Carotenoids and Photosystem II Characteristics of Upper and Lower Halves of Leaves Acclimated to High Light

1996 ◽  
Vol 23 (6) ◽  
pp. 669 ◽  
Author(s):  
WW Iii Adams ◽  
B Demmig-Adams ◽  
DH Barker ◽  
S Kiley
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Total Energy ◽  
Xanthophyll Cycle ◽  
Lower Surface ◽  
Thylakoid Membranes ◽  
High Light ◽  
Pigment Composition ◽  
Light Gradient

Acclimation of the leaves or stems of four succulent species to different light environments and to the light gradient across high light-acclimated tissues was examined through measurements of chlorophyll fluorescence and characterisation of the pigment composition of the thylakoid membranes. Whereas the total amounts of light striking the upper (sun-exposed) and lower (self-shaded) surfaces were quite different, resulting in a much smaller pool of the xanthophyll cycle carotenoids in the lower halves of high light-acclimated tissues, the conversion state of the xanthophyll cycle (the degree to which violaxanthin is converted to antheraxanthin and zeaxanthin) was similar throughout the tissues during exposure to natural sunlight. Under full sunlight, less than 25% of the light absorbed by the upper surface was utilised through photosynthesis, with the majority of the remaining excitation energy being dissipated thermally. In contrast, a considerably greater fraction of the light absorbed by the lower surface was utilised in photosynthesis, ranging from one-third to more than two-thirds of the total energy absorbed.

Xanthophyll cycle, light energy dissipation and photosystem II down-regulation in senescent leaves of wheat plants grown in the field

2001 ◽  
Vol 28 (10) ◽  
pp. 1023 ◽  
Author(s):  
Congming Lu ◽  
Qingtao Lu ◽  
Jianhua Zhang ◽  
Qide Zhang ◽  
Tingyun Kuang
Keyword(s):  
Energy Dissipation ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Xanthophyll Cycle ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Down Regulation ◽  
Psii Efficiency ◽  
Psii Photochemistry ◽  
Assimilation Capacity

Photosynthesis, the xanthophyll cycle, light energy dissipation and down-regulation of photosystem II (PSII) in senescent leaves of wheat plants grown in the field were investigated. With the progress of senescence, maximal efficiency of PSII photochemistry decreased only slightly early in the morning but substantially at midday. Actual PSII efficiency, photochemical quenching, efficiency of excitation capture by open PSII centres, and the I–P phase of fluorescence induction curves decreased significantly and such decreases were much more evident at midday than in the morning. At the same time, non-photochemical quenching, thermal dissipation and de-epoxidation status of the xanthophyll cycle increased, with much greater increases at midday than in the morning. These results suggest that the xanthophyll cycle played a role in photoprotection of PSII in senescent leaves by dissipating excess excitation energy. Taking into account the substantial decrease in photosynthetic capacity in senescent leaves, our data seem to support the view that the decrease in actual PSII efficiency in senescent leaves may represent a mechanism to down-regulate photosynthetic electron transport to match the decreased CO2 assimilation capacity and avoid photodamage of PSII from excess excitation energy.

scholarly journals Changes in Photo-Protective Energy Dissipation of Photosystem II in Response to Beneficial Bacteria Consortium in Durum Wheat under Drought and Salinity Stresses

2020 ◽  
Vol 10 (15) ◽  
pp. 5031 ◽  
Author(s):  
Mohammad Yaghoubi Khanghahi ◽  
Sabrina Strafella ◽  
Carmine Crecchio
Keyword(s):  
Chlorophyll Fluorescence ◽  
Energy Dissipation ◽  
Quantum Yield ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Durum Wheat ◽  
Photochemical Quenching ◽  
Plant Growth Promoting Bacteria ◽  
Psii Photochemistry ◽  
Non Photochemical Quenching

The present research aimed at evaluating the harmless dissipation of excess excitation energy by durum wheat (Triticum durum Desf.) leaves in response to the application of a bacterial consortium consisting of four plant growth-promoting bacteria (PGPB). Three pot experiments were carried out under non-stress, drought (at 40% field capacity), and salinity (150 mM NaCl) conditions. The results showed that drought and salinity affected photo-protective energy dissipation of photosystem II (PSII) increasing the rate of non-photochemical chlorophyll fluorescence quenching (NPQ (non-photochemical quenching) and qCN (complete non-photochemical quenching)), as well as decreasing the total quenching of chlorophyll fluorescence (qTQ), total quenching of variable chlorophyll fluorescence (qTV) and the ratio of the quantum yield of actual PSII photochemistry, in light-adapted state to the quantum yield of the constitutive non-regulatory NPQ (PQ rate). Our results also indicated that the PGPB inoculants can mitigate the adverse impacts of stresses on leaves, especially the saline one, in comparison with the non-fertilized (control) treatment, by increasing the fraction of light absorbed by the PSII antenna, PQ ratio, qTQ, and qTV. In the light of findings, our beneficial bacterial strains showed the potential in reducing reliance on traditional chemical fertilizers, in particular in saline soil, by improving the grain yield and regulating the amount of excitation energy.

