Figure 1.

Etiolated Arabidopsis and tomato (cv Ailsa Craig) seedlings had measurable basipetal PAT in excised hypocotyl sections. A, The PAT assay. The donor agar block contained 10⁻⁷ m [³H]IAA; 10 μm NPA was added to the receiver agar block in the NPA control. B, Radioactivity in the upper half (U), lower half (L), and receiver (R) was determined separately at the end of the transport period. C, PAT in 6-d dark-grown Arabidopsis and 4-d dark-grown tomato hypocotyls after a 3-h transport period (n = 10). Similar results were also obtained using 8-d dark-grown Arabidopsis plants. Percentage auxin transport equals the percentage of radioactivity in L and R divided by the sum of L, R, and U. Error bars represent se. [See online article for color version of this figure.]