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

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 Enhanced Relative Electron Transport Rate Contributes to Increased Photosynthetic Capacity in Autotetraploid Pak Choi

2020 ◽  
Vol 61 (4) ◽  
pp. 761-774 ◽  
Author(s):  
Changwei Zhang ◽  
Huiyu Wang ◽  
Yuanyuan Xu ◽  
Shuning Zhang ◽  
Jianjun Wang ◽  
...  
Keyword(s):  
Electron Transport ◽  
Powdery Mildew Resistance ◽  
Photosynthetic Activity ◽  
Photosynthetic Capacity ◽  
Electron Transport Rate ◽  
Ectopic Expression ◽  
Transport Rate ◽  
Pak Choi ◽  
Relative Electron Transport Rate ◽  
Relative Electron

Abstract Autopolyploids often show growth advantages over their diploid progenitors because of their increased photosynthetic activity; however, the underlying molecular basis of such mechanism remains elusive. In this study, we aimed to characterize autotetraploid pak choi (Brassica rapa ssp. chinensis) at the physiological, cellular and molecular levels. Autotetraploid pak choi has thicker leaves than its diploid counterparts, with relatively larger intercellular spaces and cell size and greater grana thylakoid height. Photosynthetic data showed that the relative electron transport rate (rETR) was markedly higher in autotetraploid than in diploid pak choi. Transcriptomic data revealed that the expressions of genes involved in ‘photosynthesis’ biological process and ‘thylakoids’ cellular component were mainly regulated in autotetraploids. Overall, our findings suggested that the increased rETR in the thylakoids contributed to the increased photosynthetic capacity of autotetraploid leaves. Furthermore, we found that the enhanced rETR is associated with increased BrPetC expression, which is likely altered by histone modification. The ectopic expression of BrPetC in Arabidopsis thaliana led to increased rETR and biomass, which were decreased in BrPetC-silenced pak choi. Autotetraploid pak choi also shows altered hormone levels, which was likely responsible for the increased drought resistance and the impaired powdery mildew resistance of this lineage. Our findings further our understanding on how autotetraploidy provides growth advantages to plants.

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.

scholarly journals Comparative stomatal conductance and chlorophyll a fluorescence in leaves vs. fruits of the cerrado legume tree, Dalbergia miscolobium

2004 ◽  
Vol 16 (2) ◽  
pp. 89-93 ◽  
Author(s):  
José Pires de Lemos Filho ◽  
Rosy Mary dos Santos Isaias
Keyword(s):  
Water Vapor ◽  
Stomatal Conductance ◽  
Quantum Yield ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Electron Transport Rate ◽  
Early Morning ◽  
Effective Quantum Yield ◽  
Quantum Yield Of Psii ◽  
Chronic Photoinhibition

The aim of this study was to compare water vapor conductance and chlorophyll a fluorescence between leaflets and fruits of Dalbergia miscolobium, the Jacaranda tree. The frequency of stomata on the leaflets was 20 times higher than that observed on the fruits, and this was related with the lower conductance of the fruits in comparison with the leaflets. The potential quantum yield of PSII (Fv /Fmax) was significantly lower in fruits than in leaflets. The Fv /Fmax values for leaflets increased to over 0.8 during the afternoon, indicating the occurrence of dynamic photoinhibition. In contrast, Fv /Fmax values for fruits remained low even at early morning, indicating the occurrence of chronic photoinhibition. The maximum values of effective quantum yield (deltaF/F'm), and of the apparent electron transport rate (ETRmax) were higher in leaflets than in fruits. It was concluded that, like other green tissues, the pericarp of D. miscolobium was photosynthetically active, and therefore can contribute to the maintenance of the fruits and/or to the development of the seeds.

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.

scholarly journals Photosynthetic capacity of three phytoplanktonic species measured by a pulse amplitude fluorometric method

2009 ◽  
Vol 21 (3) ◽  
pp. 167-174 ◽  
Author(s):  
Cleber Cunha Figueredo ◽  
Alessandra Giani ◽  
José Pires Lemos Filho
Keyword(s):  
Electron Transport ◽  
Quantum Yield ◽  
Photosystem Ii ◽  
Photosynthetic Capacity ◽  
Electron Transport Rate ◽  
Morphological Characteristics ◽  
Volume Ratio ◽  
Photochemical Reactions ◽  
Transport Rate ◽  
Photosynthetic Parameters

During photosynthesis, absorbed energy that is not used in photochemical reactions dissipates as fluorescence. Fluorescence provides important information on the physiological conditions of the studied organisms and its measurement is widely used by plant physiologists and can be valuable in phytoplankton studies. We describe a method adapting a plant fluorometric equipment to measure the photosynthetic capacity of microalgae. Unialgal cultures of three planktonic chlorophytes were exposed to 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II, at concentrations of 0.1, 1.0 and 10.0 µmol.L-1. Estimates were made of photosynthetic parameters, including operational and potential photosystem II quantum yield and electron transport rate between photosystems, using algal cells concentrated on glass-fiber filters. The technique allowed reliable measurements of fluorescence, and detection of distinct levels of inhibition. Physiological or morphological characteristics of the selected species might provide an explanation for the observed results: differences on the surface/volume ratio of the cells and colony morphology, for example, were associated with contrasting resistance to the toxicant. To characterize inhibition on phytoplanktonic photosynthesis, we suggest operational quantum yield and electron transport rate as best parameters, once they were more sensitive to the DCMU toxicity.

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.

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;

Marine benthic diatoms in the newly discovered coral reefs, off Basra coast, Southern Iraq

Phytotaxa ◽  
2018 ◽  
Vol 372 (2) ◽  
pp. 111
Author(s):  
ADIL Y. AL-HANDAL ◽  
EVAN W. THOMAS ◽  
CHIARA PENNESI
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Persian Gulf ◽  
Temperature Fluctuation ◽  
Benthic Diatoms ◽  
Large Species ◽  
Rare Occurrence ◽  
Benthic Assemblages ◽  
Diatom Communities ◽  
Southern Iraq

The recent discovery of coral reefs off Basra, Southern Iraq, have prompted the investigation of marine benthic assemblages in this unexplored ecosystem. These corals are thriving in an environment with conditions not usually considered typical for reefs, such as increased turbidity, temperature fluctuation, and currents. This study documents 96 diatom taxa belonging to 33 genera, 18 of which were not previously known from the Arabian (Persian) Gulf including six taxa of Amphora and five of Campylodiscus. The most common genera were Amphora with 17 taxa, Nitzschia with 10 taxa, and Navicula with nine taxa. Most notably is the very rare occurrence of Mastogloia, which has been previously documented as speciose in coral reef habitats. Similarly, araphid and monoraphid species were uncommon in these diatom communities. The large species of the epipelic diatom Trachyneis are well represented and appeared commonly in all samples examined.

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