Experimental in vivo measurements of light emission in plants: a perspective dedicated to David Walker

Abstract

This review is dedicated to David Walker (1928-2012), a pioneer in the field of photosynthesis and chlorophyll fluorescence. We begin this review by presenting the history of light emission studies, from the ancient times. Light emission from plants is of several kinds: prompt fluorescence (PF), delayed fluorescence (DF), thermoluminescence, and phosphorescence. In this article, we focus on PF and DF. Chlorophyll a fluorescence measurements have been used for more than 80 years to study photosynthesis, particularly photosystem II (PSII) since 1961. This technique has become a regular trusted probe in agricultural and biological research. Many measured and calculated parameters are good biomarkers or indicators of plant tolerance to different abiotic and biotic stressors. This would never have been possible without the rapid development of new fluorometers. To date, most of these instruments are based mainly on two different operational principles for measuring variable chlorophyll a fluorescence: (1) a PF signal produced following a pulse-amplitude-modulated excitation and (2) a PF signal emitted during a strong continuous actinic excitation. In addition to fluorometers, other instruments have been developed to measure additional signals, such as DF, originating from PSII, and light-induced absorbance changes due to the photooxidation of P700, from PSI, measured as the absorption decrease (photobleaching) at about 705 nm, or increase at 820 nm. In this review, the technical and theoretical basis of newly developed instruments, allowing for simultaneous measurement of the PF and the DF as well as other parameters is discussed. Special emphasis has been given to a description of comparative measurements on PF and DF. However, DF has been discussed in greater details, since it is much less used and less known than PF, but has a great potential to provide useful qualitative new information on the back reactions of PSII electron transfer. A review concerning the history of fluorometers is also presented.

Using the quantum yields of photosystem II and the rate of net photosynthesis to monitor high irradiance and temperature stress in chrysanthemum (Dendranthema grandiflora)

“…The measurement was done in the morning (2 h after the light was switched on) and in the afternoon (3 h before the light was switched off) using a plant efficiency analyser (PEA) (Hansatech Instruments, Kings Lynn, UK) after dark-adapting the leaves for 30 min using a leaf clip (Hansatech, Instruments, Kings Lynn, UK), and then subsequently exposing the leaves to 3000 µmol m -2 s -1 measuring irradiance to generate maximal fluorescence (Fm) [30][31][32][33], to measure the maximum photochemical efficiency Fv/Fm = (Fm -Fo)/Fm of dark adapted leaves. In parallel, a MINI-PAM (Walz, Effeltrich, Germany) was used to measure the PSII operating efficiency F′q/F′m = (F′m -F′)/F′m [34] and linear electron transport rate (ETR), which were calculated as described by…”

Salt pretreatment alleviated salt-induced photoinhibition in sweet sorghum

“…The operating mechanism of this instrument has been elucidated in detail by (Strasser et al (2010); Kalaji et al 2012). The leaves were adapted in dark for 30 min before the measurement (Kalaji et al 2014b).…”

The application of potato starch effluent causes a reduction in the photosynthetic efficiency and growth of Scots pine (Pinus sylvestris L.)

“…Chlorophyll fluorescence (ChlF) measurements have recently become a widely adopted to evaluate the impact of stress factors on photosynthesis (Kalaji et al 2012). They represent a simple, non-destructive, inexpensive and rapid tool for analysing light-dependent photosynthetic reactions and for indirectly estimating chlorophyll content within the same sample tissue.…”

“…The technical advantages of ChlF approaches have made it a popular technique amongst plant breeders (e.g. for crop phenotyping and monitoring), biotechnologists, plant physiologists, farmers, gardeners, ecophysiologists and foresters (Kalaji et al 2012). We applied these measurements to check if the waste water containing N, P and K affect trees photosynthetic efficiency.…”