Figure 4.

Pulse-induced phototropism in wild-type and nph4 mutant seedlings. A, Fluence response curves for BL pulse-induced phototropism. Seventy-two-h-old etiolated seedlings were irradiated with five pulses of BL at the indicated fluence, and 2 h after the final pulse, curvatures were measured as described in “Materials and Methods.” Data represent the mean response of at least 28 seedlings from five replicate experiments. B, Fluence response curves for RL-dependent enhancement of BL pulse-induced phototropism. Experiments were as described for A, except that 2 h prior to BL irradiation (five pulses at 0.03 μmol m⁻² s⁻¹), seedlings were exposed to the indicated fluence of RL. Data represent the mean response from at least 15 seedlings from three replicate experiments. ●, Wild type; ○, nph4.