Analysing the fluorescence parameter F0, Fm, Fv and Fv/Fm, the authors could verify damages in
PSII 24 h post infection, even without finding or rating typical
necrotic spots. In this context, it has been shown that pulse-amplitude
modulate fluorescence imaging may partially underestimate
Fv/Fm under some conditions (e.g. Vieira et al., 2013). Nevertheless,
a minor effect on Fv/Fm was accepted because all measurements
were made under the same environment.