Measurements of photosynthetic parameters
Gas-exchange measurements were performed with an open-flow infrared
gas-exchange analyzer system (Li-Cor 6400XT) with a portable
photosynthesis system. Light was supplied from a series of
light-emitting diodes located above the cuvette, providing an irradiance
of 150 μmol photons m-2 s-1, similar
to the growth conditions aforementioned. The reference
CO2 concentration was set at 400 mmol
CO2 mol-1 air. All measurements were
performed at 25°C, and the vapor pressure deficit was maintained at 0.2
kPa, while the amount of blue light was set to 10% of photon flux
density to optimize stomatal aperture. The determination of the
photosynthetic parameters was performed in 4-week-old plants.F v/F m, which corresponds to the potential quantum yield of
the photochemical reactions of PSII and represents a measure of
photochemical efficiency, was measured as described previously (Oh et
al., 1996).