scholarly journals Combined chlorophyll fluorescence techniques to study environmental impact on the mountain moss Polytrichum commune

2021 ◽  
Vol 11 (1) ◽  
pp. 161-173
Author(s):  
Gabriella Nora Maria Giudici
Keyword(s):  
Chlorophyll Fluorescence ◽  
Conformational Changes ◽  
Heat Dissipation ◽  
Fluorescence Induction ◽  
High Light ◽  
Chlorophyll Fluorescence Induction ◽  
Photochemical Quenching ◽  
Light Harvesting Complexes ◽  
Polytrichum Commune ◽  
Non Photochemical Quenching

Two chlorophyll fluorescence (ChlF) methods were used to study the effects of high light (photoinhibition) and dehydration, common stressors of the alpine environment, on primary photosynthetic processes in the moss Polytrichum commune from the Czech Republic, the Jeseníky Mountains. Photoinhibition (PI) was studied in fully hydrated thalli of P. commune and during the period of spontaneous desiccation. Time courses of Kautsky kinetics (KK) of ChlF and derived parameters: maximum quantum yield (FV/FM), effective quantum yeld (ΦPSII), and non-photochemical quenching parameters, were measured before and after the samples were treated with high light (1500 µmol m-2 s-1 PAR) for 60 min. Dehydration effects were tested in two sets of experiments with a Pulse-Amplitude-Modulation fluorometry (PAM) and Fast Chlorophyll Fluorescence induction curve (OJIP) techniques. In PAM tests, the desiccating samples were exposed to saturating light pulses every 10 min. in order to obtain ΦPSII and non-photochemical quenching (NPQ). In the second dehydration experiment, OJIP transients of ChlF were repeatedly recorded, OJIP-derived ChlF parameters were plotted against relative water content (RWC) monitored during desiccation. Combined ChF techniques provided insights into the mechanisms activated during P. commune desiccation, such as dissipation of excess absorbed energy through heat dissipation, and conformational changes or destructions of the light harvesting complexes. Combination of stressors resulted in amplified interference with the photosynthetic machinery, even when the added stressor (dehydration) was applied in low dose.

Contrasting pH-Optima of Light-Driven O2-and H2O2-Reduction in Spinach Chloroplasts as Measured via Chlorophyll Fluorescence Quenching

1991 ◽  
Vol 46 (7-8) ◽  
pp. 635-643 ◽  
Author(s):  
Ulrich Schreiber ◽  
Heinz Reising ◽  
Christian Neubauer
Keyword(s):  
Chlorophyll Fluorescence ◽  
Ascorbate Peroxidase ◽  
Electron Flow ◽  
Chlorophyll Fluorescence Induction ◽  
Monodehydroascorbate Reductase ◽  
Photochemical Quenching ◽  
Illumination Time ◽  
Saturation Pulse ◽  
Spinach Chloroplasts ◽  
Non Photochemical Quenching

Abstract Quenching analysis of chlorophyll fluorescence by the saturation pulse method is used to investigate the pH-dependency of O2-dependent electron flow in intact spinach chloroplasts with high ascorbate peroxidase activity. When carboxylase/oxygenase activity is blocked, pho­tochemical and non-photochemical quenching are initially low and increase with illumination time. Quenching shows a pH-optimum around pH 6.5, but only when ΔpH-formation is al­ lowed. It is suggested that overall O2-dependent electron flow involves two major components, namely O2-reduction (Mehlerreaction) and reduction of the H2O2 formed in the Mehlerreaction, involving enzymic activity of ascorbate peroxidase and monodehydroascorbate reductase. The separated pH-dependencies of light driven O2-reduction (presence of KCN) and of H2O2-reduction (anaerobic conditions) reveal contrasting pH-optima around pH 5 and 8.5, respectively. Energy-dependent, dark relaxable non-photochemical quenching is not observed with O2-reduction but with H2O2-reduction, and only at pH-values above 6.5. The relevance of these findings with respect to regulation of photosynthetic electron flow is discussed. It is suggested that upon limitation of assimilatory electron flow O2-dependent non-assimilatory flow is responsible for ΔpH-formation, by which it is autocatalytically stimulated. It is proposed that this autocatalytical reaction sequence is the basis of the so-called “Kautsky effect” of chlorophyll fluorescence induction.

