2005; Hakala et al. 2005), but, at the same time, may have additional affects on the PSII RC (e.g., Vass et al. 1996) and, thereby, on the fluorescence kinetics. For both drought

stress and sulfate deficiency, it was shown that they affect PSI (Oukarroum et al. 2009; Ceppi et al. 2012). Again, a combination of experimental phenomena is needed to find more distinguish these stress conditions. Another complication is that the PSII to PSI ratio that affects the parameter ΔV IP is regulated by the growth light intensity and quality as well (Leong and Anderson 1984b; Lee and Whitmarsh 1989; Chow et al. 1990a, b). Finally, there are considerable kinetic differences between the OJIP transients obtained from different plant species (Kirova et al. 2009). This means that good references

are needed to determine if eFT508 something is a stress effect, taking into account the normal plasticity of the OJIP transients. The available physiological studies often concentrate on the effects of severe stress under laboratory conditions. In the field, milder stress effects are often observed, which possibly have to be distinguished from other sources of variability, so that additional research efforts will be needed to obtain reliable “fingerprints” for a particular stress. An example of the type of research needed is a study by Kalaji (2011) who characterized the effects of 16 abiotic stresses on the fluorescence properties of two Syrian landraces (cvs. Arabi Abiad and Arabi Aswad) of barley (see

also Kalaji and Guo 2008). Another approach is to make mathematical analyses of sets of OJIP transients in combination with DF and 820 nm transmission this website transients. Goltsev et al. (2012) trained an artificial neural network to estimate the relative water content (RWC) of leaves; they obtained a correlation value of R 2 = 0.98 between the estimated RWC value and the gravimetrically determined RWC value of the analyzed leaves. In France, commercial software was developed that compares measured OJIP transients with a database of fluorescence transients measured on plants of dozens of genotypes of agricultural and horticultural crops suffering from deficiencies of the following elements: N, Fe, Mn, Mg, P, S, Ca, and B. This approach has similarities with the one discussed above, but it is more ambitious in its scope. This software is at the moment very Cytidine deaminase popular among farmers, especially in Poland, Ukraine, and Russia, where it is promoted by producers of fertilizer. Kalaji et al. (unpublished data, 2013) did many experiments to test the software and suggested analysis, comparing the fluorescence analysis with the chemical analysis of several plant species grown under different conditions of nutrient deficiency. These studies suggested that this method needs further improvements to achieve a general validity. For the moment, it is not possible to identify specific stresses using Chl a fluorescence. As noted above, different stresses may have similar effects on the photosynthetic system.