Figure 2.

Reversal of the increase in the apparent F_o in light-acclimated sunflower leaves by far-red illumination. Leaves were exposed to growth chamber light (650 μmol quanta m⁻² s⁻¹ PPFD) for 4 h, and the apparent F_o was measured following a preillumination treatment with (•) or without (○) CO. CO and preillumination conditions are the same as described in Figure 1. The effects of far-red light on a dark-adapted leaf (10 h) that was preilluminated for 5 min with 1000 μmol quanta m⁻² s⁻¹ green light are also depicted (□). The beginning of the 10-s far-red light pulses (approximately 730 nm, 10 μmol quanta m⁻² s⁻¹) is indicated by arrows.