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Hydrogen Photoproduction by Oxygenic Photosynthetic Microorganisms
Published in Farshad Darvishi Harzevili, Serge Hiligsmann, Microbial Fuels, 2017
Fabrice Franck, Bart Ghysels, Damien Godaux
Screening procedures based on chlorophyll fluorescence are widely used to spot mutants impaired in photosynthetic activity (Kruse et al., 1999; Houille-Vernes et al., 2011; Tolleter et al., 2011). The screening system requires sophisticated fluorescence imaging equipment, composed of a fast digital camera able to record the time course of chlorophyll fluorescence in response to light from a large number of algal colonies or cultures simultaneously (on a petri dish or in wells of multiwell plates) (Johnson et al., 2009). Such a system has been used for the isolation of algal insertional mutants deficient in H2 photoproduction, with the aim of identifying novel genes involved in the process. Recently, a new fluorescence-based screening method was developed in our group to isolate mutants impaired in hydrogenase expression or activity, as well as mutants altered in related H2 metabolism in anoxia (Godaux et al., 2013). The screen is based on the relationship between the PSII photochemical quantum yield (calculated from the fluorescence signal) and the hydrogenase capacity during the first seconds of illumination after a prolonged dark anoxic period. Such a relationship is expected because hydrogenase is the main electron sink for the whole electron transport chain for short illumination times under anoxia. Compared with previously described screens for mutants impaired in H2 metabolism and hydrogenase function (Seibert et al., 2001; Wecker et al., 2011), the fluorescence-based screening method is remarkably fast (thousands of transformants analyzed per day) and sensitive (due to the linear relationship between hydrogenase activity and the fluorescence signal).
The importance of the calcium-to-magnesium ratio for phytoremediation of dairy industry wastewater using the aquatic plant Lemna minor L.
Published in International Journal of Phytoremediation, 2020
Éamonn Walsh, Simona Paolacci, Gavin Burnell, Marcel A. K. Jansen
Chlorophyll a fluorescence was measured using pulse amplitude modulated chlorophyll a fluorometry (WALZ Imaging fluorometer, Effeltrich, Germany). For chlorophyll a fluorescence analysis, plants were adapted for dark condition for 15 min immediately before measurements. Then, three random colonies from each Magenta were taken for analysis; the measured values of these three colonies were averaged together and treated as one replicate. The chlorophyll fluorescence analysis procedure is as follows; first, a low-intensity modulated measuring light was turned on to measure F0 on the dark-adapted plant, and secondly a saturating pulse of light (2700 µmol/m2/s) was applied to obtain the maximum fluorescence Fm. Subsequently, actinic light (photosynthetically active light of 186 µmol/m2/s) was applied to the plants and at 20 s intervals saturating pulses were applied to measure Fm', the maximum fluorescence under light-adapted conditions. Ft is the value of fluorescence immediately before the saturating pulse is applied, i.e., the steady-state value of fluorescence. Fv/Fm, the maximum quantum efficiency of photosystem II (PSII), and Y(II), the quantum efficiency of PSII under steady state light conditions were calculated according to Maxwell and Johnson (2000) using the following equations:
Effects of lead and cadmium on photosynthesis in Amaranthus spinosus and assessment of phytoremediation potential
Published in International Journal of Phytoremediation, 2019
Yingping Huang, Ying Xi, Long Gan, David Johnson, Yonghong Wu, Dong Ren, Huigang Liu
Cd and Pb affect plant life in various ways, including reduction of chlorophyll content and interference with electron transfer and photosynthesis, thereby decreasing the growth rate and biomass of plants (Zhang et al.2018; Lee et al.2018; Li et al.2018). Measurement of photosynthetic processes can be used to determine the extent of stress caused by heavy metals (Arena et al.2017). Heavy metals interfere with photosynthesis (Eckmekçi et al. 2008) and decrease the net rate of photosynthesis due to both stomatal and non-stomatal factors (Ogweno et al.2008). Chlorophyll fluorescence is a reliable, non-invasive technique for studying the health of plants (Ahammed et al.2012). In this study, plant growth and photosynthetic parameters were used to indicate the stress induced by exposure to various levels of Pb and Cd.
Implications of environmental conditions for health status and biomechanics of freshwater macrophytes in hydraulic laboratories
Published in Journal of Ecohydraulics, 2020
Davide Vettori, Stephen P. Rice
A suitable and robust technique to monitor plant health status is chlorophyll fluorescence analysis. This technique provides information about the photosynthetic activity in leaves by measuring the fluorescence signal re-emitted by chlorophyll pigments and is very sensitive to health stress (e.g. Murchie and Lawson 2013). Chlorophyll fluorescence analysis has been used to assess stress induced by light irradiance and/or chemicals in freshwater macrophytes (Marwood et al. 2001; Hanelt et al. 2006; Hussner et al. 2010; Knauert et al. 2010).