scholarly journals High-Light versus Low-Light: Effects on Paired Photosystem II Supercomplex Structural Rearrangement in Pea Plants

2020 ◽  
Vol 21 (22) ◽  
pp. 8643
Author(s):  
Alessandro Grinzato ◽  
Pascal Albanese ◽  
Roberto Marotta ◽  
Paolo Swuec ◽  
Guido Saracco ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photosystem Ii ◽  
Structural Rearrangement ◽  
Structural Features ◽  
Thylakoid Membranes ◽  
Variable Number ◽  
High Light ◽  
Low Light ◽  
Cryo Electron Microscopy ◽  
Light Effects

In plant grana thylakoid membranes Photosystem II (PSII) associates with a variable number of antenna proteins (LHCII) to form different types of supercomplexes (PSII-LHCII), whose organization is dynamically adjusted in response to light cues, with the C2S2 more abundant in high-light and the C2S2M2 in low-light. Paired PSII-LHCII supercomplexes interacting at their stromal surface from adjacent thylakoid membranes were previously suggested to mediate grana stacking. Here, we present the cryo-electron microscopy maps of paired C2S2 and C2S2M2 supercomplexes isolated from pea plants grown in high-light and low-light, respectively. These maps show a different rotational offset between the two supercomplexes in the pair, responsible for modifying their reciprocal interaction and energetic connectivity. This evidence reveals a different way by which paired PSII-LHCII supercomplexes can mediate grana stacking at diverse irradiances. Electrostatic stromal interactions between LHCII trimers almost completely overlapping in the paired C2S2 can be the main determinant by which PSII-LHCII supercomplexes mediate grana stacking in plants grown in high-light, whereas the mutual interaction of stromal N-terminal loops of two facing Lhcb4 subunits in the paired C2S2M2 can fulfil this task in plants grown in low-light. The high-light induced accumulation of the Lhcb4.3 protein in PSII-LHCII supercomplexes has been previously reported. Our cryo-electron microscopy map at 3.8 Å resolution of the C2S2 supercomplex isolated from plants grown in high-light suggests the presence of the Lhcb4.3 protein revealing peculiar structural features of this high-light-specific antenna important for photoprotection.

Antarctic strain of green filamentous alga Zygnema sp. shows a high resistance to photoinhibition under simulated polar conditions

2015 ◽  
Vol 5 (2) ◽  
pp. 176-184 ◽  
Author(s):  
Giridharan Thangaraj
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
High Resistance ◽  
Austral Summer ◽  
High Light ◽  
Filamentous Alga ◽  
Fluorescence Signal ◽  
Light Harvesting Complexes ◽  
Chlorophyll Fluorescence Parameters ◽  
Fluorescence Parameters

This study deals with treatment-dependent differences in sensitivity of Antarctic filamentous alga Zygnema sp. to photoinhibition. Zygnema sp. (strain EEL201) was collected at the James Ross Island, Antarctica (57° 52´ 57´´ W, 63° 48´ 02´´ S). In a laboratory, the alga was cultivated on agar first and then innoculated to liquid medium. They were exposed to a short-term (30 min.) high light (HL) treatments. Particular treatments comprised 600, 1 400 and 2 100 and 3 500 μmol m-2 s-1 of photosynthetically active radiation (PAR). Photosynthetic efficiency of Zygnema sp. in individual HL treatments was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. Zygnema sp. showed a high resistance to HL since it both chlorophyll fluorescence parameters recovered to about 70% of initial values after 4 h in dark. Chlorophyll fluorescence measured immediately after particular treatment, showed HL-dependent decrease in absolute values of chlorophyll fluorescence signal and consequent uncompleted recovery as well. Quenching of F0, an indicator of changes in light-harvesting complexes of photosystem II, did not show dose-dependent response, however, general trend was a decrease found immediately HL treatment with consequent uncompleated recovery. In general, Zygnema sp. exhibited high resistance to PAR doses that the species can whitness in the field during austral summer. Thus the species could be considered highly adapted for high light and has effective mechanisms to cope with photoinhibition. Involvement of particular photoprotective mechanism, their activation and share in natural environment is a topic for future studies.

scholarly journals Slr0320 is Crucial for Optimal Function of Photosystem II during High Light Acclimation in Synechocystis sp. PCC 6803

