Modulated chlorophyll fluorescence was measured with a
FMS-2 pulse-modulated fluorometer (Hansatech, UK). The lightfluorescence
measurement protocol was as follows: the
light-adapted leaves were continuously illuminated by actinic light
at 400 lmol mol1 from the FMS-2 light source, steady-state fluorescence
(Fs) was recorded after 2 min illumination, and a 0.8 s saturating
light of 8000 lmol m2 s1 was imposed to obtain the
maximum fluorescence in the light-adapted state (Fm0). The actinic
light was then turned off, and the minimum fluorescence in the
light-adapted state (Fo0) was determined by a 3 s illumination with
far-red light.