scholarly journals Tolerance of tropical marine microphytobenthos exposed to elevated irradiance and temperature

2021 ◽  
Vol 18 (19) ◽  
pp. 5313-5326
Author(s):  
Sazlina Salleh ◽  
Andrew McMinn
Keyword(s):  
Quantum Yield ◽  
Photosynthetic Activity ◽  
Elevated Temperatures ◽  
High Tide ◽  
Temperature Threshold ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Irreversible Damage ◽  
Recovery Rates

Abstract. The photosynthetic productivity of tropical microphytobenthos (MPB) is largely driven by changes in light intensities and temperature at the surface of sediment flats during emersion. Here, the response of the MPB community to temperature and light was examined. Changes in temperature and irradiance during tidal cycles in the Tanjung Rhu estuary, Langkawi, Malaysia, in 2007 significantly affected the photosynthetic capacities of the MPB. Higher photosynthetic parameters, such as the maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), maximum quantum yield (Fv/Fm), and effective quantum yield (ΔF/Fm′), were recorded at high tide when the temperatures were lower. However, when the community was experimentally exposed to irradiances of 1800 µmol photons m−2 s−1, it was only able to photosynthesize at temperatures < 50 ∘C. Above this temperature, no photosynthetic activity was observed. Not only did high temperatures at high irradiance affect the algal communities, but limited photosynthetic activity was also observed in samples when exposed to limited irradiance. Recovery rates were highest at the lowest temperatures and decreased as the temperature increased. The recovery rates for samples exposed to temperatures of 40 ∘C were 4.01×10-3±0.002 s−1 and decreased to 1.01×10-5±0.001 s−1 at 60 ∘C, indicating irreversible damage to Photosystem II (PSII). These characteristics suggest that the MPB communities in this estuary were able to adapt to temperature variation. However, enhanced photoinhibition would result if exposed to elevated temperatures, especially during low tide where in situ temperature was already 43 ∘C. Hence, if in situ temperature were to further increase during tidal emersion, 50 ∘C could be a temperature threshold for photosynthetic performance of tropical estuarine benthic microalgal communities.

scholarly journals Response of tomato seedlings inoculated with mycorrhizal fungi on the photosynthetic activity, growth, and health status of plants after infection with the fungus Colletotrichum coccodes

2019 ◽  
Vol 72 (4) ◽  
Author(s):  
Agnieszka Jamiołkowska ◽  
Barbara Skwaryło-Bednarz ◽  
Władysław Michałek
Keyword(s):  
Health Status ◽  
Quantum Yield ◽  
Mycorrhizal Fungi ◽  
Photosynthetic Activity ◽  
Pathogenic Fungus ◽  
Colletotrichum Coccodes ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Tomato Seedlings ◽  
Absolute Control

The aim of this study was to estimate the effect of mycorrhizal fungi (MF) on the photosynthetic activity, growth, and health status of tomato seedlings (‘Pelikan F<sub>1</sub>’) infected with the pathogenic fungus <em>Colletotrichum coccodes</em>. A commercial mycorrhizal inoculum (Mycoflor, Poland) containing spores and dormant mycelium of MF was used in the experiment. It was carried out in a growth chamber where 1-week-old seedlings were inoculated with 3 mL of mycorrhizal inoculum applied into the soil. Three-week old mycorrhized and nonmycorrhized tomato seedlings were infected with the pathogenic fungus. Seedlings planted in sterile horticultural soil without the mycorrhizal inoculum constituted an absolute control. The growth, disease index, and photosynthetic activity of the plants were measured after 4 weeks. There was no significant effect of the mycorrhiza on the photosynthetic parameters analyzed. However, it was noted that the mycorrhized and pathogen-infected seedlings had higher maximum quantum yield of PSII (F<sub>v</sub>/F<sub>m</sub>), higher effective quantum yield (Y) and more favorable photochemical (qP) and nonphotochemical fluorescence quenching (qN) coefficients than did the pathogen-infected seedlings. The experiment showed that the mycorrhizal commercial inoculum had varied effects on the health status of tomato seedlings depending on the pathogenic fungus isolate. Mycorrhiza did not have a significant effect on the length of roots and stems, whereas the roots inoculated with MF were better developed than those infected with the pathogenic fungus. It can be assumed also that not only the pathogen but also the mycorrhiza is a stress factor towards the seedlings and affects the growth performance parameters mentioned above.

