FIGURE 4.

Effects of 5-alkoxy-IAA and 7-alkoxy-NAA on polar auxin transport in Arabidopsis seedling and maize coleoptile. A–E, inhibitory effects of alkoxy-auxin on polar auxin transport in maize coleoptile. A, maize coleoptile tip (3 mm) was excised and then the inhibitor solution was loaded into the inner surface of the coleoptile. The transported IAA from the coleoptile tip was trapped in the receiver agar block. The block was replaced at 30-min intervals and the transported IAA content in the block was measured by GC-MS (33). Error bars (n = 3) indicate the mean ± S.E. F and G, inhibitory effects of alkoxy-auxin on polar auxin transport from the Arabidopsis shoot apex to root in wild-type and the abcb1/acbcb19 mutant. F, 10 μm Bz-IAA (t test p = 0.04) and Bz-NAA (p = 0.02) reduced the ³H-labeled IAA transport levels to 65 and 82% of the untreated plant, respectively. G, in the abcb1/19 mutant, the [³H]IAA movement was reduced to 23% of the level of wild-type (p < 0.001). 10 μm Bz-IAA (p = 0.08) and Bz-NAA (p = 0.09) further reduced the 55 and 58% levels of the [³H]IAA transport in the abcb1/abcb19 mutant. Error bars represent the S.D. (n = 5). Asterisks indicate p < 0.001.