Endolithic algae photoacclimate to increased irradiance during coral bleaching

2004 ◽  
Vol 55 (1) ◽  
pp. 115 ◽  
Author(s):  
Maoz Fine ◽  
Laura Steindler ◽  
Yossi Loya
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosynthetic Efficiency ◽  
Photosynthetic Electron Transport ◽  
Pulse Amplitude ◽  
Coral Tissue ◽  
Pam Fluorometry ◽  
Endolithic Algae ◽  
Symbiotic Dinoflagellates ◽  
Pam Chlorophyll Fluorescence

The photoacclimation of endolithic algae (of the genus Ostreobium) inhabiting the skeleton of the Mediterranean coral Oculina patagonica during a bleaching event was examined. Pulse amplitude modulated (PAM) chlorophyll fluorescence techniques in situ were used to assess the photosynthetic efficiency of endolithic algae in the coral skeleton and the symbiotic dinoflagellates (zooxanthellae) in the coral tissue. Relative photosynthetic electron transport rates (ETRs) of the endolithic algae under bleached areas of the colony were significantly higher than those of endolithic algae from a healthy section of the colony and those of zooxanthellae isolated from the same section. Endolithic algae under healthy parts of the colony demonstrated an ETRmax of 16.5% that of zooxanthellae from tissue in the same section whereas endolithic algae under bleached sections showed ETRmax values that were 39% of those found for healthy zooxanthellae. The study demonstrates that endolithic algae undergo photoacclimation with increased irradiance reaching the skeleton. As PAM fluorometry has become a major tool for assessing levels of stress and bleaching in corals, the importance of considering the contribution of the endolithic algae to the overall chlorophyll fluorescence measured is highlighted.

Use of pulse amplitude modulated (PAM) fluorometry for in situ measurements of photosynthesis in two Red Sea faviid corals

1998 ◽  
Vol 131 (4) ◽  
pp. 607-612 ◽  
Author(s):  
S. Beer ◽  
M. Ilan ◽  
A. Eshel ◽  
A. Weil ◽  
I. Brickner
Keyword(s):  
Red Sea ◽  
Pulse Amplitude ◽  
In Situ Measurements ◽  
Pam Fluorometry

scholarly journals Low-Cost Chlorophyll Fluorescence Imaging for Stress Detection

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2055
Author(s):  
Reeve Legendre ◽  
Nicholas T. Basinger ◽  
Marc W. van Iersel
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Fluorescence Imaging ◽  
Low Cost ◽  
Pulse Amplitude ◽  
Chlorophyll Fluorescence Imaging ◽  
Stress Index ◽  
Pam Fluorometry ◽  
Pixel Intensity ◽  
Pam Fluorometer

Plants naturally contain high levels of the stress-responsive fluorophore chlorophyll. Chlorophyll fluorescence imaging (CFI) is a powerful tool to measure photosynthetic efficiency in plants and provides the ability to detect damage from a range of biotic and abiotic stresses before visible symptoms occur. However, most CFI systems are complex, expensive systems that use pulse amplitude modulation (PAM) fluorometry. Here, we test a simple CFI system, that does not require PAM fluorometry, but instead simply images fluorescence emitted by plants. We used this technique to visualize stress induced by the photosystem II-inhibitory herbicide atrazine. After applying atrazine as a soil drench, CFI and color images were taken at 15-minute intervals, alongside measurements from a PAM fluorometer and a leaf reflectometer. Pixel intensity of the CFI images was negatively correlated with the quantum yield of photosystem II (ΦPSII) (p < 0.0001) and positively correlated with the measured reflectance in the spectral region of chlorophyll fluorescence emissions (p < 0.0001). A fluorescence-based stress index was developed using the reflectometer measurements based on wavelengths with the highest (741.2 nm) and lowest variability (548.9 nm) in response to atrazine damage. This index was correlated with ΦPSII (p < 0.0001). Low-cost CFI imaging can detect herbicide-induced stress (and likely other stressors) before there is visual damage.

