Figure 3.

CUL3 Function Is Necessary for Normal Hypocotyl Phototropism, but Not Gravitropism, in Arabidopsis.

(A) Hypocotyl phototropism in seedlings exposed to 4 h of low-intensity unilateral BL (0.1 μmol m⁻² s⁻¹). Col, the wild type. Data represent the mean ± se of at least 70 seedlings for each genotype. Mean responses differing significantly (P < 0.001; Students t test) from that of the wild type are indicated by asterisks.

(B) Hypocotyl gravitropism in etiolated seedlings. Seedlings were germinated and grown on agar-solidified 0.5× MS medium in vertically oriented plates for 3 d in darkness and then the plates were rotated on-edge 90° to induce a gravitropic response, as described previously (Stowe-Evans et al., 1998). Col, the wild type. Data represent the mean ± se of at least 70 seedlings for each genotype. Student’s t test revealed that no genotype exhibited a response significantly different from that of the wild type (P > 0.05).

(C) Hypocotyl phototropism in seedlings exposed to high-intensity unilateral BL (120 μmol m⁻² s⁻¹) for 2 (white bars), 4 (gray bars), or 6 h (black bars). Data represent the mean ± se of at least 53 seedlings for each genotype. Col, the wild type. Mean responses differing significantly (P < 0.01; Student’s t test) from that of the wild type are indicated by asterisks.