scholarly journals Photosystem II Subunit PsbS Is Involved in the Induction of LHCSR Protein-dependent Energy Dissipation in Chlamydomonas reinhardtii

2016 ◽  
Vol 291 (33) ◽  
pp. 17478-17487 ◽  
Author(s):  
Viviana Correa-Galvis ◽  
Petra Redekop ◽  
Katharine Guan ◽  
Annika Griess ◽  
Thuy B. Truong ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Conformational Changes ◽  
Light Exposure ◽  
Complex Stress ◽  
High Light ◽  
Photochemical Quenching ◽  
Light Illumination ◽  
Non Photochemical Quenching ◽  
Psbs Protein

Non-photochemical quenching of excess excitation energy is an important photoprotective mechanism in photosynthetic organisms. In Arabidopsis thaliana, a high quenching capacity is constitutively present and depends on the PsbS protein. In the green alga Chlamydomonas reinhardtii, non-photochemical quenching becomes activated upon high light acclimation and requires the accumulation of light harvesting complex stress-related (LHCSR) proteins. Expression of the PsbS protein in C. reinhardtii has not been reported yet. Here, we show that PsbS is a light-induced protein in C. reinhardtii, whose accumulation under high light is further controlled by CO2 availability. PsbS accumulated after several hours of high light illumination at low CO2. At high CO2, however, PsbS was only transiently expressed under high light and was degraded after 1 h of high light exposure. PsbS accumulation correlated with an enhanced non-photochemical quenching capacity in high light-acclimated cells grown at low CO2. However, PsbS could not compensate for the function of LHCSR in an LHCSR-deficient mutant. Knockdown of PsbS accumulation led to reduction of both non-photochemical quenching capacity and LHCSR3 accumulation. Our data suggest that PsbS is essential for the activation of non-photochemical quenching in C. reinhardtii, possibly by promoting conformational changes required for activation of LHCSR3-dependent quenching in the antenna of photosystem II.

scholarly journals OJIP chlorophyll fluorescence induction profiles and plastoquinone binding affinity of the Photosystem II assembly intermediate PSII-I from Thermosynechococcus elongatus

2021 ◽  
Author(s):  
Jure Zabret ◽  
Marc M Nowaczyk
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Binding Affinity ◽  
Conformational Changes ◽  
Charge Recombination ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Acceptor Side ◽  
Assembly Intermediate

Binding of Psb28 to the photosystem II assembly intermediate PSII-I induces conformational changes to the PSII acceptor side that impact charge recombination and reduce the in situ production of singlet oxygen (Zabret et al. 2021, Nat. Plants 7, 524-538). A detailed fluorometric analysis of the PSII-I assembly intermediate compared with OEC-disrupted and Mn-depleted PSII complexes showed differences between their variable (OJIP) chlorophyll fluorescence induction profiles. These revealed a distinct destabilisation of the QA- state in the PSII-I assembly intermediate and inactivated PSII samples related to an increased rate of direct and safe charge recombination. Furthermore, inactivation or removal of the OEC increases the binding affinity for plastoquinone analogues like DCBQ to the different PSII complexes. These results might indicate a mechanism that further contributes to the protection of PSII during biogenesis or repair.

scholarly journals Linking remote sensing parameters to CO2 assimilation rates at a leaf scale

2021 ◽  
Author(s):  
Kouki Hikosaka ◽  
Katsuto Tsujimoto
Keyword(s):  
Remote Sensing ◽  
Chlorophyll Fluorescence ◽  
Heat Dissipation ◽  
Spatial Scales ◽  
Photochemical Efficiency ◽  
Co2 Assimilation ◽  
Photochemical Quenching ◽  
Future Prediction ◽  
Environmental Responses ◽  
Non Photochemical Quenching

