scholarly journals Improving the accuracy of single turnover active fluorometry (STAF) for the estimation of phytoplankton primary productivity (PhytoPP)

2019 ◽  
Author(s):  
Tobias G. Boatman ◽  
Richard J. Geider ◽  
Kevin Oxborough
Keyword(s):  
Primary Productivity ◽  
Water Oxidation ◽  
Photochemical Efficiency ◽  
Fluorescence Emission ◽  
Reducing Power ◽  
Direct Methods ◽  
Reliable Estimate ◽  
Single Turnover ◽  
Package Effect ◽  
Psii Photochemistry

AbstractPhotosystem II (PSII) photochemistry is the ultimate source of reducing power for phytoplankton primary productivity (PhytoPP). Single turnover active chlorophyll fluorometry (STAF) provides a non-intrusive method that has the potential to measure PhytoPP on much wider spatiotemporal scales than is possible with more direct methods such as 14C fixation and O2 evolved through water oxidation. Application of a STAF-derived absorption coefficient for PSII light-harvesting (aLHII) provides a method for estimating PSII photochemical flux on a unit volume basis (JVPII). Within this study, we assess potential errors in the calculation of JVPII arising from sources other than photochemically active PSII complexes (baseline fluorescence) and the package effect. Although our data show that such errors can be significant, we identify fluorescence-based correction procedures that can be used to minimize their impact. For baseline fluorescence, the correction incorporates an assumed consensus PSII photochemical efficiency for dark-adapted material. The error generated by the package effect can be minimized through the ratio of variable fluorescence measured within narrow wavebands centered at 730 nm, where the re-absorption of PSII fluorescence emission is minimal, and at 680 nm, where re-absorption of PSII fluorescence emission is maximal. We conclude that, with incorporation of these corrective steps, STAF can provide a reliable estimate of JVPII and, if used in conjunction with simultaneous satellite measurements of ocean color, could take us significantly closer to achieving the objective of obtaining reliable autonomous estimates of PhytoPP.

scholarly journals Size-dependent susceptibility of lake phytoplankton to light stress: An implication for succession of large green algae in a deep oligotrophic lake

2021 ◽  
Author(s):  
Takehiro Kazama ◽  
Kazuhide Hayakawa ◽  
Takamaru Nagata ◽  
Koichi Shimotori ◽  
Akio Imai ◽  
...  
Keyword(s):  
Algal Blooms ◽  
Light Stress ◽  
Photochemical Efficiency ◽  
Early Summer ◽  
Photochemical Quenching ◽  
P Deficiency ◽  
Chl A ◽  
Psii Photochemistry ◽  
Small Phytoplankton ◽  
Nutrient Bioassay

Field observations of the population dynamics and measurements of photophysiology in Lake Biwa were conducted by size class (< vs. > 30 μm) from early summer to autumn to investigate the relationships between susceptibility to light stress and cell size. Also, a nutrient bioassay was conducted to clarify whether the growth rate and photosystem II (PSII) photochemistry of small and large phytoplankton are limited by nutrient availability. Large phytoplankton, which have lower intracellular Chl-a concentrations, had higher maximum PSII photochemical efficiency (Fv/Fm) but lower non-photochemical quenching (NPQNSV) than small phytoplankton under both dark and increased light conditions. The nutrient bioassay revealed that the PSII photochemistry of small phytoplankton was restricted by N and P deficiency at the pelagic site even at the end of the stratification period, while that of large phytoplankton was not. These results suggest that large phytoplankton have lower susceptibility to PSII photodamage than small phytoplankton due to lower intracellular Chl-a concentrations. The size dependency of susceptibility to PSII photoinactivation may play a key role in large algal blooms in oligotrophic water.