scholarly journals Response of tropical marine benthic diatoms exposed to elevated irradiance and temperature

2021 ◽  
Author(s):  
Sazlina Salleh ◽  
Andrew McMinn
Keyword(s):  
Quantum Yield ◽  
Electron Transport Rate ◽  
High Tide ◽  
Benthic Diatoms ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Tidal Cycles ◽  
Relative Electron Transport Rate ◽  
Diatom Communities ◽  
Relative Electron

Abstract. Shallow tropical marine environments are likely to experience future water temperatures that will challenge the ability of life to survive. Changes in temperature and irradiance during tidal cycles in the Tanjung Rhu estuary, Langkawi, Malaysia in 2007 did not significantly affect the benthic diatom communities, although, higher photosynthetic parameters, such as maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), maximum quantum yield (Fv/Fm) and effective quantum yield (∆F/Fm'), were recorded at high tide when the temperatures were lower. However, when benthic diatoms were experimentally exposed to irradiances of 1800 µmol photons m−2 s−1, they were only able to photosynthesize at temperatures

Local adaptation of a Lessepsian invader species to winter conditions in the Mediterranean Sea

2021 ◽  
Author(s):  
Débora Silva Raposo ◽  
Raphaël Morard ◽  
Christiane Schmidt ◽  
Michal Kucera
Keyword(s):  
Quantum Yield ◽  
Mediterranean Sea ◽  
Red Sea ◽  
Photosynthetic Activity ◽  
Eastern Mediterranean ◽  
Effective Quantum Yield ◽  
Mediterranean Populations ◽  
Cold Temperatures ◽  
Invasion Front ◽  
The Mediterranean

&lt;p&gt;In recent decades the &amp;#8220;Lessepsian&amp;#8221; migration caused a rapid change in the marine community composition due to the invasion of alien species from the Red Sea into the Mediterranean Sea. Among these invaders is the large benthic foraminifera &lt;em&gt;Amphistegina lobifera&lt;/em&gt;, a diatom-bearing species that recently reached the invasion front in Sicily. There it copes with colder winters and broader temperature than in its original source, the Red Sea. It is not yet known how (or if) the population from the invasion front has developed adaptation to this new thermal regime. Understanding the modern marine invasive patterns is a crucial tool to predict future invasive successes in marine environments. Therefore, in this study we aim to evaluate the physiological responses to cold temperatures of &lt;em&gt;A. lobifera&lt;/em&gt; populations at three different invasive stages: source (Red Sea), early invader (Eastern Mediterranean) and invasion front (Sicily). For this, we conducted a culturing experiment in which we monitored the responses of the foraminifera (growth, motility) to temperatures of 10, 13, 16, 19&amp;#176;C + control (25&amp;#176;C) over four weeks. To address what is the role of their endosymbionts in the adaptation process, we also monitored their photosynthetic activity (Pulse Amplitude Modulation - PAM fluorometer) during the experiment. The growth rate of the foraminifera was reduced for all populations below 19&amp;#176;C as well as the motility, reduced until 16&amp;#176;C and dropping to zero below 13&amp;#176;C. The response of the endosymbionts was however different. There was a reduced photosynthetic activity of the Red Sea and Eastern Mediterranean populations at colder temperatures observed by the lower maximum quantum yield (Fv:Fm) and effective quantum yield (Y(II)), when compared to their initial levels and to the other treatments. In the meantime, the endosymbionts of the Sicily population stood out with the highest photosynthetic activity (Fv:Fm and Y(II)) in the treatments bellow 13 &amp;#176;C (P &lt; 0.05). In conclusion, we observed that while the host responses were similar between the three populations, the endosymbionts from the invasion front population shows the best performance at colder temperatures. This suggests that the photo-symbiosis has an important role in adaptation, most likely being a key factor to the success of past and future migrations.&lt;/p&gt;

scholarly journals PHOTOSYNTHETIC PARAMETERS AS PHYSIOLOGICAL INDICATORS OF TOLERANCE TO CADMIUM STRESS IN SUNFLOWER GENOTYPES