AbstractSolar-induced chlorophyll fluorescence (SIF) and photochemical reflectance index (PRI) are expected to be useful for remote sensing of photosynthetic activity at various spatial scales. This review discusses how chlorophyll fluorescence and PRI are related to the CO2 assimilation rate at a leaf scale. Light energy absorbed by photosystem II chlorophylls is allocated to photochemistry, fluorescence, and heat dissipation evaluated as non-photochemical quenching (NPQ). PRI is correlated with NPQ because it reflects the composition of xanthophylls, which are involved in heat dissipation. Assuming that NPQ is uniquely related to the photochemical efficiency (quantum yield of photochemistry), photochemical efficiencies can be assessed from either chlorophyll fluorescence or PRI. However, this assumption may not be held under some conditions such as low temperatures and photoinhibitory environments. Even in such cases, photosynthesis may be estimated more accurately if both chlorophyll fluorescence and PRI are determined simultaneously. To convert from photochemical efficiency to CO2 assimilation, environmental responses in stomatal conductance also need to be considered. Models linking chlorophyll fluorescence and PRI with CO2 assimilation rates will contribute to understanding and future prediction of the global carbon cycle.

Light Absorption and Partitioning in Response to Nitrogen in Apple Leaves

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 541a-541
Author(s):  
Lailiang Cheng ◽  
Leslie H. Fuchigami ◽  
Patrick J. Breen
Keyword(s):  
High Light ◽  
Thermal Dissipation ◽  
Photochemical Quenching ◽  
Light Conditions ◽  
Psii Efficiency ◽  
Fluorescence Measurements ◽  
Free Radical Formation ◽  
Highly Correlated ◽  
Non Photochemical Quenching ◽  
Leaf N

Bench-grafted Fuji/M26 apple trees were fertigated with different concentrations of nitrogen by using a modified Hoagland solution for 6 weeks, resulting in a range of leaf N from 1.0 to 4.3 g·m–2. Over this range, leaf absorptance increased curvilinearly from 75% to 92.5%. Under high light conditions (1500 (mol·m–2·s–1), the amount of absorbed light in excess of that required to saturate CO2 assimilation decreased with increasing leaf N. Chlorophyll fluorescence measurements revealed that the maximum photosystem II (PSII) efficiency of dark-adapted leaves was relatively constant over the leaf N range except for a slight drop at the lower end. As leaf N increased, non-photochemical quenching under high light declined and there was a corresponding increase in the efficiency with which the absorbed photons were delivered to open PSII centers. Photochemical quenching coefficient decreased significantly at the lower end of the leaf N range. Actual PSII efficiency increased curvilinearly with increasing leaf N, and was highly correlated with light-saturated CO2 assimilation. The fraction of absorbed light potentially used for free radical formation was estimated to be about 10% regardless of the leaf N status. It was concluded that increased thermal dissipation protected leaves from photo-oxidation as leaf N declined.

scholarly journals Gradual Response of Cyanobacterial Thylakoids to Acute High-Light Stress—Importance of Carotenoid Accumulation

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1916
Author(s):  
Myriam Canonico ◽  
Grzegorz Konert ◽  
Aurélie Crepin ◽  
Barbora Šedivá ◽  
Radek Kaňa
Keyword(s):  
Single Cell ◽  
Thylakoid Membrane ◽  
Intermediate Phase ◽  
Light Stress ◽  
Fast Response ◽  
High Light ◽  
Photochemical Quenching ◽  
Second Phase ◽  
Ros Scavenging ◽  
Non Photochemical Quenching

