(2004). In the JIP test, OJIP transients are used to make a flux analysis, i.e., an analysis of the fate of photons absorbed by the PSII 7-Cl-O-Nec1 mouse antennae (trapping, forward electron transport beyond Q A and dissipation as heat). In the JIP test, the J-step is taken as the border between single and multiple turnovers. If we define multiple turnovers here as events related to

electron transport beyond PSII, then this claim still remains valid. The JIP test depends strongly on the assumption that the F O-to-F M rise reflects the reduction of Q A. The concept is internally consistent but the theoretical foundation of the interpretation of the parameters disappears the moment that this assumption turns out to be wrong (see Schansker et al. 2011, 2014 for a discussion of this point). An alternative approach to the interpretation of the OJIP transients is a classical physiological DZNeP research buy characterization of the various features of the fluorescence rise. In the JIP test, it is assumed that the relative position of the J-step between F O and F M (i.e., V

J, giving rise to the JIP-parameter 1 − V J or Ψ O) gives information on photosynthetic electron transport beyond Q A (e.g., Strasser et al. 1995, 2004). A physiological characterization of this feature, on the other hand, selleck compound suggests that the parameter V J depends on the redox state of the PQ-pool MRIP in darkness (Tóth et al. 2007a) and, under certain stress conditions, may also be affected by other factors, possibly the extent of stacking of the thylakoid membranes. In this case, electron transport beyond Q A means a slowdown of the re-oxidation of Q A − as the PQ-pool becomes more reduced, and fewer PQ molecules are bound to the Q B-site. Changes in Ψ O may certainly point to

stress. In the JIP test, the parameters F O and F M were suggested to be a measure for the absorption flux (i.e., the number of photons absorbed per unit of time) per cross section (Strasser et al. 1995, 2004). With respect to this interpretation, it may be noted that a characterization of the changes in the F O and F M levels as a function of the Chl content of leaves showed that they are nearly insensitive to changes in the leaf chlorophyll content as long as the antenna sizes of the RCs remain unaffected (Dinç et al. 2012). However, we note that this observation probably does not apply to dilute algal and thylakoid suspensions. Malkin (1966) and Murata et al. (1966) showed that the complementary area between the fluorescence transient and F M in the presence of DCMU is proportional to the population of reduced Q A molecules.