Photosynthetic CO₂ fixation and stomatal conductance were measured using a gas exchange system (LI-6400; LI-COR) equipped with an Arabidopsis (Arabidopsis thaliana) chamber (LI-COR) as previously described (Doi et al., 2004). Red light was provided from a tungsten lamp (MHF-G150LR; Moritex) by passing the light through a red cutoff filter (2-61; Corning) or from an LED Lamp Drive unit (SS-001; Shimatec) equipped with a red LED (WBS-Φ-30-16R, λ = 656 ± 18 nm). Blue light was provided by a metal halide lamp (LS-M250; Moritex) by passing the light through a blue filter (5-60; Corning) or an LED Lamp Drive unit equipped with a blue LED (WBS-Φ-30-16B, λ = 467 ± 19 nm). Green light was provided from a tungsten lamp by passing the light through a green interference filter (λ = 500 ± 26 nm; Optical Coatings Japan). Far-red light was provided from an LED Lamp Drive unit equipped with a far-red LED (WBS 720; λ = 723 ± 12 nm). PFD was measured using an LI-2500 light meter with an LI190SA quantum sensor (LI-COR) and an SKR 110 sensor (Skye Instruments). To administer DCMU to Adiantum leaves, we cut off the leaf with its petiole and placed the petiole in water under darkness. The next morning, the leaf was transferred to 0.05% ethanol solution that contained 50 μm DCMU and was kept under fluorescent light at 30 μmol m⁻² s⁻¹ for 1 h. Then, the Adiantum leaf was returned to the darkness for 3 h and used for the measurement.