scholarly journals Photosynthetic responses of Halophila stipulacea to a light gradient. I. In situ energy partitioning of non-photochemical quenching

2009 ◽  
Vol 7 ◽  
pp. 143-152 ◽  
Author(s):  
JW Runcie ◽  
D Paulo ◽  
R Santos ◽  
Y Sharon ◽  
S Beer ◽  
...  
Keyword(s):  
Energy Partitioning ◽  
Photochemical Quenching ◽  
Halophila Stipulacea ◽  
Light Gradient ◽  
Photosynthetic Responses ◽  
Non Photochemical Quenching

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.

scholarly journals Photosynthetic responses of <i>Emiliania huxleyi</i> to UV radiation and elevated temperature: roles of calcified coccoliths

2011 ◽  
Vol 8 (6) ◽  
pp. 1441-1452 ◽  
Author(s):  
K. Xu ◽  
K. Gao ◽  
V. E. Villafañe ◽  
E. W. Helbling
Keyword(s):  
Elevated Temperature ◽  
Carbon Fixation ◽  
Emiliania Huxleyi ◽  
Photochemical Quenching ◽  
Photosynthetic Carbon Fixation ◽  
Level 3 ◽  
Two Temperatures ◽  
Photosynthetic Responses ◽  
Radiation Treatments ◽  
Non Photochemical Quenching

Abstract. Changes in calcification of coccolithophores may affect their photosynthetic responses to both, ultraviolet radiation (UVR, 280–400 nm) and temperature. We operated semi-continuous cultures of Emiliania huxleyi (strain CS-369) at reduced (0.1 mM, LCa) and ambient (10 mM, HCa) Ca2+ concentrations and, after 148 generations, we exposed cells to six radiation treatments (>280, >295, >305, >320, >350 and >395 nm by using Schott filters) and two temperatures (20 and 25 °C) to examine photosynthesis and calcification responses. Overall, our study demonstrated that: (1) decreased calcification resulted in a down regulation of photoprotective mechanisms (i.e., as estimated via non-photochemical quenching, NPQ), pigments contents and photosynthetic carbon fixation; (2) calcification (C) and photosynthesis (P) (as well as their ratio) have different responses related to UVR with cells grown under the high Ca2+ concentration being more resistant to UVR than those grown under the low Ca2+ level; (3) elevated temperature increased photosynthesis and calcification of E. huxleyi grown at high Ca2+ concentrations whereas decreased both processes in low Ca2+ grown cells. Therefore, a decrease in calcification rates in E. huxleyi is expected to decrease photosynthesis rates, resulting in a negative feedback that further reduces calcification.

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.

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.

scholarly journals Decreased calcification affects photosynthetic responses of <i>Emiliania huxleyi</i> exposed to UV radiation and elevated temperature

2011 ◽  
Vol 8 (1) ◽  
pp. 857-884
Author(s):  
K. Xu ◽  
K. Gao ◽  
V. E. Villafañe ◽  
E. W. Helbling
Keyword(s):  
Elevated Temperature ◽  
Carbon Fixation ◽  
Emiliania Huxleyi ◽  
Photochemical Quenching ◽  
Pigment Contents ◽  
Level 3 ◽  
Two Temperatures ◽  
Photosynthetic Responses ◽  
Radiation Treatments ◽  
Non Photochemical Quenching

Abstract. Changes in calcification of coccolithophores may affect their photosynthetic responses to both, ultraviolet radiation (UVR, 280–400 nm) and temperature. We operated semi-continuous cultures of Emiliania huxleyi (strain CS-369) at reduced (0.1 mM, LCa) and ambient (10 mM, HCa) Ca2+ concentrations and, after 148 generations, we exposed cells to six radiation treatments (>280, >295, >305, >320, >350 and >395 nm by using Schott filters) and two temperatures (20 and 25 °C) to examine photosynthesis and calcification responses. Overall, our study has demonstrated that: (1) decreased calcification resulted in a down regulation of photoprotective mechanisms (i.e., as estimated via non-photochemical quenching, NPQ), pigment contents and photosynthetic carbon fixation; (2) Calcification (C) and photosynthesis (P) (as well as their ratio) have different responses related to UVR with cells grown under the high Ca2+ concentration having a better performance as compared to those grown under the low Ca2+ level; (3) elevated temperature increased photosynthesis and calcification of E. huxleyi grown at high Ca2+ concentrations whereas the opposite was observed in low Ca2+ grown cells. Therefore, a decrease in calcification rates in E. huxleyi is expected to decrease photosynthesis rates and producing also a negative feedback, further reducing calcification.

scholarly journals Photosynthetic responses of Halophila stipulacea to a light gradient. II. Acclimations following transplantation

2009 ◽  
Vol 7 ◽  
pp. 153-157 ◽  
Author(s):  
Y Sharon ◽  
J Silva ◽  
R Santos ◽  
JW Runcie ◽  
M Chernihovsky ◽  
...  
Keyword(s):  
Halophila Stipulacea ◽  
Light Gradient ◽  
Photosynthetic Responses
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