Photosynthesis of an epiphytic resurrection fern Davallia angustata (Wall .ex Hook. & Grev.)

2017 ◽  
Vol 65 (4) ◽  
pp. 348 ◽  
Author(s):  
Rosanne Quinnell ◽  
Daniel Howell ◽  
Raymond J. Ritchie
Keyword(s):  
Photosynthetic Efficiency ◽  
Photosynthetic Electron Transport ◽  
Pulse Amplitude ◽  
Resurrection Plant ◽  
Simple Relationship ◽  
Chl A ◽  
Palm Trees ◽  
Titratable Acid ◽  
Cam Plant ◽  
Epiphytic Fern

Davallia (Pachypleuria) angustata (Wall. ex Hook. & Grev.) is a common epiphytic fern that grows on tree trucks and palm trees in south-east Asia. The plant is a resurrection plant, capable of rapid recovery from desiccation, but is not a CAM plant like some other epiphytic ferns. Under well-watered conditions Davallia shows a diurnal cycle of photosynthesis with maxima in mid-morning ~0900 hours (solar time). Under optimum conditions, the optimum irradiance (Eopt) = 879.3 ± 65.31 μmol photons m–2 s–1 or ~45% of full sunlight qualifying it as a sun plant. The maximum photosynthetic electron transport rate (ETRmax) was 77.77 ± 3.423 μmol e– m–2 s–1 or, on a Chl a basis 350 ± 36.0 μmol g–1 (Chl a) s–1. The photosynthetic efficiency (α0) is α0 = 0.2404 ± 0.02076 e– photon–1 or 1.082 ± 0.137 e– photon m2 g–1 (Chl a). Eopt and maximum photosynthesis (ETRmax) are directly proportional to one another (y = mx, r = 0.8813, P < <0.001). The slope of the line is the average photosynthetic efficiency at optimum irradiance (ETRmax/Eopt or αEopt = 0.07505 ± 0.00262 e– photon–1), equivalent to a mean asymptotic photosynthetic efficiency (α0) of 0.2040 ± 0.00712 e– photon–1. This simple relationship between ETRmax and Eopt does not appear to have been noted before. There is some accumulation of titratable acid in the morning but no accumulation of organic acids at night. Davallia is not a CAM plant. A simple pulse amplitude modulation (PAM) protocol shows that Davallia is a homiochlorophyllous resurrection plant.

Photosynthetic Performance of Marestail (Hippuris vulgaris Linn.) across a Water Temperature Gradient

2014 ◽  
Vol 1010-1012 ◽  
pp. 1165-1169
Author(s):  
Lin An Gao
Keyword(s):  
Water Temperature ◽  
Photosynthetic Activity ◽  
Pulse Amplitude ◽  
High Water ◽  
Photosynthetic Performance ◽  
Light Curves ◽  
Pam Fluorometry ◽  
Photosynthetic Responses ◽  
Hippuris Vulgaris

we examined the photosynthetic responses of submerged marestail in three lakes using pulse amplitude modulated (PAM) fluorometry. Three lakes were studied across a gradient of water temperature, with low water temperature conditions in Grass Lake and Arrow Bamboo Lake, and higher water temperature in Five Colored Lake. In the field, electron transport rates (ETRmax) were measured as rapid light curves (RLCs) by in situ yield measurements. Submerged marestail showed higher photosynthetic activity in Five Colored Lake compared to the other lakes, a response consistent with the adaptation of marestail in Five Colored Lake to high water temperature. The optimal temperature for photosynthesis of submerged marestail in Jiuzhaigou is about 12 °C. These results indicate that in different lakes the function of these aquatic plants is associated with a diversity of place-dependent environmental conditions, especially water temperature that leads to pronounced differences in the plant’s ecophysiological reactions.

scholarly journals Effect of light on photosynthetic efficiency of sequestered chloroplasts in intertidal benthic foraminifera (<i>Haynesina germanica</i> and <i>Ammonia tepida</i>)

