Chlorophyll
fluorescence was determined between 10:30 and
11:30 h using a portable plant efficiency analyzer (Model,
MK29414, Hansatech Instrument Ltd., UK) on the same leaves
where Ps measurements were taken. Leaf clips for dark adaptation
were placed on the adaxial side of the leaves 30 min before
measurement and then exposed to red light of 650 nm through LED
at excitation irradiance of 3000 mmol m2 s1. Minimum
fluorescence
(Fo) and maximum
fluorescence (Fm) were measured from
which variable
fluorescence (Fv = Fm
Fo) was calculated. The ratio
of variable and maximal
fluorescence (Fv/Fm) representing maximal
photochemical efficiency of PSII was calculated as: Fv/
Fm= (Fm
Fo)/Fm.