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Umina Beach, Australia

Ritchie R.J.,Prince of Songkla University | Runcie J.W.,Aquation Pty Ltd | Runcie J.W.,University of Sydney
Photochemistry and Photobiology | Year: 2013

Blue diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) in a purple nonsulfur anoxygenic photobacterium, Afifella (Rhodopseudomonas) marina. Rhodopseudomonads have a reaction center light harvesting antenna complex containing an RC-2 type bacteriochlorophyll a protein (BChl a RC-2-LH1) which has a blue absorption peak and variable fluorescence similar to PSII. Absorptance of cells filtered onto glass fiber disks was measured using a blue-diode-based absorptance meter (Blue-RAT) so that absolute ETR could be calculated from PAM experiments. Maximum quantum yield (Y) was ≈0.6, decreasing exponentially as irradiance increased. ETR vs irradiance (P vs E) curves fitted the waiting-in-line model (ETR = (ETRmax × E/Eopt) × exp(1 - E/E opt)). Maximum ETR (ETRmax) was ≈1000-2000 μmol e- mg-1 BChl a h-1. Fe2+, bisulfite and thiosulfate act as photosynthetic electron donors. Optimum irradiance was ≈100 μmol m-2 s-1 PPFD even in Afifella grown in sunlight. Quantum efficiencies (α) were ≈0.3-0.4 mol e- mol hλ-1; or ≈11.8 ± 2.9 mol e- mol hλ-1 m2 μg-1 BChl a). An underlying layer of Afifella in a constructed algal/photosynthetic bacterial mat has little effect on the measured ETR of the overlying oxyphotoautotroph (Chlorella). Readily available blue-diode based pulse amplitude modulation (PAM) fluorimeters can be used to measure photosynthetic electron transport (ETR) in nonsulfur purple photosynthetic bacteria. PAM machines can measure photosynthesis not only in oxygenic photorganisms and in those with a RC-2 photosystem. Figure shows a comparison of the electron transport rate (ETR) vs irradiance of acetate-grown Afifella cells with and without added acetate (5 mol m-3). ETR in both cases show a waiting-in-line saturation curve with inhibition at high irradiances (r > 0.9731). Added acetate increases ETR but increases optimum irradiance as well. © 2012 The American Society of Photobiology.

Ritchie R.J.,Prince of Songkla University | Runcie J.W.,University of Sydney | Runcie J.W.,Aquation Pty Ltd
Photosynthetica | Year: 2014

PAM (pulse amplitude modulation) fluorometers can be used to estimate the electron transport rate (ETR) [μmol(e−) m−2 s−1] from photosynthetic yield determinations, provided the absorptance (Abtλ) of the photoorganism is known. The standard assumed value used for absorptance is 0.84 (leaf absorptance factor, AbtF). We described a reflectance-absorptancetransmittance (RAT) meter for routine experimental measurements of the actual absorptance of leaves. The RAT uses a red-green-blue (RGB) LED diode light source to measure absorptances at wavelengths suitable for use with PAM fluorometers and infrared gas analysers. Results using the RAT were compared to Abtλ spectra using a Taylor integrating sphere on bird’s nest fern (Asplenium nidus), banana, Doryanthes excelsa, Kalanchoe daigremontiana, and sugarcane. Parallel venation had no significant effect upon Abt465 in banana, Doryanthes, a Dendrobium orchid, pineapple, and sugarcane, but there was a slight difference in the case of the fern A. nidus. The average Abt465 (≈ 0.96) and Abt625 (≈ 0.89) were ≈14% and 6% higher than the standard value (AbtF = 0.84). The PAR-range Abt400–700 was only ≈ 5% higher than the standard value (≈ 0.88) based on averaged absorptance from the blue, green, and red light data and from where the RGB-diode was used as a ‘white’ light source. In some species, absorptances at blue and red wavelengths are quite different (e.g. water lily). Reflectance measurements of leaves using the RAT would also be useful for remote sensing studies. © 2014, The Institute of Experimental Botany.