Further Studies of Proton Translocations in Chloroplasts After Single-Turnover Flashes. II. Proton Deposition

1984 ◽  
Vol 11 (4) ◽  
pp. 267 ◽  
Author(s):  
AB Hope ◽  
DB Matthews
Keyword(s):  
Electron Acceptor ◽  
Water Oxidation ◽  
Electron Flow ◽  
Neutral Red ◽  
S Phase ◽  
Cyclic Electron Flow ◽  
Slow Phase ◽  
Single Turnover ◽  
Q Cycle ◽  
Average Size

The deposition of protons in the inside spaces of pea class C chloroplasts was studied by means of the acidification of neutral red measured spectrophotometrically, with the outside space buffered. Careful kinetic analysis of such signals revealed three components, during non-cyclic electron flow induced by single-turnover flashes. These components included a 'slow' phase not emphasized in previous studies. The half-times of these phases were: 'Fast', < 1 ms (not resolved); 'Intermediate', 13-25 ms with added electron acceptor or 4 ms without; and 'Slow', 70-90 ms. Under conditions for cyclic electron flow only the I phase remained; it was the same magnitude as the I phase in non-cyclic flow, and its half-time was c. 3 ms. The F phase, which is usually attributed to protons from the oxidation of water, increased in average size with number of flashes (taken four flashes at a time) and was not fully patent until more than 20 flashes. The size of the I phase, which is usually attributed to protons from the oxidation of plastohydroquinone, when measured in a sequence of flashes to dark-adapted suspensions under non- cyclic conditions, had a binary oscillation in phase with the oscillation in proton uptake reported previously. It was concluded that protons leave PQH2 two at a time on alternate flashes. The S phase (average in 10 test flashes) was reduced by fast preflashes; an origin near photosystem II is suggested. The S phase may imply a small pool of proton-sequestering ability near the water oxidation site, or a number of other possibilities. In steady-state conditions, the ratio of the protons from PQH2 to those from water was 1.0 under all conditions examined except in the absence of added electron acceptor, when it was as high as 1.6. This was the only condition apparently indicating a Q-cycle, with infrequent single-turnover flashes.

Conformational Changes of the Membrane-Bound ATPase of Bacterial Chromatophores Revealed by Fluorescence Changes of Fluorescamine-Labelled Coupling Factors

1978 ◽  
Vol 33 (5-6) ◽  
pp. 421-427
Author(s):  
Peter Gräber ◽  
Sathamm Saphon
Keyword(s):  
Conformational Changes ◽  
Fluorescence Emission ◽  
Continuous Light ◽  
Coupling Factor ◽  
Single Turnover ◽  
Fluorescence Change ◽  
Transfer Inhibitor ◽  
Membrane Bound ◽  
Coupling Factors ◽  
Kinetics Of

Abstract The solubilized coupling factor (F1) of Rps. sphaeroides chromatophores was allowed to react with fiuorescamine which led to a fluorescence labelled F1 . After reconstitution with the depleted membranes the fluorescence-labelled F1 was shown to restore photophosphorylation in continuous light in a similar way to the non-labelled F1 . In parallel, a decrease of the fluorescence emission of the labelled and reconstituted coupling factor was observed. The solubilized and labelled F1 showed also a fluorescence decrease as the polarity of the medium was increased. In single turnover flashes the fluorescence change was found to be inhibited by an uncoupling agent such as FCCP. The kinetics of the change were sensitive to phosphorylating agents and to an “energy transfer inhibitor” such as venturicidin. It is suggested that the observed fluorescence changes reflect conformational changes of the ATPase enzyme complex.

scholarly journals Excess Zinc Supply Reduces Cadmium Uptake and Mitigates Cadmium Toxicity Effects on Chloroplast Structure, Oxidative Stress, and Photosystem II Photochemical Efficiency in Salvia sclarea Plants

Toxics ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 36
Author(s):  
Ilektra Sperdouli ◽  
Ioannis-Dimosthenis S. Adamakis ◽  
Anelia Dobrikova ◽  
Emilia Apostolova ◽  
Anetta Hanć ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Photosystem Ii ◽  
Adverse Effects ◽  
Cadmium Toxicity ◽  
Photochemical Efficiency ◽  
Antimicrobial Properties ◽  
Chloroplast Ultrastructure ◽  
Salvia Sclarea ◽  
Psii Photochemistry ◽  
Hoagland Nutrient Solution

