Using integrating sphere spectrophotometry in unicellular algal research
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Using integrating sphere spectrophotometry in unicellular algal research Raymond J. Ritchie 1
&
Suhailar Sma-Air 1
Received: 10 June 2020 / Revised and accepted: 13 August 2020 # Springer Nature B.V. 2020
Abstract Scanning spectrophotometers equipped with integrating spheres were once highly specialized spectrophotometric equipment but are now more readily available commercially. They are particularly useful for objectively assessing the spectral absorption and reflectance of algal cell suspensions. Ordinary dual-beam spectrometers do not give valid measurements of the spectral properties of cells due to light scattering. Spectra of unicellular algae using integrating sphere spectroscopy can measure the absorbance (Abs), transmissions (%T) and reflectance (%R) and hence the actual absorptance (%Abt) of turbid cell suspensions and hence the in vivo pigment absorption properties of photosynthetic organisms. These results were compared with those obtained using conventional dual-beam spectrophotometry scans on turbid cell suspensions and the in solvent spectra of photosynthetic pigments. The common unicellular green alga, Chlorella sp., is used as an example of an oxygenic photo-organism with chlorophyll a as the primary photosynthetic pigment and comparisons made to other unicellular algae such as a cyanobacterium (Synechococcus), Acaryochloris and a diatom (Chaetoceros). Photosynthetic bacteria, such as Rhodopseudomonas palustris, are photosynthetic but do not produce oxygen, and their photosynthesis is usually based on bacteriochlorophyll a. Comparisons are made of integrating sphere vs. dualbeam transmission spectroscopy of BChl a and BChl b organisms in solvent and in vivo of anoxygenic photosynthetic bacteria (Afifella & Thermochromatium [BChl a], Blastochloris [BChl b]) and with oxygenic organisms. Keywords Integrating sphere spectroscopy . Absorbance (Abs) . Transmission (%T) . Reflectance (%R) . Absorptance (%Abt) . Oxygenic photo-organisms . Anoxygenic photo-organisms
Introduction Scanning spectrophotometers equipped with integrating spheres were once highly specialized spectrophotometric equipment (Jávorfi et al. 2006) but are now more readily available commercially. They are particularly useful for objectively assessing the spectral absorption and reflectance of algal cell suspensions and so provide a measurement of what light photosynthetic organisms are actually absorbing in vivo. This is important because the spectral properties of Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10811-020-02232-y) contains supplementary material, which is available to authorized users. * Raymond J. Ritchie [email protected]; [email protected] 1
ANED (Andaman Environment and Natural Disaster Research Centre) and Tropical Plant Biology Unit, Faculty of Technology and Environment, Prince of Songkla University-Phuket, Phuket 83120, Thailand
chlorophylls (Chl) and in particular bacteriochlorophylls (BChl) bound inside protein complexes are considerabl
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