In Vivo Measurements of Light Emission in Plants (original) (raw)

2014, Photosynthesis: Open Questions and What We Know Today, Allakhverdiev S. I., Rubin A. B., Shuvalov V.A. (eds.)

There are several types of light emission in plants: prompt fluorescence, delayed fluorescence, thermoluminescence, and phosphorescence. This chapter focuses on two of them: prompt and delayed fluorescence. Chlorophyll a fluorescence measurements have been used for more than 80 years to study photosynthesis; since 1961, it has been used, particularly, for the analysis of PhotosystemII (PS II). Fluorescence is now used routinely in agricultural and biological research where many measured and calculated parameters are used as biomarkers or indicators of plant tolerance to different abiotic and biotic stress. This has been made possible by the rapid development of new fluorometers. Most of these instruments are mainly based on two different operational principles for the measurement of variable chlorophyll a fluorescence: (1) pulse-amplitude-modulated (PAM) excitation followed by measurement of prompt fluorescence and (2) a strong continuous actinic excitation leading to prompt fluorescence. In addition to fluorometers, other instruments have been developed to measure other signals, such as delayed fluorescence, originating mainly from PS II, and light-induced absorbance changes due to the photo-oxidation of the reaction center P700 of PS I, measured as absorption decrease (photobleaching) at about 705 nm, or increase at 820 nm. This chapter includes technical and theoretical basis of newly developed instruments that allow for simultaneous measurement of the prompt fluorescence (PF) and the delayed fluorescence (DF) as well as some other In vivo MEASUREMENTS OF LIGHT EMISSION IN PLANTS 3 parameters. Special emphasis is given here to a description of comparativemeasurements on PF and DF. Since DF is much less used and less known than PF, it is discussed in greater details; it has great potential to provide useful, and qualitatively new information on the back reactions of PS II electron transfer. This chapter, which also deals with the history of fluorometers, is dedicated to David Walker (1928–2012), who was a pioneer in the field of photosynthesis and chlorophyll fluorescence.