Figure 1.

The Al-Induced Auxin Response in the TZ Is Crucial for Root Growth Inhibition in Arabidopsis.

(A) Expression of the DR5rev:GFP transgene in roots exposed for 2 h to 0, 10, or 25 μM AlCl₃ or to 10 μM AlCl₃ plus 15 μM PEO-IAA. Control indicates nontreated roots. The top row shows DR5rev:GFP signals in the epidermis, and the bottom row shows DR5rev:GFP signals in the cortex. Cell boundaries appear red following PI staining. The TZ is marked by yellow arrowheads. Bar = 100 μm.

(B) IAA concentration in root tips (1 mm long) exposed to 6, 8, and 10 μM AlCl₃ for 0, 3, 6, and 12 h. Asterisks indicate significant differences at *P < 0.05 and **P < 0.01 (t test). Values represent means ± sd (n = 3). FW, fresh weight.

(C) and (D) Primary root growth after exposure to 0, 6, 8, and 10 μM AlCl₃ and either 0 or 0.5 μM PEO-IAA for 7 d. Asterisks indicate that differences between the PEO-IAA treatments are significant at *P < 0.05 and **P < 0.01 (t test). Values in (D) represent means ± sd (n = 30).