Figure 3.

Action spectra for hypocotyl elongation. Fluence rate response curves shown in Figure 2 were used to determine the fluence rate that induced a relative hypocotyl length of 0.6. The value obtained for WS wild type at 720 nm (0.166 μmol m⁻² s⁻¹) was set to 1, and the relative photon effectiveness for the mutants and the wild type at different wavelength was calculated accordingly. A, Action spectrum for the WS wild type. B, Action spectra for spa1. The corrected action spectra [spa1(corr)] was determined to eliminate errors that might occur because of the different shape of the spa1 fluence rate response curves (see Fig. 2). To correct for the increased level of hypocotyl inhibition at the onset of HIR in spa1, the mean of all values obtained for hypocotyl inhibition at the plateau level of the fluence rate response curves was determined. This mean (0.72) was set to 1, and fluence rate response curves were recalculated. Photon fluence rates that led to a relative hypocotyl length of 0.6 were again determined as described above. C, Action spectra for eid1-3 and eid1-5.