Chlorophyll fluorescence (Fv/Fm) was measured on the same
leaves used for gas exchange measurement with a portable chlorophyll
fluorometer (Handy-PEA; Hansatech Instruments, King’s
Lynn, Norfolk, UK), which emits light of 650 nm wavelength with
an intensity of 2500 mol photons m−2 s−1. Measurements were
taken from dark-adapted leaves (30 min dark adapted).