Salvia sclarea L. is a Cd2+ tolerant medicinal herb with antifungal and antimicrobial properties cultivated for its pharmacological properties. However, accumulation of high Cd2+ content in its tissues increases the adverse health effects of Cd2+ in humans. Therefore, there is a serious demand to lower human Cd2+ intake. The purpose of our study was to evaluate the mitigative role of excess Zn2+ supply to Cd2+ uptake/translocation and toxicity in clary sage. Salvia plants were treated with excess Cd2+ (100 μM CdSO4) alone, and in combination with Zn2+ (900 μM ZnSO4), in modified Hoagland nutrient solution. The results demonstrate that S. sclarea plants exposed to Cd2+ toxicity accumulated a significant amount of Cd2+ in their tissues, with higher concentrations in roots than in leaves. Cadmium exposure enhanced total Zn2+ uptake but also decreased its translocation to leaves. The accumulated Cd2+ led to a substantial decrease in photosystem II (PSII) photochemistry and disrupted the chloroplast ultrastructure, which coincided with an increased lipid peroxidation. Zinc application decreased Cd2+ uptake and translocation to leaves, while it mitigated oxidative stress, restoring chloroplast ultrastructure. Excess Zn2+ ameliorated the adverse effects of Cd2+ on PSII photochemistry, increasing the fraction of energy used for photochemistry (ΦPSII) and restoring PSII redox state and maximum PSII efficiency (Fv/Fm), while decreasing excess excitation energy at PSII (EXC). We conclude that excess Zn2+ application eliminated the adverse effects of Cd2+ toxicity, reducing Cd2+ uptake and translocation and restoring chloroplast ultrastructure and PSII photochemical efficiency. Thus, excess Zn2+ application can be used as an important method for low Cd2+-accumulating crops, limiting Cd2+ entry into the food chain.

scholarly journals Fast enzymatic HCO3- dehydration supports photosynthetic water oxidation in Photosystem II from pea

2021 ◽  
Author(s):  
Alexandr V. Shitov ◽  
Vasily V. Terentyev ◽  
Govindjee Govindjee
Keyword(s):  
Photosystem Ii ◽  
Pisum Sativum ◽  
Water Oxidation ◽  
Photochemical Reactions ◽  
O2 Evolution ◽  
Donor Side ◽  
Psii Photochemistry ◽  
Similar Dependence ◽  
Enzymatic Nature ◽  
Photosynthetic Water Oxidation

Carbonic anhydrase (CA) activity, associated with Photosystem II (PSII) from Pisum sativum, has been shown to enhance water oxidation. But, the nature of the CA activity, its origin and role in photochemistry has been under debate, since the rates of CA reactions, measured earlier, were less than the rates of photochemical reactions. Here, we demonstrate high CA activity in PSII from Pisum sativum, measured by HCO3- dehydration at pH 6.5 (i.e. under optimal condition for PSII photochemistry), with kinetic parameters Km of 2.7 mM; Vmax of 2.74·10-2 mM·sec-1; kcat of 1.16·103 sec-1 and kcat/Km of 4.1·105 M-1 sec-1, showing the enzymatic nature of this activity, which kcat exceeds by ~13 times the rate of PSII, as measured by O2 evolution. The similar dependence of HCO3- dehydration, of the maximal quantum yield of photochemical reactions and of O2 evolution on the ratio of chlorophyll/photochemical reaction center II demonstrate the interconnection of these processes on the electron donor side of PSII. Since the removal of protons is critical for fast water oxidation, and since HCO3- dehydration consumes a proton, we suggest that CA activity, catalyzing very fast removal of protons, supports efficient water oxidation in PSII and, thus, photosynthesis in general.

scholarly journals Boosting photosynthetic machinery and defense priming with chitosan application on tomato plants infected with Fusarium oxysporum f. sp. lycopersici

2020 ◽  
Author(s):  
Sandra L. Carmona ◽  
Andrea del Pilar Villarreal-Navarrete ◽  
Diana Burbano-David ◽  
Magda Gómez-Marroquín ◽  
Esperanza Torres-Rojas ◽  
...  
Keyword(s):  
Fusarium Oxysporum ◽  
Stomatal Closure ◽  
Photochemical Efficiency ◽  
Defense Responses ◽  
Dry Mass ◽  
Systemic Resistance ◽  
Photochemical Quenching ◽  
Molecular Responses ◽  
Tomato Plants ◽  
Psii Photochemistry

