an active self-sealing cement (SSC) system that would seal microannuli or small fissures around the tubing and gauge cables was designed. The set cement sealant characteristics include low Young’s modulus to resist failure from wellbore stresses and the ability to regenerate the original seal upon contact with any hydrocarbons that may seep through any isolation defects through the life of the abandoned well. To achieve proper cement placement, advanced fluid simulation software and carefully tailored fluid density and rheology profiles were used. During the operation, a plug of the SSC sealant was pumped through the production tubing and squeezed into the perforations to create a permanent barrier across the reservoir section. Next, a mechanical plug was set inside the production tubing to isolate the lower section, and the tubing was perforated to provide access to the A-annulus above; subsequently, a balanced plug of SSC system was spotted above. After 30 hours, the plug passed a 3.4-MPa [500-psi] verification pressure test. The operator estimated the operation saved 2 to 3 days of rig time, valued at approximately GBP 400,000 to 600,000. The operator also avoided the risk of leaving the well on long-term suspension with mechanical plugs while waiting for a rig to complete the isolation, and the operation minimized the number of intervention steps required for abandonment, thereby limiting scope growth. Operators are constantly looking for ways to increase reliability, improve efficiency, and minimize risks; and therefore, abandonment techniques are evolving. The developed solution is a novel and robust alternative to conventional well abandonment using an advanced cement sealant technology for the first time and an innovative placement technique.

scholarly journals Antenna Protein Clustering In Vitro Unveiled by Fluorescence Correlation Spectroscopy

2021 ◽  
Vol 22 (6) ◽  
pp. 2969
Author(s):  
Aurélie Crepin ◽  
Edel Cunill-Semanat ◽  
Eliška Kuthanová Trsková ◽  
Erica Belgio ◽  
Radek Kaňa
Keyword(s):  
Fluorescence Correlation Spectroscopy ◽  
Higher Plants ◽  
Fluorescence Emission ◽  
Correlation Spectroscopy ◽  
Photochemical Quenching ◽  
High Ph ◽  
Fluorescence Correlation ◽  
Non Photochemical Quenching

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.

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