Life ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 279
Author(s):  
Hao Zhang ◽  
Haitao Ge ◽  
Ye Zhang ◽  
Yingchun Wang ◽  
Pengpeng Zhang
Keyword(s):  
Electron Transfer ◽  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Expression Profiles ◽  
Net Photosynthesis ◽  
High Light ◽  
Psii Activity ◽  
Optimal Function ◽  
Synechocystis Sp ◽  
Pcc 6803

Upon exposure of photosynthetic organisms to high light (HL), several HL acclimation responses are triggered. Herein, we identified a novel gene, slr0320, critical for HL acclimation in Synechocystis sp. PCC 6803. The growth rate of the Δslr0320 mutant was similar to wild type (WT) under normal light (NL) but severely declined under HL. Net photosynthesis of the mutant was lower under HL, but maximum photosystem II (PSII) activity was higher under NL and HL. Immunodetection revealed the accumulation and assembly of PSII were similar between WT and the mutant. Chlorophyll fluorescence traces showed the stable fluorescence of the mutant under light was much higher. Kinetics of single flash‐induced chlorophyll fluorescence increase and decay revealed the slower electron transfer from QA to QB in the mutant. These data indicate that, in the Δslr0320 mutant, the number of functional PSIIs was comparable to WT even under HL but the electron transfer between QA and QB was inefficient. Quantitative proteomics and real‐time PCR revealed that expression profiles of psbL, psbH and psbI were significantly altered in the Δslr0320 mutant. Thus, Slr0320 protein plays critical roles in optimizing PSII activity during HL acclimation and is essential for PSII electron transfer from QA to QB.

Mechanism of Non-Photochemical Chlorophyll Fluorescence Quenching. I. The Role of De-Epoxidised Xanthophylls and Sequestered Thylakoid Membrane Protons as Probed by Dibucaine

1995 ◽  
Vol 22 (2) ◽  
pp. 231 ◽  
Author(s):  
N Mohanty ◽  
HY Yamamoto
Keyword(s):  
Chlorophyll Fluorescence ◽  
Fluorescence Quenching ◽  
Xanthophyll Cycle ◽  
Thylakoid Membranes ◽  
Photochemical Quenching ◽  
Chlorophyll Fluorescence Quenching ◽  
Mechanism Of Inhibition ◽  
Non Photochemical Quenching ◽  
Energy Dependent

Dibucaine reportedly inhibits the light-induced transthylakoid proton gradient of chloroplasts without inhibiting energy-dependent non-photochemical chlorophyll fluorescence quenching (Laasch, H. and Weis, E. (1989). Photosynthesis Research 22, 137-146). We show that dibucaine can inhibit fluorescence quenching, depending on the de-epoxidation state of the xanthophyll cycle. Whereas dibucaine (20-40 μM) had little effect on fluorescence quenching in pre-illuminated-type thylakoids (loaded with zeaxanthin and antheraxanthin), it strongly inhibited quenching in dark-adapted-type thylakoids (no preinduction of de-epoxidation). Dibucaine inhibited lumen acidification similarly in both types of thylakoids and also the induction of violaxanthin de-epoxidation in dark-adapted thylakoids. Thus dark-adapted and pre-illuminated thylakoids differed in de-epoxidation states and their suspectibility to dibucaine inhibition of fluorescence quenching corresponded to this difference. The mechanism of inhibition of de-epoxidation by dibucaine is unclear. It could be due to the inhibition of lumen acidification but an inhibition of the violaxanthin available for de-epoxidation is not excluded. High dibucaine concentrations inhibited de-epoxidase activity directly. Dibucaine inhibition of fluorescence quenching, however, is not limited to the inhibition of de-epoxidation. Small but clear effects on fluorescence quenching were present in thylakoids even with de-epoxidation preinduced. Moreover, thylakoids with preinduced de-epoxidation were more resistant to dibucaine inhibition of fluorescene quenching when poised by salt treatments for proton partitioning into membrane-sequestered domains than when poised for proton partitioning into delocalised domains. We conclude that non-photochemical quenching of chlorophyll fluorescence depends on both de-epoxidised xanthophylls and sequestered proton domains in the thylakoid membranes

scholarly journals The carotenoid pathway: what is important for excitation quenching in plant antenna complexes?

2017 ◽  
Vol 19 (34) ◽  
pp. 22957-22968 ◽  
Author(s):  
Kieran F. Fox ◽  
Vytautas Balevičius ◽  
Jevgenij Chmeliov ◽  
Leonas Valkunas ◽  
Alexander V. Ruban ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Excitation Energy ◽  
Light Harvesting ◽  
High Light ◽  
Photochemical Quenching ◽  
Non Photochemical Quenching ◽  
Carotenoid Pathway

Plant light-harvesting is regulated by the Non-Photochemical Quenching (NPQ) mechanism involving the slow trapping of excitation energy by carotenoids in the Photosystem II (PSII) antenna in response to high light.

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