AbstractPhysiological processes of plants infected by vascular pathogens are mainly affected by vascular bundle obstruction, decreasing the absorption of water and nutrients and gas exchange by stomatal closure, and inducing oxidative cascades and PSII alterations. Chitosan, a derivative of chitin present in the cell wall of some organisms including fungi, induces plant defense responses, activating systemic resistance. In this study, the effect of chitosan on the physiological and molecular responses of tomato plants infected with Fusarium oxysporum f. sp. lycopersici (Fol) was studied, evaluating the maximum potential quantum efficiency of PSII photochemistry (Fv/Fm), photochemical efficiency of PSII (Y(II)), photochemical quenching (qP), stomatal conductance (gs), relative water content (RWC), proline content, photosynthetic pigments, dry mass, and differential gene expression (PAL, LOXA, ERF1, and PR1) of defense markers. A reduction of 70% in the incidence and 91% in the severity of the disease was achieved in plants treated with chitosan, mitigating the damage caused by Fol on Fv/Fm, Y(II), and chlorophyll contents by 23%, 36%, and 47%, respectively. Less impact was observed on qP, gs, RWC, and dry mass (16%, 11%, and 26%, respectively). Chitosan-treated and Fol-infected plants over-expressed PR1a gene suggesting a priming-associated response. These results demonstrate the high potential of chitosan to protect tomato plants against Fol by regulating physiological and molecular responses in tomato plants.

scholarly journals Seasonal ecophysiological responses and behavior of phillyrea latifoliaspecie to climate change in Tunisia

2020 ◽  
Author(s):  
Khaoula Nefzi ◽  
Baraket Mokhtar ◽  
Maroua Herzi ◽  
Zouhair Nasr
Keyword(s):  
Climate Change ◽  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Photochemical Efficiency ◽  
Arid Ecosystems ◽  
Maximum Efficiency ◽  
Spring Season ◽  
Phillyrea Latifolia ◽  
Psii Photochemistry ◽  
Ecophysiological Responses

Abstract Background As part of global climate change, variation in precipitation in arid ecosystems is leading to plant adaptation in water-use strategies; significant interspecific differences in ecophysiological response will change the plant behavior. The mainaim of this study was to investigate the ecophysiological responses of Phillyrea latifolia species to seasonal drought stress. Measurements were conducted between March and December 2018. The parameters studied were the Leaf Water Potential (ψ leaf ), Net photosynthesis (Pn), stomatal conductance (gs) and leaf transpiration (Tr), maximum efficiency of PSII photochemistry (Fv/ Fm), and Hydraulic conductivity. Main results The results showed that all measured parameters varied significantly with the season(P <.0001). The results of ψ leaf showed the highest average in summer (−2.99±0.08 MPa). Likewise, the highest values of the maximal photochemical efficiency of PSII (Fv/Fm) were observed in summer (0.83±0.06). However, the highest values of Pn (3.62±0.41 µmol m -2 s -1 )and Tr (0.3±0.028 µmol m -2 s -1 ) were noted in autumn. The Initial Hydraulic Conductivity ( K in ) value was in spring (1.34 -04 ±110 -5 mmol s -1 m -2 MPa -1 ) and autumn (1.1810 -04 ±2.3010 -6 mmol s -1 m -2 MPa -1 ) and the Maximal Hydraulic Conductivity ( K max ) was the highest during the spring season (3.4510 -04 ±2.7010 -11 mmol s -1 m -2 MPa -1 ). The results of the Stomatal Conductance (gs)were showed that the lowest values were recorded in summer (0.19±0.04 MPa). The percentage of loss conductivity (PLC) reached 66%. During the spring season, the soil had a decreasing moisture profile as it moved to the depths and varied from 15.23±5.48% at 20cm to 6.26±2.46% at 80 cm. Conclusions The best physiological performances of Phillyrea latifolia reported in spring and autumn may be attributed to favorable environmental conditions. The answers depend not only on the specie but also on the climates in which they grow.

