Simultaneous measurement of changes in red and blue fluorescence in illuminated isolated chloroplasts and leaf pieces: The contribution of NADPH to the blue fluorescence signal

Abstract

A newly developed nitrogen laser fluorimeter insensitive to actinic illumination was used to follow simultaneously the light induced changes in red and blue fluorescence of intact isolated spinach chloroplasts and leaf pieces. The recorded variable blue fluorescence was linked to a water soluble component of intact isolated chloroplasts, depended on Photosystem I, and was related to changes in carbon metabolism. From the comparison of changes in intact and broken chloroplasts and from fluorescence spectra under different conditions, it was concluded that the variation in NADPH was the major cause for the changes in blue fluorescence. This study opens a path towards continuous and non-destructive monitoring of NADPH redox state in chloroplasts and leaves.

In Vivo Interactions between Photosynthesis, Mitorespiration, and Chlororespiration in Chlamydomonas reinhardtii

“…Chl fluorescence is related to the redox level of the PS II acceptor (Q A ) and reflects the redox status of the PQ pool. Variations in blue-green fluorescence have been reported to be related to changes in the reduction status of NAD(P) (Cerovic et al, 1993;Latouche et al, 2000). In WT C. reinhardtii cells, a dark-to-light transition induced a strong and fast increase in bluegreen fluorescence (Fig.…”

“…Fluorescence measurements were performed in a front-face configuration on a new version of the pulsed fluorimeter described elsewhere (Cerovic et al, 1993), simultaneously recording blue-green (pyridine nucleotide) and red (Chl) fluorescence. A high-power xenon flash lamp (L4633, Hamamatsu, Massy, France) was used as a pulsed excitation light source (1-s duration).…”

Reduction of the primary donor P700 of photosystem I during steady-state photosynthesis under low light in Arabidopsis

“…It appears difficult to generalize the redox state of the NADP system from these early data, but the NADP system is likely to be partly reduced, even in low-light, to an extent comparable to that in high-light. On the other hand, as discussed previously in terms of the mass action ratio of the PGA (3-phosphoglycerate) reducing system (Takahama et al 1981;Dietz and Heber 1984;Cerovic et al 1993;Oja et al 2003), the redox state of the NADP system is controlled by the ratio of PGA to DHAP (dihydroxyacetone phosphate) and by the phosphorylation potential [ [Pi]. It is therefore possible to assume that the reduction level of NADP system rises even in low-light due to a low PGA/DHAP ratio and low phosphorylation potential.…”

“…Under conditions where reducing power accumulates in the stroma, electron acceptors in PSI, such as F X , F A , and F B are reduced. Forward electron transfer reactions compete with back reactions, which are possible between radical pairs of P700 1 and any reduced acceptors in PSI (for review, Brettel and Leibl 2001). Therefore, within a time scale of some 10 ns (for P700 1 A 0 2 ) to \100 ms (for P700 1 F A 2 /F B 2 ), radical pairs may undergo a charge recombination reaction and then P700 1 may return, partly via a triplet excited state, to a singlet ground state while dissipating the excess excitation energy as heat (Brettel and Leibl 2001;Shinkarev et al 2002).…”

“…Extreme variations can be found in the literature describing the redox state of the NADP system in the stroma (Takahama et al 1981;Dietz and Heber 1984;Rebeille and Hatch 1986;Cerovic et al 1993). For example, the NADP system is not much reduced even in high-light in sunflower (Laisk et al 1991) and in pea (Foyer et al 1992), whereas it is significantly reduced even in the dark and in low-light in spinach (Heineke et al 1991) and in barley (Forti et al 2003).…”