2016 ◽  
Author(s):  
Thierry Jauffrais ◽  
Bruno Jesus ◽  
Edouard Metzger ◽  
Jean-Luc Mouget ◽  
Frans Jorissen ◽  
...  
Keyword(s):  
Benthic Foraminifera ◽  
Spectral Reflectance ◽  
Photosynthetic Efficiency ◽  
Pulse Amplitude ◽  
High Light ◽  
Feeding Strategies ◽  
Oxygen Production ◽  
Pam Fluorometry ◽  
Light History ◽  
Effect Of Light

Abstract. Some benthic foraminifera have the ability to incorporate functional chloroplasts from diatoms (kleptoplasty). Our objective was to investigate chloroplast functionality of two benthic foraminifera (Haynesina germanica and Ammonia tepida) exposed to different irradiance levels (0, 25, 70 μmol photon m-2 s-1) using spectral reflectance, epifluorescence observations, oxygen evolution and pulse amplitude modulated (PAM) fluorometry. Our results clearly showed that H. germanica was capable of using its kleptoplasts for more than one week while A. tepida showed very limited kleptoplastic ability with maximum photosystem II quantum efficiency (Fv/Fm = 0.4), much lower than H. germanica and decreasing to zero in only one day. Only H. germanica showed net oxygen production with a compensation point at 24 μmol photon m-2 s-1 and a production up to 1000 pmol O2 cell-1 day-1 at 300 μmol photon m-2 s-1. Haynesina germanica Fv/Fm slowly decreased from 0.65 to 0.55 in 7 days when kept in darkness; however, it quickly decreased to 0.2 under high light. Kleptoplast functional time was thus estimated between 11 and 21 days in darkness and between 7 and 8 days at high light. These results emphasize that studies about foraminifera kleptoplasty must take into account light history. Additionally, this study showed that the kleptoplasts are unlikely to be completely functional, thus requiring continuous chloroplast resupply from foraminifera food source. The advantages of keeping functional chloroplasts are discussed but more information is needed to better understand foraminifera feeding strategies.

scholarly journals A Novel Thin-Film Technique to Improve Accuracy of Fluorescence-Based Estimates for Periphytic Biofilms

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1464
Author(s):  
Leon Katona ◽  
Yvonne Vadeboncoeur ◽  
Christopher T. Nietch ◽  
Katie Hossler
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Light Attenuation ◽  
Pulse Amplitude ◽  
Light Signal ◽  
Photosynthetic Parameters ◽  
Pam Fluorometry ◽  
Attenuation Coefficients ◽  
Thin Film Technique ◽  
Relative Errors

Recent studies suggest that photophysiological parameters for intact substrates with depth (e.g., periphytic biofilms, microphytobenthos) are overestimated by pulse-amplitude modulated (PAM) fluorometry. This overestimation results from depth-integration effects, following the activation of deeper photosynthesizing layers by an attenuated light signal. To mitigate this error, we propose a novel slide-based thin-film technique in which fluorescence is measured on a vertically representative subsample of the biofilm, spread evenly on a microscope slide. We compared bias and precision for photosynthetic parameters estimated through conventional PAM fluorometry on intact biofilms and through our novel slide-based technique, both theoretically and empirically. Numerical simulations confirmed the consistent overestimation of key parameters for intact biofilms, with relative errors up to 145%, compared to, at most, 52% on thin films. Paired empirical observations likewise demonstrated that estimates based on intact biofilms were consistently higher (up to 248%, p<0.001) than estimates from thin films. Numerical simulation suggested greater precision with the slide-based technique for homogeneous biofilms, but potentially less precision for heterogeneous biofilms with improper subsampling. Our empirical comparison, however, demonstrated some improvement in precision with the slide-based technique (e.g., the coefficient of variation for the maximum electron transport rate was reduced 30%, p=0.009). We recommend the use of the slide-based technique, particularly for biofilms that are thick or have small light attenuation coefficients. Care should be taken, however, to obtain vertically representative subsamples of the biofilm for measurement.

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