2018 ◽  
Vol 31 (4) ◽  
pp. 907-916 ◽  
Author(s):  
Bárbara Lima do Sacramento ◽  
André Dias de Azevedo Neto ◽  
Andréia Teixeira Alves ◽  
Silvany Cardim Moura ◽  
Rogério Ferreira Ribas
Keyword(s):  
Stomatal Conductance ◽  
Quantum Yield ◽  
Nutrient Solution ◽  
Photosynthetic Pigment ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Cd Stress ◽  
Physiological Indicators ◽  
Net Assimilation ◽  
Tolerance To Cadmium

ABSTRACT The objective of the present study was to evaluate the tolerance to cadmium (Cd) of sunflower genotypes grown in greenhouse conditions, and the effectiveness of using photosynthetic parameters as physiological indicators of this tolerance. Seeds of two sunflower genotypes previously identified as tolerant (H358) and Cd-sensitive (AG960) to Cd were used. The seeds were germinated in plastic cups containing plant substrate; after 9 days, the seedlings were transplanted to plastic basins containing a nutrient solution with 0 or 10 µM of Cd, where they remained for 16 days. Samples of the plants were harvested every 5 days. The experiment was carried out in a randomized complete design, using a 4×2×2 factorial arrangement (4 days of grown in a nutrient solution with Cd, 2 sunflower genotypes, and 2 Cd levels) with four replications. Cd stress decreased CO2 net assimilation, stomatal conductance, carboxylation efficiency, photosynthetic pigment contents, potential quantum yield (Fv/Fm), and effective quantum yield of plants of the two evaluated genotypes. The decrease in photosynthetic rates of these plants was caused by both stomatal and non-stomatal limitations. Plants of the AG960 genotype showed more pronounced deleterious effects due to Cd stress than those of the H358 genotype. Thus, CO2 net assimilation rate, stomatal conductance, and chloroplast pigment content are good physiological indicators of sunflower tolerance to Cd and can at least in part, explain the greater tolerance of the H358 genotype to Cd stress when compared to the AG960 genotype.

scholarly journals Fire Blight Management: Physiological Assessment of Cultural Control By Pruning in Pear Orchards

2020 ◽  
Vol 66 (3) ◽  
pp. 128-136
Author(s):  
Rafael J. Mendes ◽  
Nuno Mariz-Ponte ◽  
Cristiana V. Correia ◽  
Maria Celeste Dias ◽  
Miguel Leão De Sousa ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Gas Exchange ◽  
Fire Blight ◽  
Soluble Sugars ◽  
Photosynthetic Performance ◽  
Cultural Control ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Total Soluble Sugars ◽  
Bisphosphate Carboxylase

AbstractThe aim of this work was to evaluate the photosynthetic performance of Pear trees (cv. ‘Rocha’) infected with Erwinia amylovora, three months after suffering a pruning of infected branches (P-trees) compared with asymptomatic trees (C-trees) of the same orchard. Three months after pruning, P-trees looked healthy and were negative for the presence of E. amylovora. In September of 2018, fully expanded leaves of both P- and C- trees were sampled and analysed for photosynthetic parameters related to chlorophyll a fluorescence and gas exchange, alongside with pigments, total soluble sugars, starch, and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) contents. No significant differences were found in chlorophyll and carotenoids levels, but anthocyanins significantly decreased in P-trees. Also, despite the maximum quantum yield (Fv/Fm) significantly decreased in P-trees, the effective quantum yield of the PSII was maintained, paralleled with no changes in gas exchange parameters (PN, gs, Ci, E, iWUE, PN/gs), nor in RuBisCO relative content. Finally, the maintenance of the levels of total soluble sugars and starch also supports that the photosynthetic performance of P-trees, three months after pruning, reached values similar to those of the C-trees, contributing to the normal development and ripening of the fruit. Data support that pruning represents a reliable control measure against this quarantine pathogen. This work is the first evaluation of pruning in fire blight management regarding carbon metabolism in P. communis trees.

