Deriving fluorometer-specific values of relative PSI fluorescence intensity from quenching of F 0 fluorescence in leaves of Arabidopsis thaliana and Zea mays

Abstract

The effect of stepwise increments of red light intensities on pulse-amplitude modulated (PAM) chlorophyll (Chl) fluorescence from leaves of A. thaliana and Z. mays was investigated. Minimum and maximum fluorescence were measured before illumination (F(0) and F(M), respectively) and at the end of each light step (F'(0) and F'(M), respectively). Calculated F'(0) values derived from F(0), F(M) and F'(M) fluorescence according to Oxborough and Baker (1997) were lower than the corresponding measured F'(0) values. Based on the concept that calculated F'(0) values are under-estimated because the underlying theory ignores PSI fluorescence, a method was devised to gain relative PSI fluorescence intensities from differences between calculated and measured F'(0). This method yields fluorometer-specific PSI data as its input data (F(0), F(M), F'(0) and F'(M)) depend solely on the spectral properties of the fluorometer used. Under the present conditions, the PSI contribution to F (0) fluorescence was 0.24 in A. thaliana and it was independent on the light acclimation status; the corresponding value was 0.50 in Z. mays. Correction for PSI fluorescence affected Z. mays most: the linear relationship between PSI and PSII photochemical yields was clearly shifted toward the one-to-one proportionality line and maximum electron transport was increased by 50 %. Further, correction for PSI fluorescence increased the PSII reaction center-specific parameter, 1/F(0) - 1/F(M), up to 50 % in A. thaliana and up to 400 % in Z. mays.

Low PSI content limits the photoprotection of PSI and PSII in early growth stages of chlorophyll b-deficient wheat mutant lines

“…However, this says nothing about the PSI/PSII ratio, as the number of PSII RCs can be decreased as well. On the other hand, the basal fluorescence (F 0 ) can be considered as a reliable indicator of the PSI/PSII ratio, as the F 0 signal measured by common fluorometers (including PAM-system used here) contains an important contribution by PSI fluorescence (Pfündel et al 2013). Although it has been previously suggested that F 0 can serve as a measure of Chl content (Strasser et al 2004), the experimental results clearly document that the F 0 and F m values were essentially insensitive to the Chl content of the leaf as long as the Chl a/b ratio remained unaffected.…”

Photosynthetic proton and electron transport in wheat leaves under prolonged moderate drought stress

“…It was documented that F 0 level usually contains app. 20-30% of PSI fluorescence in C 3 plants [31,60]. While some parameters (e.g.…”

“…qP) are insensitive to the contribution of PSI fluorescence, omission of PSI fluorescence leads to the improper estimation of some key parameters, e.g. to underestimation of PSII quantum yield [60]. This can lead to some inaccuracy if we compare the quantum yield of two samples differing in contribution of PSI fluorescence.…”

Dynamic photosynthesis under a fluctuating environment: a modelling-based analysis

“…This phenomenon has also been confirmed by measurements of fluorescence lifetime (Renger et al, 1995;Gilmore et al, 1996;Matsubara and Chow, 2004). These fluorescence yields are defined as: This model explicitly does not take into account the effect of charge recombination within PSII reaction centres (de Wijn and van Gorkom, 2002;Laisk et al, 2012) or contributions from Photosystem I to fluorescence yield (Pfündel et al, 2013). The variable C VVT should be taken as an apparent quantum yield that includes, implicitly, these effects.…”

“…Although the quantum yield of energy transfer to the reaction centre (. / ) is not exactly 1 since PSIac emit a small amount of fluorescence at ambient temperature (Pfündel et al, 2013), energy losses at PSIac are generally not considered an important component in energy balance of PSI, especially given the strong quenching by P "77 ) which has a longer lifetime than P 567 ) at PSII. It is further assumed that all excitations transferred to a reaction centre containing P "77 ) are quenched as heat and that the PSIac are highly interconnected (Lavergne and Trissl, 1995).…”