Thermostability and Photostability of Photosystem II of the Resurrection Plant Haberlea rhodopensis Studied by Chlorophyll Fluorescence

2006 ◽  
Vol 61 (3-4) ◽  
pp. 234-240 ◽  
Author(s):  
Katya Georgieva ◽  
Liliana Maslenkova
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Quantum Yield ◽  
Photochemical Efficiency ◽  
Resurrection Plant ◽  
Haberlea Rhodopensis ◽  
Photochemical Efficiency Of Psii ◽  
Light Intensities ◽  
Psii Photochemistry ◽  
Quantum Yield Of Psii

The stability of PSII in leaves of the resurrection plant Haberlea rhodopensis to high temperature and high light intensities was studied by means of chlorophyll fluorescence measurements. The photochemical efficiency of PSII in well-hydrated Haberlea leaves was not significantly influenced by temperatures up to 40 °C. F0 reached a maximum at 50 °C, which is connected with blocking of electron transport in reaction center II. The intrinsic efficiency of PSII photochemistry, monitored as Fv/Fm was less vulnerable to heat stress than the quantum yield of PSII electron transport under illumination (ΦPSII). The reduction of ΦPSII values was mainly due to a decrease in the proportion of open PSII centers (qP). Haberlea rhodopensis was very sensitive to photoinhibition. The light intensity of 120 μmol m−2 s−1 sharply decreased the quantum yield of PSII photochemistry and it was almost fully inhibited at 350 μmol m−2 s−1. As could be expected decreased photochemical efficiency of PSII was accompanied by increased proportion of thermal energy dissipation, which is considered as a protective effect regulating the light energy distribution in PSII. When differentiating between the three components of qN it was evident that the energy-dependent quenching, qE, was prevailing over photoinhibitory quenching, qI, and the quenching related to state 1-state 2 transitions, qT, at all light intensities at 25 °C. However, the qE values declined with increasing temperature and light intensities. The qI was higher than qE at 40 °C and it was the major part of qN at 45 °C, indicating a progressing photoinhibition of the photosynthetic apparatus.

scholarly journals   Arbuscular mycorrhizae improves photosynthesis and water status of Zea mays L. under drought stress

2012 ◽  
Vol 58 (No. 4) ◽  
pp. 186-191 ◽  
Author(s):  
X.C. Zhu ◽  
F.B. Song ◽  
S.Q. Liu ◽  
T.D. Liu ◽  
X. Zhou
Keyword(s):  
Zea Mays ◽  
Drought Stress ◽  
Zea Mays L ◽  
Water Status ◽  
Chlorophyll Concentration ◽  
Photochemical Efficiency ◽  
Fluorescence Maximum ◽  
Psii Photochemistry ◽  
Maize Plants ◽  
Mycorrhizal Plants

The influences of arbuscular mycorrhizal (AM) fungus on growth, gas exchange, chlorophyll concentration, chlorophyll fluorescence and water status of maize (Zea mays L.) plants were studied in pot culture under well-watered and drought stress conditions. The maize plants were grown in a sand and black soil mixture for 4 weeks, and then exposed to drought stress for 4 weeks. Drought stress significantly decreased AM colonization and total dry weight. AM symbioses notably enhanced net photosynthetic rate and transpiration rate, but decreased intercellular CO<sub>2</sub> concentration of maize plants regardless of water treatments. Mycorrhizal plants had higher stomatal conductance than non-mycorrhizal plants under drought stress. The concentrations of chlorophyll were higher in mycorrhizal than non-mycorrhizal plants under drought stress. AM colonization significantly increased maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency, but decreased primary fluorescence under well-watered and droughted conditions. Mycorrhizal maize plants had higher relative water content and water use efficiency under drought stress compared with non-mycorrhizal plants. The results indicated that AM symbiosis alleviates the toxic effect of drought stress via improving photosynthesis and water status of maize plants. &nbsp;

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