Research Note: Measuring variability in chlorophyll-fluorescence-derived photosynthetic parameters in situ with a programmable multi-channel fluorometer

2004 ◽  
Vol 31 (5) ◽  
pp. 559 ◽  
Author(s):  
John W. Runcie ◽  
Martin J. Riddle
Keyword(s):  
Chlorophyll Fluorescence ◽  
Single Channel ◽  
Light Response ◽  
Photosynthetic Parameters ◽  
Effective Quantum Yield ◽  
Response Curves ◽  
Mean Values ◽  
Pam Fluorometer ◽  
Relative Electron

A submersible device was constructed for simultaneous in situ measurement of the effective quantum yield of chlorophyll fluorescence (ΔF / Fm′) of eight macroalgal samples. The device incorporated a commercially available PAM fluorometer. Four samples each of the macroalgae Iridaea mawsonii (Lucas) and Monostroma hariotii (Gain) were examined. ΔF / Fm′ and light-response curves (LCs) were regularly applied over 24 h to estimate diel changes in relative electron transport rates and the relative efficiency of photon conversion at low irradiances (α), and the variance attributable to mean values of both ΔF / Fm′ and α were estimated. A second commercial single-channel fluorometer provided an independent measure of variability in LC parameters between individual samples, and the magnitude of this variability was within the range measured with the multi-channel device. Between-sample variability at noon, measured with the multi-channel device, was significantly greater than at other times of the day. ΔF / Fm′ of M. hariotii were not significantly different throughout most of the day except at midnight, when values were significantly higher. In contrast, over 24-h only ΔF / Fm′ of I. mawsonii at noon (growing in low light) was significantly lower. By providing replicate LCs at each time point, the programmable multi-channel fluorometer enables testing of significant differences in photosynthetic parameters over a diel period.

Photosynthesis ecophysiology of polar Vaucheria sp. – inter-annual comparison

2019 ◽  
Vol 9 (2) ◽  
pp. 141-151
Author(s):  
Jana Kvíderová ◽  
Josef Elster
Keyword(s):  
Quantum Yield ◽  
Air Temperature ◽  
Microbial Mats ◽  
Photosynthetic Activity ◽  
Red Light ◽  
Ex Situ ◽  
Effective Quantum Yield ◽  
Excitation Light ◽  
Fluorescence Measurements ◽  
Arctic Summer

The Vaucheria sp. microbial mats represent the most important primary producer in the tidal flat in Adventdalen, Svalbard. Its photosynthetic activity was monitored ex situ in a microcosm in late Arctic summer in 2016 and 2017 using variable chlorophyll fluorescence measurements with blue and red excitation lights. The effective quantum yield (FPSII) was measured, and the photosynthetic relative electron transport rate (rETR) was calculated. During the measurement period, the microclimate data, air temperature and photosynthetically active radiation (PAR), were recorded as well. Year 2016 was slightly warmer than year 2017. Despite of higher maximum PAR values found in 2016, the mean irradiance reached higher values in 2017 than 2016. When using red light excitation, the rETR and effective quantum yield values were lower than those measured using blue excitation light in 2016. However, opposite results were recorded in 2017, indicating thus rather sample-specific differences. According to redundancy analysis, the PAR was confirmed as the main driver of photosynthesis in late Arctic summer in both years. No serious photoinhibition, expressed as serious systematic decline of the rETR, was observed in both years indicating rapid photoacclimation of Vaucheria sp. photosynthesis to changing light environment. The air temperature was found to be less important driver of the photosynthetic activity. The inter-annual comparisons showed increased photosynthetic activity in 2017, probably caused by higher PAR in 2017, by differences in microcosmos design and/or heterogeneity of samples.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

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