Light plays an essential role in photosynthesis; however, its excess can cause damage to cellular components. Photosynthetic organisms thus developed a set of photoprotective mechanisms (e.g., non-photochemical quenching, photoinhibition) that can be studied by a classic biochemical and biophysical methods in cell suspension. Here, we combined these bulk methods with single-cell identification of microdomains in thylakoid membrane during high-light (HL) stress. We used Synechocystis sp. PCC 6803 cells with YFP tagged photosystem I. The single-cell data pointed to a three-phase response of cells to acute HL stress. We defined: (1) fast response phase (0–30 min), (2) intermediate phase (30–120 min), and (3) slow acclimation phase (120–360 min). During the first phase, cyanobacterial cells activated photoprotective mechanisms such as photoinhibition and non-photochemical quenching. Later on (during the second phase), we temporarily observed functional decoupling of phycobilisomes and sustained monomerization of photosystem II dimer. Simultaneously, cells also initiated accumulation of carotenoids, especially ɣ–carotene, the main precursor of all carotenoids. In the last phase, in addition to ɣ-carotene, we also observed accumulation of myxoxanthophyll and more even spatial distribution of photosystems and phycobilisomes between microdomains. We suggest that the overall carotenoid increase during HL stress could be involved either in the direct photoprotection (e.g., in ROS scavenging) and/or could play an additional role in maintaining optimal distribution of photosystems in thylakoid membrane to attain efficient photoprotection.

Fluorescence as a tool in photosynthesis research: application in studies of photoinhibition, cold acclimation and freezing stress

1989 ◽  
Vol 323 (1216) ◽  
pp. 281-293 ◽  
Keyword(s):  
Quantum Yield ◽  
Cold Acclimation ◽  
Spinacia Oleracea ◽  
Photosynthetic Apparatus ◽  
Fluorescence Induction ◽  
High Light ◽  
Thermal Dissipation ◽  
Freezing Stress ◽  
Chlorophyll Fluorescence Induction ◽  
Freezing And Thawing

Chlorophyll fluorescence induction (at 20 °C and 77 K) and quenching were analysed in relation to effects of environmental stresses imposed by chilling in high light and by freezing and thawing of spinach ( Spinacia oleracea L.) leaves. The data indicate that cold acclimation of spinach plants, which leads to increased frost tolerance of the leaves, results in decreased susceptibility to photoinhibition of photosynthesis at chilling temperatures. When plants acclimated to 18 °C and 260-300 µmol quanta m -2 s -1 were exposed to higher light (550 µmol quanta m -2 s -1 ) at 4 °C, they developed strong photoinhibition, as characterized by decreased quantum yield of O 2 evolution and decreased ratio of variable: maximum fluorescence (F V /F M ) of photosystem II. The decrease in F V /F M resulted from a decline in F V and an increase in F 0 . The F V /F M ratio was lowered to a significantly greater extent when induction was recorded at 20 °C, as compared with 77 K. The effects related to photoinhibition were fully reversible at 18 °C in dim light. Plants that had been cold-acclimated for 10 days exhibited slightly decreased quantum yield and lowered F V /F M ratio. However, they did not show further photoinhibition on exposure to 550 µmol quanta m -2 s -1 at 4 °C. The reversible photoinhibition is discussed as a protective pathway serving for thermal dissipation of excessive light energy. It is hypothesized that such a mechanism prevents destruction of the photosynthetic apparatus, until other means of protection become effective during long-term acclimation to high light. Inhibition of photosynthetic carbon assimilation caused by freezing and thawing of leaves in the dark was closely correlated with inhibition of photochemical fluorescence quenching (q Q ). As a sensitive response of the thylakoid membranes to freezing stress, the energy-dependent quenching, q E , was inhibited. Only more severe impact of freezing caused a significant decline in the F V /F M ratio. It is concluded that measurements of fluorescence induction signals ( F V /F M ratios) provide a sensitive tool with which to investigate photoinhibition, whereas freezing damage to the photosynthetic system can be detected more readily by the quenching coefficients q Q and q E than by F V /F M ratios.

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