According
to the methods of Demmig-Adams and Adams (1996), the
capture efficiency of excitation energy was calculated as:
Fv´/Fm´= (Fm´–Fo´)/Fm´. The actual PSII efficiency under
irradiance was calculated as: ΦPSII= (Fm´–Fs)/Fm´; and the
non-photochemical quenching was calculated as: NPQ=
(Fm/Fm´)−1