Martins N.T.,University of Adelaide | Martins N.T.,Federal University of Rio de Janeiro | Runcie J.W.,University of Sydney | Runcie J.W.,Aquation Pty Ltd | And 3 more authors.
Aquatic Botany | Year: 2015

Calculations of absolute ETR require accurate measurements of plant tissue Photosynthetic Active Radiation light absorption (AL(PAR)). The default leaf-specific AL(PAR) value of 0.84 estimated from and applicable to nearly all higher plants does not apply for marine macroalgae which are phylogenetically, structurally and chemically very different from higher plants and quite variable among themselves. Consequently, to date there is no default AL(PAR) value for all macroalgae, and hence AL(PAR) values always need to be recalculated from live specimens on every new study. This study compared AL(PAR) values from thalli of Ulva australis (Chlorophyta) preserved under different methods to test whether usable AL(PAR) data can be obtained from samples other than live ones. Light absorption measurements were made using an Integrating Sphere attached to a spectrophotometer. No statistically significant differences in AL(PAR) values were observed among live and pressed material whether recently collected (=4 days old) or stored more than seventy years but there were significant differences among live, frozen, formalin-preserved and bleached material. No significant differences in absorptance at wavelength of 675nm were observed between fresh, frozen and formalin preserved material. AL(PAR)=0.74 appeared to be an appropriate AL(PAR) default value for this species. This study demonstrated that accurate AL(PAR) can be obtained from some pressed herbarium preserved species while some commonly used methods of field tissue preservation in macroalgal photochemical studies fails to do so. © 2014 Elsevier B.V..

Runcie J.W.,University of Sydney | Runcie J.W.,Australian Antarctic Division | Runcie J.W.,Aquation Pty Ltd | Riddle M.J.,Australian Antarctic Division
European Journal of Phycology | Year: 2012

Photosynthetic activity of marine macroalgae in the Windmill Islands, East Antarctica, was measured in situ using submersible modulated fluorometers. An empirical relation incorporating terms for respiration and non-linear electron transport was derived from simultaneous in vivo measurements of effective quantum yield (ΦPSII′) and oxygen evolution. This relation was used with in situ measurements of and photosynthetic photon flux density acquired over 24-h periods to estimate oxygen evolution rates of algae over the course of the measurement period. Productivity ranged from -8 to 19 μmol O2g-1 FW h-1 (FW = fresh weight), with daily carbon gain ranging from -1.5 to 3.6 mg C g-1 FW d-1 for midnight ice-covered algae and midday ice-free algae, respectively. These values were similar to published values of productivity of Antarctic species derived from oxygen- and carbon-based techniques. The technique described here provides a simple and rapid means of estimating primary productivity in marine systems. © 2012 Copyright Taylor and Francis Group, LLC.

Runcie J.W.,University of Sydney | Runcie J.W.,Australian Antarctic Division | Runcie J.W.,Aquation Pty Ltd | Riddle M.J.,Australian Antarctic Division
European Journal of Phycology | Year: 2011

The quantum yield of chlorophyll a fluorescence of an Antarctic macroalga, Iridaea cordata, was measured in situ using logging fluorometers with an automated dark-acclimation capability throughout several diel periods. Application of far-red light and dark acclimation enabled the automated determination of photochemical quenching and non-photochemical quenching parameters that have until recently been restricted to manual measurement in terrestrial and shallow water environments. Our results show that non-photochemical quenching processes in Iridaea thalli that have been exposed to moderately high irradiances during the day, take all night to relax. We also show that, for algae exposed to relatively high light during the day, around 30-40% of total excitation flux is allocated to basal intrinsic non-radiative decay processes, with the remainder allocated to downregulation or photochemistry. The ability to evaluate the allocation of energy to these fundamentally different non-photochemical quenching processes has direct applications in assessing algal responses to both natural and anthropogenic stress. With this technology we open the door to a far more detailed examination of the regulation and kinetics of in situ photosynthesis and associated non-photochemical processes. © 2011 British Phycological Society.

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